[svn-r5834] Purpose:

    Large code cleanup/re-write

Description:
    This is phase 1 of the data I/O re-architecture, with the following changes:
        - Changed the selection drivers to not actually do any I/O, they
            only generate the sequences of offset/length pairs needed for
            the I/O (or memory access, in the case of iterating or filling
            a selection in a memory buffer)
        - Wrote more abstract I/O routines which get the sequence of offset/
            length pairs for each selection and access perform the I/O or
            memory access.

    Benefits of this change include:
        - Removed ~3400 lines of quite redundant code, with corresponding
            reduction in the size of library binary.
        - Any selection can now directly access memory when performing I/O,
            if no type conversions are required, instead of just "regular"
            hyperslab and 'all' selections, which speeds up I/O.
        - Sped up I/O for hyperslab selections which have contiguous lower
            dimensions by "flattening" them out into lesser dimensional objects
            for the I/O.

    No file format or API changes were necessary for this change.

    The next phase will be to create a "selection driver" for each type of
        selection, allowing each type of selection to directly call certain
        methods that only apply to that type of selection, instead of passing
        through dozens of functions which have switch statements to call the
        appropriate method for each selection type.  This will also reduce
        the amount of code in the library and speed things up a bit more.

    Phase 3 will involve generating an MPI datatype for all types of selections,
        instead of only "regular" hyperslab and 'all' selections.  This will
        allow collective parallel I/O for all I/O operations which don't
        require type conversions.  It will also open up the door for allowing
        collective I/O on datasets which require type conversion.

    Phase 4 will involve changing the access pattern to deal with chunked
        datasets in a more optimal way (in serial).

    Phase 5 will deal with accessing chunked datasets more optimally for
        collective parallel I/O operations.

Platforms tested:
    FreeBSD 4.6 (sleipnir) w/ parallel & C++ and IRIX64 6.5 (modi4) w/parallel

1 files changed, 1224 insertions, 41 deletions

diff --git a/src/H5Sselect.c b/src/H5Sselect.c
index c4a6bdb..7c239bb 100644
--- a/src/H5Sselect.c
+++ b/src/H5Sselect.c
@@ -10,13 +10,13 @@
 
 #define H5S_PACKAGE		/*suppress error about including H5Spkg	  */
 
-#include "H5private.h"
-#include "H5Eprivate.h"
-#include "H5FLprivate.h"	/*Free Lists	  */
-#include "H5Iprivate.h"
-#include "H5MMprivate.h"
-#include "H5Spkg.h"
-#include "H5Vprivate.h"
+#include "H5private.h"		/* Generic Functions			  */
+#include "H5Dprivate.h"         /* Datasets (for their properties) */
+#include "H5Eprivate.h"		/* Error handling		  */
+#include "H5FLprivate.h"	/* Free Lists	  */
+#include "H5Iprivate.h"		/* ID Functions		  */
+#include "H5Spkg.h"		/* Dataspace functions			  */
+#include "H5Vprivate.h"         /* Vector functions */
 
 /* Interface initialization */
 #define PABLO_MASK      H5Sselect_mask
@@ -32,6 +32,18 @@ static herr_t H5S_get_select_bounds(H5S_t *space, hsize_t *start, hsize_t *end);
 /* Declare external the free list for hssize_t arrays */
 H5FL_ARR_EXTERN(hssize_t);
 
+/* Declare a free list to manage arrays of size_t */
+H5FL_ARR_DEFINE_STATIC(size_t,-1);
+
+/* Declare a free list to manage arrays of hsize_t */
+H5FL_ARR_DEFINE_STATIC(hsize_t,-1);
+
+/* Declare a free list to manage the H5S_sel_iter_t struct */
+H5FL_DEFINE_STATIC(H5S_sel_iter_t);
+
+/* Declare a free list to manage blocks of single datatype element data */
+H5FL_BLK_EXTERN(type_elem);
+
 
 /*--------------------------------------------------------------------------
  NAME
@@ -207,6 +219,7 @@ H5Sget_select_npoints(hid_t spaceid)
 
     FUNC_LEAVE (ret_value);
 }   /* H5Sget_select_npoints() */
+
 
 /*--------------------------------------------------------------------------
  NAME
@@ -258,6 +271,7 @@ H5S_get_select_npoints (const H5S_t *space)
 
     FUNC_LEAVE (ret_value);
 }   /* H5S_get_select_npoints() */
+
 
 /*--------------------------------------------------------------------------
  NAME
@@ -1220,6 +1234,59 @@ H5S_select_contiguous(const H5S_t *space)
 
 /*--------------------------------------------------------------------------
  NAME
+    H5S_select_iter_init
+ PURPOSE
+    Construct an iterator for a dataspace & selection
+ USAGE
+    herr_t H5S_select_iter_init(space, elmt_size, iter)
+        H5S_t *space;   IN: Dataspace object containing selection to iterate over
+        size_t elmt_size;   IN: Size of element in dataspace
+        H5S_sel_iter_t *iter;   OUT: Iterator to initialize
+ RETURNS
+    Non-negative on success, negative on failure
+ DESCRIPTION
+    Genericly initializes an iterator, based on the type of selection in the
+    dataspace.
+--------------------------------------------------------------------------*/
+herr_t
+H5S_select_iter_init(const H5S_t *space, size_t elmt_size, H5S_sel_iter_t *iter)
+{
+    herr_t ret_value=FAIL;  /* return value */
+
+    FUNC_ENTER_NOINIT(H5S_select_iter_init);
+
+    assert(space);
+    assert(iter);
+
+    /* Initialize iterator */
+    switch(space->select.type) {
+        case H5S_SEL_POINTS:         /* Sequence of points selected */
+            ret_value=H5S_point_init(space,elmt_size,iter);
+            break;
+
+        case H5S_SEL_HYPERSLABS:     /* Hyperslab selection defined */
+            ret_value=H5S_hyper_init(space,elmt_size,iter);
+            break;
+
+        case H5S_SEL_ALL:            /* Entire extent selected */
+            ret_value=H5S_all_init(space,elmt_size,iter);
+            break;
+
+        case H5S_SEL_NONE:           /* Nothing selected */
+            ret_value=FALSE;
+            break;
+
+        case H5S_SEL_ERROR:
+        case H5S_SEL_N:
+            break;
+    }
+
+    FUNC_LEAVE (ret_value);
+} /* end H5S_select_iter_init() */
+
+
+/*--------------------------------------------------------------------------
+ NAME
     H5S_select_iterate
  PURPOSE
     Iterate over the selected elements in a memory buffer.
@@ -1250,37 +1317,137 @@ herr_t
 H5S_select_iterate(void *buf, hid_t type_id, H5S_t *space, H5D_operator_t op,
         void *operator_data)
 {
-    herr_t ret_value=FAIL;
+    H5T_t *dt;                  /* Datatype structure */
+    H5P_genplist_t *dx_plist;   /* Dataset transfer property list */
+    H5S_sel_iter_t *iter=NULL;  /* Selection iteration info */
+    uint8_t *loc;               /* Current element location in buffer */
+    hssize_t coords[H5O_LAYOUT_NDIMS];  /* Coordinates of element in dataspace */
+    hssize_t nelmts;            /* Number of elements in selection */
+    hsize_t space_size[H5O_LAYOUT_NDIMS]; /* Dataspace size */
+    hsize_t *off=NULL;          /* Array to store sequence offsets */
+    hsize_t curr_off;           /* Current offset within sequence */
+    hsize_t tmp_off;            /* Temporary offset within sequence */
+    size_t *len=NULL;           /* Array to store sequence lengths */
+    size_t curr_len;            /* Length of bytes left to process in sequence */
+    size_t vector_size;         /* Value for vector size */
+    size_t nseq;                /* Number of sequences generated */
+    size_t curr_seq;            /* Current sequnce being worked on */
+    size_t nbytes;              /* Number of bytes used in sequences */
+    size_t max_bytes;           /* Maximum number of bytes allowed in sequences */
+    size_t elmt_size;           /* Datatype size */
+    int ndims;                  /* Number of dimensions in dataspace */
+    int	i;			/* Local Index variable */
+    herr_t user_ret=0;          /* User's return value */
+    herr_t ret_value=SUCCEED;   /* Return value */
 
     FUNC_ENTER_NOAPI(H5S_select_iterate, FAIL);
 
     /* Check args */
     assert(buf);
+    assert(H5I_DATATYPE == H5I_get_type(type_id));
     assert(space);
     assert(op);
-    assert(H5I_DATATYPE == H5I_get_type(type_id));
 
-    switch(space->select.type) {
-        case H5S_SEL_POINTS:         /* Sequence of points selected */
-            ret_value=H5S_point_select_iterate(buf,type_id,space,op,operator_data);
-            break;
+    /* Get the hyperslab vector size */
+    /* (from the default data transfer property list, for now) */
+    dx_plist = H5I_object(H5P_DATASET_XFER_DEFAULT);
+    assert(dx_plist);
+    if (H5P_get(dx_plist,H5D_XFER_HYPER_VECTOR_SIZE_NAME,&vector_size)<0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "unable to get value");
+
+    /* Allocate the vector I/O arrays */
+    if((len = H5FL_ARR_ALLOC(size_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O length vector array");
+    if((off = H5FL_ARR_ALLOC(hsize_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O offset vector array");
+
+    /* Get the datatype size */
+    if (NULL==(dt=H5I_object(type_id)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not an valid base datatype");
+    if((elmt_size=H5T_get_size(dt))==0)
+        HGOTO_ERROR(H5E_DATATYPE, H5E_BADSIZE, FAIL, "datatype size invalid");
+
+    /* Allocate iterator */
+    if((iter = H5FL_ALLOC(H5S_sel_iter_t,1))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate selection iterator");
+
+    /* Initialize iterator */
+    if (H5S_select_iter_init(space, elmt_size, iter)<0)
+        HGOTO_ERROR (H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to initialize selection iterator");
+
+    /* Get the number of elements in selection */
+    if((nelmts = H5S_get_select_npoints(space))<0)
+        HGOTO_ERROR (H5E_DATASPACE, H5E_CANTCOUNT, FAIL, "can't get number of elements selected");
+
+    /* Get the rank of the dataspace */
+    ndims=space->extent.u.simple.rank;
+
+    /* Copy the size of the space */
+    assert(space->extent.u.simple.size);
+    assert(ndims>0);
+    HDmemcpy(space_size, space->extent.u.simple.size, ndims*sizeof(hsize_t));
+    space_size[ndims]=elmt_size;
+
+    /* Compute the maximum number of bytes required */
+    H5_ASSIGN_OVERFLOW(max_bytes,nelmts*elmt_size,hsize_t,size_t);
+
+    /* Loop, while elements left in selection */
+    while(max_bytes>0 && user_ret==0) {
+        /* Get the sequences of bytes */
+        if(H5S_select_get_seq_list(0,space,iter,elmt_size,vector_size,max_bytes,&nseq,&nbytes,off,len)<0)
+            HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
+
+        /* Loop, while sequences left to process */
+        for(curr_seq=0; curr_seq<nseq && user_ret==0; curr_seq++) {
+            /* Get the current offset */
+            curr_off=off[curr_seq];
+
+            /* Get the number of bytes in sequence */
+            curr_len=len[curr_seq];
+
+            /* Loop, while bytes left in sequence */
+            while(curr_len>0 && user_ret==0) {
+                /* Compute the coordinate from the offset */
+                for(i=ndims, tmp_off=curr_off; i>=0; i--) {
+                    coords[i]=tmp_off%space_size[i];
+                    tmp_off/=space_size[i];
+                } /* end for */
+
+                /* Get the location within the user's buffer */
+                loc=(unsigned char *)buf+curr_off;
+
+                /* Call user's callback routine */
+                user_ret=(*op)(loc,type_id,(hsize_t)ndims,coords,operator_data);
+
+                /* Increment offset in dataspace */
+                curr_off+=elmt_size;
+
+                /* Decrement number of bytes left in sequence */
+                curr_len-=elmt_size;
+            } /* end while */
+        } /* end for */
 
-        case H5S_SEL_HYPERSLABS:     /* Hyperslab selection defined */
-            ret_value=H5S_hyper_select_iterate(buf,type_id,space,op,operator_data);
-            break;
+        /* Decrement number of elements left to process */
+        assert((nbytes%elmt_size)==0);
+        max_bytes-=nbytes;
+    } /* end while */
 
-        case H5S_SEL_ALL:            /* Entire extent selected */
-            ret_value=H5S_all_select_iterate(buf,type_id,space,op,operator_data);
-            break;
+    /* Set return value */
+    ret_value=user_ret;
 
-        case H5S_SEL_NONE:           /* Nothing selected */
-            ret_value=H5S_none_select_iterate(buf,type_id,space,op,operator_data);
-            break;
+done:
+    /* Release selection iterator */
+    if(iter!=NULL) {
+        if (H5S_sel_iter_release(space, iter)<0)
+            HGOTO_ERROR (H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "unable to release selection iterator");
+	H5FL_FREE(H5S_sel_iter_t,iter);
+    } /* end if */
 
-        case H5S_SEL_ERROR:
-        case H5S_SEL_N:
-            break;
-    }
+    /* Release length & offset vectors */
+    if(len!=NULL)
+        H5FL_ARR_FREE(size_t,len);
+    if(off!=NULL)
+        H5FL_ARR_FREE(hsize_t,off);
 
     FUNC_LEAVE(ret_value);
 }   /* end H5S_select_iterate() */
@@ -1565,10 +1732,21 @@ H5S_select_regular(const H5S_t *space)
  REVISION LOG
 --------------------------------------------------------------------------*/
 herr_t
-H5S_select_fill(void *_fill, size_t fill_size, const H5S_t *space, void *buf)
+H5S_select_fill(void *_fill, size_t fill_size, const H5S_t *space, void *_buf)
 {
+    H5P_genplist_t *dx_plist;   /* Dataset transfer property list */
+    H5S_sel_iter_t *iter=NULL;  /* Selection iteration info */
+    uint8_t *buf;               /* Current location in buffer */
     void *fill=_fill;           /* Alias for fill-value buffer */
-    herr_t ret_value=FAIL;      /* return value */
+    hssize_t nelmts;            /* Number of elements in selection */
+    hsize_t *off=NULL;          /* Array to store sequence offsets */
+    size_t *len=NULL;           /* Array to store sequence lengths */
+    size_t vector_size;         /* Value for vector size */
+    size_t nseq;                /* Number of sequences generated */
+    size_t curr_seq;            /* Current sequnce being worked on */
+    size_t nbytes;              /* Number of bytes used in sequences */
+    size_t max_bytes;           /* Total number of bytes in selection */
+    herr_t ret_value=SUCCEED;   /* return value */
 
     FUNC_ENTER_NOAPI(H5S_select_fill, FAIL);
 
@@ -1579,27 +1757,151 @@ H5S_select_fill(void *_fill, size_t fill_size, const H5S_t *space, void *buf)
 
     /* Check if we need a temporary fill value buffer */
     if(fill==NULL) {
-        if (NULL==(fill = H5MM_calloc(fill_size)))
+        if (NULL==(fill = H5FL_BLK_ALLOC(type_elem,fill_size,1)))
             HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "fill value buffer allocation failed");
     } /* end if */
 
-    /* Fill the selection in the memory buffer */
+    /* Get the hyperslab vector size */
+    /* (from the default data transfer property list, for now) */
+    dx_plist = H5I_object(H5P_DATASET_XFER_DEFAULT);
+    assert(dx_plist);
+    if (H5P_get(dx_plist,H5D_XFER_HYPER_VECTOR_SIZE_NAME,&vector_size)<0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "unable to get value");
+
+    /* Allocate the vector I/O arrays */
+    if((len = H5FL_ARR_ALLOC(size_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O length vector array");
+    if((off = H5FL_ARR_ALLOC(hsize_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O offset vector array");
+
+    /* Allocate iterator */
+    if((iter = H5FL_ALLOC(H5S_sel_iter_t,1))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate selection iterator");
+
+    /* Initialize iterator */
+    if (H5S_select_iter_init(space, fill_size, iter)<0)
+        HGOTO_ERROR (H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to initialize selection iterator");
+
+    /* Get the number of elements in selection */
+    if((nelmts = H5S_get_select_npoints(space))<0)
+        HGOTO_ERROR (H5E_DATASPACE, H5E_CANTCOUNT, FAIL, "can't get number of elements selected");
+
+    /* Compute the number of bytes to process */
+    H5_CHECK_OVERFLOW(nelmts,hssize_t,size_t);
+    max_bytes=(size_t)nelmts*fill_size;
+
+    /* Loop, while elements left in selection */
+    while(max_bytes>0) {
+        /* Get the sequences of bytes */
+        if(H5S_select_get_seq_list(0,space,iter,fill_size,vector_size,max_bytes,&nseq,&nbytes,off,len)<0)
+            HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
+
+        /* Loop over sequences */
+        for(curr_seq=0; curr_seq<nseq; curr_seq++) {
+            /* Get offset in memory buffer */
+            buf=(uint8_t *)_buf+off[curr_seq];
+
+            /* Fill each sequence in memory with fill value */
+            assert((len[curr_seq]%fill_size)==0);
+            H5V_array_fill(buf, fill, fill_size, (len[curr_seq]/fill_size));
+        } /* end for */
+
+        /* Decrement number of bytes left to process */
+        max_bytes-=nbytes;
+    } /* end while */
+
+done:
+    /* Release selection iterator */
+    if(iter!=NULL) {
+        if (H5S_sel_iter_release(space, iter)<0)
+            HGOTO_ERROR (H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "unable to release selection iterator");
+	H5FL_FREE(H5S_sel_iter_t,iter);
+    } /* end if */
+
+    /* Release length & offset vectors */
+    if(len!=NULL)
+        H5FL_ARR_FREE(size_t,len);
+    if(off!=NULL)
+        H5FL_ARR_FREE(hsize_t,off);
+
+    /* Release fill value, if allocated */
+    if(_fill==NULL && fill)
+        H5FL_BLK_FREE(type_elem,fill);
+
+    FUNC_LEAVE (ret_value);
+}   /* H5S_select_fill() */
+
+
+/*--------------------------------------------------------------------------
+ NAME
+    H5S_select_get_seq_list
+ PURPOSE
+    Create a list of offsets & lengths for a selection
+ USAGE
+    herr_t H5S_select_get_file_list(flags,space,iter,flag,elem_size,maxseq,maxbytes,nseq,off,len)
+        unsigned flags;         IN: Flags for extra information about operation
+        H5S_t *space;           IN: Dataspace containing selection to use.
+        H5S_sel_iter_t *iter;   IN/OUT: Selection iterator describing last
+                                    position of interest in selection.
+        unsigned flag;          IN: Flag to indicate whether to update the
+                                    iterator or not.
+        size_t elem_size;       IN: Size of an element
+        size_t maxseq;          IN: Maximum number of sequences to generate
+        size_t maxbytes;        IN: Maximum number of bytes to include in the
+                                    generated sequences
+        size_t *nseq;           OUT: Actual number of sequences generated
+        hsize_t *off;           OUT: Array of offsets
+        hsize_t *len;           OUT: Array of lengths
+ RETURNS
+    Non-negative on success/Negative on failure.
+ DESCRIPTION
+    Use the selection in the dataspace to generate a list of byte offsets and
+    lengths for the region(s) selected.  Start/Restart from the position in the
+    ITER parameter.  Updating the iterator is controlled with the FLAG
+    parameter.  The number of sequences generated is limited by the MAXSEQ
+    parameter and the number of sequences actually generated is stored in the
+    NSEQ parameter.
+ GLOBAL VARIABLES
+ COMMENTS, BUGS, ASSUMPTIONS
+ EXAMPLES
+ REVISION LOG
+--------------------------------------------------------------------------*/
+herr_t
+H5S_select_get_seq_list(unsigned flags, const H5S_t *space,H5S_sel_iter_t *iter,
+    size_t elem_size, size_t maxseq, size_t maxbytes, size_t *nseq, size_t *nbytes,
+    hsize_t *off, size_t *len)
+{
+    herr_t ret_value=SUCCEED;      /* return value */
+
+    FUNC_ENTER_NOAPI (H5S_select_get_seq_list, FAIL);
+
+    /* Check args */
+    assert(space);
+    assert(iter);
+    assert(elem_size>0);
+    assert(maxseq>0);
+    assert(maxbytes>0);
+    assert(nseq);
+    assert(off);
+    assert(len);
+
+    /* Get the list of sequences for each type selection */
     /* [Defer (mostly) to the selection routines] */
     switch(space->select.type) {
-        case H5S_SEL_POINTS:         /* Sequence of points selected */
-            ret_value=H5S_point_select_fill(fill,fill_size,space,buf);
+        case H5S_SEL_POINTS:        /* Sequence of points selected */
+            ret_value=H5S_point_select_get_seq_list(flags,space,iter,elem_size,maxseq,maxbytes,nseq,nbytes,off,len);
             break;
 
-        case H5S_SEL_HYPERSLABS:     /* Hyperslab selection defined */
-            ret_value=H5S_hyper_select_fill(fill,fill_size,space,buf);
+        case H5S_SEL_HYPERSLABS:    /* Hyperslab selection defined */
+            ret_value=H5S_hyper_select_get_seq_list(flags,space,iter,elem_size,maxseq,maxbytes,nseq,nbytes,off,len);
             break;
 
-        case H5S_SEL_ALL:            /* Entire extent selected */
-            ret_value=H5S_all_select_fill(fill,fill_size,space,buf);
+        case H5S_SEL_ALL:           /* Entire extent selected */
+            ret_value=H5S_all_select_get_seq_list(flags,space,iter,elem_size,maxseq,maxbytes,nseq,nbytes,off,len);
             break;
 
-        case H5S_SEL_NONE:           /* Nothing selected */
-            ret_value=SUCCEED;
+        case H5S_SEL_NONE:          /* Nothing selected */
+            *nseq=0;                /* Set the number of sequences generated */
             break;
 
         case H5S_SEL_ERROR:
@@ -1608,10 +1910,891 @@ H5S_select_fill(void *_fill, size_t fill_size, const H5S_t *space, void *buf)
             break;
     } /* end switch */
 
+#ifdef LATER
 done:
-    if(_fill==NULL && fill)
-        H5MM_xfree(fill);
+#endif /* LATER */
+    FUNC_LEAVE (ret_value);
+}   /* H5S_select_get_seq_list() */
 
+
+/*-------------------------------------------------------------------------
+ * Function:	H5S_select_favail
+ *
+ * Purpose:	Figure out the optimal number of elements to transfer to/from
+ *		the file.
+ *
+ * Return:	non-negative number of elements on success, zero on
+ *		failure.
+ *
+ * Programmer:	Quincey Koziol
+ *              Wednesday, July 24, 2002
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+hsize_t
+H5S_select_favail(const H5S_t *space, const H5S_sel_iter_t *iter, hsize_t max)
+{
+    hsize_t ret_value=0;      /* Return value */
+
+    FUNC_ENTER_NOAPI (H5S_select_favail, 0);
+
+    /* Check args */
+    assert(space);
+    assert(iter);
+    assert(max>0);
+
+    /* Get the number of elements to transfer for each type of selection */
+    /* [Defer (mostly) to the selection routines] */
+    switch(space->select.type) {
+        case H5S_SEL_POINTS:        /* Sequence of points selected */
+            ret_value=H5S_point_favail(space,iter,max);
+            break;
+
+        case H5S_SEL_HYPERSLABS:    /* Hyperslab selection defined */
+            ret_value=H5S_hyper_favail(space,iter,max);
+            break;
+
+        case H5S_SEL_ALL:           /* Entire extent selected */
+            ret_value=H5S_all_favail(space,iter,max);
+            break;
+
+        case H5S_SEL_NONE:          /* Nothing selected */
+            ret_value=0;            /* Set the number of elements to transfer */
+            break;
+
+        case H5S_SEL_ERROR:
+        case H5S_SEL_N:
+            assert(0 && "Invalid selection type!");
+            break;
+    } /* end switch */
+
+#ifdef LATER
+done:
+#endif /* LATER */
     FUNC_LEAVE (ret_value);
-}   /* H5S_select_fill() */
+}   /* H5S_select_favail() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5S_select_fscat
+ *
+ * Purpose:	Scatters dataset elements from the type conversion buffer BUF
+ *		to the file F where the data points are arranged according to
+ *		the file data space FILE_SPACE and stored according to
+ *		LAYOUT and EFL. Each element is ELMT_SIZE bytes.
+ *		The caller is requesting that NELMTS elements are copied.
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Thursday, June 20, 2002
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5S_select_fscat (H5F_t *f, const struct H5O_layout_t *layout,
+                 H5P_genplist_t *dc_plist, size_t elmt_size,
+		 const H5S_t *file_space, H5S_sel_iter_t *file_iter,
+		 hsize_t nelmts, hid_t dxpl_id, const void *_buf)
+{
+    const uint8_t *buf=_buf;       /* Alias for pointer arithmetic */
+    hsize_t *off=NULL;             /* Array to store sequence offsets */
+    size_t *len=NULL;              /* Array to store sequence lengths */
+    size_t vector_size;            /* Value for vector size */
+    size_t maxbytes;               /* Number of bytes in the buffer */
+    size_t  nseq;                  /* Number of sequences generated */
+    size_t  nbytes;                /* Number of bytes used in sequences */
+    H5P_genplist_t *dx_plist;      /* Dataset transfer property list */
+    herr_t  ret_value=SUCCEED;     /* Return value */
+
+    FUNC_ENTER_NOAPI(H5S_select_fscat, FAIL);
+
+    /* Check args */
+    assert (f);
+    assert (layout);
+    assert (elmt_size>0);
+    assert (file_space);
+    assert (file_iter);
+    assert (nelmts>0);
+    assert (_buf);
+
+    /* Get the hyperslab vector size */
+    if(TRUE!=H5P_isa_class(dxpl_id,H5P_DATASET_XFER) || NULL == (dx_plist = H5I_object(dxpl_id)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a file access property list");
+    if (H5P_get(dx_plist,H5D_XFER_HYPER_VECTOR_SIZE_NAME,&vector_size)<0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "unable to get value");
+
+    /* Allocate the vector I/O arrays */
+    if((len = H5FL_ARR_ALLOC(size_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O length vector array");
+    if((off = H5FL_ARR_ALLOC(hsize_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O offset vector array");
+
+    /* Compute the number of bytes available in buffer */
+    H5_ASSIGN_OVERFLOW(maxbytes,nelmts*elmt_size,hsize_t,size_t);
+
+    /* Loop until all elements are written */
+    while(maxbytes>0) {
+        /* Get list of sequences for selection to write */
+        if(H5S_select_get_seq_list(H5S_GET_SEQ_LIST_SORTED,file_space,file_iter,elmt_size,vector_size,maxbytes,&nseq,&nbytes,off,len)<0)
+            HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
+
+        /* Write sequence list out */
+        if (H5F_seq_writev(f, dxpl_id, layout, dc_plist, file_space, elmt_size, nseq, len, off, buf)<0)
+            HGOTO_ERROR(H5E_DATASPACE, H5E_WRITEERROR, FAIL, "write error");
+
+        /* Update buffer */
+        buf += nbytes;
+
+        /* Decrement number of elements left to process */
+        assert(nbytes%elmt_size==0);
+        maxbytes -= nbytes;
+    } /* end while */
+
+done:
+    if(len!=NULL)
+        H5FL_ARR_FREE(size_t,len);
+    if(off!=NULL)
+        H5FL_ARR_FREE(hsize_t,off);
+    FUNC_LEAVE (ret_value);
+} /* H5S_select_fscat() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5S_select_fgath
+ *
+ * Purpose:	Gathers data points from file F and accumulates them in the
+ *		type conversion buffer BUF.  The LAYOUT argument describes
+ *		how the data is stored on disk and EFL describes how the data
+ *		is organized in external files.  ELMT_SIZE is the size in
+ *		bytes of a datum which this function treats as opaque.
+ *		FILE_SPACE describes the data space of the dataset on disk
+ *		and the elements that have been selected for reading (via
+ *		hyperslab, etc).  This function will copy at most NELMTS
+ *		elements.
+ *
+ * Return:	Success:	Number of elements copied.
+ *		Failure:	0
+ *
+ * Programmer:	Quincey Koziol
+ *              Monday, June 24, 2002
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+hsize_t
+H5S_select_fgath (H5F_t *f, const struct H5O_layout_t *layout,
+               H5P_genplist_t *dc_plist,
+	       size_t elmt_size, const H5S_t *file_space,
+	       H5S_sel_iter_t *file_iter, hsize_t nelmts, hid_t dxpl_id,
+	       void *_buf/*out*/)
+{
+    uint8_t *buf=_buf;          /* Alias for pointer arithmetic */
+    hsize_t *off=NULL;          /* Array to store sequence offsets */
+    size_t *len=NULL;           /* Array to store sequence lengths */
+    size_t vector_size;         /* Value for vector size */
+    size_t maxbytes;            /* Number of bytes in the buffer */
+    size_t nseq;                /* Number of sequences generated */
+    size_t nbytes;              /* Number of bytes used in sequences */
+    H5P_genplist_t *dx_plist;   /* Dataset transfer property list */
+    hsize_t ret_value=nelmts;   /* Return value */
+
+    FUNC_ENTER_NOAPI(H5S_select_fgath, 0);
+
+    /* Check args */
+    assert (f);
+    assert (layout);
+    assert (elmt_size>0);
+    assert (file_space);
+    assert (file_iter);
+    assert (nelmts>0);
+    assert (_buf);
+
+    /* Get the hyperslab vector size */
+    if(TRUE!=H5P_isa_class(dxpl_id,H5P_DATASET_XFER) || NULL == (dx_plist = H5I_object(dxpl_id)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, 0, "not a file access property list");
+    if (H5P_get(dx_plist,H5D_XFER_HYPER_VECTOR_SIZE_NAME,&vector_size)<0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, 0, "unable to get value");
+
+    /* Allocate the vector I/O arrays */
+    if((len = H5FL_ARR_ALLOC(size_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, 0, "can't allocate I/O length vector array");
+    if((off = H5FL_ARR_ALLOC(hsize_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, 0, "can't allocate I/O offset vector array");
+
+    /* Compute the number of bytes available in buffer */
+    H5_ASSIGN_OVERFLOW(maxbytes,nelmts*elmt_size,hsize_t,size_t);
+
+    /* Loop until all elements are written */
+    while(maxbytes>0) {
+        /* Get list of sequences for selection to write */
+        if(H5S_select_get_seq_list(H5S_GET_SEQ_LIST_SORTED,file_space,file_iter,elmt_size,vector_size,maxbytes,&nseq,&nbytes,off,len)<0)
+            HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, 0, "sequence length generation failed");
+
+        /* Read sequence list in */
+        if (H5F_seq_readv(f, dxpl_id, layout, dc_plist, file_space, elmt_size, nseq, len, off, buf)<0)
+            HGOTO_ERROR(H5E_DATASPACE, H5E_READERROR, 0, "read error");
+
+        /* Update buffer */
+        buf += nbytes;
+
+        /* Decrement number of elements left to process */
+        assert(nbytes%elmt_size==0);
+        maxbytes -= nbytes;
+    } /* end while */
+
+done:
+    if(len!=NULL)
+        H5FL_ARR_FREE(size_t,len);
+    if(off!=NULL)
+        H5FL_ARR_FREE(hsize_t,off);
+    FUNC_LEAVE (ret_value);
+} /* H5S_select_fgath() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5S_select_mscat
+ *
+ * Purpose:	Scatters NELMTS data points from the scatter buffer
+ *		TSCAT_BUF to the application buffer BUF.  Each element is
+ *		ELMT_SIZE bytes and they are organized in application memory
+ *		according to SPACE.
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Monday, July 8, 2002
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5S_select_mscat (const void *_tscat_buf, size_t elmt_size, const H5S_t *space,
+    H5S_sel_iter_t *iter, hsize_t nelmts, hid_t dxpl_id, void *_buf/*out*/)
+{
+    H5P_genplist_t *dx_plist;   /* Dataset transfer property list */
+    uint8_t *buf=(uint8_t *)_buf;   /* Get local copies for address arithmetic */
+    const uint8_t *tscat_buf=(const uint8_t *)_tscat_buf;
+    hsize_t *off=NULL;          /* Array to store sequence offsets */
+    size_t vector_size;         /* Value for vector size */
+    size_t *len=NULL;           /* Array to store sequence lengths */
+    size_t curr_len;            /* Length of bytes left to process in sequence */
+    size_t maxbytes;            /* Number of bytes in the buffer */
+    size_t nseq;                /* Number of sequences generated */
+    size_t curr_seq;            /* Current sequence being processed */
+    size_t nbytes;              /* Number of bytes used in sequences */
+    herr_t ret_value=SUCCEED;   /* Number of elements scattered */
+
+    FUNC_ENTER_NOAPI(H5S_select_mscat, FAIL);
+
+    /* Check args */
+    assert (tscat_buf);
+    assert (elmt_size>0);
+    assert (space);
+    assert (iter);
+    assert (nelmts>0);
+    assert (buf);
+
+    /* Get the hyperslab vector size */
+    if(TRUE!=H5P_isa_class(dxpl_id,H5P_DATASET_XFER) || NULL == (dx_plist = H5I_object(dxpl_id)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset transfer property list");
+    if (H5P_get(dx_plist,H5D_XFER_HYPER_VECTOR_SIZE_NAME,&vector_size)<0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "unable to get value");
+
+    /* Allocate the vector I/O arrays */
+    if((len = H5FL_ARR_ALLOC(size_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O length vector array");
+    if((off = H5FL_ARR_ALLOC(hsize_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O offset vector array");
+
+    /* Compute the number of bytes available in buffer */
+    H5_ASSIGN_OVERFLOW(maxbytes,nelmts*elmt_size,hsize_t,size_t);
+
+    /* Loop until all elements are written */
+    while(maxbytes>0) {
+        /* Get list of sequences for selection to write */
+        if(H5S_select_get_seq_list(0,space,iter,elmt_size,vector_size,maxbytes,&nseq,&nbytes,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 in sequence */
+            curr_len=len[curr_seq];
+
+            HDmemcpy(buf+off[curr_seq],tscat_buf,curr_len);
+
+            /* Advance offset in destination buffer */
+            tscat_buf+=curr_len;
+        } /* end for */
+
+        /* Decrement number of elements left to process */
+        assert(nbytes%elmt_size==0);
+        maxbytes -= nbytes;
+    } /* end while */
+
+done:
+    if(len!=NULL)
+        H5FL_ARR_FREE(size_t,len);
+    if(off!=NULL)
+        H5FL_ARR_FREE(hsize_t,off);
+    FUNC_LEAVE(ret_value);
+}   /* H5S_select_mscat() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5S_select_mgath
+ *
+ * Purpose:	Gathers dataset elements from application memory BUF and
+ *		copies them into the gather buffer TGATH_BUF.
+ *		Each element is ELMT_SIZE bytes and arranged in application
+ *		memory according to SPACE.  
+ *		The caller is requesting that at most NELMTS be gathered.
+ *
+ * Return:	Success:	Number of elements copied.
+ *		Failure:	0
+ *
+ * Programmer:	Quincey Koziol
+ *              Monday, June 24, 2002
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+hsize_t
+H5S_select_mgath (const void *_buf, size_t elmt_size, const H5S_t *space,
+    H5S_sel_iter_t *iter, hsize_t nelmts, hid_t dxpl_id, void *_tgath_buf/*out*/)
+{
+    H5P_genplist_t *dx_plist;   /* Dataset transfer property list */
+    const uint8_t *buf=(const uint8_t *)_buf;   /* Get local copies for address arithmetic */
+    uint8_t *tgath_buf=(uint8_t *)_tgath_buf;
+    hsize_t *off=NULL;          /* Array to store sequence offsets */
+    size_t vector_size;         /* Value for vector size */
+    size_t *len=NULL;           /* Array to store sequence lengths */
+    size_t curr_len;            /* Length of bytes left to process in sequence */
+    size_t maxbytes;            /* Number of bytes in the buffer */
+    size_t nseq;                /* Number of sequences generated */
+    size_t curr_seq;            /* Current sequence being processed */
+    size_t nbytes;              /* Number of bytes used in sequences */
+    hsize_t ret_value=nelmts;   /* Number of elements gathered */
+
+    FUNC_ENTER_NOAPI(H5S_select_mgath, 0);
+
+    /* Check args */
+    assert (buf);
+    assert (elmt_size>0);
+    assert (space);
+    assert (iter);
+    assert (nelmts>0);
+    assert (tgath_buf);
+
+    /* Get the hyperslab vector size */
+    if(TRUE!=H5P_isa_class(dxpl_id,H5P_DATASET_XFER) || NULL == (dx_plist = H5I_object(dxpl_id)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, 0, "not a dataset transfer property list");
+    if (H5P_get(dx_plist,H5D_XFER_HYPER_VECTOR_SIZE_NAME,&vector_size)<0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, 0, "unable to get value");
+
+    /* Allocate the vector I/O arrays */
+    if((len = H5FL_ARR_ALLOC(size_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, 0, "can't allocate I/O length vector array");
+    if((off = H5FL_ARR_ALLOC(hsize_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, 0, "can't allocate I/O offset vector array");
+
+    /* Compute the number of bytes available in buffer */
+    H5_ASSIGN_OVERFLOW(maxbytes,nelmts*elmt_size,hsize_t,size_t);
+
+    /* Loop until all elements are written */
+    while(maxbytes>0) {
+        /* Get list of sequences for selection to write */
+        if(H5S_select_get_seq_list(0,space,iter,elmt_size,vector_size,maxbytes,&nseq,&nbytes,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 in sequence */
+            curr_len=len[curr_seq];
+
+            HDmemcpy(tgath_buf,buf+off[curr_seq],curr_len);
+
+            /* Advance offset in gather buffer */
+            tgath_buf+=curr_len;
+        } /* end for */
+
+        /* Decrement number of elements left to process */
+        assert(nbytes%elmt_size==0);
+        maxbytes -= nbytes;
+    } /* end while */
+
+done:
+    if(len!=NULL)
+        H5FL_ARR_FREE(size_t,len);
+    if(off!=NULL)
+        H5FL_ARR_FREE(hsize_t,off);
+    FUNC_LEAVE(ret_value);
+}   /* H5S_select_mgath() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5S_select_read
+ *
+ * Purpose:	Reads directly from file into application memory.
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Tuesday, July 23, 2002
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5S_select_read(H5F_t *f, const H5O_layout_t *layout, H5P_genplist_t *dc_plist,
+            size_t elmt_size, const H5S_t *file_space,
+	    const H5S_t *mem_space, hid_t dxpl_id, void *_buf/*out*/)
+{
+    H5P_genplist_t *dx_plist;   /* Dataset transfer property list */
+    H5S_sel_iter_t *mem_iter=NULL;   /* Memory selection iteration info */
+    H5S_sel_iter_t *file_iter=NULL;  /* File selection iteration info */
+    uint8_t *buf;               /* Local buffer pointer, for address arithmetic */
+    hsize_t *mem_off=NULL;      /* Array to store sequence offsets in memory */
+    hsize_t *file_off=NULL;     /* Array to store sequence offsets in the file */
+    size_t vector_size;         /* Value for vector size */
+    size_t *mem_len=NULL;       /* Array to store sequence lengths in memory */
+    size_t *file_len=NULL;      /* Array to store sequence lengths in the file */
+    size_t maxbytes;            /* Number of bytes in selection */
+    size_t mem_nseq;            /* Number of sequences generated in the file */
+    size_t file_nseq;           /* Number of sequences generated in memory */
+    size_t mem_nbytes;          /* Number of bytes used in memory sequences */
+    size_t file_nbytes;         /* Number of bytes used in file sequences */
+    size_t curr_mem_seq;        /* Current memory sequence to operate on */
+    size_t curr_file_seq;       /* Current file sequence to operate on */
+    size_t tmp_file_len;        /* Temporary number of bytes in file sequence */
+    unsigned partial_file;      /* Whether a partial file sequence was accessed */
+    size_t orig_file_len;       /* Original file sequence length for partial file access */
+    size_t orig_file_seq;       /* Original file sequence to operate on */
+    size_t tot_file_seq;        /* Number of file sequences to access */
+    herr_t ret_value=SUCCEED;   /* Return value */
+
+    FUNC_ENTER_NOAPI(H5S_select_read, FAIL);
+
+    /* Get the hyperslab vector size */
+    if(TRUE!=H5P_isa_class(dxpl_id,H5P_DATASET_XFER) || NULL == (dx_plist = H5I_object(dxpl_id)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset transfer property list");
+    if (H5P_get(dx_plist,H5D_XFER_HYPER_VECTOR_SIZE_NAME,&vector_size)<0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "unable to get value");
+
+    /* Allocate the vector I/O arrays */
+    if((mem_len = H5FL_ARR_ALLOC(size_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O length vector array");
+    if((mem_off = H5FL_ARR_ALLOC(hsize_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O offset vector array");
+    if((file_len = H5FL_ARR_ALLOC(size_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O length vector array");
+    if((file_off = H5FL_ARR_ALLOC(hsize_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O offset vector array");
+
+    /* Allocate file iterator */
+    if((file_iter = H5FL_ALLOC(H5S_sel_iter_t,1))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate selection iterator");
+
+    /* Initialize file iterator */
+    if (H5S_select_iter_init(file_space, elmt_size, file_iter)<0)
+        HGOTO_ERROR (H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to initialize selection iterator");
+
+    /* Allocate memory iterator */
+    if((mem_iter = H5FL_ALLOC(H5S_sel_iter_t,1))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate selection iterator");
+
+    /* Initialize memory iterator */
+    if (H5S_select_iter_init(mem_space, elmt_size, mem_iter)<0)
+        HGOTO_ERROR (H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to initialize selection iterator");
+
+    /* Get number of bytes in selection */
+    maxbytes=H5S_get_select_npoints(file_space)*elmt_size;
+
+    /* Initialize sequence counts */
+    curr_mem_seq=curr_file_seq=0;
+    mem_nseq=file_nseq=0;
+
+    /* Loop, until all bytes are processed */
+    while(maxbytes>0) {
+        /* Check if more file sequences are needed */
+        if(curr_file_seq>=file_nseq) {
+            /* Get sequences for file selection */
+            if(H5S_select_get_seq_list(H5S_GET_SEQ_LIST_SORTED,file_space,file_iter,elmt_size,vector_size,maxbytes,&file_nseq,&file_nbytes,file_off,file_len)<0)
+                HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
+
+            /* Start at the beginning of the sequences again */
+            curr_file_seq=0;
+        } /* end if */
+
+        /* Check if more memory sequences are needed */
+        if(curr_mem_seq>=mem_nseq) {
+            /* Get sequences for memory selection */
+            if(H5S_select_get_seq_list(0,mem_space,mem_iter,elmt_size,vector_size,maxbytes,&mem_nseq,&mem_nbytes,mem_off,mem_len)<0)
+                HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
+
+            /* Start at the beginning of the sequences again */
+            curr_mem_seq=0;
+
+            /* Set the buffer pointer using the first sequence */
+            H5_CHECK_OVERFLOW(mem_off[0],hsize_t,size_t);
+            buf=(uint8_t *)_buf+(size_t)mem_off[0];
+        } /* end if */
+
+        /* Check if current file sequence will fit into current memory sequence */
+        if(mem_len[curr_mem_seq]>=file_len[curr_file_seq]) {
+            /* Save the current number file sequence */
+            orig_file_seq=curr_file_seq;
+
+            /* Determine how many file sequences will fit into current memory sequence */
+            tmp_file_len=0;
+            tot_file_seq=0;
+            while((tmp_file_len+file_len[curr_file_seq])<=mem_len[curr_mem_seq] && curr_file_seq<file_nseq) {
+                tmp_file_len+=file_len[curr_file_seq];
+                curr_file_seq++;
+                tot_file_seq++;
+            } /* end while */
+
+            /* Check for partial file sequence */
+            if(tmp_file_len<mem_len[curr_mem_seq] && curr_file_seq<file_nseq) {
+                /* Get the original file sequence length */
+                orig_file_len=file_len[curr_file_seq];
+
+                /* Make the last file sequence a partial access */
+                file_len[curr_file_seq]=mem_len[curr_mem_seq]-tmp_file_len;
+
+                /* Increase the number of bytes to access */
+                tmp_file_len=mem_len[curr_mem_seq];
+
+                /* Indicate that there is an extra sequence to include in the file access */
+                tot_file_seq++;
+
+                /* Indicate a partial file sequence */
+                partial_file=1;
+            } /* end if */
+            else
+                partial_file=0;
+
+            /* Read file sequences into current memory sequence */
+            if (H5F_seq_readv(f, dxpl_id, layout, dc_plist, file_space, elmt_size, tot_file_seq, &file_len[orig_file_seq], &file_off[orig_file_seq], buf)<0)
+                HGOTO_ERROR(H5E_DATASPACE, H5E_READERROR, FAIL, "read error");
+
+            /* Update last file sequence, if it was partially accessed */
+            if(partial_file) {
+                file_off[curr_file_seq]+=orig_file_len-file_len[curr_file_seq];
+                file_len[curr_file_seq]=orig_file_len-file_len[curr_file_seq];
+            } /* end if */
+
+            /* Check if the current memory sequence was only partially accessed */
+            if(tmp_file_len<mem_len[curr_mem_seq]) {
+                /* Adjust current memory sequence */
+                mem_off[curr_mem_seq]+=tmp_file_len;
+                mem_len[curr_mem_seq]-=tmp_file_len;
+
+                /* Adjust memory buffer pointer */
+                buf+=tmp_file_len;
+            } /* end if */
+            else {
+                /* Must have used entire memory sequence, advance to next one */
+                curr_mem_seq++;
+
+                /* Check if it is valid to adjust buffer pointer */
+                if(curr_mem_seq<mem_nseq) {
+                    H5_CHECK_OVERFLOW(mem_off[curr_mem_seq],hsize_t,size_t);
+                    buf=(uint8_t *)_buf+(size_t)mem_off[curr_mem_seq];
+                } /* end if */
+            } /* end else */
+
+            /* Decrement number of bytes left to process */
+            maxbytes-=tmp_file_len;
+        } /* end if */
+        else {
+            /* Save number of bytes to access */
+            tmp_file_len=mem_len[curr_mem_seq];
+
+            /* Read part of current file sequence into current memory sequence */
+            if (H5F_seq_read(f, dxpl_id, layout, dc_plist, file_space, elmt_size, tmp_file_len, file_off[curr_file_seq], buf)<0)
+                HGOTO_ERROR(H5E_DATASPACE, H5E_READERROR, FAIL, "read error");
+
+            /* Update current file sequence information */
+            file_off[curr_file_seq]+=tmp_file_len;
+            file_len[curr_file_seq]-=tmp_file_len;
+
+            /* Increment memory sequence */
+            curr_mem_seq++;
+
+            /* Check if it is valid to adjust buffer pointer */
+            if(curr_mem_seq<mem_nseq) {
+                H5_CHECK_OVERFLOW(mem_off[curr_mem_seq],hsize_t,size_t);
+                buf=(uint8_t *)_buf+(size_t)mem_off[curr_mem_seq];
+            } /* end if */
+
+            /* Decrement number of bytes left to process */
+            maxbytes-=tmp_file_len;
+        } /* end else */
+    } /* end while */
+
+done:
+    /* Release file selection iterator */
+    if(file_iter!=NULL) {
+        if (H5S_sel_iter_release(file_space, file_iter)<0)
+            HGOTO_ERROR (H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "unable to release selection iterator");
+	H5FL_FREE(H5S_sel_iter_t,file_iter);
+    } /* end if */
+
+    /* Release memory selection iterator */
+    if(mem_iter!=NULL) {
+        if (H5S_sel_iter_release(mem_space, mem_iter)<0)
+            HGOTO_ERROR (H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "unable to release selection iterator");
+	H5FL_FREE(H5S_sel_iter_t,mem_iter);
+    } /* end if */
+
+    /* Free vector arrays */
+    if(file_len!=NULL)
+        H5FL_ARR_FREE(size_t,file_len);
+    if(file_off!=NULL)
+        H5FL_ARR_FREE(hsize_t,file_off);
+    if(mem_len!=NULL)
+        H5FL_ARR_FREE(size_t,mem_len);
+    if(mem_off!=NULL)
+        H5FL_ARR_FREE(hsize_t,mem_off);
+    FUNC_LEAVE(ret_value);
+} /* end H5S_select_read() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5S_select_write
+ *
+ * Purpose:	Writes directly from application memory into a file
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Tuesday, July 23, 2002
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5S_select_write(H5F_t *f, const H5O_layout_t *layout, H5P_genplist_t *dc_plist,
+            size_t elmt_size, const H5S_t *file_space,
+	    const H5S_t *mem_space, hid_t dxpl_id, const void *_buf/*out*/)
+{
+    H5P_genplist_t *dx_plist;   /* Dataset transfer property list */
+    H5S_sel_iter_t *mem_iter=NULL;   /* Memory selection iteration info */
+    H5S_sel_iter_t *file_iter=NULL;  /* File selection iteration info */
+    const uint8_t *buf;         /* Local buffer pointer, for address arithmetic */
+    hsize_t *mem_off=NULL;      /* Array to store sequence offsets in memory */
+    hsize_t *file_off=NULL;     /* Array to store sequence offsets in the file */
+    size_t vector_size;         /* Value for vector size */
+    size_t *mem_len=NULL;       /* Array to store sequence lengths in memory */
+    size_t *file_len=NULL;      /* Array to store sequence lengths in the file */
+    size_t maxbytes;            /* Number of bytes in selection */
+    size_t mem_nseq;            /* Number of sequences generated in the file */
+    size_t file_nseq;           /* Number of sequences generated in memory */
+    size_t mem_nbytes;          /* Number of bytes used in memory sequences */
+    size_t file_nbytes;         /* Number of bytes used in file sequences */
+    size_t curr_mem_seq;        /* Current memory sequence to operate on */
+    size_t curr_file_seq;       /* Current file sequence to operate on */
+    size_t tmp_file_len;        /* Temporary number of bytes in file sequence */
+    unsigned partial_file;      /* Whether a partial file sequence was accessed */
+    size_t orig_file_len;       /* Original file sequence length for partial file access */
+    size_t orig_file_seq;       /* Original file sequence to operate on */
+    size_t tot_file_seq;        /* Number of file sequences to access */
+    herr_t ret_value=SUCCEED;   /* Return value */
+
+    FUNC_ENTER_NOAPI(H5S_select_write, FAIL);
+
+    /* Get the hyperslab vector size */
+    if(TRUE!=H5P_isa_class(dxpl_id,H5P_DATASET_XFER) || NULL == (dx_plist = H5I_object(dxpl_id)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset transfer property list");
+    if (H5P_get(dx_plist,H5D_XFER_HYPER_VECTOR_SIZE_NAME,&vector_size)<0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "unable to get value");
+
+    /* Allocate the vector I/O arrays */
+    if((mem_len = H5FL_ARR_ALLOC(size_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O length vector array");
+    if((mem_off = H5FL_ARR_ALLOC(hsize_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O offset vector array");
+    if((file_len = H5FL_ARR_ALLOC(size_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O length vector array");
+    if((file_off = H5FL_ARR_ALLOC(hsize_t,vector_size,0))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate I/O offset vector array");
+
+    /* Allocate file iterator */
+    if((file_iter = H5FL_ALLOC(H5S_sel_iter_t,1))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate selection iterator");
+
+    /* Initialize file iterator */
+    if (H5S_select_iter_init(file_space, elmt_size, file_iter)<0)
+        HGOTO_ERROR (H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to initialize selection iterator");
+
+    /* Allocate memory iterator */
+    if((mem_iter = H5FL_ALLOC(H5S_sel_iter_t,1))==NULL)
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't allocate selection iterator");
+
+    /* Initialize memory iterator */
+    if (H5S_select_iter_init(mem_space, elmt_size, mem_iter)<0)
+        HGOTO_ERROR (H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to initialize selection iterator");
+
+    /* Get number of bytes in selection */
+    maxbytes=H5S_get_select_npoints(file_space)*elmt_size;
+
+    /* Initialize sequence counts */
+    curr_mem_seq=curr_file_seq=0;
+    mem_nseq=file_nseq=0;
+
+    /* Loop, until all bytes are processed */
+    while(maxbytes>0) {
+        /* Check if more file sequences are needed */
+        if(curr_file_seq>=file_nseq) {
+            /* Get sequences for file selection */
+            if(H5S_select_get_seq_list(H5S_GET_SEQ_LIST_SORTED,file_space,file_iter,elmt_size,vector_size,maxbytes,&file_nseq,&file_nbytes,file_off,file_len)<0)
+                HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
+
+            /* Start at the beginning of the sequences again */
+            curr_file_seq=0;
+        } /* end if */
+
+        /* Check if more memory sequences are needed */
+        if(curr_mem_seq>=mem_nseq) {
+            /* Get sequences for memory selection */
+            if(H5S_select_get_seq_list(0,mem_space,mem_iter,elmt_size,vector_size,maxbytes,&mem_nseq,&mem_nbytes,mem_off,mem_len)<0)
+                HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
+
+            /* Start at the beginning of the sequences again */
+            curr_mem_seq=0;
+
+            /* Set the buffer pointer using the first sequence */
+            H5_CHECK_OVERFLOW(mem_off[0],hsize_t,size_t);
+            buf=(const uint8_t *)_buf+(size_t)mem_off[0];
+        } /* end if */
+
+        /* Check if current file sequence will fit into current memory sequence */
+        if(mem_len[curr_mem_seq]>=file_len[curr_file_seq]) {
+            /* Save the current number file sequence */
+            orig_file_seq=curr_file_seq;
+
+            /* Determine how many file sequences will fit into current memory sequence */
+            tmp_file_len=0;
+            tot_file_seq=0;
+            while((tmp_file_len+file_len[curr_file_seq])<=mem_len[curr_mem_seq] && curr_file_seq<file_nseq) {
+                tmp_file_len+=file_len[curr_file_seq];
+                curr_file_seq++;
+                tot_file_seq++;
+            } /* end while */
+
+            /* Check for partial file sequence */
+            if(tmp_file_len<mem_len[curr_mem_seq] && curr_file_seq<file_nseq) {
+                /* Get the original file sequence length */
+                orig_file_len=file_len[curr_file_seq];
+
+                /* Make the last file sequence a partial access */
+                file_len[curr_file_seq]=mem_len[curr_mem_seq]-tmp_file_len;
+
+                /* Increase the number of bytes to access */
+                tmp_file_len=mem_len[curr_mem_seq];
+
+                /* Indicate that there is an extra sequence to include in the file access */
+                tot_file_seq++;
+
+                /* Indicate a partial file sequence */
+                partial_file=1;
+            } /* end if */
+            else
+                partial_file=0;
+
+            /* Write current memory sequence into file sequences */
+            if (H5F_seq_writev(f, dxpl_id, layout, dc_plist, file_space, elmt_size, tot_file_seq, &file_len[orig_file_seq], &file_off[orig_file_seq], buf)<0)
+                HGOTO_ERROR(H5E_DATASPACE, H5E_WRITEERROR, FAIL, "write error");
+
+            /* Update last file sequence, if it was partially accessed */
+            if(partial_file) {
+                file_off[curr_file_seq]+=orig_file_len-file_len[curr_file_seq];
+                file_len[curr_file_seq]=orig_file_len-file_len[curr_file_seq];
+            } /* end if */
+
+            /* Check if the current memory sequence was only partially accessed */
+            if(tmp_file_len<mem_len[curr_mem_seq]) {
+                /* Adjust current memory sequence */
+                mem_off[curr_mem_seq]+=tmp_file_len;
+                mem_len[curr_mem_seq]-=tmp_file_len;
+
+                /* Adjust memory buffer pointer */
+                buf+=tmp_file_len;
+            } /* end if */
+            else {
+                /* Must have used entire memory sequence, advance to next one */
+                curr_mem_seq++;
+
+                /* Check if it is valid to adjust buffer pointer */
+                if(curr_mem_seq<mem_nseq) {
+                    H5_CHECK_OVERFLOW(mem_off[curr_mem_seq],hsize_t,size_t);
+                    buf=(const uint8_t *)_buf+(size_t)mem_off[curr_mem_seq];
+                } /* end if */
+            } /* end else */
+
+            /* Decrement number of bytes left to process */
+            maxbytes-=tmp_file_len;
+        } /* end if */
+        else {
+            /* Save number of bytes to access */
+            tmp_file_len=mem_len[curr_mem_seq];
+
+            /* Write part of current memory sequence to current file sequence */
+            if (H5F_seq_write(f, dxpl_id, layout, dc_plist, file_space, elmt_size, tmp_file_len, file_off[curr_file_seq], buf)<0)
+                HGOTO_ERROR(H5E_DATASPACE, H5E_WRITEERROR, FAIL, "write error");
+
+            /* Update current file sequence information */
+            file_off[curr_file_seq]+=tmp_file_len;
+            file_len[curr_file_seq]-=tmp_file_len;
+
+            /* Increment memory sequence */
+            curr_mem_seq++;
+
+            /* Check if it is valid to adjust buffer pointer */
+            if(curr_mem_seq<mem_nseq) {
+                H5_CHECK_OVERFLOW(mem_off[curr_mem_seq],hsize_t,size_t);
+                buf=(const uint8_t *)_buf+(size_t)mem_off[curr_mem_seq];
+            } /* end if */
+
+            /* Decrement number of bytes left to process */
+            maxbytes-=tmp_file_len;
+        } /* end else */
+    } /* end while */
+
+done:
+    /* Release file selection iterator */
+    if(file_iter!=NULL) {
+        if (H5S_sel_iter_release(file_space, file_iter)<0)
+            HGOTO_ERROR (H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "unable to release selection iterator");
+	H5FL_FREE(H5S_sel_iter_t,file_iter);
+    } /* end if */
+
+    /* Release memory selection iterator */
+    if(mem_iter!=NULL) {
+        if (H5S_sel_iter_release(mem_space, mem_iter)<0)
+            HGOTO_ERROR (H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "unable to release selection iterator");
+	H5FL_FREE(H5S_sel_iter_t,mem_iter);
+    } /* end if */
+
+    /* Free vector arrays */
+    if(file_len!=NULL)
+        H5FL_ARR_FREE(size_t,file_len);
+    if(file_off!=NULL)
+        H5FL_ARR_FREE(hsize_t,file_off);
+    if(mem_len!=NULL)
+        H5FL_ARR_FREE(size_t,mem_len);
+    if(mem_off!=NULL)
+        H5FL_ARR_FREE(hsize_t,mem_off);
+    FUNC_LEAVE(ret_value);
+} /* end H5S_select_write() */