[svn-r14903] Undoing change committed in r14902.

1 files changed, 379 insertions, 2838 deletions

diff --git a/src/H5Dio.c b/src/H5Dio.c
index 8576464..17bab19 100644
--- a/src/H5Dio.c
+++ b/src/H5Dio.c
@@ -28,27 +28,17 @@
 #include "H5Eprivate.h"		/* Error handling		  	*/
 #include "H5FLprivate.h"	/* Free Lists                           */
 #include "H5Iprivate.h"		/* IDs			  		*/
-#include "H5MMprivate.h"	/* Memory management			*/
-#include "H5Sprivate.h"		/* Dataspace functions			*/
-#include "H5SLprivate.h"	/* Skip lists				*/
-#include "H5Vprivate.h"		/* Vector and array functions		*/
 
 #ifdef H5_HAVE_PARALLEL
 /* Remove this if H5R_DATASET_REGION is no longer used in this file */
-#   include "H5Rpublic.h"
+#include "H5Rpublic.h"
 #endif /*H5_HAVE_PARALLEL*/
 
+
 /****************/
 /* Local Macros */
 /****************/
 
-#define H5D_DEFAULT_SKIPLIST_HEIGHT     8
-
-/* Macros for iterating over chunks to operate on */
-#define H5D_CHUNK_GET_FIRST_NODE(map) (map.use_single ? (H5SL_node_t *)(1) : H5SL_first(map.sel_chunks))
-#define H5D_CHUNK_GET_NODE_INFO(map, node)  (map.use_single ? map.single_chunk_info : (H5D_chunk_info_t *)H5SL_item(node))
-#define H5D_CHUNK_GET_NEXT_NODE(map, node)  (map.use_single ? (H5SL_node_t *)NULL : H5SL_next(node))
-
 
 /******************/
 /* Local Typedefs */
@@ -59,64 +49,36 @@
 /* Local Prototypes */
 /********************/
 
+/* Internal I/O routines */
 static herr_t H5D_read(H5D_t *dataset, hid_t mem_type_id,
-			const H5S_t *mem_space, const H5S_t *file_space,
-			hid_t dset_xfer_plist, void *buf/*out*/);
+    const H5S_t *mem_space, const H5S_t *file_space, hid_t dset_xfer_plist,
+    void *buf/*out*/);
 static herr_t H5D_write(H5D_t *dataset, hid_t mem_type_id,
-			 const H5S_t *mem_space, const H5S_t *file_space,
-			 hid_t dset_xfer_plist, const void *buf);
-static herr_t H5D_contig_read(H5D_io_info_t *io_info, hsize_t nelmts,
-            const H5T_t *mem_type, const H5S_t *mem_space,
-            const H5S_t *file_space, H5T_path_t *tpath,
-            hid_t src_id, hid_t dst_id,  void *buf/*out*/);
-static herr_t H5D_contig_write(H5D_io_info_t *io_info, hsize_t nelmts,
-            const H5T_t *mem_type, const H5S_t *mem_space,
-	    const H5S_t *file_space, H5T_path_t *tpath,
-            hid_t src_id, hid_t dst_id, const void *buf);
-static herr_t H5D_chunk_read(H5D_io_info_t *io_info, hsize_t nelmts,
-            const H5T_t *mem_type, const H5S_t *mem_space,
-            const H5S_t *file_space, H5T_path_t *tpath,
-            hid_t src_id, hid_t dst_id, void *buf/*out*/);
-static herr_t H5D_chunk_write(H5D_io_info_t *io_info, hsize_t nelmts,
-            const H5T_t *mem_type, const H5S_t *mem_space,
-	    const H5S_t *file_space, H5T_path_t *tpath,
-            hid_t src_id, hid_t dst_id, const void *buf);
-static herr_t H5D_compound_opt_read(size_t nelmts, const H5S_t *mem_space,
-            H5S_sel_iter_t *iter, const H5D_dxpl_cache_t *dxpl_cache, 
-            hid_t src_id, hid_t dst_id, H5T_subset_t subset, void *data_buf, 
-            void *user_buf/*out*/);
-static herr_t H5D_compound_opt_write(size_t nelmts, hid_t src_id, hid_t dst_id, 
-            void *data_buf);
+    const H5S_t *mem_space, const H5S_t *file_space, hid_t dset_xfer_plist,
+    const void *buf);
 
+/* Setup/teardown routines */
+static herr_t H5D_ioinfo_init(H5D_t *dset, const H5D_dxpl_cache_t *dxpl_cache,
+    hid_t dxpl_id, const H5D_type_info_t *type_info, H5D_storage_t *store,
+    H5D_io_info_t *io_info);
+static herr_t H5D_typeinfo_init(const H5D_t *dset, const H5D_dxpl_cache_t *dxpl_cache,
+    hid_t dxpl_id, hid_t mem_type_id, hbool_t do_write,
+    H5D_type_info_t *type_info);
 #ifdef H5_HAVE_PARALLEL
+static herr_t H5D_ioinfo_adjust(H5D_io_info_t *io_info, const H5D_t *dset,
+    const H5D_dxpl_cache_t *dxpl_cache, hid_t dxpl_id,
+    const H5S_t *file_space, const H5S_t *mem_space,
+    const H5D_type_info_t *type_info, const H5D_chunk_map_t *fm);
 static herr_t H5D_ioinfo_term(H5D_io_info_t *io_info);
 #endif /* H5_HAVE_PARALLEL */
+static herr_t H5D_typeinfo_term(const H5D_type_info_t *type_info);
 
-/* I/O info operations */
-static herr_t H5D_ioinfo_init(H5D_t *dset, const H5D_dxpl_cache_t *dxpl_cache,
-    hid_t dxpl_id, const H5S_t *mem_space, const H5S_t *file_space,
-    H5T_path_t *tpath, H5D_io_info_t *io_info);
-
-/* Chunk operations */
-static herr_t H5D_create_chunk_map(H5D_chunk_map_t *fm, const H5D_io_info_t *io_info,
-    hsize_t nelmts, const H5S_t *file_space, const H5S_t *mem_space,
-    const H5T_t *mem_type);
-static herr_t H5D_destroy_chunk_map(const H5D_chunk_map_t *fm);
-static herr_t H5D_free_chunk_info(void *item, void *key, void *opdata);
-static herr_t H5D_create_chunk_map_single(H5D_chunk_map_t *fm,
-    const H5D_io_info_t *io_info);
-static herr_t H5D_create_chunk_file_map_hyper(H5D_chunk_map_t *fm,
-    const H5D_io_info_t *io_info);
-static herr_t H5D_create_chunk_mem_map_hyper(const H5D_chunk_map_t *fm);
-static herr_t H5D_chunk_file_cb(void *elem, hid_t type_id, unsigned ndims,
-    const hsize_t *coords, void *fm);
-static herr_t H5D_chunk_mem_cb(void *elem, hid_t type_id, unsigned ndims,
-    const hsize_t *coords, void *fm);
 
 /*********************/
 /* Package Variables */
 /*********************/
 
+
 /*******************/
 /* Local Variables */
 /*******************/
@@ -124,142 +86,6 @@ static herr_t H5D_chunk_mem_cb(void *elem, hid_t type_id, unsigned ndims,
 /* Declare a free list to manage blocks of type conversion data */
 H5FL_BLK_DEFINE(type_conv);
 
-/* Declare a free list to manage the H5D_chunk_info_t struct */
-H5FL_DEFINE(H5D_chunk_info_t);
-
-/* Declare a free list to manage sequences of size_t */
-H5FL_SEQ_DEFINE_STATIC(size_t);
-
-/* Declare a free list to manage sequences of hsize_t */
-H5FL_SEQ_DEFINE_STATIC(hsize_t);
-
-
-
-/*--------------------------------------------------------------------------
- NAME
-    H5D_get_dxpl_cache_real
- PURPOSE
-    Get all the values for the DXPL cache.
- USAGE
-    herr_t H5D_get_dxpl_cache_real(dxpl_id, cache)
-        hid_t dxpl_id;          IN: DXPL to query
-        H5D_dxpl_cache_t *cache;IN/OUT: DXPL cache to fill with values
- RETURNS
-    Non-negative on success/Negative on failure.
- DESCRIPTION
-    Query all the values from a DXPL that are needed by internal routines
-    within the library.
- GLOBAL VARIABLES
- COMMENTS, BUGS, ASSUMPTIONS
- EXAMPLES
- REVISION LOG
---------------------------------------------------------------------------*/
-herr_t
-H5D_get_dxpl_cache_real(hid_t dxpl_id, H5D_dxpl_cache_t *cache)
-{
-    H5P_genplist_t *dx_plist;   /* Data transfer property list */
-    herr_t ret_value=SUCCEED;   /* Return value */
-
-    FUNC_ENTER_NOAPI(H5D_get_dxpl_cache_real,FAIL)
-
-    /* Check args */
-    assert(cache);
-
-    /* Get the dataset transfer property list */
-    if (NULL == (dx_plist = (H5P_genplist_t *)H5I_object(dxpl_id)))
-        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset transfer property list")
-
-    /* Get maximum temporary buffer size */
-    if(H5P_get(dx_plist, H5D_XFER_MAX_TEMP_BUF_NAME, &cache->max_temp_buf) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve maximum temporary buffer size")
-
-    /* Get temporary buffer pointer */
-    if(H5P_get(dx_plist, H5D_XFER_TCONV_BUF_NAME, &cache->tconv_buf) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve temporary buffer pointer")
-
-    /* Get background buffer pointer */
-    if(H5P_get(dx_plist, H5D_XFER_BKGR_BUF_NAME, &cache->bkgr_buf) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve background buffer pointer")
-
-    /* Get background buffer type */
-    if(H5P_get(dx_plist, H5D_XFER_BKGR_BUF_TYPE_NAME, &cache->bkgr_buf_type) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve background buffer type")
-
-    /* Get B-tree split ratios */
-    if(H5P_get(dx_plist, H5D_XFER_BTREE_SPLIT_RATIO_NAME, &cache->btree_split_ratio) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve B-tree split ratios")
-
-    /* Get I/O vector size */
-    if(H5P_get(dx_plist, H5D_XFER_HYPER_VECTOR_SIZE_NAME, &cache->vec_size) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve I/O vector size")
-
-#ifdef H5_HAVE_PARALLEL
-    /* Collect Parallel I/O information for possible later use */
-     if(H5P_get(dx_plist, H5D_XFER_IO_XFER_MODE_NAME, &cache->xfer_mode) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve parallel transfer method")
-     if(H5P_get(dx_plist, H5D_XFER_IO_XFER_OPT_MODE_NAME, &cache->xfer_opt_mode) < 0)
-       HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve parallel transfer method")
-#endif /*H5_HAVE_PARALLEL*/
-
-    /* Get error detection properties */
-    if(H5P_get(dx_plist, H5D_XFER_EDC_NAME, &cache->err_detect) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve error detection info")
-
-    /* Get filter callback function */
-    if(H5P_get(dx_plist, H5D_XFER_FILTER_CB_NAME, &cache->filter_cb) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve filter callback function")
-
-    /* Get the data transform property */
-    if(H5P_get(dx_plist, H5D_XFER_XFORM_NAME, &cache->data_xform_prop) < 0)
-        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "Can't retrieve data transform info")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-}   /* H5D_get_dxpl_cache_real() */
-
-
-/*--------------------------------------------------------------------------
- NAME
-    H5D_get_dxpl_cache
- PURPOSE
-    Get all the values for the DXPL cache.
- USAGE
-    herr_t H5D_get_dxpl_cache(dxpl_id, cache)
-        hid_t dxpl_id;          IN: DXPL to query
-        H5D_dxpl_cache_t *cache;IN/OUT: DXPL cache to fill with values
- RETURNS
-    Non-negative on success/Negative on failure.
- DESCRIPTION
-    Query all the values from a DXPL that are needed by internal routines
-    within the library.
- GLOBAL VARIABLES
- COMMENTS, BUGS, ASSUMPTIONS
-    The CACHE pointer should point at already allocated memory to place
-    non-default property list info.  If a default property list is used, the
-    CACHE pointer will be changed to point at the default information.
- EXAMPLES
- REVISION LOG
---------------------------------------------------------------------------*/
-herr_t
-H5D_get_dxpl_cache(hid_t dxpl_id, H5D_dxpl_cache_t **cache)
-{
-    herr_t ret_value=SUCCEED;   /* Return value */
-
-    FUNC_ENTER_NOAPI(H5D_get_dxpl_cache,FAIL)
-
-    /* Check args */
-    assert(cache);
-
-    /* Check for the default DXPL */
-    if(dxpl_id==H5P_DATASET_XFER_DEFAULT)
-        *cache=&H5D_def_dxpl_cache;
-    else
-        if(H5D_get_dxpl_cache_real(dxpl_id,*cache) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "Can't retrieve DXPL values")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-}   /* H5D_get_dxpl_cache() */
 
 
 /*-------------------------------------------------------------------------
@@ -300,7 +126,7 @@ H5Dread(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
     const H5S_t		   *mem_space = NULL;
     const H5S_t		   *file_space = NULL;
     char                    fake_char;
-    herr_t                  ret_value=SUCCEED;  /* Return value */
+    herr_t                  ret_value = SUCCEED;  /* Return value */
 
     FUNC_ENTER_API(H5Dread, FAIL)
     H5TRACE6("e", "iiiiix", dset_id, mem_type_id, mem_space_id, file_space_id,
@@ -316,7 +142,7 @@ H5Dread(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
 	    HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a data space")
 
 	/* Check for valid selection */
-	if(H5S_SELECT_VALID(mem_space)!=TRUE)
+	if(H5S_SELECT_VALID(mem_space) != TRUE)
 	    HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "selection+offset not within extent")
     } /* end if */
     if(H5S_ALL != file_space_id) {
@@ -324,33 +150,33 @@ H5Dread(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
 	    HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a data space")
 
 	/* Check for valid selection */
-	if(H5S_SELECT_VALID(file_space)!=TRUE)
+	if(H5S_SELECT_VALID(file_space) != TRUE)
 	    HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "selection+offset not within extent")
-    }
+    } /* end if */
 
     /* Get the default dataset transfer property list if the user didn't provide one */
     if (H5P_DEFAULT == plist_id)
         plist_id= H5P_DATASET_XFER_DEFAULT;
     else
-        if (TRUE!=H5P_isa_class(plist_id,H5P_DATASET_XFER))
+        if(TRUE != H5P_isa_class(plist_id, H5P_DATASET_XFER))
             HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not xfer parms")
-    if (!buf && H5S_GET_SELECT_NPOINTS(file_space)!=0)
+    if(!buf && H5S_GET_SELECT_NPOINTS(file_space) != 0)
 	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no output buffer")
 
     /* If the buffer is nil, and 0 element is selected, make a fake buffer.
      * This is for some MPI package like ChaMPIon on NCSA's tungsten which 
      * doesn't support this feature. 
      */ 
-    if (!buf)
+    if(!buf)
         buf = &fake_char;
 
     /* read raw data */
-    if (H5D_read(dset, mem_type_id, mem_space, file_space, plist_id, buf/*out*/) < 0)
+    if(H5D_read(dset, mem_type_id, mem_space, file_space, plist_id, buf/*out*/) < 0)
 	HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read data")
 
 done:
     FUNC_LEAVE_API(ret_value)
-}
+} /* end H5Dread() */
 
 
 /*-------------------------------------------------------------------------
@@ -392,7 +218,7 @@ H5Dwrite(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
     const H5S_t		   *mem_space = NULL;
     const H5S_t		   *file_space = NULL;
     char                    fake_char;
-    herr_t                  ret_value=SUCCEED;  /* Return value */
+    herr_t                  ret_value = SUCCEED;  /* Return value */
 
     FUNC_ENTER_API(H5Dwrite, FAIL)
     H5TRACE6("e", "iiiii*x", dset_id, mem_type_id, mem_space_id, file_space_id,
@@ -408,7 +234,7 @@ H5Dwrite(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
 	    HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a data space")
 
 	/* Check for valid selection */
-	if (H5S_SELECT_VALID(mem_space)!=TRUE)
+	if(H5S_SELECT_VALID(mem_space) != TRUE)
 	    HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "memory selection+offset not within extent")
     } /* end if */
     if(H5S_ALL != file_space_id) {
@@ -416,7 +242,7 @@ H5Dwrite(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
 	    HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a data space")
 
 	/* Check for valid selection */
-	if(H5S_SELECT_VALID(file_space)!=TRUE)
+	if(H5S_SELECT_VALID(file_space) != TRUE)
 	    HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "file selection+offset not within extent")
     } /* end if */
 
@@ -424,16 +250,16 @@ H5Dwrite(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
     if(H5P_DEFAULT == plist_id)
         plist_id= H5P_DATASET_XFER_DEFAULT;
     else
-        if(TRUE!=H5P_isa_class(plist_id,H5P_DATASET_XFER))
+        if(TRUE != H5P_isa_class(plist_id, H5P_DATASET_XFER))
             HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not xfer parms")
-    if(!buf && H5S_GET_SELECT_NPOINTS(file_space)!=0)
+    if(!buf && H5S_GET_SELECT_NPOINTS(file_space) != 0)
 	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no output buffer")
     
     /* If the buffer is nil, and 0 element is selected, make a fake buffer.
      * This is for some MPI package like ChaMPIon on NCSA's tungsten which 
      * doesn't support this feature. 
      */ 
-    if (!buf)
+    if(!buf)
         buf = &fake_char;
 
     /* write raw data */
@@ -442,7 +268,7 @@ H5Dwrite(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
 
 done:
     FUNC_LEAVE_API(ret_value)
-}
+} /* end H5Dwrite() */
 
 
 /*-------------------------------------------------------------------------
@@ -462,16 +288,18 @@ static herr_t
 H5D_read(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
 	 const H5S_t *file_space, hid_t dxpl_id, void *buf/*out*/)
 {
+    H5D_chunk_map_t fm;                 /* Chunk file<->memory mapping */
+    H5D_io_info_t io_info;              /* Dataset I/O info     */
+    H5D_type_info_t type_info;          /* Datatype info for operation */
+    H5D_storage_t store;                /*union of EFL and chunk pointer in file space */
     hssize_t	snelmts;                /*total number of elmts	(signed) */
     hsize_t	nelmts;                 /*total number of elmts	*/
-    H5T_path_t	*tpath = NULL;		/*type conversion info	*/
-    const H5T_t	*mem_type = NULL;       /* Memory datatype */
-    H5D_io_info_t io_info;              /* Dataset I/O info     */
 #ifdef H5_HAVE_PARALLEL
     hbool_t     io_info_init = FALSE;   /* Whether the I/O info has been initialized */
 #endif /*H5_HAVE_PARALLEL*/
+    hbool_t     io_op_init = FALSE;     /* Whether the I/O op has been initialized */
     H5D_dxpl_cache_t _dxpl_cache;       /* Data transfer property cache buffer */
-    H5D_dxpl_cache_t *dxpl_cache=&_dxpl_cache;   /* Data transfer property cache */
+    H5D_dxpl_cache_t *dxpl_cache = &_dxpl_cache;   /* Data transfer property cache */
     herr_t	ret_value = SUCCEED;	/* Return value	*/
 
     FUNC_ENTER_NOAPI_NOINIT(H5D_read)
@@ -479,10 +307,6 @@ H5D_read(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
     /* check args */
     HDassert(dataset && dataset->oloc.file);
 
-    /* Get memory datatype */
-    if(NULL == (mem_type = (const H5T_t *)H5I_object_verify(mem_type_id, H5I_DATATYPE)))
-	HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a datatype")
-
     if(!file_space)
         file_space = dataset->shared->space;
     if(!mem_space)
@@ -492,23 +316,27 @@ H5D_read(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
     H5_ASSIGN_OVERFLOW(nelmts,snelmts,hssize_t,hsize_t);
 
     /* Fill the DXPL cache values for later use */
-    if(H5D_get_dxpl_cache(dxpl_id,&dxpl_cache) < 0)
+    if(H5D_get_dxpl_cache(dxpl_id, &dxpl_cache) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't fill dxpl cache")
 
+    /* Set up datatype info for operation */
+    if(H5D_typeinfo_init(dataset, dxpl_cache, dxpl_id, mem_type_id, FALSE, &type_info) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up type info")
+
 #ifdef H5_HAVE_PARALLEL
     /* Collective access is not permissible without a MPI based VFD */
-    if (dxpl_cache->xfer_mode==H5FD_MPIO_COLLECTIVE && !IS_H5FD_MPI(dataset->oloc.file))
+    if(dxpl_cache->xfer_mode == H5FD_MPIO_COLLECTIVE && !IS_H5FD_MPI(dataset->oloc.file))
         HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "collective access for MPI-based drivers only")
 #endif /*H5_HAVE_PARALLEL*/
 
     /* Make certain that the number of elements in each selection is the same */
-    if (nelmts!=(hsize_t)H5S_GET_SELECT_NPOINTS(file_space))
+    if(nelmts != (hsize_t)H5S_GET_SELECT_NPOINTS(file_space))
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "src and dest data spaces have different sizes")
 
     /* Make sure that both selections have their extents set */
-    if( !(H5S_has_extent(file_space)) )
+    if(!(H5S_has_extent(file_space)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "file dataspace does not have extent set")
-    if( !(H5S_has_extent(mem_space)) )
+    if(!(H5S_has_extent(mem_space)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "memory dataspace does not have extent set")
 
     /* Retrieve dataset properties */
@@ -539,49 +367,56 @@ H5D_read(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
             HGOTO_DONE(SUCCEED)
 
         /* Go fill the user's selection with the dataset's fill value */
-        if(H5D_fill(dataset->shared->dcpl_cache.fill.buf, dataset->shared->type, buf, mem_type, mem_space, dxpl_id) < 0)
+        if(H5D_fill(dataset->shared->dcpl_cache.fill.buf, dataset->shared->type, buf, type_info.mem_type, mem_space, dxpl_id) < 0)
             HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "filling buf failed")
         else
             HGOTO_DONE(SUCCEED)
     } /* end if */
 
-    /*
-     * Locate the type conversion function and data space conversion
-     * functions, and set up the element numbering information. If a data
-     * type conversion is necessary then register datatype atoms. Data type
-     * conversion is necessary if the user has set the `need_bkg' to a high
-     * enough value in xfer_parms since turning off datatype conversion also
-     * turns off background preservation.
-     */
-    if (NULL==(tpath=H5T_path_find(dataset->shared->type, mem_type, NULL, NULL, dxpl_id, FALSE)))
-        HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "unable to convert between src and dest datatype")
-
     /* Set up I/O operation */
-    if(H5D_ioinfo_init(dataset,dxpl_cache,dxpl_id,mem_space,file_space,tpath,&io_info) < 0)
+    io_info.op_type = H5D_IO_OP_READ;
+    io_info.u.rbuf = buf;
+    if(H5D_ioinfo_init(dataset, dxpl_cache, dxpl_id, &type_info, &store, &io_info) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "unable to set up I/O operation")
 #ifdef H5_HAVE_PARALLEL
     io_info_init = TRUE;
 #endif /*H5_HAVE_PARALLEL*/
 
-    /* Determine correct I/O routine to invoke */
-    if(dataset->shared->layout.type!=H5D_CHUNKED) {
-        if(H5D_contig_read(&io_info, nelmts, mem_type, mem_space, file_space, tpath,
-                dataset->shared->type_id, mem_type_id, buf) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read data")
-    } /* end if */
-    else {
-        if(H5D_chunk_read(&io_info, nelmts, mem_type, mem_space, file_space, tpath,
-                dataset->shared->type_id, mem_type_id, buf) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read data")
-    } /* end else */
+    /* Sanity check that space is allocated, if there are elements */
+    if(nelmts > 0)
+        HDassert(((dataset->shared->layout.type == H5D_CONTIGUOUS && H5F_addr_defined(dataset->shared->layout.u.contig.addr))
+                || (dataset->shared->layout.type == H5D_CHUNKED && H5F_addr_defined(dataset->shared->layout.u.chunk.addr)))
+                || dataset->shared->dcpl_cache.efl.nused > 0
+                || dataset->shared->layout.type == H5D_COMPACT);
+
+    /* Call storage method's I/O initialization routine */
+    if(io_info.layout_ops.init && (*io_info.layout_ops.init)(&io_info, &type_info, nelmts, file_space, mem_space, &fm) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't initialize I/O info")
+    io_op_init = TRUE;
+
+#ifdef H5_HAVE_PARALLEL
+    /* Adjust I/O info for any parallel I/O */
+    if(H5D_ioinfo_adjust(&io_info, dataset, dxpl_cache, dxpl_id, file_space, mem_space, &type_info, &fm) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to adjust I/O info for parallel I/O")
+#endif /*H5_HAVE_PARALLEL*/
+
+    /* Invoke correct "high level" I/O routine */
+    if((*io_info.io_ops.multi_read)(&io_info, &type_info, nelmts, file_space, mem_space, &fm) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read data")
 
 done:
+    /* Shut down the I/O op information */
+    if(io_op_init && io_info.layout_ops.term && (*io_info.layout_ops.term)(&fm) < 0)
+        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down I/O op info")
 #ifdef H5_HAVE_PARALLEL
     /* Shut down io_info struct */
-    if (io_info_init)
+    if(io_info_init)
         if(H5D_ioinfo_term(&io_info) < 0)
             HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "can't shut down io_info")
 #endif /*H5_HAVE_PARALLEL*/
+    /* Shut down datatype info for operation */
+    if(H5D_typeinfo_term(&type_info) < 0)
+        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down type info")
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5D_read() */
@@ -604,16 +439,18 @@ static herr_t
 H5D_write(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
 	  const H5S_t *file_space, hid_t dxpl_id, const void *buf)
 {
+    H5D_chunk_map_t fm;                 /* Chunk file<->memory mapping */
+    H5D_io_info_t io_info;              /* Dataset I/O info     */
+    H5D_type_info_t type_info;          /* Datatype info for operation */
+    H5D_storage_t store;                /*union of EFL and chunk pointer in file space */
     hssize_t	snelmts;                /*total number of elmts	(signed) */
     hsize_t	nelmts;                 /*total number of elmts	*/
-    H5T_path_t	*tpath = NULL;		/*type conversion info	*/
-    const H5T_t	*mem_type = NULL;       /* Memory datatype */
-    H5D_io_info_t io_info;              /* Dataset I/O info     */
 #ifdef H5_HAVE_PARALLEL
     hbool_t     io_info_init = FALSE;   /* Whether the I/O info has been initialized */
 #endif /*H5_HAVE_PARALLEL*/
+    hbool_t     io_op_init = FALSE;     /* Whether the I/O op has been initialized */
     H5D_dxpl_cache_t _dxpl_cache;       /* Data transfer property cache buffer */
-    H5D_dxpl_cache_t *dxpl_cache=&_dxpl_cache;   /* Data transfer property cache */
+    H5D_dxpl_cache_t *dxpl_cache = &_dxpl_cache;   /* Data transfer property cache */
     herr_t	ret_value = SUCCEED;	/* Return value	*/
 
     FUNC_ENTER_NOAPI_NOINIT(H5D_write)
@@ -621,33 +458,33 @@ H5D_write(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
     /* check args */
     HDassert(dataset && dataset->oloc.file);
 
-    /* Get the memory datatype */
-    if(NULL == (mem_type = (const H5T_t *)H5I_object_verify(mem_type_id, H5I_DATATYPE)))
-	HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a datatype")
-
     /* All filters in the DCPL must have encoding enabled. */
     if(!dataset->shared->checked_filters) {
-        if(H5Z_can_apply(dataset->shared->dcpl_id, dataset->shared->type_id) <0)
+        if(H5Z_can_apply(dataset->shared->dcpl_id, dataset->shared->type_id) < 0)
             HGOTO_ERROR(H5E_PLINE, H5E_CANAPPLY, FAIL, "can't apply filters")
 
         dataset->shared->checked_filters = TRUE;
     } /* end if */
 
     /* Check if we are allowed to write to this file */
-    if(0==(H5F_get_intent(dataset->oloc.file) & H5F_ACC_RDWR))
+    if(0 == (H5F_INTENT(dataset->oloc.file) & H5F_ACC_RDWR))
 	HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "no write intent on file")
 
     /* Fill the DXPL cache values for later use */
-    if(H5D_get_dxpl_cache(dxpl_id,&dxpl_cache) < 0)
+    if(H5D_get_dxpl_cache(dxpl_id, &dxpl_cache) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't fill dxpl cache")
 
+    /* Set up datatype info for operation */
+    if(H5D_typeinfo_init(dataset, dxpl_cache, dxpl_id, mem_type_id, TRUE, &type_info) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up type info")
+
     /* Various MPI based checks */
 #ifdef H5_HAVE_PARALLEL
     if(IS_H5FD_MPI(dataset->oloc.file)) {
         /* If MPI based VFD is used, no VL datatype support yet. */
         /* This is because they use the global heap in the file and we don't */
         /* support parallel access of that yet */
-        if(H5T_detect_class(mem_type, H5T_VLEN)>0)
+        if(H5T_detect_class(type_info.mem_type, H5T_VLEN) > 0)
             HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "Parallel IO does not support writing VL datatypes yet")
 
         /* If MPI based VFD is used, no VL datatype support yet. */
@@ -656,42 +493,48 @@ H5D_write(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
         /* We should really use H5T_detect_class() here, but it will be difficult
          * to detect the type of the reference if it is nested... -QAK
          */
-        if (H5T_get_class(mem_type, TRUE)==H5T_REFERENCE &&
-                H5T_get_ref_type(mem_type)==H5R_DATASET_REGION)
+        if(H5T_get_class(type_info.mem_type, TRUE) == H5T_REFERENCE &&
+                H5T_get_ref_type(type_info.mem_type) == H5R_DATASET_REGION)
             HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "Parallel IO does not support writing region reference datatypes yet")
+
+        /* Can't write to chunked datasets with filters, in parallel */
+        if(dataset->shared->layout.type == H5D_CHUNKED &&
+                dataset->shared->dcpl_cache.pline.nused > 0)
+            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "cannot write to chunked storage with filters in parallel")
     } /* end if */
     else {
         /* Collective access is not permissible without a MPI based VFD */
-        if (dxpl_cache->xfer_mode==H5FD_MPIO_COLLECTIVE)
+        if(dxpl_cache->xfer_mode == H5FD_MPIO_COLLECTIVE)
             HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "collective access for MPI-based driver only")
     } /* end else */
 #endif /*H5_HAVE_PARALLEL*/
 
-    if (!file_space)
+    /* Initialize dataspace information */
+    if(!file_space)
         file_space = dataset->shared->space;
-    if (!mem_space)
+    if(!mem_space)
         mem_space = file_space;
     if((snelmts = H5S_GET_SELECT_NPOINTS(mem_space)) < 0)
 	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "src dataspace has invalid selection")
-    H5_ASSIGN_OVERFLOW(nelmts,snelmts,hssize_t,hsize_t);
+    H5_ASSIGN_OVERFLOW(nelmts, snelmts, hssize_t, hsize_t);
 
     /* Make certain that the number of elements in each selection is the same */
-    if (nelmts!=(hsize_t)H5S_GET_SELECT_NPOINTS(file_space))
+    if(nelmts != (hsize_t)H5S_GET_SELECT_NPOINTS(file_space))
 	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "src and dest data spaces have different sizes")
 
     /* Make sure that both selections have their extents set */
-    if( !(H5S_has_extent(file_space)) )
+    if(!(H5S_has_extent(file_space)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "file dataspace does not have extent set")
-    if( !(H5S_has_extent(mem_space)) )
+    if(!(H5S_has_extent(mem_space)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "memory dataspace does not have extent set")
 
     /* Retrieve dataset properties */
     /* <none needed currently> */
 
     /* Allocate data space and initialize it if it hasn't been. */
-    if(nelmts > 0 && dataset->shared->dcpl_cache.efl.nused==0 &&
-            ((dataset->shared->layout.type==H5D_CONTIGUOUS && !H5F_addr_defined(dataset->shared->layout.u.contig.addr))
-                || (dataset->shared->layout.type==H5D_CHUNKED && !H5F_addr_defined(dataset->shared->layout.u.chunk.addr)))) {
+    if(nelmts > 0 && dataset->shared->dcpl_cache.efl.nused == 0 &&
+            ((dataset->shared->layout.type == H5D_CONTIGUOUS && !H5F_addr_defined(dataset->shared->layout.u.contig.addr))
+                || (dataset->shared->layout.type == H5D_CHUNKED && !H5F_addr_defined(dataset->shared->layout.u.chunk.addr)))) {
         hssize_t file_nelmts;   /* Number of elements in file dataset's dataspace */
         hbool_t full_overwrite; /* Whether we are over-writing all the elements */
 
@@ -703,42 +546,36 @@ H5D_write(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
         if(H5T_detect_class(dataset->shared->type, H5T_VLEN))
             full_overwrite = FALSE;
         else
-            full_overwrite = (hsize_t)file_nelmts==nelmts ? TRUE : FALSE;
+            full_overwrite = (hsize_t)file_nelmts == nelmts ? TRUE : FALSE;
 
  	/* Allocate storage */
         if(H5D_alloc_storage(dataset->oloc.file, dxpl_id, dataset, H5D_ALLOC_WRITE, full_overwrite) < 0)
             HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize storage")
     } /* end if */
 
-    /*
-     * Locate the type conversion function and data space conversion
-     * functions, and set up the element numbering information. If a data
-     * type conversion is necessary then register datatype atoms. Data type
-     * conversion is necessary if the user has set the `need_bkg' to a high
-     * enough value in xfer_parms since turning off datatype conversion also
-     * turns off background preservation.
-     */
-    if (NULL==(tpath=H5T_path_find(mem_type, dataset->shared->type, NULL, NULL, dxpl_id, FALSE)))
-	HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "unable to convert between src and dest datatype")
-
     /* Set up I/O operation */
-    if(H5D_ioinfo_init(dataset,dxpl_cache,dxpl_id,mem_space,file_space,tpath,&io_info) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "unable to set up I/O operation")
+    io_info.op_type = H5D_IO_OP_WRITE;
+    io_info.u.wbuf = buf;
+    if(H5D_ioinfo_init(dataset, dxpl_cache, dxpl_id, &type_info, &store, &io_info) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up I/O operation")
 #ifdef H5_HAVE_PARALLEL
     io_info_init = TRUE;
 #endif /*H5_HAVE_PARALLEL*/
 
-    /* Determine correct I/O routine to invoke */
-    if(dataset->shared->layout.type!=H5D_CHUNKED) {
-        if(H5D_contig_write(&io_info, nelmts, mem_type, mem_space, file_space, tpath,
-                mem_type_id, dataset->shared->type_id, buf) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "can't write data")
-    } /* end if */
-    else {
-        if(H5D_chunk_write(&io_info, nelmts, mem_type, mem_space, file_space, tpath,
-                mem_type_id, dataset->shared->type_id, buf) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "can't write data")
-    } /* end else */
+    /* Call storage method's I/O initialization routine */
+    if(io_info.layout_ops.init && (*io_info.layout_ops.init)(&io_info, &type_info, nelmts, file_space, mem_space, &fm) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't initialize I/O info")
+    io_op_init = TRUE;
+
+#ifdef H5_HAVE_PARALLEL
+    /* Adjust I/O info for any parallel I/O */
+    if(H5D_ioinfo_adjust(&io_info, dataset, dxpl_cache, dxpl_id, file_space, mem_space, &type_info, &fm) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to adjust I/O info for parallel I/O")
+#endif /*H5_HAVE_PARALLEL*/
+
+    /* Invoke correct "high level" I/O routine */
+    if((*io_info.io_ops.multi_write)(&io_info, &type_info, nelmts, file_space, mem_space, &fm) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "can't write data")
 
 #ifdef OLD_WAY
 /*
@@ -756,2667 +593,325 @@ H5D_write(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
 #endif /* OLD_WAY */
 
 done:
+    /* Shut down the I/O op information */
+    if(io_op_init && io_info.layout_ops.term && (*io_info.layout_ops.term)(&fm) < 0)
+        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down I/O op info")
 #ifdef H5_HAVE_PARALLEL
     /* Shut down io_info struct */
-    if (io_info_init)
-        if(H5D_ioinfo_term(&io_info) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "can't shut down io_info")
+    if(io_info_init && H5D_ioinfo_term(&io_info) < 0)
+        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "can't shut down io_info")
 #endif /*H5_HAVE_PARALLEL*/
+    /* Shut down datatype info for operation */
+    if(H5D_typeinfo_term(&type_info) < 0)
+        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down type info")
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5D_write() */
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5D_contig_read
+ * Function:	H5D_ioinfo_init
  *
- * Purpose:	Read from a contiguous dataset.
+ * Purpose:	Routine for determining correct I/O operations for
+ *              each I/O action.
  *
  * Return:	Non-negative on success/Negative on failure
  *
- * Programmer:	Raymond Lu
- *		Thursday, April 10, 2003
+ * Programmer:	Quincey Koziol
+ *		Thursday, September 30, 2004
  *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5D_contig_read(H5D_io_info_t *io_info, hsize_t nelmts,
-    const H5T_t *mem_type, const H5S_t *mem_space,
-    const H5S_t *file_space, H5T_path_t *tpath,
-    hid_t src_id, hid_t dst_id, void *buf/*out*/)
+H5D_ioinfo_init(H5D_t *dset, const H5D_dxpl_cache_t *dxpl_cache, hid_t dxpl_id,
+    const H5D_type_info_t *type_info, H5D_storage_t *store, H5D_io_info_t *io_info)
 {
-    H5D_t *dataset=io_info->dset;       /* Local pointer to dataset info */
-    const H5D_dxpl_cache_t *dxpl_cache=io_info->dxpl_cache;     /* Local pointer to dataset transfer info */
-    herr_t      status;                 /*function return status*/
-#ifdef H5S_DEBUG
-    H5_timer_t	timer;
-#endif
-    size_t	src_type_size;		/*size of source type	*/
-    size_t	dst_type_size;	        /*size of destination type*/
-    size_t	max_type_size;	        /* Size of largest source/destination type */
-    size_t	target_size;		/*desired buffer size	*/
-    size_t	request_nelmts;		/*requested strip mine	*/
-    H5S_sel_iter_t mem_iter;            /*memory selection iteration info*/
-    hbool_t	mem_iter_init=0;	/*memory selection iteration info has been initialized */
-    H5S_sel_iter_t bkg_iter;            /*background iteration info*/
-    hbool_t	bkg_iter_init=0;	/*background iteration info has been initialized */
-    H5S_sel_iter_t file_iter;           /*file selection iteration info*/
-    hbool_t	file_iter_init=0;	/*file selection iteration info has been initialized */
-    H5T_bkg_t	need_bkg;		/*type of background buf*/
-    uint8_t	*tconv_buf = NULL;	/*datatype conv buffer	*/
-    uint8_t	*bkg_buf = NULL;	/*background buffer	*/
-    hsize_t	smine_start;		/*strip mine start loc	*/
-    size_t	n, smine_nelmts;	/*elements per strip	*/
-    H5D_storage_t store;                /*union of storage info for dataset */
-
-
-    herr_t	ret_value = SUCCEED;	/*return value		*/
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_contig_read)
-
-    assert (buf);
-
-    /* Initialize storage info for this dataset */
-    if (dataset->shared->dcpl_cache.efl.nused > 0)
-        HDmemcpy(&store.efl, &(dataset->shared->dcpl_cache.efl), sizeof(H5O_efl_t));
-    else {
-        store.contig.dset_addr = dataset->shared->layout.u.contig.addr;
-        store.contig.dset_size = dataset->shared->layout.u.contig.size;
-    } /* end if */
-
-    /* Set dataset storage for I/O info */
-    io_info->store=&store;
-
-    /*
-     * If there is no type conversion then read directly into the
-     * application's buffer.  This saves at least one mem-to-mem copy.
-     */
-    if ( H5Z_xform_noop(dxpl_cache->data_xform_prop) && H5T_path_noop(tpath)) {
-#ifdef H5S_DEBUG
-	H5_timer_begin(&timer);
-#endif
-  	/* Sanity check dataset, then read it */
-        assert(((dataset->shared->layout.type == H5D_CONTIGUOUS && H5F_addr_defined(dataset->shared->layout.u.contig.addr))
-                || (dataset->shared->layout.type == H5D_CHUNKED && H5F_addr_defined(dataset->shared->layout.u.chunk.addr)))
-                || dataset->shared->dcpl_cache.efl.nused > 0 || 0 == nelmts
-                || dataset->shared->layout.type==H5D_COMPACT);
-        H5_CHECK_OVERFLOW(nelmts,hsize_t,size_t);
-
-#ifdef H5_HAVE_PARALLEL
-	if(io_info->dxpl_cache->xfer_mode == H5FD_MPIO_COLLECTIVE) {
-	  if(H5D_contig_collective_io(io_info,file_space,mem_space,buf,FALSE) < 0)
-	    HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "contiguous read failed in collective mode");
-	}
-	else
-#endif
-        {
-            if((io_info->ops.read)(io_info, (size_t)nelmts,
-                    H5T_get_size(dataset->shared->type), file_space, mem_space,
-                    (haddr_t)0, NULL, buf/*out*/) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "contiguous read failed ");
-	}
-
-#ifdef H5S_DEBUG
-        H5_timer_end(&(io_info->stats->stats[1].read_timer), &timer);
-        io_info->stats->stats[1].read_nbytes += nelmts * H5T_get_size(dataset->shared->type);
-        io_info->stats->stats[1].read_ncalls++;
-#endif
-
-            /* direct xfer accomplished successfully */
-            HGOTO_DONE(SUCCEED)
-    } /* end if */
-
-    /*
-     * This is the general case (type conversion, usually).
-     */
-    if(nelmts==0)
-        HGOTO_DONE(SUCCEED)
-
-    /* Compute element sizes and other parameters */
-    src_type_size = H5T_get_size(dataset->shared->type);
-    dst_type_size = H5T_get_size(mem_type);
-    max_type_size = MAX(src_type_size, dst_type_size);
-    target_size = dxpl_cache->max_temp_buf;
-    /* XXX: This could cause a problem if the user sets their buffer size
-     * to the same size as the default, and then the dataset elements are
-     * too large for the buffer... - QAK
-     */
-    if(target_size == H5D_TEMP_BUF_SIZE) {
-        /* If the buffer is too small to hold even one element, make it bigger */
-        if(target_size<max_type_size)
-            target_size = max_type_size;
-        /* If the buffer is too large to hold all the elements, make it smaller */
-        else if(target_size>(nelmts*max_type_size))
-            target_size=(size_t)(nelmts*max_type_size);
-    } /* end if */
-    request_nelmts = target_size / max_type_size;
-
-    /* Sanity check elements in temporary buffer */
-    if (request_nelmts==0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "temporary buffer max size is too small")
-
-    /* Figure out the strip mine size. */
-    if (H5S_select_iter_init(&file_iter, file_space, src_type_size) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize file selection information")
-    file_iter_init=1;	/*file selection iteration info has been initialized */
-    if (H5S_select_iter_init(&mem_iter, mem_space, dst_type_size) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize memory selection information")
-    mem_iter_init=1;	/*file selection iteration info has been initialized */
-    if (H5S_select_iter_init(&bkg_iter, mem_space, dst_type_size) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize background selection information")
-    bkg_iter_init=1;	/*file selection iteration info has been initialized */
-
-    /*
-     * Get a temporary buffer for type conversion unless the app has already
-     * supplied one through the xfer properties. Instead of allocating a
-     * buffer which is the exact size, we allocate the target size.  The
-     * malloc() is usually less resource-intensive if we allocate/free the
-     * same size over and over.
-     */
-    if (H5T_path_bkg(tpath)) {
-        H5T_bkg_t path_bkg;     /* Type conversion's background info */
-
-        /* Retrieve the bkgr buffer property */
-        need_bkg=dxpl_cache->bkgr_buf_type;
-        path_bkg = H5T_path_bkg(tpath);
-        need_bkg = MAX(path_bkg, need_bkg);
-    } else {
-        need_bkg = H5T_BKG_NO; /*never needed even if app says yes*/
-    } /* end else */
-    if(NULL == (tconv_buf = (uint8_t *)dxpl_cache->tconv_buf)) {
-        /* Allocate temporary buffer */
-        if(NULL == (tconv_buf = H5FL_BLK_MALLOC(type_conv, target_size)))
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for type conversion")
-    } /* end if */
-    if(need_bkg && NULL == (bkg_buf = (uint8_t *)dxpl_cache->bkgr_buf)) {
-        /* Allocate background buffer */
-        /* (Need calloc()-like call since memory needs to be initialized) */
-        if(NULL == (bkg_buf = H5FL_BLK_CALLOC(type_conv, (request_nelmts * dst_type_size))))
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for background conversion")
-    } /* end if */
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5D_ioinfo_init)
 
-    /* Start strip mining... */
-    for (smine_start=0; smine_start<nelmts; smine_start+=smine_nelmts) {
-        /* Go figure out how many elements to read from the file */
-        assert(H5S_SELECT_ITER_NELMTS(&file_iter)==(nelmts-smine_start));
-        smine_nelmts = (size_t)MIN(request_nelmts, (nelmts-smine_start));
+    /* check args */
+    HDassert(dset);
+    HDassert(dset->oloc.file);
+    HDassert(type_info);
+    HDassert(type_info->tpath);
+    HDassert(io_info);
 
-        /*
-         * Gather the data from disk into the datatype conversion
-         * buffer. Also gather data from application to background buffer
-         * if necessary.
-         */
-#ifdef H5S_DEBUG
-	H5_timer_begin(&timer);
-#endif
-	/* Sanity check that space is allocated, then read data from it */
-        HDassert(((dataset->shared->layout.type == H5D_CONTIGUOUS && H5F_addr_defined(dataset->shared->layout.u.contig.addr))
-                || (dataset->shared->layout.type == H5D_CHUNKED && H5F_addr_defined(dataset->shared->layout.u.chunk.addr)))
-            || dataset->shared->dcpl_cache.efl.nused > 0 ||
-             dataset->shared->layout.type == H5D_COMPACT);
-        n = H5D_select_fgath(io_info, file_space, &file_iter, smine_nelmts, (haddr_t)0, NULL, tconv_buf/*out*/);
-
-#ifdef H5S_DEBUG
-	H5_timer_end(&(io_info->stats->stats[1].gath_timer), &timer);
-	io_info->stats->stats[1].gath_nbytes += n * src_type_size;
-	io_info->stats->stats[1].gath_ncalls++;
-#endif
-	if (n!=smine_nelmts)
-            HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "file gather failed")
-
-        /* If the source and destination are compound types and subset of each other
-         * and no conversion is needed, copy the data directly into user's buffer and 
-         * bypass the rest of steps.  This optimization is for Chicago company */
-        if(H5T_SUBSET_SRC==H5T_path_compound_subset(tpath)) {
-            if(H5D_compound_opt_read(smine_nelmts, mem_space, &mem_iter, dxpl_cache,
-                src_id, dst_id, H5T_SUBSET_SRC, tconv_buf, buf /*out*/)<0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "datatype conversion failed")
-
-            continue;
-        } else if(H5T_SUBSET_DST==H5T_path_compound_subset(tpath)) {
-            if(H5D_compound_opt_read(smine_nelmts, mem_space, &mem_iter, dxpl_cache,
-                src_id, dst_id, H5T_SUBSET_DST, tconv_buf, buf /*out*/)<0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "datatype conversion failed")
-
-            continue;
-        }
-
-        if (H5T_BKG_YES==need_bkg) {
-#ifdef H5S_DEBUG
-            H5_timer_begin(&timer);
-#endif
-            n = H5D_select_mgath(buf, mem_space, &bkg_iter,
-				 smine_nelmts, dxpl_cache, bkg_buf/*out*/);
-#ifdef H5S_DEBUG
-            H5_timer_end(&(io_info->stats->stats[1].bkg_timer), &timer);
-            io_info->stats->stats[1].bkg_nbytes += n * dst_type_size;
-            io_info->stats->stats[1].bkg_ncalls++;
-#endif
-            if (n!=smine_nelmts)
-                HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "mem gather failed")
-        } /* end if */
+    /* Set up "normal" I/O fields */
+    io_info->dset = dset;
+    io_info->dxpl_cache = dxpl_cache;
+    io_info->dxpl_id = dxpl_id;
+    io_info->store = store;
 
-	/*
-         * Perform datatype conversion.
-         */
-        if (H5T_convert(tpath, src_id, dst_id, smine_nelmts, (size_t)0, (size_t)0, tconv_buf, bkg_buf, io_info->dxpl_id) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "datatype conversion failed")
+    /* Set I/O operations to initial values */
+    io_info->layout_ops = *dset->shared->layout_ops;
 
-	/* Do the data transform after the conversion (since we're using type mem_type) */
-        if(!H5Z_xform_noop(dxpl_cache->data_xform_prop))
-             if( H5Z_xform_eval(dxpl_cache->data_xform_prop, tconv_buf, smine_nelmts, mem_type) < 0)
-		    HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "Error performing data transform")
+    /* Set the "high-level" I/O operations for the dataset */
+    io_info->io_ops.multi_read = dset->shared->layout_ops->ser_read;
+    io_info->io_ops.multi_write = dset->shared->layout_ops->ser_write;
 
+    /* Set the I/O operations for reading/writing single blocks on disk */
+    if(type_info->is_xform_noop && type_info->is_conv_noop) {
         /*
-         * Scatter the data into memory.
+         * If there is no data transform or type conversion then read directly into
+         *  the application's buffer.  This saves at least one mem-to-mem copy.
          */
-#ifdef H5S_DEBUG
-	H5_timer_begin(&timer);
-#endif
-        status = H5D_select_mscat(tconv_buf, mem_space,
-                          &mem_iter, smine_nelmts, dxpl_cache, buf/*out*/);
-#ifdef H5S_DEBUG
-	H5_timer_end(&(io_info->stats->stats[1].scat_timer), &timer);
-	io_info->stats->stats[1].scat_nbytes += smine_nelmts * dst_type_size;
-	io_info->stats->stats[1].scat_ncalls++;
-#endif
-	if (status<0)
-            HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "scatter failed")
-    } /* end for */
-
-done:
-    /* Release selection iterators */
-    if(file_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&file_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
+        io_info->io_ops.single_read = H5D_select_read;
+        io_info->io_ops.single_write = H5D_select_write;
     } /* end if */
-    if(mem_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&mem_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-    if(bkg_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&bkg_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-
-    if (tconv_buf && NULL==dxpl_cache->tconv_buf)
-        (void)H5FL_BLK_FREE(type_conv,tconv_buf);
-    if (bkg_buf && NULL==dxpl_cache->bkgr_buf)
-        (void)H5FL_BLK_FREE(type_conv,bkg_buf);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_contig_read() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_contig_write
- *
- * Purpose:	Write to a contiguous dataset.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Raymond Lu
- *		Thursday, April 10, 2003
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5D_contig_write(H5D_io_info_t *io_info, hsize_t nelmts,
-    const H5T_t *mem_type, const H5S_t *mem_space,
-    const H5S_t *file_space, H5T_path_t *tpath,
-    hid_t src_id, hid_t dst_id, const void *buf)
-{
-    H5D_t *dataset=io_info->dset;       /* Local pointer to dataset info */
-    const H5D_dxpl_cache_t *dxpl_cache=io_info->dxpl_cache;     /* Local pointer to dataset transfer info */
-    herr_t      status;                 /*function return status*/
-#ifdef H5S_DEBUG
-    H5_timer_t	timer;
-#endif
-    size_t	src_type_size;		/*size of source type	*/
-    size_t	dst_type_size;	        /*size of destination type*/
-    size_t	max_type_size;	        /* Size of largest source/destination type */
-    size_t	target_size;		/*desired buffer size	*/
-    size_t	request_nelmts;		/*requested strip mine	*/
-    H5S_sel_iter_t mem_iter;            /*memory selection iteration info*/
-    hbool_t	mem_iter_init=0;	/*memory selection iteration info has been initialized */
-    H5S_sel_iter_t bkg_iter;            /*background iteration info*/
-    hbool_t	bkg_iter_init=0;	/*background iteration info has been initialized */
-    H5S_sel_iter_t file_iter;           /*file selection iteration info*/
-    hbool_t	file_iter_init=0;	/*file selection iteration info has been initialized */
-    H5T_bkg_t	need_bkg;		/*type of background buf*/
-    uint8_t	*tconv_buf = NULL;	/*datatype conv buffer	*/
-    uint8_t	*bkg_buf = NULL;	/*background buffer	*/
-    hsize_t	smine_start;		/*strip mine start loc	*/
-    size_t	n, smine_nelmts;	/*elements per strip	*/
-    H5D_storage_t store;                /*union of storage info for dataset */
-
-    herr_t	ret_value = SUCCEED;	/*return value		*/
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_contig_write)
-
-    assert (buf);
-
-    /* Initialize storage info for this dataset */
-    if(dataset->shared->dcpl_cache.efl.nused > 0)
-        HDmemcpy(&store.efl, &(dataset->shared->dcpl_cache.efl), sizeof(H5O_efl_t));
     else {
-        store.contig.dset_addr = dataset->shared->layout.u.contig.addr;
-        store.contig.dset_size = dataset->shared->layout.u.contig.size;
-    } /* end if */
-
-    /* Set dataset storage for I/O info */
-    io_info->store = &store;
-
-    /*
-     * If there is no type conversion then write directly from the
-     * application's buffer.  This saves at least one mem-to-mem copy.
-     */
-    if(H5Z_xform_noop(dxpl_cache->data_xform_prop) && H5T_path_noop(tpath)) {
-#ifdef H5S_DEBUG
-	H5_timer_begin(&timer);
-#endif
-        H5_CHECK_OVERFLOW(nelmts,hsize_t,size_t);
-#ifdef H5_HAVE_PARALLEL
-	if(io_info->dxpl_cache->xfer_mode == H5FD_MPIO_COLLECTIVE) {
-	  if(H5D_contig_collective_io(io_info, file_space, mem_space, buf, TRUE) < 0)
-	    HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "contiguous write failed in collective mode")
-	}
-	else
-#endif
-        {
-            if((io_info->ops.write)(io_info, (size_t)nelmts,
-                    H5T_get_size(dataset->shared->type), file_space, mem_space,
-                    (haddr_t)0, NULL, buf/*out*/) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "contiguous write failed ")
-	}
-
-#ifdef H5S_DEBUG
-        H5_timer_end(&(io_info->stats->stats[0].write_timer), &timer);
-        io_info->stats->stats[0].write_nbytes += nelmts * H5T_get_size(mem_type);
-        io_info->stats->stats[0].write_ncalls++;
-#endif
-
-	    /* direct xfer accomplished successfully */
-	    HGOTO_DONE(SUCCEED)
-    } /* end if */
-
-    /*
-     * This is the general case.
-     */
-    if(nelmts==0)
-        HGOTO_DONE(SUCCEED)
-
-    /* Compute element sizes and other parameters */
-    src_type_size = H5T_get_size(mem_type);
-    dst_type_size = H5T_get_size(dataset->shared->type);
-    max_type_size = MAX(src_type_size, dst_type_size);
-    target_size = dxpl_cache->max_temp_buf;
-    /* XXX: This could cause a problem if the user sets their buffer size
-     * to the same size as the default, and then the dataset elements are
-     * too large for the buffer... - QAK
-     */
-    if(target_size == H5D_TEMP_BUF_SIZE) {
-        /* If the buffer is too small to hold even one element, make it bigger */
-        if(target_size<max_type_size)
-            target_size = max_type_size;
-        /* If the buffer is too large to hold all the elements, make it smaller */
-        else if(target_size>(nelmts*max_type_size))
-            target_size=(size_t)(nelmts*max_type_size);
-    } /* end if */
-    request_nelmts = target_size / max_type_size;
-
-    /* Sanity check elements in temporary buffer */
-    if (request_nelmts==0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "temporary buffer max size is too small")
-
-    /* Figure out the strip mine size. */
-    if (H5S_select_iter_init(&file_iter, file_space, dst_type_size) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize file selection information")
-    file_iter_init=1;	/*file selection iteration info has been initialized */
-    if (H5S_select_iter_init(&mem_iter, mem_space, src_type_size) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize memory selection information")
-    mem_iter_init=1;	/*file selection iteration info has been initialized */
-    if (H5S_select_iter_init(&bkg_iter, file_space, dst_type_size) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize background selection information")
-    bkg_iter_init=1;	/*file selection iteration info has been initialized */
-
-    /*
-     * Get a temporary buffer for type conversion unless the app has already
-     * supplied one through the xfer properties.  Instead of allocating a
-     * buffer which is the exact size, we allocate the target size. The
-     * malloc() is usually less resource-intensive if we allocate/free the
-     * same size over and over.
-     */
-    if(H5T_detect_class(dataset->shared->type, H5T_VLEN)) {
-	/* Old data is retrieved into background buffer for VL datatype.  The
-	 * data is used later for freeing heap objects. */
-        need_bkg = H5T_BKG_YES;
-    } else if (H5T_path_bkg(tpath)) {
-        H5T_bkg_t path_bkg;     /* Type conversion's background info */
-
-        /* Retrieve the bkgr buffer property */
-        need_bkg=dxpl_cache->bkgr_buf_type;
-        path_bkg = H5T_path_bkg(tpath);
-        need_bkg = MAX (path_bkg, need_bkg);
-    } else {
-        need_bkg = H5T_BKG_NO; /*never needed even if app says yes*/
-    } /* end else */
-    if(NULL == (tconv_buf = (uint8_t *)dxpl_cache->tconv_buf)) {
-        /* Allocate temporary buffer */
-        if(NULL == (tconv_buf = H5FL_BLK_MALLOC(type_conv, target_size)))
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for type conversion")
-    } /* end if */
-    if(need_bkg && NULL == (bkg_buf = (uint8_t *)dxpl_cache->bkgr_buf)) {
-        /* Allocate background buffer */
-        /* (Don't need calloc()-like call since file data is already initialized) */
-        if(NULL == (bkg_buf = H5FL_BLK_MALLOC(type_conv, (request_nelmts * dst_type_size))))
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for background conversion")
-    } /* end if */
-
-    /* Start strip mining... */
-    for (smine_start=0; smine_start<nelmts; smine_start+=smine_nelmts) {
-        /* Go figure out how many elements to read from the file */
-        assert(H5S_SELECT_ITER_NELMTS(&file_iter)==(nelmts-smine_start));
-        smine_nelmts = (size_t)MIN(request_nelmts, (nelmts-smine_start));
-
-        /*
-         * Gather data from application buffer into the datatype conversion
-         * buffer. Also gather data from the file into the background buffer
-         * if necessary.
-         */
-#ifdef H5S_DEBUG
-	H5_timer_begin(&timer);
-#endif
-        n = H5D_select_mgath(buf, mem_space, &mem_iter,
-			     smine_nelmts, dxpl_cache, tconv_buf/*out*/);
-#ifdef H5S_DEBUG
-	H5_timer_end(&(io_info->stats->stats[0].gath_timer), &timer);
-	io_info->stats->stats[0].gath_nbytes += n * src_type_size;
-	io_info->stats->stats[0].gath_ncalls++;
-#endif
-        if (n!=smine_nelmts)
-            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "mem gather failed")
-
-        /* If the source and destination are compound types and the destination is
-         * is a subset of the source and no conversion is needed, copy the data 
-         * directly into user's buffer and bypass the rest of steps.  If the source
-         * is a subset of the destination, the optimization is done in conversion
-         * function H5T_conv_struct_opt to protect the background data.  This
-         * optimization is for Chicago company */
-        if(H5T_SUBSET_DST==H5T_path_compound_subset(tpath)) {
-            if(H5D_compound_opt_write(smine_nelmts, src_id, dst_id, tconv_buf)<0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "datatype conversion failed")
-        } else {
-            if (H5T_BKG_YES==need_bkg) {
-#ifdef H5S_DEBUG
-                H5_timer_begin(&timer);
-#endif
-                n = H5D_select_fgath(io_info, file_space, &bkg_iter, smine_nelmts,
-                                    (haddr_t)0, NULL, bkg_buf/*out*/);
-
-#ifdef H5S_DEBUG
-                H5_timer_end(&(io_info->stats->stats[0].bkg_timer), &timer);
-                io_info->stats->stats[0].bkg_nbytes += n * dst_type_size;
-                io_info->stats->stats[0].bkg_ncalls++;
-#endif
-                if (n!=smine_nelmts)
-                    HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file gather failed")
-            } /* end if */
-
-	    /*
-             * Perform datatype conversion.
-             */
-            if(H5T_convert(tpath, src_id, dst_id, smine_nelmts, (size_t)0, (size_t)0, tconv_buf, bkg_buf, io_info->dxpl_id) < 0)
-                 HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "datatype conversion failed")
-
-	    /* Do the data transform after the type conversion (since we're using dataset->shared->type). */
-	    if(!H5Z_xform_noop(dxpl_cache->data_xform_prop))
-	        if( H5Z_xform_eval(dxpl_cache->data_xform_prop, tconv_buf, smine_nelmts, dataset->shared->type) < 0)
-		    HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "Error performing data transform")
-        }
-
         /*
-         * Scatter the data out to the file.
+         * This is the general case (type conversion, usually).
          */
-#ifdef H5S_DEBUG
-        H5_timer_begin(&timer);
-#endif
-	status = H5D_select_fscat(io_info, file_space, &file_iter, smine_nelmts,
-                    (haddr_t)0, NULL, tconv_buf);
-#ifdef H5S_DEBUG
-        H5_timer_end(&(io_info->stats->stats[0].scat_timer), &timer);
-        io_info->stats->stats[0].scat_nbytes += smine_nelmts * dst_type_size;
-        io_info->stats->stats[0].scat_ncalls++;
-#endif
-        if (status<0)
-            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "scatter failed")
-    } /* end for */
-
-done:
-    /* Release selection iterators */
-    if(file_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&file_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-    if(mem_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&mem_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-    if(bkg_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&bkg_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-
-    if (tconv_buf && NULL==dxpl_cache->tconv_buf)
-        (void)H5FL_BLK_FREE(type_conv,tconv_buf);
-    if (bkg_buf && NULL==dxpl_cache->bkgr_buf)
-        (void)H5FL_BLK_FREE(type_conv,bkg_buf);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_contig_write() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_chunk_read
- *
- * Purpose:	Read from a chunked dataset.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Raymond Lu
- *		Thursday, April 10, 2003
- *
- * Modification: 
- *              Raymond Lu
- *              20 July 2007
- *              Moved H5D_istore_lock and H5D_istore_unlock to this level
- *              from H5D_istore_readvv to avoid frequent lock and unlock
- *              and to improve performance.
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5D_chunk_read(H5D_io_info_t *io_info, hsize_t nelmts,
-    const H5T_t *mem_type, const H5S_t *mem_space,
-    const H5S_t *file_space, H5T_path_t *tpath,
-    hid_t src_id, hid_t dst_id, void *buf/*out*/)
-{
-    H5D_t *dataset=io_info->dset;       /* Local pointer to dataset info */
-    const H5D_dxpl_cache_t *dxpl_cache=io_info->dxpl_cache;     /* Local pointer to dataset transfer info */
-    H5D_chunk_map_t      fm;            /* File<->memory mapping */
-    H5SL_node_t *chunk_node;            /* Current node in chunk skip list */
-    herr_t      status;                 /*function return status*/
-#ifdef H5S_DEBUG
-    H5_timer_t	timer;
-#endif
-    size_t	src_type_size;		/*size of source type	*/
-    size_t	dst_type_size;	        /*size of destination type*/
-    size_t	max_type_size;	        /* Size of largest source/destination type */
-    size_t	target_size;		/*desired buffer size	*/
-    size_t	request_nelmts;		/*requested strip mine	*/
-    hsize_t     smine_start;            /*strip mine start loc  */
-    size_t      n, smine_nelmts;        /*elements per strip    */
-    size_t      accessed_bytes = 0;     /*total accessed size in a chunk */
-    H5S_sel_iter_t mem_iter;            /*memory selection iteration info*/
-    hbool_t	mem_iter_init = FALSE;	/*memory selection iteration info has been initialized */
-    H5S_sel_iter_t bkg_iter;            /*background iteration info*/
-    hbool_t	bkg_iter_init = FALSE;	/*background iteration info has been initialized */
-    H5S_sel_iter_t file_iter;           /*file selection iteration info*/
-    hbool_t	file_iter_init = FALSE;	/*file selection iteration info has been initialized */
-    H5T_bkg_t	need_bkg;		/*type of background buf*/
-    uint8_t	*tconv_buf = NULL;	/*datatype conv buffer	*/
-    uint8_t	*bkg_buf = NULL;	/*background buffer	*/
-    H5D_storage_t store;                /*union of EFL and chunk pointer in file space */
-    void        *chunk = NULL;
-    haddr_t	chunk_addr;             /* Chunk address on disk */
-    H5D_istore_ud1_t udata;		/*B-tree pass-through	*/
-    unsigned    idx_hint=0;             /* Cache index hint      */
-    herr_t	ret_value = SUCCEED;	/*return value		*/
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_chunk_read)
-
-    assert (buf);
-
-    /* Map elements between file and memory for each chunk*/
-    if(H5D_create_chunk_map(&fm, io_info, nelmts, file_space, mem_space, mem_type) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't build chunk mapping")
-
-    /* Set dataset storage for I/O info */
-    io_info->store=&store;
-
-    /* Compute element sizes */
-    src_type_size = H5T_get_size(dataset->shared->type);
-    dst_type_size = H5T_get_size(mem_type);
-    max_type_size = MAX(src_type_size, dst_type_size);
-
-    /*
-     * If there is no type conversion then read directly into the
-     * application's buffer.  This saves at least one mem-to-mem copy.
-     */
-    if ( H5Z_xform_noop(dxpl_cache->data_xform_prop) && H5T_path_noop(tpath)) {
-#ifdef H5S_DEBUG
-	H5_timer_begin(&timer);
-#endif
-  	/* Sanity check dataset, then read it */
-        HDassert(((dataset->shared->layout.type == H5D_CONTIGUOUS && H5F_addr_defined(dataset->shared->layout.u.contig.addr))
-                || (dataset->shared->layout.type == H5D_CHUNKED && H5F_addr_defined(dataset->shared->layout.u.chunk.addr)))
-                || dataset->shared->dcpl_cache.efl.nused > 0 || 0 == nelmts
-                || dataset->shared->layout.type == H5D_COMPACT);
-
-#ifdef H5_HAVE_PARALLEL
-        /* Check whether the collective mode can be turned off globally*/
-#ifndef H5_MPI_SPECIAL_COLLECTIVE_IO_WORKS
-        if(io_info->dxpl_cache->xfer_mode == H5FD_MPIO_COLLECTIVE) {
-            if(H5D_mpio_chunk_adjust_iomode(io_info ,&fm))
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't adjust collective I/O")
-        }
-#endif /* H5_MPI_SPECIAL_COLLECTIVE_IO_WORKS */
-	/* Temporarily shut down collective IO for chunking */
-	if(io_info->dxpl_cache->xfer_mode == H5FD_MPIO_COLLECTIVE) {
-            if(H5D_chunk_collective_io(io_info, &fm, buf, FALSE) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "chunked read failed in collective mode")
-	}
-	else {/* sequential or independent read */
-#endif
-            /* Get first node in chunk skip list */
-            chunk_node = H5D_CHUNK_GET_FIRST_NODE(fm);
-
-            while(chunk_node) {
-                H5D_chunk_info_t *chunk_info;   /* chunk information */
-
-                /* Get the actual chunk information from the skip list node */
-                chunk_info = H5D_CHUNK_GET_NODE_INFO(fm, chunk_node);
-
-                /* Pass in chunk's coordinates in a union. */
-                store.chunk.offset = chunk_info->coords;
-                store.chunk.index = chunk_info->index;
-
-                /* Load the chunk into cache and lock it. */
-		chunk_addr = H5D_istore_get_addr(io_info, &udata);
-                if(H5D_istore_if_load(io_info, chunk_addr)) {
-		    if(NULL == (chunk = H5D_istore_lock(io_info, &udata, FALSE, &idx_hint)))
-			HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "unable to read raw data chunk")
-		} else
-		    chunk = NULL;
-
-                /* Perform the actual read operation */
-                if((io_info->ops.read)(io_info, chunk_info->chunk_points,
-                        src_type_size, chunk_info->fspace,
-                        chunk_info->mspace, chunk_addr, chunk, buf) < 0)
-                    HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, " chunked read failed")
-  
-                /* Release the cache lock on the chunk. */
-                if(chunk) {
-                    accessed_bytes = chunk_info->chunk_points * src_type_size;
-		    if(H5D_istore_unlock(io_info, FALSE, idx_hint, chunk, accessed_bytes) < 0)
-			HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "unable to unlock raw data chunk")
-		} /* end if */
-
-                /* Advance to next chunk in list */
-                chunk_node = H5D_CHUNK_GET_NEXT_NODE(fm, chunk_node);
-            } /* end while */
-#ifdef H5_HAVE_PARALLEL
-	}
-#endif
-
-
-#ifdef H5S_DEBUG
-        H5_timer_end(&(io_info->stats->stats[1].read_timer), &timer);
-        io_info->stats->stats[1].read_nbytes += nelmts * src_type_size;
-        io_info->stats->stats[1].read_ncalls++;
-#endif
-
-	/* direct xfer accomplished successfully */
-        HGOTO_DONE(SUCCEED)
-    } /* end if */
-
-    /*
-     * This is the general case (type conversion, usually).
-     */
-    if(nelmts==0)
-        HGOTO_DONE(SUCCEED)
-
-    /* Compute buffer  sizes and other parameters */
-    target_size = dxpl_cache->max_temp_buf;
-    /* XXX: This could cause a problem if the user sets their buffer size
-     * to the same size as the default, and then the dataset elements are
-     * too large for the buffer... - QAK
-     */
-    if(target_size == H5D_TEMP_BUF_SIZE) {
-        /* If the buffer is too small to hold even one element, make it bigger */
-        if(target_size<max_type_size)
-            target_size = max_type_size;
-        /* If the buffer is too large to hold all the elements, make it smaller */
-        else if(target_size>(nelmts*max_type_size))
-            target_size=(size_t)(nelmts*max_type_size);
-    } /* end if */
-    request_nelmts = target_size / max_type_size;
-
-    /* Sanity check elements in temporary buffer */
-    if (request_nelmts==0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "temporary buffer max size is too small")
-
-    /*
-     * Get a temporary buffer for type conversion unless the app has already
-     * supplied one through the xfer properties. Instead of allocating a
-     * buffer which is the exact size, we allocate the target size.  The
-     * malloc() is usually less resource-intensive if we allocate/free the
-     * same size over and over.
-     */
-    if (H5T_path_bkg(tpath)) {
-        H5T_bkg_t path_bkg;     /* Type conversion's background info */
-
-        /* Retrieve the bkgr buffer property */
-        need_bkg=dxpl_cache->bkgr_buf_type;
-        path_bkg = H5T_path_bkg(tpath);
-        need_bkg = MAX(path_bkg, need_bkg);
-    } else {
-        need_bkg = H5T_BKG_NO; /*never needed even if app says yes*/
+        io_info->io_ops.single_read = H5D_scatgath_read;
+        io_info->io_ops.single_write = H5D_scatgath_write;
     } /* end else */
-    if(NULL == (tconv_buf = (uint8_t *)dxpl_cache->tconv_buf)) {
-        /* Allocate temporary buffer */
-        if(NULL == (tconv_buf = H5FL_BLK_MALLOC(type_conv, target_size)))
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for type conversion")
-    } /* end if */
-    if(need_bkg && NULL == (bkg_buf = (uint8_t *)dxpl_cache->bkgr_buf)) {
-        /* Allocate background buffer */
-        /* (Need calloc()-like call since memory needs to be initialized) */
-        if(NULL == (bkg_buf = H5FL_BLK_CALLOC(type_conv, (request_nelmts * dst_type_size))))
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for background conversion")
-    } /* end if */
-
-    /* Loop over all the chunks, performing I/O on each */
-
-    /* Get first node in chunk skip list */
-    chunk_node = H5D_CHUNK_GET_FIRST_NODE(fm);
-
-    /* Iterate through chunks to be operated on */
-    while(chunk_node) {
-        H5D_chunk_info_t *chunk_info;   /* chunk information */
-
-        /* Get the actual chunk information from the skip list nodes */
-        chunk_info = H5D_CHUNK_GET_NODE_INFO(fm, chunk_node);
-
-        /* initialize selection iterator */
-        if (H5S_select_iter_init(&file_iter, chunk_info->fspace, src_type_size) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize file selection information")
-        file_iter_init = TRUE;	/*file selection iteration info has been initialized */
-        if (H5S_select_iter_init(&mem_iter, chunk_info->mspace, dst_type_size) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize memory selection information")
-        mem_iter_init = TRUE;	/*file selection iteration info has been initialized */
-        if (H5S_select_iter_init(&bkg_iter, chunk_info->mspace, dst_type_size) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize background selection information")
-        bkg_iter_init = TRUE;	/*file selection iteration info has been initialized */
-
-        /* Pass in chunk's coordinates in a union*/
-        store.chunk.offset = chunk_info->coords;
-        store.chunk.index = chunk_info->index;
-
-        /* Load the chunk into cache and lock it. */
-        chunk_addr = H5D_istore_get_addr(io_info, &udata);
-
-        if(H5D_istore_if_load(io_info, chunk_addr)) {
-            if(NULL == (chunk = H5D_istore_lock(io_info, &udata, FALSE, &idx_hint)))
-                HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "unable to read raw data chunk")
-        } else
-            chunk = NULL;
-
-        for(smine_start=0; smine_start<chunk_info->chunk_points; smine_start+=smine_nelmts) {
-            /* Go figure out how many elements to read from the file */
-            assert(H5S_SELECT_ITER_NELMTS(&file_iter)==(chunk_info->chunk_points-smine_start));
-            smine_nelmts = (size_t)MIN(request_nelmts, (chunk_info->chunk_points-smine_start));
-
-            /*
-             * Gather the data from disk into the datatype conversion
-             * buffer. Also gather data from application to background buffer
-             * if necessary.
-             */
-#ifdef H5S_DEBUG
-            H5_timer_begin(&timer);
-#endif
-            /* Sanity check that space is allocated, then read data from it */
-            HDassert(((dataset->shared->layout.type == H5D_CONTIGUOUS && H5F_addr_defined(dataset->shared->layout.u.contig.addr))
-                    || (dataset->shared->layout.type == H5D_CHUNKED && H5F_addr_defined(dataset->shared->layout.u.chunk.addr)))
-                || dataset->shared->dcpl_cache.efl.nused > 0 || dataset->shared->layout.type == H5D_COMPACT);
-
-            if(chunk) {
-                n = H5D_select_mgath(chunk, chunk_info->fspace, &file_iter, 
-                                 smine_nelmts, dxpl_cache, tconv_buf/*out*/);
-            } else {
-                n = H5D_select_fgath(io_info, chunk_info->fspace, &file_iter, smine_nelmts, 
-                                 chunk_addr, NULL, tconv_buf/*out*/);
-            }
-
-#ifdef H5S_DEBUG
-            H5_timer_end(&(io_info->stats->stats[1].gath_timer), &timer);
-            io_info->stats->stats[1].gath_nbytes += n * src_type_size;
-            io_info->stats->stats[1].gath_ncalls++;
-#endif
-            if(n != smine_nelmts)
-                HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "file gather failed")
-
-            /* If the source and destination are compound types and subset of each other
-             * and no conversion is needed, copy the data directly into user's buffer and 
-             * bypass the rest of steps.  This optimization is for Chicago company */
-            if(H5T_SUBSET_SRC==H5T_path_compound_subset(tpath)) {
-                if(H5D_compound_opt_read(smine_nelmts, chunk_info->mspace, &mem_iter, dxpl_cache,
-                    src_id, dst_id, H5T_SUBSET_SRC, tconv_buf, buf /*out*/)<0)
-                    HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "datatype conversion failed")
-
-                continue;
-            } else if(H5T_SUBSET_DST==H5T_path_compound_subset(tpath)) {
-                if(H5D_compound_opt_read(smine_nelmts, chunk_info->mspace, &mem_iter, dxpl_cache,
-                    src_id, dst_id, H5T_SUBSET_DST, tconv_buf, buf /*out*/)<0)
-                    HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "datatype conversion failed")
-
-                continue;
-            }
-
-            if(H5T_BKG_YES == need_bkg) {
-#ifdef H5S_DEBUG
-                H5_timer_begin(&timer);
-#endif
-                n = H5D_select_mgath(buf, chunk_info->mspace, &bkg_iter, smine_nelmts, dxpl_cache, bkg_buf/*out*/);
-#ifdef H5S_DEBUG
-                H5_timer_end(&(io_info->stats->stats[1].bkg_timer), &timer);
-                io_info->stats->stats[1].bkg_nbytes += n * dst_type_size;
-                io_info->stats->stats[1].bkg_ncalls++;
-#endif
-                if(n != smine_nelmts)
-                    HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "mem gather failed")
-            } /* end if */
-
-            /*
-             * Perform datatype conversion.
-             */
-            if(H5T_convert(tpath, src_id, dst_id, smine_nelmts, (size_t)0, (size_t)0, tconv_buf, bkg_buf, io_info->dxpl_id) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "datatype conversion failed")
-
-           /* Do the data transform after the conversion (since we're using type mem_type) */
-            if(!H5Z_xform_noop(dxpl_cache->data_xform_prop))
-	        if(H5Z_xform_eval(dxpl_cache->data_xform_prop, tconv_buf, smine_nelmts, mem_type) < 0)
-                    HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "Error performing data transform")
-
-            /*
-             * Scatter the data into memory.
-             */
-#ifdef H5S_DEBUG
-            H5_timer_begin(&timer);
-#endif
-            status = H5D_select_mscat(tconv_buf, chunk_info->mspace, &mem_iter, smine_nelmts, dxpl_cache, buf/*out*/);
-#ifdef H5S_DEBUG
-            H5_timer_end(&(io_info->stats->stats[1].scat_timer), &timer);
-            io_info->stats->stats[1].scat_nbytes += smine_nelmts * dst_type_size;
-            io_info->stats->stats[1].scat_ncalls++;
-#endif
-            if(status < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "scatter failed")
-        } /* end for */
-
-        /* Release the cache lock on the chunk. */
-        if(chunk) {
-            accessed_bytes = chunk_info->chunk_points * src_type_size;
-            if(H5D_istore_unlock(io_info, FALSE, idx_hint, chunk, accessed_bytes) < 0)
-                HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "unable to unlock raw data chunk")
-        } /* end if */
-
-        /* Release selection iterators */
-        if(file_iter_init) {
-            if(H5S_SELECT_ITER_RELEASE(&file_iter) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-            file_iter_init = FALSE;
-        } /* end if */
-        if(mem_iter_init) {
-            if(H5S_SELECT_ITER_RELEASE(&mem_iter) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-            mem_iter_init = FALSE;
-        } /* end if */
-        if(bkg_iter_init) {
-            if(H5S_SELECT_ITER_RELEASE(&bkg_iter) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-            bkg_iter_init = FALSE;
-        } /* end if */
-
-        /* Get the next chunk node in the skip list */
-        chunk_node = H5D_CHUNK_GET_NEXT_NODE(fm, chunk_node);
-    } /* end while */
-
-done:
-    /* Release selection iterators, if necessary */
-    if(file_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&file_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-    if(mem_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&mem_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-    if(bkg_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&bkg_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-
-    if(tconv_buf && NULL == dxpl_cache->tconv_buf)
-        (void)H5FL_BLK_FREE(type_conv, tconv_buf);
-    if(bkg_buf && NULL == dxpl_cache->bkgr_buf)
-        (void)H5FL_BLK_FREE(type_conv, bkg_buf);
-
-    /* Release chunk mapping information */
-    if(H5D_destroy_chunk_map(&fm) < 0)
-        HDONE_ERROR(H5E_DATASET, H5E_CANTRELEASE, FAIL, "can't release chunk mapping")
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* H5D_chunk_read() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_chunk_write
- *
- * Purpose:	Writes to a chunked dataset.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Raymond Lu
- *		Thursday, April 10, 2003
- *
- * Modification: 
- *              Raymond Lu
- *              20 July 2007
- *              Moved H5D_istore_lock and H5D_istore_unlock to this level
- *              from H5D_istore_writevv to avoid frequent lock and unlock
- *              and to improve performance.
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5D_chunk_write(H5D_io_info_t *io_info, hsize_t nelmts,
-    const H5T_t *mem_type, const H5S_t *mem_space,
-    const H5S_t *file_space, H5T_path_t *tpath,
-    hid_t src_id, hid_t dst_id, const void *buf)
-{
-    H5D_t *dataset=io_info->dset;       /* Local pointer to dataset info */
-    const H5D_dxpl_cache_t *dxpl_cache=io_info->dxpl_cache;     /* Local pointer to dataset transfer info */
-    H5D_chunk_map_t      fm;            /* File<->memory mapping */
-    H5SL_node_t *chunk_node;            /* Current node in chunk skip list */
-    herr_t      status;                 /*function return status*/
-#ifdef H5S_DEBUG
-    H5_timer_t	timer;
-#endif
-    size_t	src_type_size;		/*size of source type	*/
-    size_t	dst_type_size;	        /*size of destination type*/
-    size_t	max_type_size;	        /* Size of largest source/destination type */
-    size_t	target_size;		/*desired buffer size	*/
-    size_t	request_nelmts;		/*requested strip mine	*/
-    size_t      accessed_bytes;         /*total accessed size in a chunk */
-    hsize_t     smine_start;            /*strip mine start loc  */
-    size_t      n, smine_nelmts;        /*elements per strip    */
-    H5S_sel_iter_t mem_iter;            /*memory selection iteration info*/
-    hbool_t	mem_iter_init=0;	/*memory selection iteration info has been initialized */
-    H5S_sel_iter_t bkg_iter;            /*background iteration info*/
-    hbool_t	bkg_iter_init=0;	/*background iteration info has been initialized */
-    H5S_sel_iter_t file_iter;           /*file selection iteration info*/
-    hbool_t	file_iter_init=0;	/*file selection iteration info has been initialized */
-    H5T_bkg_t	need_bkg;		/*type of background buf*/
-    uint8_t	*tconv_buf = NULL;	/*datatype conv buffer	*/
-    uint8_t	*bkg_buf = NULL;	/*background buffer	*/
-    H5D_storage_t store;                /*union of EFL and chunk pointer in file space */
-    void     *chunk = NULL;
-    haddr_t	chunk_addr;             /* Chunk address on disk */
-    H5D_istore_ud1_t udata;		/*B-tree pass-through	*/
-    unsigned    idx_hint=0;             /* Cache index hint      */
-    hbool_t     relax=TRUE;             /* Whether whole chunk is selected */
-    herr_t	ret_value = SUCCEED;	/*return value		*/
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_chunk_write)
-
-    assert (buf);
-
-    /* Map elements between file and memory for each chunk*/
-    if(H5D_create_chunk_map(&fm, io_info, nelmts, file_space, mem_space, mem_type) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "can't build chunk mapping")
-
-    /* Set dataset storage for I/O info */
-    io_info->store=&store;
-
-#ifdef H5_HAVE_PARALLEL
-    /* Additional sanity checks when operating in parallel */
-    if(io_info->using_mpi_vfd) {
-        if (chunk_addr==HADDR_UNDEF)
-            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "unable to locate raw data chunk")
-        if (dataset->shared->dcpl_cache.pline.nused>0)
-            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "cannot write to chunked storage with filters in parallel")
-    } /* end if */
-#endif /* H5_HAVE_PARALLEL */
-
-    /* Compute element sizes and other parameters */
-    src_type_size = H5T_get_size(mem_type);
-    dst_type_size = H5T_get_size(dataset->shared->type);
-    max_type_size = MAX(src_type_size, dst_type_size);
-
-    /*
-     * If there is no type conversion then write directly from the
-     * application's buffer.  This saves at least one mem-to-mem copy.
-     */
-    if ( H5Z_xform_noop(dxpl_cache->data_xform_prop) && H5T_path_noop(tpath)) {
-#ifdef H5S_DEBUG
-	H5_timer_begin(&timer);
-#endif
 
 #ifdef H5_HAVE_PARALLEL
-        /* Check whether the collective mode can be turned off globally*/
-#ifndef H5_MPI_SPECIAL_COLLECTIVE_IO_WORKS
-        if(io_info->dxpl_cache->xfer_mode == H5FD_MPIO_COLLECTIVE) {
-            if(H5D_mpio_chunk_adjust_iomode(io_info,&fm))
-                HGOTO_ERROR(H5E_DATASET,H5E_CANTGET,FAIL,"can't adjust collective I/O")
-        }
-#endif /* H5_MPI_SPECIAL_COLLECTIVE_IO_WORKS */
-	/* Temporarily shut down collective IO for chunking */
-        if(io_info->dxpl_cache->xfer_mode == H5FD_MPIO_COLLECTIVE) {
-            if(H5D_chunk_collective_io(io_info,&fm,buf,TRUE) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "chunked write failed in collective mode");
-	}
-	else {/* sequential or independent write */
+    /* Determine if the file was opened with an MPI VFD */
+    io_info->using_mpi_vfd = IS_H5FD_MPI(dset->oloc.file);
 #endif /* H5_HAVE_PARALLEL */
-            /* Get first node in chunk skip list */
-            chunk_node = H5D_CHUNK_GET_FIRST_NODE(fm);
-
-            while(chunk_node) {
-                H5D_chunk_info_t *chunk_info;       /* Chunk information */
-
-                /* Get the actual chunk information from the skip list node */
-                chunk_info = H5D_CHUNK_GET_NODE_INFO(fm, chunk_node);
-
-                /* Pass in chunk's coordinates in a union. */
-                store.chunk.offset = chunk_info->coords;
-                store.chunk.index = chunk_info->index;
-
-                /* Load the chunk into cache.  But if the whole chunk is written,
-                 * simply allocate space instead of load the chunk. */
-                chunk_addr = H5D_istore_get_addr(io_info, &udata);
-
-                if(H5D_istore_if_load(io_info, chunk_addr)) {
-                    accessed_bytes = chunk_info->chunk_points * dst_type_size;
-                    if(accessed_bytes != dataset->shared->layout.u.chunk.size)
-                        relax = FALSE;
-
-		    if(NULL == (chunk = H5D_istore_lock(io_info, &udata, relax, &idx_hint)))
-			HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "unable to read raw data chunk")
-		} else
-		    chunk = NULL;
-
-                /* Perform the actual read operation */
-                if((io_info->ops.write)(io_info, chunk_info->chunk_points,
-                        dst_type_size, chunk_info->fspace,
-                        chunk_info->mspace, chunk_addr, chunk, buf) < 0)
-                    HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, " chunked write failed")
-
-                /* Release the cache lock on the chunk. */
-                if(chunk) {
-		    if(H5D_istore_unlock(io_info, TRUE, idx_hint, chunk, accessed_bytes) < 0)
-			HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "unable to unlock raw data chunk")
-		} /* end if */
-                relax = TRUE;
-
-                /* Advance to next chunk in list */
-                chunk_node = H5D_CHUNK_GET_NEXT_NODE(fm, chunk_node);
-            } /* end while */
-#ifdef H5_HAVE_PARALLEL
-	}
-#endif
-
-#ifdef H5S_DEBUG
-	H5_timer_end(&(io_info->stats->stats[0].write_timer), &timer);
-	io_info->stats->stats[0].write_nbytes += nelmts * src_type_size;
-	io_info->stats->stats[0].write_ncalls++;
-#endif
-
-	/* direct xfer accomplished successfully */
-	HGOTO_DONE(SUCCEED)
-    } /* end if */
-
-    /*
-     * This is the general case (type conversion, usually).
-     */
-    if(nelmts==0)
-        HGOTO_DONE(SUCCEED)
-
-    /* Compute buffer sizes and other parameters */
-    target_size = dxpl_cache->max_temp_buf;
-    /* XXX: This could cause a problem if the user sets their buffer size
-     * to the same size as the default, and then the dataset elements are
-     * too large for the buffer... - QAK
-     */
-    if(target_size == H5D_TEMP_BUF_SIZE) {
-        /* If the buffer is too small to hold even one element, make it bigger */
-        if(target_size<max_type_size)
-            target_size = max_type_size;
-        /* If the buffer is too large to hold all the elements, make it smaller */
-        else if(target_size>(nelmts*max_type_size))
-            target_size=(size_t)(nelmts*max_type_size);
-    } /* end if */
-    request_nelmts = target_size / max_type_size;
-
-    /* Sanity check elements in temporary buffer */
-    if (request_nelmts==0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "temporary buffer max size is too small")
 
-    /*
-     * Get a temporary buffer for type conversion unless the app has already
-     * supplied one through the xfer properties.  Instead of allocating a
-     * buffer which is the exact size, we allocate the target size. The
-     * malloc() is usually less resource-intensive if we allocate/free the
-     * same size over and over.
-     */
-    if(H5T_detect_class(dataset->shared->type, H5T_VLEN)) {
-	/* Old data is retrieved into background buffer for VL datatype.  The
-	 * data is used later for freeing heap objects. */
-        need_bkg = H5T_BKG_YES;
-    } else if (H5T_path_bkg(tpath)) {
-        H5T_bkg_t path_bkg;     /* Type conversion's background info */
-
-        /* Retrieve the bkgr buffer property */
-        need_bkg=dxpl_cache->bkgr_buf_type;
-        path_bkg = H5T_path_bkg(tpath);
-        need_bkg = MAX (path_bkg, need_bkg);
-    } else {
-        need_bkg = H5T_BKG_NO; /*never needed even if app says yes*/
-    } /* end else */
-    if(NULL == (tconv_buf = (uint8_t *)dxpl_cache->tconv_buf)) {
-        /* Allocate temporary buffer */
-        if(NULL == (tconv_buf = H5FL_BLK_MALLOC(type_conv, target_size)))
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for type conversion")
-    } /* end if */
-    if(need_bkg && NULL == (bkg_buf = (uint8_t *)dxpl_cache->bkgr_buf)) {
-        /* Allocate background buffer */
-        /* (Don't need calloc()-like call since file data is already initialized) */
-        if(NULL == (bkg_buf = H5FL_BLK_MALLOC(type_conv, (request_nelmts * dst_type_size))))
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for background conversion")
-    } /* end if */
-
-    /* Loop over all the chunks, performing I/O on each */
-
-    /* Get first node in chunk skip list */
-    chunk_node = H5D_CHUNK_GET_FIRST_NODE(fm);
-
-    /* Iterate through chunks to be operated on */
-    while(chunk_node) {
-        H5D_chunk_info_t *chunk_info;   /* chunk information */
-
-        /* Get the actual chunk information from the skip list node */
-        chunk_info = H5D_CHUNK_GET_NODE_INFO(fm, chunk_node);
-
-        /* initialize selection iterator */
-        if (H5S_select_iter_init(&file_iter, chunk_info->fspace, dst_type_size) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize file selection information")
-        file_iter_init=1;	/*file selection iteration info has been initialized */
-        if (H5S_select_iter_init(&mem_iter, chunk_info->mspace, src_type_size) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize memory selection information")
-        mem_iter_init=1;	/*file selection iteration info has been initialized */
-        if (H5S_select_iter_init(&bkg_iter, chunk_info->fspace, dst_type_size) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize background selection information")
-        bkg_iter_init=1;	/*file selection iteration info has been initialized */
-
-        /*pass in chunk's coordinates in a union*/
-        store.chunk.offset = chunk_info->coords;
-        store.chunk.index = chunk_info->index;
-
-        /* Load the chunk into cache.  But if the whole chunk is written,
-         * simply allocate space instead of load the chunk. */
-        chunk_addr = H5D_istore_get_addr(io_info, &udata);
-
-        if(H5D_istore_if_load(io_info, chunk_addr)) {
-            accessed_bytes = chunk_info->chunk_points * dst_type_size;
-            if(accessed_bytes != dataset->shared->layout.u.chunk.size)
-                relax=FALSE;
-            if(relax) {
-                accessed_bytes = H5S_GET_SELECT_NPOINTS(chunk_info->mspace) * src_type_size;
-                if(accessed_bytes != dataset->shared->layout.u.chunk.size)
-                    relax = FALSE;
-            }
-
-	    if(NULL == (chunk = H5D_istore_lock(io_info, &udata, relax, &idx_hint)))
-		HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "unable to read raw data chunk")
-	} else
-	    chunk = NULL;
-
-        for(smine_start=0; smine_start<chunk_info->chunk_points; smine_start+=smine_nelmts) {
-            /* Go figure out how many elements to read from the file */
-            assert(H5S_SELECT_ITER_NELMTS(&file_iter)==(chunk_info->chunk_points-smine_start));
-            smine_nelmts = (size_t)MIN(request_nelmts, (chunk_info->chunk_points-smine_start));
-
-            /*
-             * Gather the data from disk into the datatype conversion
-             * buffer. Also gather data from application to background buffer
-             * if necessary.
-             */
-#ifdef H5S_DEBUG
-            H5_timer_begin(&timer);
-#endif
-            n = H5D_select_mgath(buf, chunk_info->mspace, &mem_iter,
-                                 smine_nelmts, dxpl_cache, tconv_buf/*out*/);
-
-#ifdef H5S_DEBUG
-            H5_timer_end(&(io_info->stats->stats[1].gath_timer), &timer);
-            io_info->stats->stats[1].gath_nbytes += n * src_type_size;
-            io_info->stats->stats[1].gath_ncalls++;
-#endif
-            if (n!=smine_nelmts)
-                HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "file gather failed")
-
-            /* If the source and destination are compound types and the destination is
-             * is a subset of the source and no conversion is needed, copy the data 
-             * directly into user's buffer and bypass the rest of steps.  If the source
-             * is a subset of the destination, the optimization is done in conversion
-             * function H5T_conv_struct_opt to protect the background data.  This
-             * optimization is for Chicago company */
-            if(H5T_SUBSET_DST==H5T_path_compound_subset(tpath)) {
-                if(H5D_compound_opt_write(smine_nelmts, src_id, dst_id, tconv_buf)<0)
-                    HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "datatype conversion failed")
-            } else {
-                if (H5T_BKG_YES==need_bkg) {
-#ifdef H5S_DEBUG
-                    H5_timer_begin(&timer);
-#endif
-                    if(chunk) {
-                        n = H5D_select_mgath(chunk, chunk_info->fspace, &bkg_iter, 
-                                 smine_nelmts, dxpl_cache, bkg_buf/*out*/);
-                    } else {
-                        n = H5D_select_fgath(io_info, chunk_info->fspace, &bkg_iter, smine_nelmts, 
-                                 chunk_addr, NULL, bkg_buf/*out*/);
-                    }
-
-#ifdef H5S_DEBUG
-                    H5_timer_end(&(io_info->stats->stats[0].bkg_timer), &timer);
-                    io_info->stats->stats[0].bkg_nbytes += n * dst_type_size;
-                    io_info->stats->stats[0].bkg_ncalls++;
-#endif
-                    if (n!=smine_nelmts)
-                        HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file gather failed")
-                } /* end if */
-
-	        /*
-                 * Perform datatype conversion.
-                 */
-                if(H5T_convert(tpath, src_id, dst_id, smine_nelmts, (size_t)0, (size_t)0, tconv_buf, bkg_buf, io_info->dxpl_id) < 0)
-                    HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "datatype conversion failed")
-
- 	        /* Do the data transform after the type conversion (since we're using dataset->shared->type) */
-                if(!H5Z_xform_noop(dxpl_cache->data_xform_prop))
-	            if( H5Z_xform_eval(dxpl_cache->data_xform_prop, tconv_buf, smine_nelmts, dataset->shared->type) < 0)
-		        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "Error performing data transform")
-            }
-
-            /*
-             * Scatter the data out to the file.
-             */
-#ifdef H5S_DEBUG
-            H5_timer_begin(&timer);
-#endif
-            status = H5D_select_fscat(io_info,
-                chunk_info->fspace, &file_iter, smine_nelmts,
-                chunk_addr, chunk, tconv_buf);
-
-#ifdef H5S_DEBUG
-            H5_timer_end(&(io_info->stats->stats[0].scat_timer), &timer);
-            io_info->stats->stats[0].scat_nbytes += n * dst_type_size;
-            io_info->stats->stats[0].scat_ncalls++;
-#endif
-            if (status<0)
-                HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "scatter failed")
-        } /* end for */
-
-        /* Release the cache lock on the chunk. */
-        if(chunk) {
-            accessed_bytes = chunk_info->chunk_points * dst_type_size;
-	    if(H5D_istore_unlock(io_info, TRUE, idx_hint, chunk, accessed_bytes) < 0)
-		HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "unable to unlock raw data chunk")
-	} /* end if */
-        relax = TRUE;
-
-        /* Release selection iterators */
-        if(file_iter_init) {
-            if(H5S_SELECT_ITER_RELEASE(&file_iter) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-            file_iter_init=0;
-        } /* end if */
-        if(mem_iter_init) {
-            if(H5S_SELECT_ITER_RELEASE(&mem_iter) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-            mem_iter_init=0;
-        } /* end if */
-        if(bkg_iter_init) {
-            if(H5S_SELECT_ITER_RELEASE(&bkg_iter) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-            bkg_iter_init=0;
-        } /* end if */
-
-        /* Get the next chunk node in the skip list */
-        chunk_node = H5D_CHUNK_GET_NEXT_NODE(fm, chunk_node);
-    } /* end while */
-
-done:
-    /* Release selection iterators, if necessary */
-    if(file_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&file_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-    if(mem_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&mem_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-    if(bkg_iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&bkg_iter) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't release selection iterator")
-    } /* end if */
-
-    if (tconv_buf && NULL==dxpl_cache->tconv_buf)
-        (void)H5FL_BLK_FREE(type_conv,tconv_buf);
-    if (bkg_buf && NULL==dxpl_cache->bkgr_buf)
-        (void)H5FL_BLK_FREE(type_conv,bkg_buf);
-
-    /* Release chunk mapping information */
-    if(H5D_destroy_chunk_map(&fm) < 0)
-        HDONE_ERROR(H5E_DATASET, H5E_CANTRELEASE, FAIL, "can't release chunk mapping")
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* H5D_chunk_write() */
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5D_ioinfo_init() */
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5D_compound_opt_read
+ * Function:	H5D_typeinfo_init
  *
- * Purpose:	A shortcut optimization for the Chicago company for 
- *              a special optimization case when the source and 
- *              destination members are a subset of each other, and 
- *              the order is the same, and no conversion is needed.  
- *              For example:
- *                  struct source {            struct destination {
- *                      TYPE1 A;      -->          TYPE1 A;
- *                      TYPE2 B;      -->          TYPE2 B;
- *                      TYPE3 C;      -->          TYPE3 C;
- *                  };                             TYPE4 D;
- *                                                 TYPE5 E;
- *                                             };
- *              or
- *                  struct destination {       struct source {
- *                      TYPE1 A;      <--          TYPE1 A;
- *                      TYPE2 B;      <--          TYPE2 B;
- *                      TYPE3 C;      <--          TYPE3 C;
- *                  };                             TYPE4 D;
- *                                                 TYPE5 E;
- *                                             };
- *              The optimization is simply moving data to the appropriate 
- *              places in the buffer.
+ * Purpose:	Routine for determining correct datatype information for
+ *              each I/O action.
  *
  * Return:	Non-negative on success/Negative on failure
  *
- * Programmer:	Raymond Lu
- *		11 June 2007
+ * Programmer:	Quincey Koziol
+ *		Tuesday, March  4, 2008
  *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5D_compound_opt_read(size_t nelmts, const H5S_t *space,
-    H5S_sel_iter_t *iter, const H5D_dxpl_cache_t *dxpl_cache,
-    hid_t src_id, hid_t dst_id, H5T_subset_t subset, 
-    void *data_buf, void *user_buf/*out*/)
+H5D_typeinfo_init(const H5D_t *dset, const H5D_dxpl_cache_t *dxpl_cache,
+    hid_t dxpl_id, hid_t mem_type_id, hbool_t do_write,
+    H5D_type_info_t *type_info)
 {
-    uint8_t    *dbuf = (uint8_t *)data_buf;    /*cast for pointer arithmetic	*/
-    uint8_t    *ubuf = (uint8_t *)user_buf;    /*cast for pointer arithmetic	*/
-    uint8_t    *xdbuf;
-    uint8_t    *xubuf;
-
-    hsize_t    _off[H5D_IO_VECTOR_SIZE];       /* Array to store sequence offsets */
-    hsize_t    *off=NULL;                      /* Pointer to sequence offsets */
-    size_t     _len[H5D_IO_VECTOR_SIZE];       /* Array to store sequence lengths */
-    size_t     *len=NULL;                      /* Pointer to sequence lengths */
-    size_t     nseq;                           /* Number of sequences generated */
-    size_t     curr_off;                       /* offset of bytes left to process in sequence */
-    size_t     curr_seq;                       /* Current sequence being processed */
-    size_t     curr_len;                       /* Length of bytes left to process in sequence */
-    size_t     curr_nelmts;		       /* number of elements to process in sequence   */
-    size_t     i;
-
-    H5T_t      *src, *dst;
-    size_t     src_stride, dst_stride, type_size = 0;
-    size_t     elmtno;			/*element counter		*/
-
-    herr_t     ret_value = SUCCEED;	       /*return value		*/
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_compound_opt_read)
-
-    /* Check args */
-    assert (data_buf);
-    assert (user_buf);
-    assert (space);
-    assert (iter);
-    assert (nelmts>0);
-
-    /* Allocate the vector I/O arrays */
-    if(dxpl_cache->vec_size != H5D_IO_VECTOR_SIZE) {
-        if((len = H5FL_SEQ_MALLOC(size_t,dxpl_cache->vec_size))==NULL)
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O length vector array");
-        if((off = H5FL_SEQ_MALLOC(hsize_t,dxpl_cache->vec_size))==NULL)
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O offset vector array");
-    } /* end if */
-    else {
-        len=_len;
-        off=_off;
-    } /* end else */
-
-    if (NULL == (src = (H5T_t *)H5I_object(src_id)) || NULL == (dst = (H5T_t *)H5I_object(dst_id)))
-        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a data type");
-
-    src_stride = H5T_get_size(src);
-    dst_stride = H5T_get_size(dst);
-
-    if(H5T_SUBSET_SRC == subset)
-        type_size = src_stride;
-    else if(H5T_SUBSET_DST == subset)
-        type_size = dst_stride;
-
-    xdbuf = dbuf;
-
-    /* Loop until all elements are written */
-    while(nelmts>0) {
-        /* Get list of sequences for selection to write */
-        if(H5S_SELECT_GET_SEQ_LIST(space,0,iter,dxpl_cache->vec_size,nelmts,&nseq,&elmtno,off,len)<0)
-            HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, 0, "sequence length generation failed");
-
-        /* Loop, while sequences left to process */
-        for(curr_seq=0; curr_seq<nseq; curr_seq++) {
-            /* Get the number of bytes and offset in sequence */
-            curr_len=len[curr_seq];
-            curr_off=off[curr_seq];
-
-            /* Decide the number of elements and position in the buffer. */
-            curr_nelmts = curr_len/dst_stride;
-            xubuf = ubuf + curr_off;
+    const H5T_t	*src_type;              /* Source datatype */
+    const H5T_t	*dst_type;              /* Destination datatype */
+    herr_t	ret_value = SUCCEED;	/* Return value	*/
 
-            /* Copy the data into the right place. */
-            for(i=0; i<curr_nelmts; i++) {
-                HDmemmove(xubuf, xdbuf, type_size); 
+    FUNC_ENTER_NOAPI_NOINIT(H5D_typeinfo_init)
 
-                /* Update pointers */
-                xdbuf += src_stride;
-                xubuf += dst_stride;
-            }
+    /* check args */
+    HDassert(type_info);
+    HDassert(dset);
 
-        } /* end for */
+    /* Initialize type info safely */
+    HDmemset(type_info, 0, sizeof(H5D_type_info_t));
 
-        /* Decrement number of elements left to process */
-        nelmts -= elmtno;
-    } /* end while */
+    /* Get the memory & dataset datatypes */
+    if(NULL == (type_info->mem_type = (const H5T_t *)H5I_object_verify(mem_type_id, H5I_DATATYPE)))
+	HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a datatype")
+    type_info->dset_type = dset->shared->type;
 
-done:
-    if(dxpl_cache->vec_size != H5D_IO_VECTOR_SIZE) {
-        if(len!=NULL)
-            H5FL_SEQ_FREE(size_t,len);
-        if(off!=NULL)
-            H5FL_SEQ_FREE(hsize_t,off);
+    if(do_write) {
+        src_type = type_info->mem_type;
+        dst_type = dset->shared->type;
+        type_info->src_type_id = mem_type_id;
+        type_info->dst_type_id = dset->shared->type_id;
     } /* end if */
+    else {
+        src_type = dset->shared->type;
+        dst_type = type_info->mem_type;
+        type_info->src_type_id = dset->shared->type_id;
+        type_info->dst_type_id = mem_type_id;
+    } /* end else */
 
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_compound_opt_read() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_compound_opt_write
- *
- * Purpose:	A shortcut optimization for the Chicago company for 
- *              a special optimization case when the source and 
- *              destination members are a subset of each other, and 
- *              the order is the same, and no conversion is needed.  
- *              For example:
- *                  struct source {            struct destination {
- *                      TYPE1 A;      -->          TYPE1 A;
- *                      TYPE2 B;      -->          TYPE2 B;
- *                      TYPE3 C;      -->          TYPE3 C;
- *                  };                             TYPE4 D;
- *                                                 TYPE5 E;
- *                                             };
- *              or
- *                  struct destination {       struct source {
- *                      TYPE1 A;      <--          TYPE1 A;
- *                      TYPE2 B;      <--          TYPE2 B;
- *                      TYPE3 C;      <--          TYPE3 C;
- *                  };                             TYPE4 D;
- *                                                 TYPE5 E;
- *                                             };
- *              The optimization is simply moving data to the appropriate 
- *              places in the buffer.
- *
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Raymond Lu
- *		11 June 2007
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5D_compound_opt_write(size_t nelmts, hid_t src_id, hid_t dst_id, void *data_buf)
-{
-    uint8_t    *dbuf = (uint8_t *)data_buf;    /*cast for pointer arithmetic	*/
-    uint8_t    *xsbuf, *xdbuf;
-    size_t     i;
-    H5T_t      *src, *dst;
-    size_t     src_stride, dst_stride;
-    herr_t     ret_value = SUCCEED;	       /*return value		*/
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_compound_opt_write)
-
-    /* Check args */
-    assert (data_buf);
-    assert (nelmts>0);
-
-    if (NULL == (src = (H5T_t *)H5I_object(src_id)) || NULL == (dst = (H5T_t *)H5I_object(dst_id)))
-        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a data type");
-
-    src_stride = H5T_get_size(src);
-    dst_stride = H5T_get_size(dst);
-
-    xsbuf = dbuf;
-    xdbuf = dbuf;
-
-    /* Loop until all elements are written */
-    for(i=0; i<nelmts; i++) {
-        HDmemmove(xdbuf, xsbuf, dst_stride); 
-
-        /* Update pointers */
-        xsbuf += src_stride;
-        xdbuf += dst_stride;
-    }
-
-done:
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_compound_opt_write() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_create_chunk_map
- *
- * Purpose:	Creates the mapping between elements selected in each chunk
- *              and the elements in the memory selection.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Raymond Lu
- *		Thursday, April 10, 2003
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5D_create_chunk_map(H5D_chunk_map_t *fm, const H5D_io_info_t *io_info,
-    hsize_t nelmts, const H5S_t *file_space, const H5S_t *mem_space,
-    const H5T_t *mem_type)
-{
-    H5D_t *dataset=io_info->dset;       /* Local pointer to dataset info */
-    H5S_t *tmp_mspace = NULL;     /* Temporary memory dataspace */
-    hssize_t old_offset[H5O_LAYOUT_NDIMS];  /* Old selection offset */
-    htri_t file_space_normalized = FALSE;   /* File dataspace was normalized */
-    hid_t f_tid = (-1);           /* Temporary copy of file datatype for iteration */
-    hbool_t iter_init = FALSE;  /* Selection iteration info has been initialized */
-    unsigned f_ndims;           /* The number of dimensions of the file's dataspace */
-    int sm_ndims;               /* The number of dimensions of the memory buffer's dataspace (signed) */
-    H5SL_node_t *curr_node;     /* Current node in skip list */
-    H5S_sel_type fsel_type;     /* Selection type on disk */
-    char bogus;                 /* "bogus" buffer to pass to selection iterator */
-    unsigned u;                 /* Local index variable */
-    hbool_t sel_hyper_flag;
-    herr_t ret_value = SUCCEED;	/* Return value		*/
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_create_chunk_map)
-
-    /* Get layout for dataset */
-    fm->layout = &(dataset->shared->layout);
-    fm->nelmts = nelmts;
-
-    /* Check if the memory space is scalar & make equivalent memory space */
-    if((sm_ndims = H5S_GET_EXTENT_NDIMS(mem_space)) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_CANTGET, FAIL, "unable to get dimension number")
-    /* Set the number of dimensions for the memory dataspace */
-    H5_ASSIGN_OVERFLOW(fm->m_ndims, sm_ndims, int, unsigned);
-
-    /* Get dim number and dimensionality for each dataspace */
-    fm->f_ndims = f_ndims = dataset->shared->layout.u.chunk.ndims - 1;
-    if(H5S_get_simple_extent_dims(file_space, fm->f_dims, NULL) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_CANTGET, FAIL, "unable to get dimensionality")
-
-    /* Normalize hyperslab selections by adjusting them by the offset */
-    /* (It might be worthwhile to normalize both the file and memory dataspaces
-     * before any (contiguous, chunked, etc) file I/O operation, in order to
-     * speed up hyperslab calculations by removing the extra checks and/or
-     * additions involving the offset and the hyperslab selection -QAK)
+    /*
+     * Locate the type conversion function and data space conversion
+     * functions, and set up the element numbering information. If a data
+     * type conversion is necessary then register datatype atoms. Data type
+     * conversion is necessary if the user has set the `need_bkg' to a high
+     * enough value in xfer_parms since turning off datatype conversion also
+     * turns off background preservation.
      */
-    if((file_space_normalized = H5S_hyper_normalize_offset((H5S_t *)file_space, old_offset)) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_BADSELECT, FAIL, "unable to normalize dataspace by offset")
-
-    /* Decide the number of chunks in each dimension*/
-    for(u=0; u<f_ndims; u++) {
-        /* Keep the size of the chunk dimensions as hsize_t for various routines */
-        fm->chunk_dim[u]=fm->layout->u.chunk.dim[u];
-
-        /* Round up to the next integer # of chunks, to accomodate partial chunks */
-        fm->chunks[u] = ((fm->f_dims[u]+dataset->shared->layout.u.chunk.dim[u])-1) / dataset->shared->layout.u.chunk.dim[u];
-    } /* end for */
-
-    /* Compute the "down" size of 'chunks' information */
-    if(H5V_array_down(f_ndims,fm->chunks,fm->down_chunks) < 0)
-        HGOTO_ERROR(H5E_INTERNAL, H5E_BADVALUE, FAIL, "can't compute 'down' sizes")
-
-#ifdef H5_HAVE_PARALLEL
-    /* Calculate total chunk in file map*/
-    fm->select_chunk = NULL;
-    fm->total_chunks = 1;
-    for(u = 0; u < fm->f_ndims; u++)
-       fm->total_chunks = fm->total_chunks * fm->chunks[u];
-    if(io_info->using_mpi_vfd) {
-        H5_CHECK_OVERFLOW(fm->total_chunks, hsize_t, size_t);
-        if(NULL == (fm->select_chunk = (hbool_t *)H5MM_calloc((size_t)fm->total_chunks * sizeof(hbool_t))))
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate chunk info")
-    } /* end if */
-#endif /* H5_HAVE_PARALLEL */
-
-
-    /* Initialize "last chunk" information */
-    fm->last_index = (hsize_t)-1;
-    fm->last_chunk_info = NULL;
-
-    /* Point at the dataspaces */
-    fm->file_space = file_space;
-    fm->mem_space = mem_space;
-
-    /* Special case for only one element in selection */
-    /* (usually appending a record) */
-    if(nelmts == 1
-#ifdef H5_HAVE_PARALLEL
-            && !(io_info->using_mpi_vfd)
-#endif /* H5_HAVE_PARALLEL */
-        ) {
-        /* Initialize skip list for chunk selections */
-        fm->sel_chunks = NULL;
-        fm->use_single = TRUE;
-
-        /* Initialize single chunk dataspace */
-        if(NULL == dataset->shared->cache.chunk.single_space) {
-            /* Make a copy of the dataspace for the dataset */
-            if((dataset->shared->cache.chunk.single_space = H5S_copy(file_space, TRUE, FALSE)) == NULL)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTCOPY, FAIL, "unable to copy file space")
-
-            /* Resize chunk's dataspace dimensions to size of chunk */
-            if(H5S_set_extent_real(dataset->shared->cache.chunk.single_space, fm->chunk_dim) < 0)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTSET, FAIL, "can't adjust chunk dimensions")
-
-            /* Set the single chunk dataspace to 'all' selection */
-            if(H5S_select_all(dataset->shared->cache.chunk.single_space, TRUE) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTSELECT, FAIL, "unable to set all selection")
-        } /* end if */
-        fm->single_space = dataset->shared->cache.chunk.single_space;
-        HDassert(fm->single_space);
-
-        /* Allocate the single chunk information */
-        if(NULL == dataset->shared->cache.chunk.single_chunk_info) {
-            if(NULL == (dataset->shared->cache.chunk.single_chunk_info = H5FL_MALLOC(H5D_chunk_info_t)))
-                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate chunk info")
-        } /* end if */
-        fm->single_chunk_info = dataset->shared->cache.chunk.single_chunk_info;
-        HDassert(fm->single_chunk_info);
-
-        /* Reset chunk template information */
-        fm->mchunk_tmpl = NULL;
+    if(NULL == (type_info->tpath = H5T_path_find(src_type, dst_type, NULL, NULL, dxpl_id, FALSE)))
+	HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "unable to convert between src and dest datatype")
 
-        /* Set up chunk mapping for single element */
-        if(H5D_create_chunk_map_single(fm, io_info) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to create chunk selections for single element")
+    /* Precompute some useful information */
+    type_info->src_type_size = H5T_get_size(src_type);
+    type_info->dst_type_size = H5T_get_size(dst_type);
+    type_info->max_type_size = MAX(type_info->src_type_size, type_info->dst_type_size);
+    type_info->is_conv_noop = H5T_path_noop(type_info->tpath);
+    type_info->is_xform_noop = H5Z_xform_noop(dxpl_cache->data_xform_prop);
+    if(type_info->is_xform_noop && type_info->is_conv_noop) {
+        type_info->cmpd_subset = H5T_SUBSET_FALSE;
+        type_info->need_bkg = H5T_BKG_NO;
     } /* end if */
     else {
-        /* Initialize skip list for chunk selections */
-        if(NULL == dataset->shared->cache.chunk.sel_chunks) {
-            if(NULL == (dataset->shared->cache.chunk.sel_chunks = H5SL_create(H5SL_TYPE_HSIZE, 0.5, (size_t)H5D_DEFAULT_SKIPLIST_HEIGHT)))
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTCREATE, FAIL, "can't create skip list for chunk selections")
-        } /* end if */
-        fm->sel_chunks = dataset->shared->cache.chunk.sel_chunks;
-        HDassert(fm->sel_chunks);
-
-        /* We are not using single element mode */
-        fm->use_single = FALSE;
+        size_t	target_size;		/* Desired buffer size	*/
 
-        /* Get type of selection on disk & in memory */
-        if((fsel_type = H5S_GET_SELECT_TYPE(file_space)) < H5S_SEL_NONE)
-            HGOTO_ERROR(H5E_DATASET, H5E_BADSELECT, FAIL, "unable to get type of selection")
-        if((fm->msel_type = H5S_GET_SELECT_TYPE(mem_space)) < H5S_SEL_NONE)
-            HGOTO_ERROR(H5E_DATASET, H5E_BADSELECT, FAIL, "unable to get type of selection")
+        /* Check if the datatypes are compound subsets of one another */
+        type_info->cmpd_subset = H5T_path_compound_subset(type_info->tpath);
 
-        /* If the selection is NONE or POINTS, set the flag to FALSE */
-        if(fsel_type == H5S_SEL_POINTS || fsel_type == H5S_SEL_NONE)
-            sel_hyper_flag = FALSE;
-        else
-            sel_hyper_flag = TRUE;
-
-        /* Check if file selection is a not a hyperslab selection */
-        if(sel_hyper_flag) {
-            /* Build the file selection for each chunk */
-            if(H5D_create_chunk_file_map_hyper(fm, io_info) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to create file chunk selections")
-
-            /* Clean file chunks' hyperslab span "scratch" information */
-            curr_node=H5SL_first(fm->sel_chunks);
-            while(curr_node) {
-                H5D_chunk_info_t *chunk_info;   /* Pointer chunk information */
-
-                /* Get pointer to chunk's information */
-                chunk_info = (H5D_chunk_info_t *)H5SL_item(curr_node);
-                assert(chunk_info);
-
-                /* Clean hyperslab span's "scratch" information */
-                if(H5S_hyper_reset_scratch(chunk_info->fspace) < 0)
-                    HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "unable to reset span scratch info")
-
-                /* Get the next chunk node in the skip list */
-                curr_node=H5SL_next(curr_node);
-            } /* end while */
-        } /* end if */
+        /* Check if we need a background buffer */
+        if(do_write && H5T_detect_class(dset->shared->type, H5T_VLEN))
+            type_info->need_bkg = H5T_BKG_YES;
         else {
-            /* Create temporary datatypes for selection iteration */
-            if((f_tid = H5I_register(H5I_DATATYPE, H5T_copy(dataset->shared->type, H5T_COPY_ALL))) < 0)
-                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTREGISTER, FAIL, "unable to register file datatype")
-
-            /* Spaces might not be the same shape, iterate over the file selection directly */
-            if(H5S_select_iterate(&bogus, f_tid, file_space,  H5D_chunk_file_cb, fm) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to create file chunk selections")
-
-            /* Reset "last chunk" info */
-            fm->last_index=(hsize_t)-1;
-            fm->last_chunk_info=NULL;
-        } /* end else */
-
-        /* Build the memory selection for each chunk */
-        if(sel_hyper_flag && H5S_select_shape_same(file_space, mem_space) == TRUE) {
-            /* Reset chunk template information */
-            fm->mchunk_tmpl = NULL;
-
-            /* If the selections are the same shape, use the file chunk information
-             * to generate the memory chunk information quickly.
-             */
-            if(H5D_create_chunk_mem_map_hyper(fm) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to create memory chunk selections")
-        } /* end if */
-        else {
-            size_t elmt_size;           /* Memory datatype size */
-
-            /* Make a copy of equivalent memory space */
-            if((tmp_mspace = H5S_copy(mem_space, TRUE, FALSE)) == NULL)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTCOPY, FAIL, "unable to copy memory space")
-
-            /* De-select the mem space copy */
-            if(H5S_select_none(tmp_mspace) < 0)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to de-select memory space")
-
-            /* Save chunk template information */
-            fm->mchunk_tmpl=tmp_mspace;
+            H5T_bkg_t path_bkg;     /* Type conversion's background info */
 
-            /* Create temporary datatypes for selection iteration */
-            if(f_tid<0) {
-                if((f_tid = H5I_register(H5I_DATATYPE, H5T_copy(dataset->shared->type, H5T_COPY_ALL))) < 0)
-                    HGOTO_ERROR(H5E_DATATYPE, H5E_CANTREGISTER, FAIL, "unable to register file datatype")
-            } /* end if */
-
-            /* Create selection iterator for memory selection */
-            if((elmt_size=H5T_get_size(mem_type))==0)
-                HGOTO_ERROR(H5E_DATATYPE, H5E_BADSIZE, FAIL, "datatype size invalid")
-            if(H5S_select_iter_init(&(fm->mem_iter), mem_space, elmt_size) < 0)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to initialize selection iterator")
-            iter_init = TRUE;	/* Selection iteration info has been initialized */
-
-            /* Spaces aren't the same shape, iterate over the memory selection directly */
-            if(H5S_select_iterate(&bogus, f_tid, file_space,  H5D_chunk_mem_cb, fm) < 0)
-                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to create memory chunk selections")
-
-            /* Clean up hyperslab stuff, if necessary */
-            if(fm->msel_type != H5S_SEL_POINTS) {
-                /* Clean memory chunks' hyperslab span "scratch" information */
-                curr_node=H5SL_first(fm->sel_chunks);
-                while(curr_node) {
-                    H5D_chunk_info_t *chunk_info;   /* Pointer chunk information */
-
-                    /* Get pointer to chunk's information */
-                    chunk_info = (H5D_chunk_info_t *)H5SL_item(curr_node);
-                    assert(chunk_info);
-
-                    /* Clean hyperslab span's "scratch" information */
-                    if(H5S_hyper_reset_scratch(chunk_info->mspace) < 0)
-                        HGOTO_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "unable to reset span scratch info")
-
-                    /* Get the next chunk node in the skip list */
-                    curr_node=H5SL_next(curr_node);
-                } /* end while */
+            if((path_bkg = H5T_path_bkg(type_info->tpath))) {
+                /* Retrieve the bkgr buffer property */
+                type_info->need_bkg = dxpl_cache->bkgr_buf_type;
+                type_info->need_bkg = MAX(path_bkg, type_info->need_bkg);
             } /* end if */
+            else
+                type_info->need_bkg = H5T_BKG_NO; /*never needed even if app says yes*/
         } /* end else */
-    } /* end else */
-
-done:
-    /* Release the [potentially partially built] chunk mapping information if an error occurs */
-    if(ret_value<0) {
-        if(tmp_mspace && !fm->mchunk_tmpl) {
-            if(H5S_close(tmp_mspace) < 0)
-                HDONE_ERROR(H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "can't release memory chunk dataspace template")
-        } /* end if */
-
-        if (H5D_destroy_chunk_map(fm) < 0)
-            HDONE_ERROR(H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "unable to release chunk mapping")
-    } /* end if */
-
-    /* Reset the global dataspace info */
-    fm->file_space = NULL;
-    fm->mem_space = NULL;
-
-    if(iter_init) {
-        if(H5S_SELECT_ITER_RELEASE(&(fm->mem_iter)) < 0)
-            HDONE_ERROR(H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "unable to release selection iterator")
-    } /* end if */
-    if(f_tid!=(-1)) {
-        if(H5I_dec_ref(f_tid) < 0)
-            HDONE_ERROR(H5E_DATASET, H5E_CANTFREE, FAIL, "Can't decrement temporary datatype ID")
-    } /* end if */
-    if(file_space_normalized) {
-        if(H5S_hyper_denormalize_offset((H5S_t *)file_space, old_offset) < 0)
-            HGOTO_ERROR(H5E_DATASET, H5E_BADSELECT, FAIL, "unable to normalize dataspace by offset")
-    } /* end if */
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_create_chunk_map() */
-
-
-/*--------------------------------------------------------------------------
- NAME
-    H5D_free_chunk_info
- PURPOSE
-    Internal routine to destroy a chunk info node
- USAGE
-    void H5D_free_chunk_info(chunk_info)
-        void *chunk_info;    IN: Pointer to chunk info to destroy
- RETURNS
-    No return value
- DESCRIPTION
-    Releases all the memory for a chunk info node.  Called by H5SL_free
- GLOBAL VARIABLES
- COMMENTS, BUGS, ASSUMPTIONS
- EXAMPLES
- REVISION LOG
---------------------------------------------------------------------------*/
-static herr_t
-H5D_free_chunk_info(void *item, void UNUSED *key, void UNUSED *opdata)
-{
-    H5D_chunk_info_t *chunk_info = (H5D_chunk_info_t *)item;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5D_free_chunk_info)
-
-    HDassert(chunk_info);
-
-    /* Close the chunk's file dataspace, if it's not shared */
-    if(!chunk_info->fspace_shared)
-        (void)H5S_close(chunk_info->fspace);
-    else
-        H5S_select_all(chunk_info->fspace, TRUE);
-
-    /* Close the chunk's memory dataspace, if it's not shared */
-    if(!chunk_info->mspace_shared)
-        (void)H5S_close(chunk_info->mspace);
-
-    /* Free the actual chunk info */
-    H5FL_FREE(H5D_chunk_info_t, chunk_info);
-
-    FUNC_LEAVE_NOAPI(0);
-}   /* H5D_free_chunk_info() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_destroy_chunk_map
- *
- * Purpose:	Destroy chunk mapping information.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Quincey Koziol
- *		Saturday, May 17, 2003
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5D_destroy_chunk_map(const H5D_chunk_map_t *fm)
-{
-    herr_t	ret_value = SUCCEED;	/*return value		*/
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_destroy_chunk_map)
-
-    /* Single element I/O vs. multiple element I/O cleanup */
-    if(fm->use_single) {
-        /* Sanity checks */
-        HDassert(fm->sel_chunks == NULL);
-        HDassert(fm->single_chunk_info);
-        HDassert(fm->single_chunk_info->fspace_shared);
-        HDassert(fm->single_chunk_info->mspace_shared);
-
-        /* Reset the selection for the single element I/O */
-        H5S_select_all(fm->single_space, TRUE);
-    } /* end if */
-    else {
-        /* Release the nodes on the list of selected chunks */
-        if(fm->sel_chunks)
-            if(H5SL_free(fm->sel_chunks, H5D_free_chunk_info, NULL) < 0)
-                HGOTO_ERROR(H5E_PLIST, H5E_CANTNEXT, FAIL, "can't iterate over chunks")
-    } /* end else */
-
-    /* Free the memory chunk dataspace template */
-    if(fm->mchunk_tmpl)
-        if(H5S_close(fm->mchunk_tmpl) < 0)
-            HGOTO_ERROR(H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "can't release memory chunk dataspace template")
-#ifdef H5_HAVE_PARALLEL
-    if(fm->select_chunk)
-        H5MM_xfree(fm->select_chunk);
-#endif /* H5_HAVE_PARALLEL */
 
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_destroy_chunk_map() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_create_chunk_map_single
- *
- * Purpose:	Create chunk selections when appending a single record
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Quincey Koziol
- *		Tuesday, November 20, 2007
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5D_create_chunk_map_single(H5D_chunk_map_t *fm, const H5D_io_info_t
-#ifndef H5_HAVE_PARALLEL
-    UNUSED
-#endif /* H5_HAVE_PARALLEL */
-    *io_info)
-{
-    H5D_chunk_info_t *chunk_info;           /* Chunk information to insert into skip list */
-    hsize_t     sel_start[H5O_LAYOUT_NDIMS]; /* Offset of low bound of file selection */
-    hsize_t     sel_end[H5O_LAYOUT_NDIMS];  /* Offset of high bound of file selection */
-    unsigned    u;                          /* Local index variable */
-    herr_t	ret_value = SUCCEED;        /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT(H5D_create_chunk_map_single)
+        /* Set up datatype conversion/background buffers */
 
-    /* Sanity check */
-    HDassert(fm->f_ndims > 0);
+        /* Get buffer size from DXPL */
+        target_size = dxpl_cache->max_temp_buf;
 
-    /* Get coordinate for selection */
-    if(H5S_SELECT_BOUNDS(fm->file_space, sel_start, sel_end) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_CANTGET, FAIL, "can't get file selection bound info")
+        /* If the buffer is too small to hold even one element, try to make it bigger */
+        if(target_size < type_info->max_type_size) {
+            hbool_t default_buffer_info;    /* Whether the buffer information are the defaults */
 
-    /* Initialize the 'single chunk' file & memory chunk information */
-    chunk_info = fm->single_chunk_info;
-    chunk_info->chunk_points = 1;
+            /* Detect if we have all default settings for buffers */
+            default_buffer_info = (H5D_TEMP_BUF_SIZE == dxpl_cache->max_temp_buf)
+                    && (NULL == dxpl_cache->tconv_buf) && (NULL == dxpl_cache->bkgr_buf);
 
-    /* Set chunk location & hyperslab size */
-    for(u = 0; u < fm->f_ndims; u++) {
-        HDassert(sel_start[u] == sel_end[u]);
-        chunk_info->coords[u] = (sel_start[u] / fm->layout->u.chunk.dim[u]) * fm->layout->u.chunk.dim[u];
-    } /* end for */
-    chunk_info->coords[fm->f_ndims] = 0;
-
-    /* Calculate the index of this chunk */
-    if(H5V_chunk_index(fm->f_ndims, chunk_info->coords, fm->layout->u.chunk.dim, fm->down_chunks, &chunk_info->index) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "can't get chunk index")
-
-    /* Copy selection for file's dataspace into chunk dataspace */
-    if(H5S_select_copy(fm->single_space, fm->file_space, FALSE) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_CANTCOPY, FAIL, "unable to copy file selection")
-
-    /* Move selection back to have correct offset in chunk */
-    if(H5S_SELECT_ADJUST_U(fm->single_space, chunk_info->coords) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_CANTSELECT, FAIL, "can't adjust chunk selection")
-
-#ifdef H5_HAVE_PARALLEL
-    /* store chunk selection information */
-    if(io_info->using_mpi_vfd)
-        fm->select_chunk[chunk_info->index] = TRUE;
-#endif /* H5_HAVE_PARALLEL */
-
-    /* Set the file dataspace for the chunk to the shared 'single' dataspace */
-    chunk_info->fspace = fm->single_space;
-
-    /* Indicate that the chunk's file dataspace is shared */
-    chunk_info->fspace_shared = TRUE;
-
-    /* Just point at the memory dataspace & selection */
-    /* (Casting away const OK -QAK) */
-    chunk_info->mspace = (H5S_t *)fm->mem_space;
-
-    /* Indicate that the chunk's memory dataspace is shared */
-    chunk_info->mspace_shared = TRUE;
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_create_chunk_map_single() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_create_chunk_file_map_hyper
- *
- * Purpose:	Create all chunk selections in file.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Quincey Koziol
- *		Thursday, May 29, 2003
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5D_create_chunk_file_map_hyper(H5D_chunk_map_t *fm, const H5D_io_info_t
-#ifndef H5_HAVE_PARALLEL
-    UNUSED
-#endif /* H5_HAVE_PARALLEL */
-    *io_info)
-{
-    hsize_t     sel_start[H5O_LAYOUT_NDIMS];   /* Offset of low bound of file selection */
-    hsize_t     sel_end[H5O_LAYOUT_NDIMS];   /* Offset of high bound of file selection */
-    hsize_t     sel_points;                 /* Number of elements in file selection */
-    hsize_t     start_coords[H5O_LAYOUT_NDIMS];   /* Starting coordinates of selection */
-    hsize_t     coords[H5O_LAYOUT_NDIMS];   /* Current coordinates of chunk */
-    hsize_t     end[H5O_LAYOUT_NDIMS];      /* Current coordinates of chunk */
-    hsize_t     chunk_index;                /* Index of chunk */
-    int         curr_dim;                   /* Current dimension to increment */
-    unsigned    u;                          /* Local index variable */
-    herr_t	ret_value = SUCCEED;        /* Return value */
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_create_chunk_file_map_hyper)
-
-    /* Sanity check */
-    assert(fm->f_ndims>0);
-
-    /* Get number of elements selected in file */
-    sel_points = fm->nelmts;
-
-    /* Get bounding box for selection (to reduce the number of chunks to iterate over) */
-    if(H5S_SELECT_BOUNDS(fm->file_space, sel_start, sel_end) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_CANTGET, FAIL, "can't get file selection bound info")
-
-    /* Set initial chunk location & hyperslab size */
-
-    for(u=0; u<fm->f_ndims; u++) {
-        start_coords[u]=(sel_start[u]/fm->layout->u.chunk.dim[u])*fm->layout->u.chunk.dim[u];
-        coords[u]=start_coords[u];
-        end[u]=(coords[u]+fm->chunk_dim[u])-1;
-    } /* end for */
-
-
-    /* Calculate the index of this chunk */
-    if(H5V_chunk_index(fm->f_ndims,coords,fm->layout->u.chunk.dim,fm->down_chunks,&chunk_index) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "can't get chunk index")
-
-    /* Iterate through each chunk in the dataset */
-    while(sel_points) {
-        /* Check for intersection of temporary chunk and file selection */
-        /* (Casting away const OK - QAK) */
-        if(H5S_hyper_intersect_block((H5S_t *)fm->file_space,coords,end)==TRUE) {
-            H5S_t *tmp_fchunk;                  /* Temporary file dataspace */
-            H5D_chunk_info_t *new_chunk_info;   /* chunk information to insert into skip list */
-            hssize_t    schunk_points;          /* Number of elements in chunk selection */
-
-            /* Create "temporary" chunk for selection operations (copy file space) */
-            if((tmp_fchunk = H5S_copy(fm->file_space, TRUE, FALSE)) == NULL)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTCOPY, FAIL, "unable to copy memory space")
-
-            /* Make certain selections are stored in span tree form (not "optimized hyperslab" or "all") */
-            if(H5S_hyper_convert(tmp_fchunk) < 0) {
-                (void)H5S_close(tmp_fchunk);
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to convert selection to span trees")
-            } /* end if */
-
-            /* "AND" temporary chunk and current chunk */
-            if(H5S_select_hyperslab(tmp_fchunk,H5S_SELECT_AND,coords,NULL,fm->chunk_dim,NULL) < 0) {
-                (void)H5S_close(tmp_fchunk);
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTSELECT, FAIL, "can't create chunk selection")
-            } /* end if */
-
-            /* Resize chunk's dataspace dimensions to size of chunk */
-            if(H5S_set_extent_real(tmp_fchunk,fm->chunk_dim) < 0) {
-                (void)H5S_close(tmp_fchunk);
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTSELECT, FAIL, "can't adjust chunk dimensions")
-            } /* end if */
-
-            /* Move selection back to have correct offset in chunk */
-            if(H5S_SELECT_ADJUST_U(tmp_fchunk, coords) < 0) {
-                (void)H5S_close(tmp_fchunk);
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTSELECT, FAIL, "can't adjust chunk selection")
-            } /* end if */
-
-            /* Add temporary chunk to the list of chunks */
-
-            /* Allocate the file & memory chunk information */
-            if (NULL==(new_chunk_info = H5FL_MALLOC (H5D_chunk_info_t))) {
-                (void)H5S_close(tmp_fchunk);
-                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate chunk info")
-            } /* end if */
-
-            /* Initialize the chunk information */
-
-            /* Set the chunk index */
-            new_chunk_info->index=chunk_index;
-
-#ifdef H5_HAVE_PARALLEL
-            /* store chunk selection information */
-            if(io_info->using_mpi_vfd)
-                fm->select_chunk[chunk_index] = TRUE;
-#endif /* H5_HAVE_PARALLEL */
-
-            /* Set the file chunk dataspace */
-            new_chunk_info->fspace = tmp_fchunk;
-            new_chunk_info->fspace_shared = FALSE;
-
-            /* Set the memory chunk dataspace */
-            new_chunk_info->mspace=NULL;
-            new_chunk_info->mspace_shared = FALSE;
-
-            /* Copy the chunk's coordinates */
-            for(u=0; u<fm->f_ndims; u++)
-                new_chunk_info->coords[u]=coords[u];
-            new_chunk_info->coords[fm->f_ndims]=0;
-
-            /* Insert the new chunk into the skip list */
-            if(H5SL_insert(fm->sel_chunks,new_chunk_info,&new_chunk_info->index) < 0) {
-                H5D_free_chunk_info(new_chunk_info,NULL,NULL);
-                HGOTO_ERROR(H5E_DATASPACE,H5E_CANTINSERT,FAIL,"can't insert chunk into skip list")
-            } /* end if */
-
-            /* Get number of elements selected in chunk */
-            if((schunk_points=H5S_GET_SELECT_NPOINTS(tmp_fchunk)) < 0)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTGET, FAIL, "can't get file selection # of elements")
-            H5_ASSIGN_OVERFLOW(new_chunk_info->chunk_points,schunk_points,hssize_t,size_t);
-
-            /* Decrement # of points left in file selection */
-            sel_points-=(hsize_t)schunk_points;
-
-            /* Leave if we are done */
-            if(sel_points==0)
-                HGOTO_DONE(SUCCEED)
-            assert(sel_points>0);
+            /* Check if we are using the default buffer info */
+            if(default_buffer_info)
+                /* OK to get bigger for library default settings */
+                target_size = type_info->max_type_size;
+            else
+                /* Don't get bigger than the application has requested */
+                HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "temporary buffer max size is too small")
         } /* end if */
 
-        /* Increment chunk index */
-        chunk_index++;
-
-        /* Set current increment dimension */
-        curr_dim=(int)fm->f_ndims-1;
-
-        /* Increment chunk location in fastest changing dimension */
-        H5_CHECK_OVERFLOW(fm->chunk_dim[curr_dim],hsize_t,hssize_t);
-        coords[curr_dim]+=fm->chunk_dim[curr_dim];
-        end[curr_dim]+=fm->chunk_dim[curr_dim];
-
-        /* Bring chunk location back into bounds, if necessary */
-        if(coords[curr_dim]>sel_end[curr_dim]) {
-            do {
-                /* Reset current dimension's location to 0 */
-                coords[curr_dim]=start_coords[curr_dim]; /*lint !e771 The start_coords will always be initialized */
-                end[curr_dim]=(coords[curr_dim]+(hssize_t)fm->chunk_dim[curr_dim])-1;
-
-                /* Decrement current dimension */
-                curr_dim--;
-
-                /* Increment chunk location in current dimension */
-                coords[curr_dim]+=fm->chunk_dim[curr_dim];
-                end[curr_dim]=(coords[curr_dim]+fm->chunk_dim[curr_dim])-1;
-            } while(coords[curr_dim]>sel_end[curr_dim]);
-
-            /* Re-Calculate the index of this chunk */
-            if(H5V_chunk_index(fm->f_ndims,coords,fm->layout->u.chunk.dim,fm->down_chunks,&chunk_index) < 0)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "can't get chunk index")
-        } /* end if */
-    } /* end while */
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_create_chunk_file_map_hyper() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_create_chunk_mem_map_hyper
- *
- * Purpose:	Create all chunk selections in memory by copying the file
- *              chunk selections and adjusting their offsets to be correct
- *              for the memory.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Quincey Koziol
- *		Thursday, May 29, 2003
- *
- * Assumptions: That the file and memory selections are the same shape.
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5D_create_chunk_mem_map_hyper(const H5D_chunk_map_t *fm)
-{
-    H5SL_node_t *curr_node;                 /* Current node in skip list */
-    hsize_t    file_sel_start[H5O_LAYOUT_NDIMS];    /* Offset of low bound of file selection */
-    hsize_t    file_sel_end[H5O_LAYOUT_NDIMS];  /* Offset of high bound of file selection */
-    hsize_t    mem_sel_start[H5O_LAYOUT_NDIMS]; /* Offset of low bound of file selection */
-    hsize_t    mem_sel_end[H5O_LAYOUT_NDIMS];   /* Offset of high bound of file selection */
-    hssize_t adjust[H5O_LAYOUT_NDIMS];      /* Adjustment to make to all file chunks */
-    hssize_t chunk_adjust[H5O_LAYOUT_NDIMS];  /* Adjustment to make to a particular chunk */
-    unsigned    u;                          /* Local index variable */
-    herr_t	ret_value = SUCCEED;        /* Return value */
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_create_chunk_mem_map_hyper)
-
-    /* Sanity check */
-    assert(fm->f_ndims>0);
-
-    /* Check for all I/O going to a single chunk */
-    if(H5SL_count(fm->sel_chunks)==1) {
-        H5D_chunk_info_t *chunk_info;   /* Pointer to chunk information */
-
-        /* Get the node */
-        curr_node=H5SL_first(fm->sel_chunks);
-
-        /* Get pointer to chunk's information */
-        chunk_info = (H5D_chunk_info_t *)H5SL_item(curr_node);
-        assert(chunk_info);
-
-        /* Just point at the memory dataspace & selection */
-        /* (Casting away const OK -QAK) */
-        chunk_info->mspace=(H5S_t *)fm->mem_space;
-
-        /* Indicate that the chunk's memory space is shared */
-        chunk_info->mspace_shared = TRUE;
-    } /* end if */
-    else {
-        /* Get bounding box for file selection */
-        if(H5S_SELECT_BOUNDS(fm->file_space, file_sel_start, file_sel_end) < 0)
-            HGOTO_ERROR(H5E_DATASPACE, H5E_CANTGET, FAIL, "can't get file selection bound info")
-
-        /* Get bounding box for memory selection */
-        if(H5S_SELECT_BOUNDS(fm->mem_space, mem_sel_start, mem_sel_end) < 0)
-            HGOTO_ERROR(H5E_DATASPACE, H5E_CANTGET, FAIL, "can't get file selection bound info")
-
-        /* Calculate the adjustment for memory selection from file selection */
-        assert(fm->m_ndims==fm->f_ndims);
-        for(u=0; u<fm->f_ndims; u++) {
-            H5_CHECK_OVERFLOW(file_sel_start[u],hsize_t,hssize_t);
-            H5_CHECK_OVERFLOW(mem_sel_start[u],hsize_t,hssize_t);
-            adjust[u]=(hssize_t)file_sel_start[u]-(hssize_t)mem_sel_start[u];
-        } /* end for */
-
-        /* Iterate over each chunk in the chunk list */
-        curr_node=H5SL_first(fm->sel_chunks);
-        while(curr_node) {
-            H5D_chunk_info_t *chunk_info;   /* Pointer to chunk information */
-
-            /* Get pointer to chunk's information */
-            chunk_info = (H5D_chunk_info_t *)H5SL_item(curr_node);
-            assert(chunk_info);
-
-            /* Copy the information */
-
-            /* Copy the memory dataspace */
-            if((chunk_info->mspace = H5S_copy(fm->mem_space, TRUE, FALSE)) == NULL)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTCOPY, FAIL, "unable to copy memory space")
-
-            /* Release the current selection */
-            if(H5S_SELECT_RELEASE(chunk_info->mspace) < 0)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "unable to release selection")
-
-            /* Copy the file chunk's selection */
-            if(H5S_select_copy(chunk_info->mspace,chunk_info->fspace,FALSE) < 0)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTCOPY, FAIL, "unable to copy selection")
-
-            /* Compensate for the chunk offset */
-            for(u=0; u<fm->f_ndims; u++) {
-                H5_CHECK_OVERFLOW(chunk_info->coords[u],hsize_t,hssize_t);
-                chunk_adjust[u]=adjust[u]-(hssize_t)chunk_info->coords[u]; /*lint !e771 The adjust array will always be initialized */
-            } /* end for */
-
-            /* Adjust the selection */
-            if(H5S_hyper_adjust_s(chunk_info->mspace,chunk_adjust) < 0) /*lint !e772 The chunk_adjust array will always be initialized */
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTSELECT, FAIL, "can't adjust chunk selection")
-
-            /* Get the next chunk node in the skip list */
-            curr_node=H5SL_next(curr_node);
-        } /* end while */
-    } /* end else */
+        /* Compute the number of elements that will fit into buffer */
+        type_info->request_nelmts = target_size / type_info->max_type_size;
 
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_create_chunk_mem_map_hyper() */
+        /* Sanity check elements in temporary buffer */
+        if(type_info->request_nelmts == 0)
+            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "temporary buffer max size is too small")
 
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_chunk_file_cb
- *
- * Purpose:	Callback routine for file selection iterator.  Used when
- *              creating selections in file for each point selected.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Quincey Koziol
- *		Wednesday, July 23, 2003
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5D_chunk_file_cb(void UNUSED *elem, hid_t UNUSED type_id, unsigned ndims, const hsize_t *coords, void *_fm)
-{
-    H5D_chunk_map_t      *fm = (H5D_chunk_map_t *)_fm;  /* File<->memory chunk mapping info */
-    H5D_chunk_info_t *chunk_info;               /* Chunk information for current chunk */
-    hsize_t    coords_in_chunk[H5O_LAYOUT_NDIMS];        /* Coordinates of element in chunk */
-    hsize_t     chunk_index;                    /* Chunk index */
-    unsigned    u;                              /* Local index variable */
-    herr_t	ret_value = SUCCEED;            /* Return value		*/
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_chunk_file_cb)
-
-    /* Calculate the index of this chunk */
-    if(H5V_chunk_index(ndims,coords,fm->layout->u.chunk.dim,fm->down_chunks,&chunk_index) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "can't get chunk index")
-
-    /* Find correct chunk in file & memory skip list */
-    if(chunk_index==fm->last_index) {
-        /* If the chunk index is the same as the last chunk index we used,
-         * get the cached info to operate on.
-         */
-        chunk_info=fm->last_chunk_info;
-    } /* end if */
-    else {
-        /* If the chunk index is not the same as the last chunk index we used,
-         * find the chunk in the skip list.
+        /*
+         * Get a temporary buffer for type conversion unless the app has already
+         * supplied one through the xfer properties. Instead of allocating a
+         * buffer which is the exact size, we allocate the target size.  The
+         * malloc() is usually less resource-intensive if we allocate/free the
+         * same size over and over.
          */
-        /* Get the chunk node from the skip list */
-        if(NULL == (chunk_info = (H5D_chunk_info_t *)H5SL_search(fm->sel_chunks, &chunk_index))) {
-            H5S_t *fspace;                      /* Memory chunk's dataspace */
-
-            /* Allocate the file & memory chunk information */
-            if (NULL==(chunk_info = H5FL_MALLOC (H5D_chunk_info_t)))
-                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate chunk info")
-
-            /* Initialize the chunk information */
-
-            /* Set the chunk index */
-            chunk_info->index=chunk_index;
-
-            /* Create a dataspace for the chunk */
-            if((fspace = H5S_create_simple(fm->f_ndims,fm->chunk_dim,NULL))==NULL) {
-                H5FL_FREE(H5D_chunk_info_t,chunk_info);
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTCREATE, FAIL, "unable to create dataspace for chunk")
-            } /* end if */
-
-            /* De-select the chunk space */
-            if(H5S_select_none(fspace) < 0) {
-                (void)H5S_close(fspace);
-                H5FL_FREE(H5D_chunk_info_t,chunk_info);
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to de-select dataspace")
-            } /* end if */
-
-            /* Set the file chunk dataspace */
-            chunk_info->fspace = fspace;
-            chunk_info->fspace_shared = FALSE;
-
-            /* Set the memory chunk dataspace */
-            chunk_info->mspace=NULL;
-            chunk_info->mspace_shared = FALSE;
-
-            /* Set the number of selected elements in chunk to zero */
-            chunk_info->chunk_points=0;
-
-            /* Compute the chunk's coordinates */
-            for(u=0; u<fm->f_ndims; u++) {
-                H5_CHECK_OVERFLOW(fm->layout->u.chunk.dim[u],hsize_t,hssize_t);
-                chunk_info->coords[u]=(coords[u]/(hssize_t)fm->layout->u.chunk.dim[u])*(hssize_t)fm->layout->u.chunk.dim[u];
-            } /* end for */
-            chunk_info->coords[fm->f_ndims]=0;
-
-            /* Insert the new chunk into the skip list */
-            if(H5SL_insert(fm->sel_chunks,chunk_info,&chunk_info->index) < 0) {
-                H5D_free_chunk_info(chunk_info,NULL,NULL);
-                HGOTO_ERROR(H5E_DATASPACE,H5E_CANTINSERT,FAIL,"can't insert chunk into skip list")
-            } /* end if */
+        if(NULL == (type_info->tconv_buf = (uint8_t *)dxpl_cache->tconv_buf)) {
+            /* Allocate temporary buffer */
+            if(NULL == (type_info->tconv_buf = H5FL_BLK_MALLOC(type_conv, target_size)))
+                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for type conversion")
+            type_info->tconv_buf_allocated = TRUE;
+        } /* end if */
+        if(type_info->need_bkg && NULL == (type_info->bkg_buf = (uint8_t *)dxpl_cache->bkgr_buf)) {
+            size_t	bkg_size;		/* Desired background buffer size	*/
+
+            /* Compute the background buffer size */
+            /* (don't try to use buffers smaller than the default size) */
+            bkg_size = type_info->request_nelmts * type_info->dst_type_size;
+            if(bkg_size < dxpl_cache->max_temp_buf)
+                bkg_size = dxpl_cache->max_temp_buf;
+
+            /* Allocate background buffer */
+            /* (Need calloc()-like call since memory needs to be initialized) */
+            if(NULL == (type_info->bkg_buf = H5FL_BLK_CALLOC(type_conv, bkg_size)))
+                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for background conversion")
+            type_info->bkg_buf_allocated = TRUE;
         } /* end if */
-
-        /* Update the "last chunk seen" information */
-        fm->last_index=chunk_index;
-        fm->last_chunk_info=chunk_info;
-    } /* end else */
-
-    /* Get the coordinates of the element in the chunk */
-    for(u=0; u<fm->f_ndims; u++)
-        coords_in_chunk[u]=coords[u]%fm->layout->u.chunk.dim[u];
-
-    /* Add point to file selection for chunk */
-    if(H5S_select_elements(chunk_info->fspace, H5S_SELECT_APPEND, (size_t)1, coords_in_chunk) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_CANTSELECT, FAIL, "unable to select element")
-
-    /* Increment the number of elemented selected in chunk */
-    chunk_info->chunk_points++;
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_chunk_file_cb() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5D_chunk_mem_cb
- *
- * Purpose:	Callback routine for file selection iterator.  Used when
- *              creating selections in memory for each chunk.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Raymond Lu
- *		Thursday, April 10, 2003
- *
- *-------------------------------------------------------------------------
- */
-/* ARGSUSED */
-static herr_t
-H5D_chunk_mem_cb(void UNUSED *elem, hid_t UNUSED type_id, unsigned ndims, const hsize_t *coords, void *_fm)
-{
-    H5D_chunk_map_t      *fm = (H5D_chunk_map_t *)_fm;  /* File<->memory chunk mapping info */
-    H5D_chunk_info_t *chunk_info;               /* Chunk information for current chunk */
-    hsize_t    coords_in_mem[H5O_LAYOUT_NDIMS];        /* Coordinates of element in memory */
-    hsize_t     chunk_index;                    /* Chunk index */
-    herr_t	ret_value = SUCCEED;            /* Return value		*/
-
-    FUNC_ENTER_NOAPI_NOINIT(H5D_chunk_mem_cb)
-
-    /* Calculate the index of this chunk */
-    if(H5V_chunk_index(ndims,coords,fm->layout->u.chunk.dim,fm->down_chunks,&chunk_index) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "can't get chunk index")
-
-    /* Find correct chunk in file & memory skip list */
-    if(chunk_index==fm->last_index) {
-        /* If the chunk index is the same as the last chunk index we used,
-         * get the cached spaces to operate on.
-         */
-        chunk_info=fm->last_chunk_info;
-    } /* end if */
-    else {
-        /* If the chunk index is not the same as the last chunk index we used,
-         * find the chunk in the skip list.
-         */
-        /* Get the chunk node from the skip list */
-        if(NULL == (chunk_info = (H5D_chunk_info_t *)H5SL_search(fm->sel_chunks, &chunk_index)))
-            HGOTO_ERROR(H5E_DATASPACE, H5E_NOTFOUND, FAIL, "can't locate chunk in skip list")
-
-        /* Check if the chunk already has a memory space */
-        if(chunk_info->mspace==NULL) {
-            /* Copy the template memory chunk dataspace */
-            if((chunk_info->mspace = H5S_copy(fm->mchunk_tmpl, FALSE, FALSE)) == NULL)
-                HGOTO_ERROR(H5E_DATASPACE, H5E_CANTCOPY, FAIL, "unable to copy file space")
-        } /* end else */
-
-        /* Update the "last chunk seen" information */
-        fm->last_index=chunk_index;
-        fm->last_chunk_info=chunk_info;
-    } /* end else */
-
-    /* Get coordinates of selection iterator for memory */
-    if(H5S_SELECT_ITER_COORDS(&fm->mem_iter,coords_in_mem) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_CANTGET, FAIL, "unable to get iterator coordinates")
-
-    /* Add point to memory selection for chunk */
-    if(fm->msel_type==H5S_SEL_POINTS) {
-        if(H5S_select_elements(chunk_info->mspace, H5S_SELECT_APPEND, (size_t)1, coords_in_mem) < 0)
-            HGOTO_ERROR(H5E_DATASPACE, H5E_CANTSELECT, FAIL, "unable to select element")
-    } /* end if */
-    else {
-        if(H5S_hyper_add_span_element(chunk_info->mspace, fm->m_ndims, coords_in_mem) < 0)
-            HGOTO_ERROR(H5E_DATASPACE, H5E_CANTSELECT, FAIL, "unable to select element")
     } /* end else */
 
-    /* Move memory selection iterator to next element in selection */
-    if(H5S_SELECT_ITER_NEXT(&fm->mem_iter, (size_t)1) < 0)
-        HGOTO_ERROR(H5E_DATASPACE, H5E_CANTNEXT, FAIL, "unable to move to next iterator location")
-
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_chunk_mem_cb() */
+} /* end H5D_typeinfo_init() */
 
+#ifdef H5_HAVE_PARALLEL
 
 /*-------------------------------------------------------------------------
- * Function:	H5D_ioinfo_init
+ * Function:	H5D_ioinfo_adjust
  *
- * Purpose:	Routine for determining correct I/O operations for
- *              each I/O action.
+ * Purpose:	Adjust operation's I/O info for any parallel I/O
  *
  * Return:	Non-negative on success/Negative on failure
  *
  * Programmer:	Quincey Koziol
- *		Thursday, September 30, 2004
+ *		Thursday, March 27, 2008
  *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5D_ioinfo_init(H5D_t *dset, const H5D_dxpl_cache_t *dxpl_cache, hid_t dxpl_id,
-    const H5S_t
-#if !(defined H5_HAVE_PARALLEL || defined H5S_DEBUG)
-    UNUSED
-#endif /* H5_HAVE_PARALLEL */
-    *mem_space, const H5S_t
-#if !(defined H5_HAVE_PARALLEL || defined H5S_DEBUG)
-    UNUSED
-#endif /* H5_HAVE_PARALLEL */
-    *file_space, H5T_path_t
-#ifndef H5_HAVE_PARALLEL
-    UNUSED
-#endif /* H5_HAVE_PARALLEL */
-    *tpath,
-    H5D_io_info_t *io_info)
+H5D_ioinfo_adjust(H5D_io_info_t *io_info, const H5D_t *dset,
+    const H5D_dxpl_cache_t *dxpl_cache, hid_t dxpl_id,
+    const H5S_t *file_space, const H5S_t *mem_space,
+    const H5D_type_info_t *type_info, const H5D_chunk_map_t *fm)
 {
     herr_t	ret_value = SUCCEED;	/* Return value	*/
 
-#if defined H5_HAVE_PARALLEL || defined H5S_DEBUG
-    FUNC_ENTER_NOAPI_NOINIT(H5D_ioinfo_init)
-#else /* defined H5_HAVE_PARALLEL || defined H5S_DEBUG */
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5D_ioinfo_init)
-#endif /* defined H5_HAVE_PARALLEL || defined H5S_DEBUG */
+    FUNC_ENTER_NOAPI_NOINIT(H5D_ioinfo_adjust)
 
     /* check args */
     HDassert(dset);
     HDassert(dset->oloc.file);
     HDassert(mem_space);
     HDassert(file_space);
-    HDassert(tpath);
+    HDassert(type_info);
+    HDassert(type_info->tpath);
     HDassert(io_info);
 
-    /* Set up "normal" I/O fields */
-    io_info->dset=dset;
-    io_info->dxpl_cache=dxpl_cache;
-    io_info->dxpl_id=dxpl_id;
-    io_info->store=NULL;        /* Set later in I/O routine? */
-
-    /* Set I/O operations to initial values */
-    io_info->ops=dset->shared->io_ops;
-
-#ifdef H5_HAVE_PARALLEL
-    /* Start in the "not modified" xfer_mode state */
-    io_info->xfer_mode_changed = FALSE;
-    io_info->using_mpi_vfd = IS_H5FD_MPI(dset->oloc.file);
-
+    /* Make any parallel I/O adjustments */
     if(io_info->using_mpi_vfd) {
         htri_t opt;         /* Flag whether a selection is optimizable */
 
+        /* Record the original state of parallel I/O transfer options */
+        io_info->orig.xfer_mode = io_info->dxpl_cache->xfer_mode;
+        io_info->orig.coll_opt_mode = io_info->dxpl_cache->coll_opt_mode;
+        io_info->orig.io_ops.single_read = io_info->io_ops.single_read;
+        io_info->orig.io_ops.single_write = io_info->io_ops.single_write;
+
         /* Get MPI communicator */
-        if((io_info->comm = H5F_mpi_get_comm(dset->oloc.file)) == MPI_COMM_NULL)
+        if(MPI_COMM_NULL == (io_info->comm = H5F_mpi_get_comm(dset->oloc.file)))
             HGOTO_ERROR(H5E_DATASPACE, H5E_CANTGET, FAIL, "can't retrieve MPI communicator")
 
-        /*
-         * Check if we can set direct MPI-IO read/write functions
-         */
-        opt=H5D_mpio_opt_possible(io_info, mem_space, file_space, tpath);
-        if(opt==FAIL)
-            HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "invalid check for direct IO dataspace ");
+        /* Check if we can set direct MPI-IO read/write functions */
+        if((opt = H5D_mpio_opt_possible(io_info, file_space, mem_space, type_info, fm)) < 0)
+            HGOTO_ERROR(H5E_DATASPACE, H5E_BADRANGE, FAIL, "invalid check for direct IO dataspace ")
 
         /* Check if we can use the optimized parallel I/O routines */
-        if(opt==TRUE) {
-            /* Set the pointers to the MPI-specific routines */
-            io_info->ops.read = H5D_mpio_select_read;
-            io_info->ops.write = H5D_mpio_select_write;
+        if(opt == TRUE) {
+            /* Override the I/O op pointers to the MPI-specific routines */
+            io_info->io_ops.multi_read = dset->shared->layout_ops->par_read;
+            io_info->io_ops.multi_write = dset->shared->layout_ops->par_write;
+            io_info->io_ops.single_read = H5D_mpio_select_read;
+            io_info->io_ops.single_write = H5D_mpio_select_write;
         } /* end if */
         else {
-            /* Set the pointers to the non-MPI-specific routines */
-            io_info->ops.read = H5D_select_read;
-            io_info->ops.write = H5D_select_write;
-
             /* If we won't be doing collective I/O, but the user asked for
              * collective I/O, change the request to use independent I/O, but
              * mark it so that we remember to revert the change.
              */
-            if(io_info->dxpl_cache->xfer_mode==H5FD_MPIO_COLLECTIVE) {
+            if(io_info->dxpl_cache->xfer_mode == H5FD_MPIO_COLLECTIVE) {
                 H5P_genplist_t *dx_plist;           /* Data transer property list */
 
                 /* Get the dataset transfer property list */
-                if (NULL == (dx_plist = (H5P_genplist_t *)H5I_object(dxpl_id)))
+                if(NULL == (dx_plist = (H5P_genplist_t *)H5I_object(dxpl_id)))
                     HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset creation property list")
 
                 /* Change the xfer_mode to independent for handling the I/O */
                 io_info->dxpl_cache->xfer_mode = H5FD_MPIO_INDEPENDENT;
-                if(H5P_set (dx_plist, H5D_XFER_IO_XFER_MODE_NAME, &io_info->dxpl_cache->xfer_mode) < 0)
+                if(H5P_set(dx_plist, H5D_XFER_IO_XFER_MODE_NAME, &io_info->dxpl_cache->xfer_mode) < 0)
                     HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set transfer mode")
-
-                /* Indicate that the transfer mode should be restored before returning
-                 * to user.
-                 */
-                io_info->xfer_mode_changed = TRUE;
             } /* end if */
         } /* end else */
     } /* end if */
-    else {
-        /* Set the pointers to the non-MPI-specific routines */
-        io_info->ops.read = H5D_select_read;
-        io_info->ops.write = H5D_select_write;
-    } /* end else */
-#else /* H5_HAVE_PARALLEL */
-    io_info->ops.read = H5D_select_read;
-    io_info->ops.write = H5D_select_write;
-#endif /* H5_HAVE_PARALLEL */
-
-#ifdef H5S_DEBUG
-    /* Get the information for the I/O statistics */
-    if((io_info->stats=H5S_find(mem_space,file_space))==NULL)
-        HGOTO_ERROR(H5E_DATASET, H5E_BADSELECT, FAIL, "can't set up selection statistics");
-#endif /* H5S_DEBUG */
 
-#if defined H5_HAVE_PARALLEL || defined H5S_DEBUG
 done:
-#endif /* H5_HAVE_PARALLEL || H5S_DEBUG */
     FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5D_ioinfo_init() */
+} /* end H5D_ioinfo_adjust() */
 
-#ifdef H5_HAVE_PARALLEL
 
 /*-------------------------------------------------------------------------
  * Function:	H5D_ioinfo_term
@@ -3438,23 +933,69 @@ H5D_ioinfo_term(H5D_io_info_t *io_info)
 
     FUNC_ENTER_NOAPI_NOINIT(H5D_ioinfo_term)
 
-    /* Check if we need to revert the change to the xfer mode */
-    if (io_info->xfer_mode_changed) {
-        H5P_genplist_t *dx_plist;           /* Data transer property list */
+    /* Check if we used the MPI VFD for the I/O */
+    if(io_info->using_mpi_vfd) {
+        /* Check if we need to revert the change to the xfer mode */
+        if(io_info->orig.xfer_mode != io_info->dxpl_cache->xfer_mode) {
+            H5P_genplist_t *dx_plist;           /* Data transer property list */
 
-        /* Get the dataset transfer property list */
-        if (NULL == (dx_plist = (H5P_genplist_t *)H5I_object(io_info->dxpl_id)))
-            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset transfer property list")
+            /* Get the dataset transfer property list */
+            if(NULL == (dx_plist = (H5P_genplist_t *)H5I_object(io_info->dxpl_id)))
+                HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset transfer property list")
+
+            /* Restore the original parallel I/O mode */
+            if(H5P_set(dx_plist, H5D_XFER_IO_XFER_MODE_NAME, &io_info->orig.xfer_mode) < 0)
+                HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set transfer mode")
+        } /* end if */
 
-        /* Restore the original parallel I/O mode */
-        io_info->dxpl_cache->xfer_mode = H5FD_MPIO_COLLECTIVE;
-        if(H5P_set (dx_plist, H5D_XFER_IO_XFER_MODE_NAME, &io_info->dxpl_cache->xfer_mode) < 0)
-            HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set transfer mode")
+        /* Check if we need to revert the change to the collective opt mode */
+        if(io_info->orig.coll_opt_mode != io_info->dxpl_cache->coll_opt_mode) {
+            H5P_genplist_t *dx_plist;           /* Data transer property list */
+
+            /* Get the dataset transfer property list */
+            if(NULL == (dx_plist = (H5P_genplist_t *)H5I_object(io_info->dxpl_id)))
+                HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset transfer property list")
+
+            /* Restore the original parallel I/O mode */
+            if(H5P_set(dx_plist, H5D_XFER_MPIO_COLLECTIVE_OPT_NAME, &io_info->orig.coll_opt_mode) < 0)
+                HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set collective option mode")
+        } /* end if */
     } /* end if */
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5D_ioinfo_term() */
 
-#endif
+#endif /* H5_HAVE_PARALLEL */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5D_typeinfo_term
+ *
+ * Purpose:	Common logic for terminating a type info object
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *		Thursday, March  6, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5D_typeinfo_term(const H5D_type_info_t *type_info)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5D_typeinfo_term)
+
+    /* Check for releasing datatype conversion & background buffers */
+    if(type_info->tconv_buf_allocated) {
+        HDassert(type_info->tconv_buf);
+        (void)H5FL_BLK_FREE(type_conv, type_info->tconv_buf);
+    } /* end if */
+    if(type_info->bkg_buf_allocated) {
+        HDassert(type_info->bkg_buf);
+        (void)H5FL_BLK_FREE(type_conv, type_info->bkg_buf);
+    } /* end if */
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5D_typeinfo_term() */