path: root/src/H5Dio.c

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by The HDF Group.                                               *
 * Copyright by the Board of Trustees of the University of Illinois.         *
 * All rights reserved.                                                      *
 *                                                                           *
 * This file is part of HDF5.  The full HDF5 copyright notice, including     *
 * terms governing use, modification, and redistribution, is contained in    *
 * the COPYING file, which can be found at the root of the source code       *
 * distribution tree, or in https://www.hdfgroup.org/licenses.               *
 * If you do not have access to either file, you may request a copy from     *
 * help@hdfgroup.org.                                                        *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/****************/
/* Module Setup */
/****************/

#include "H5Dmodule.h" /* This source code file is part of the H5D module */

/***********/
/* Headers */
/***********/
#include "H5private.h"   /* Generic Functions                        */
#include "H5CXprivate.h" /* API Contexts                             */
#include "H5Dpkg.h"      /* Dataset functions                        */
#include "H5Eprivate.h"  /* Error handling                           */
#include "H5FLprivate.h" /* Free Lists                               */
#include "H5Iprivate.h"  /* IDs                                      */
#include "H5MMprivate.h" /* Memory management                        */
#include "H5Sprivate.h"  /* Dataspace                                */

#ifdef H5_HAVE_PARALLEL
/* Remove this if H5R_DATASET_REGION is no longer used in this file */
#include "H5Rpublic.h"
#endif /*H5_HAVE_PARALLEL*/

/****************/
/* Local Macros */
/****************/

/******************/
/* Local Typedefs */
/******************/

/********************/
/* Local Prototypes */
/********************/

/* Setup/teardown routines */
static herr_t H5D__get_offset_copy(const H5D_t *dset, const hsize_t *offset, hsize_t *offset_copy /*out*/);
static herr_t H5D__ioinfo_init(H5D_t *dset, 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, 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 H5S_t *file_space,
                                 const H5S_t *mem_space, const H5D_type_info_t *type_info);
#endif /* H5_HAVE_PARALLEL */
static herr_t H5D__typeinfo_term(const H5D_type_info_t *type_info);

/*********************/
/* Package Variables */
/*********************/

/*******************/
/* Local Variables */
/*******************/

/* 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_map_t struct */
H5FL_DEFINE(H5D_chunk_map_t);

/*-------------------------------------------------------------------------
 * Function:    H5D__get_offset_copy
 *
 * Purpose:     Gets a copy of the user's offset array that is guaraneteed
 *              to be suitable for use by the library.
 *
 * Return:      SUCCEED/FAIL
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__get_offset_copy(const H5D_t *dset, const hsize_t *offset, hsize_t *offset_copy)
{
    unsigned u;
    herr_t   ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_NOAPI(FAIL)

    HDassert(dset);
    HDassert(offset);
    HDassert(offset_copy);

    /* The library's chunking code requires the offset to terminate with a zero.
     * So transfer the offset array to an internal offset array that we
     * can properly terminate (handled via the calloc call).
     */

    HDmemset(offset_copy, 0, H5O_LAYOUT_NDIMS * sizeof(hsize_t));

    for (u = 0; u < dset->shared->ndims; u++) {
        /* Make sure the offset doesn't exceed the dataset's dimensions */
        if (offset[u] > dset->shared->curr_dims[u])
            HGOTO_ERROR(H5E_DATASPACE, H5E_BADTYPE, FAIL, "offset exceeds dimensions of dataset")

        /* Make sure the offset fall right on a chunk's boundary */
        if (offset[u] % dset->shared->layout.u.chunk.dim[u])
            HGOTO_ERROR(H5E_DATASPACE, H5E_BADTYPE, FAIL, "offset doesn't fall on chunks's boundary")

        offset_copy[u] = offset[u];
    }

done:
    FUNC_LEAVE_NOAPI(ret_value)

} /* end H5D__get_offset_copy() */

/*-------------------------------------------------------------------------
 * Function:    H5Dread
 *
 * Purpose:     Reads (part of) a DSET from the file into application
 *              memory BUF. The part of the dataset to read is defined with
 *              MEM_SPACE_ID and FILE_SPACE_ID. The data points are
 *              converted from their file type to the MEM_TYPE_ID specified.
 *              Additional miscellaneous data transfer properties can be
 *              passed to this function with the PLIST_ID argument.
 *
 *              The FILE_SPACE_ID can be the constant H5S_ALL which indicates
 *              that the entire file dataspace is to be referenced.
 *
 *              The MEM_SPACE_ID can be the constant H5S_ALL in which case
 *              the memory dataspace is the same as the file dataspace
 *              defined when the dataset was created.
 *
 *              The number of elements in the memory dataspace must match
 *              the number of elements in the file dataspace.
 *
 *              The PLIST_ID can be the constant H5P_DEFAULT in which
 *              case the default data transfer properties are used.
 *
 * Return:      Non-negative on success/Negative on failure
 *
 * Programmer:  Robb Matzke
 *              Thursday, December 4, 1997
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Dread(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id, hid_t file_space_id, hid_t dxpl_id,
        void *buf /*out*/)
{
    H5D_t *dset       = NULL;
    H5S_t *mem_space  = NULL;
    H5S_t *file_space = NULL;
    herr_t ret_value  = SUCCEED; /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE6("e", "iiiiix", dset_id, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf);

    /* Get dataset pointer */
    if (NULL == (dset = (H5D_t *)H5I_object_verify(dset_id, H5I_DATASET)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "dset_id is not a dataset ID")
    if (NULL == dset->oloc.file)
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "dataset is not associated with a file")

    /* Get validated dataspace pointers */
    if (H5S_get_validated_dataspace(mem_space_id, &mem_space) < 0)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "could not get a validated dataspace from mem_space_id")
    if (H5S_get_validated_dataspace(file_space_id, &file_space) < 0)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "could not get a validated dataspace from file_space_id")

    /* Get the default dataset transfer property list if the user didn't provide one */
    if (H5P_DEFAULT == dxpl_id)
        dxpl_id = H5P_DATASET_XFER_DEFAULT;
    else if (TRUE != H5P_isa_class(dxpl_id, H5P_DATASET_XFER))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not xfer parms")

    /* Set DXPL for operation */
    H5CX_set_dxpl(dxpl_id);

    /* Read the data */
    if (H5D__read(dset, mem_type_id, mem_space, file_space, buf) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read data")

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Dread() */

/*-------------------------------------------------------------------------
 * Function:    H5Dread_chunk
 *
 * Purpose:     Reads an entire chunk from the file directly.
 *
 * Return:      Non-negative on success/Negative on failure
 *
 * Programmer:  Matthew Strong (GE Healthcare)
 *              14 February 2016
 *
 *---------------------------------------------------------------------------
 */
herr_t
H5Dread_chunk(hid_t dset_id, hid_t dxpl_id, const hsize_t *offset, uint32_t *filters, void *buf)
{
    H5D_t * dset = NULL;
    hsize_t offset_copy[H5O_LAYOUT_NDIMS]; /* Internal copy of chunk offset */
    herr_t  ret_value = SUCCEED;           /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE5("e", "ii*h*Iu*x", dset_id, dxpl_id, offset, filters, buf);

    /* Check arguments */
    if (NULL == (dset = (H5D_t *)H5I_object_verify(dset_id, H5I_DATASET)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "dset_id is not a dataset ID")
    if (NULL == dset->oloc.file)
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "dataset is not associated with a file")
    if (H5D_CHUNKED != dset->shared->layout.type)
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a chunked dataset")
    if (!buf)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "buf cannot be NULL")
    if (!offset)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "offset cannot be NULL")
    if (!filters)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "filters cannot be NULL")

    /* Get the default dataset transfer property list if the user didn't provide one */
    if (H5P_DEFAULT == dxpl_id)
        dxpl_id = H5P_DATASET_XFER_DEFAULT;
    else if (TRUE != H5P_isa_class(dxpl_id, H5P_DATASET_XFER))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "dxpl_id is not a dataset transfer property list ID")

    /* Set DXPL for operation */
    H5CX_set_dxpl(dxpl_id);

    /* Copy the user's offset array so we can be sure it's terminated properly.
     * (we don't want to mess with the user's buffer).
     */
    if (H5D__get_offset_copy(dset, offset, offset_copy) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "failure to copy offset array")

    /* Read the raw chunk */
    if (H5D__chunk_direct_read(dset, offset_copy, filters, buf) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read unprocessed chunk data")

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Dread_chunk() */

/*-------------------------------------------------------------------------
 * Function:    H5Dwrite
 *
 * Purpose:     Writes (part of) a DSET from application memory BUF to the
 *              file. The part of the dataset to write is defined with the
 *              MEM_SPACE_ID and FILE_SPACE_ID arguments. The data points
 *              are converted from their current type (MEM_TYPE_ID) to their
 *              file datatype. Additional miscellaneous data transfer
 *              properties can be passed to this function with the
 *              PLIST_ID argument.
 *
 *              The FILE_SPACE_ID can be the constant H5S_ALL which indicates
 *              that the entire file dataspace is to be referenced.
 *
 *              The MEM_SPACE_ID can be the constant H5S_ALL in which case
 *              the memory dataspace is the same as the file dataspace
 *              defined when the dataset was created.
 *
 *              The number of elements in the memory dataspace must match
 *              the number of elements in the file dataspace.
 *
 *              The PLIST_ID can be the constant H5P_DEFAULT in which
 *              case the default data transfer properties are used.
 *
 * Return:      Non-negative on success/Negative on failure
 *
 * Programmer:  Robb Matzke
 *              Thursday, December 4, 1997
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Dwrite(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id, hid_t file_space_id, hid_t dxpl_id,
         const void *buf)
{
    H5D_t *dset       = NULL;
    H5S_t *mem_space  = NULL;
    H5S_t *file_space = NULL;
    herr_t ret_value  = SUCCEED; /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE6("e", "iiiii*x", dset_id, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf);

    /* Get dataset pointer and ensure it's associated with a file */
    if (NULL == (dset = (H5D_t *)H5I_object_verify(dset_id, H5I_DATASET)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "dset_id is not a dataset ID")
    if (NULL == dset->oloc.file)
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "dataset is not associated with a file")

    /* Get validated dataspace pointers */
    if (H5S_get_validated_dataspace(mem_space_id, &mem_space) < 0)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "could not get a validated dataspace from mem_space_id")
    if (H5S_get_validated_dataspace(file_space_id, &file_space) < 0)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "could not get a validated dataspace from file_space_id")

    /* Get the default dataset transfer property list if the user didn't provide one */
    if (H5P_DEFAULT == dxpl_id)
        dxpl_id = H5P_DATASET_XFER_DEFAULT;
    else if (TRUE != H5P_isa_class(dxpl_id, H5P_DATASET_XFER))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not xfer parms")

    /* Set DXPL for operation */
    H5CX_set_dxpl(dxpl_id);

    /* Write the data */
    if (H5D__write(dset, mem_type_id, mem_space, file_space, buf) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "can't write data")

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Dwrite() */

/*-------------------------------------------------------------------------
 * Function:    H5Dwrite_chunk
 *
 * Purpose:     Writes an entire chunk to the file directly.
 *
 * Return:      Non-negative on success/Negative on failure
 *
 * Programmer:    Raymond Lu
 *                30 July 2012
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Dwrite_chunk(hid_t dset_id, hid_t dxpl_id, uint32_t filters, const hsize_t *offset, size_t data_size,
               const void *buf)
{
    H5D_t *  dset = NULL;
    hsize_t  offset_copy[H5O_LAYOUT_NDIMS]; /* Internal copy of chunk offset */
    uint32_t data_size_32;                  /* Chunk data size (limited to 32-bits currently) */
    herr_t   ret_value = SUCCEED;           /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE6("e", "iiIu*hz*x", dset_id, dxpl_id, filters, offset, data_size, buf);

    /* Check arguments */
    if (NULL == (dset = (H5D_t *)H5I_object_verify(dset_id, H5I_DATASET)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid dataset ID")
    if (NULL == dset->oloc.file)
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "dataset is not associated with a file")
    if (H5D_CHUNKED != dset->shared->layout.type)
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a chunked dataset")
    if (!buf)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "buf cannot be NULL")
    if (!offset)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "offset cannot be NULL")
    if (0 == data_size)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "data_size cannot be zero")

    /* Make sure data size is less than 4 GiB */
    data_size_32 = (uint32_t)data_size;
    if (data_size != (size_t)data_size_32)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid data_size - chunks cannot be > 4 GiB")

    /* Get the default dataset transfer property list if the user didn't provide one */
    if (H5P_DEFAULT == dxpl_id)
        dxpl_id = H5P_DATASET_XFER_DEFAULT;
    else if (TRUE != H5P_isa_class(dxpl_id, H5P_DATASET_XFER))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "dxpl_id is not a dataset transfer property list ID")

    /* Set DXPL for operation */
    H5CX_set_dxpl(dxpl_id);

    /* Copy the user's offset array so we can be sure it's terminated properly.
     * (we don't want to mess with the user's buffer).
     */
    if (H5D__get_offset_copy(dset, offset, offset_copy) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "failure to copy offset array")

    /* Write chunk */
    if (H5D__chunk_direct_write(dset, filters, offset_copy, data_size_32, buf) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "can't write unprocessed chunk data")

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Dwrite_chunk() */

/*-------------------------------------------------------------------------
 * Function:    H5D__read
 *
 * Purpose:    Reads (part of) a DATASET into application memory BUF. See
 *        H5Dread() for complete details.
 *
 * Return:    Non-negative on success/Negative on failure
 *
 * Programmer:    Robb Matzke
 *        Thursday, December  4, 1997
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5D__read(H5D_t *dataset, hid_t mem_type_id, H5S_t *mem_space, H5S_t *file_space, void *buf /*out*/)
{
    H5D_chunk_map_t *fm = NULL;                   /* Chunk file<->memory mapping */
    H5D_io_info_t    io_info;                     /* Dataset I/O info     */
    H5D_type_info_t  type_info;                   /* Datatype info for operation */
    hbool_t          type_info_init      = FALSE; /* Whether the datatype info has been initialized */
    H5S_t *          projected_mem_space = NULL;  /* If not NULL, ptr to dataspace containing a     */
                                                  /* projection of the supplied mem_space to a new  */
                                                  /* dataspace with rank equal to that of           */
                                                  /* file_space.                                    */
                                                  /*                                                */
                                                  /* This field is only used if                     */
                                                  /* H5S_select_shape_same() returns TRUE when      */
                                                  /* comparing the mem_space and the data_space,    */
                                                  /* and the mem_space have different rank.         */
                                                  /*                                                */
                                                  /* Note that if this variable is used, the        */
                                                  /* projected mem space must be discarded at the   */
                                                  /* end of the function to avoid a memory leak.    */
    H5D_storage_t store;                          /* union of EFL and chunk pointer in file space */
    hsize_t       nelmts;                         /* total number of elmts    */
    hbool_t       io_op_init = FALSE;             /* Whether the I/O op has been initialized */
    char          fake_char;                      /* Temporary variable for NULL buffer pointers */
    herr_t        ret_value = SUCCEED;            /* Return value    */

    FUNC_ENTER_PACKAGE_TAG(dataset->oloc.addr)

    /* check args */
    HDassert(dataset && dataset->oloc.file);

    if (!file_space)
        file_space = dataset->shared->space;
    if (!mem_space)
        mem_space = file_space;
    nelmts = H5S_GET_SELECT_NPOINTS(mem_space);

    /* Set up datatype info for operation */
    if (H5D__typeinfo_init(dataset, mem_type_id, FALSE, &type_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up type info")
    type_info_init = TRUE;

#ifdef H5_HAVE_PARALLEL
    /* Check for non-MPI-based VFD */
    if (!(H5F_HAS_FEATURE(dataset->oloc.file, H5FD_FEAT_HAS_MPI))) {
        H5FD_mpio_xfer_t io_xfer_mode; /* MPI I/O transfer mode */

        /* Get I/O transfer mode */
        if (H5CX_get_io_xfer_mode(&io_xfer_mode) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get MPI-I/O transfer mode")

        /* Collective access is not permissible without a MPI based VFD */
        if (io_xfer_mode == H5FD_MPIO_COLLECTIVE)
            HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "collective access for MPI-based drivers only")
    }  /* end if */
#endif /*H5_HAVE_PARALLEL*/

    /* Make certain that the number of elements in each selection is the same */
    if (nelmts != H5S_GET_SELECT_NPOINTS(file_space))
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
                    "src and dest dataspaces have different number of elements selected")

    /* Check for a NULL buffer, after the H5S_ALL dataspace selection has been handled */
    if (NULL == buf) {
        /* Check for any elements selected (which is invalid) */
        if (nelmts > 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.
         */
        buf = &fake_char;
    } /* end if */

    /* Make sure that both selections have their extents set */
    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)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "memory dataspace does not have extent set")

    /* H5S_select_shape_same() has been modified to accept topologically identical
     * selections with different rank as having the same shape (if the most
     * rapidly changing coordinates match up), but the I/O code still has
     * difficulties with the notion.
     *
     * To solve this, we check to see if H5S_select_shape_same() returns true,
     * and if the ranks of the mem and file spaces are different.  If the are,
     * construct a new mem space that is equivalent to the old mem space, and
     * use that instead.
     *
     * Note that in general, this requires us to touch up the memory buffer as
     * well.
     */
    if (TRUE == H5S_SELECT_SHAPE_SAME(mem_space, file_space) &&
        H5S_GET_EXTENT_NDIMS(mem_space) != H5S_GET_EXTENT_NDIMS(file_space)) {
        ptrdiff_t buf_adj = 0;

        /* Attempt to construct projected dataspace for memory dataspace */
        if (H5S_select_construct_projection(mem_space, &projected_mem_space,
                                            (unsigned)H5S_GET_EXTENT_NDIMS(file_space),
                                            type_info.dst_type_size, &buf_adj) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to construct projected memory dataspace")
        HDassert(projected_mem_space);

        /* Adjust the buffer by the given amount */
        buf = (void *)(((uint8_t *)buf) + buf_adj);

        /* Switch to using projected memory dataspace & adjusted buffer */
        mem_space = projected_mem_space;
    } /* end if */

    /* Retrieve dataset properties */
    /* <none needed in the general case> */

    /* If space hasn't been allocated and not using external storage,
     * return fill value to buffer if fill time is upon allocation, or
     * do nothing if fill time is never.  If the dataset is compact and
     * fill time is NEVER, there is no way to tell whether part of data
     * has been overwritten.  So just proceed in reading.
     */
    if (nelmts > 0 && dataset->shared->dcpl_cache.efl.nused == 0 &&
        !(*dataset->shared->layout.ops->is_space_alloc)(&dataset->shared->layout.storage) &&
        !(dataset->shared->layout.ops->is_data_cached &&
          (*dataset->shared->layout.ops->is_data_cached)(dataset->shared))) {
        H5D_fill_value_t fill_status; /* Whether/How the fill value is defined */

        /* Retrieve dataset's fill-value properties */
        if (H5P_is_fill_value_defined(&dataset->shared->dcpl_cache.fill, &fill_status) < 0)
            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't tell if fill value defined")

        /* Should be impossible, but check anyway... */
        if (fill_status == H5D_FILL_VALUE_UNDEFINED &&
            (dataset->shared->dcpl_cache.fill.fill_time == H5D_FILL_TIME_ALLOC ||
             dataset->shared->dcpl_cache.fill.fill_time == H5D_FILL_TIME_IFSET))
            HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL,
                        "read failed: dataset doesn't exist, no data can be read")

        /* If we're never going to fill this dataset, just leave the junk in the user's buffer */
        if (dataset->shared->dcpl_cache.fill.fill_time == H5D_FILL_TIME_NEVER)
            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, type_info.mem_type,
                      mem_space) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "filling buf failed")
        else
            HGOTO_DONE(SUCCEED)
    } /* end if */

    /* Set up I/O operation */
    io_info.op_type = H5D_IO_OP_READ;
    io_info.u.rbuf  = buf;
    if (H5D__ioinfo_init(dataset, &type_info, &store, &io_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "unable to set up I/O operation")

    /* Sanity check that space is allocated, if there are elements */
    if (nelmts > 0)
        HDassert((*dataset->shared->layout.ops->is_space_alloc)(&dataset->shared->layout.storage) ||
                 (dataset->shared->layout.ops->is_data_cached &&
                  (*dataset->shared->layout.ops->is_data_cached)(dataset->shared)) ||
                 dataset->shared->dcpl_cache.efl.nused > 0 || dataset->shared->layout.type == H5D_COMPACT);

    /* Allocate the chunk map */
    if (NULL == (fm = H5FL_CALLOC(H5D_chunk_map_t)))
        HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "can't allocate chunk map")

    /* Call storage method's I/O initialization routine */
    if (io_info.layout_ops.io_init &&
        (*io_info.layout_ops.io_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, file_space, mem_space, &type_info) < 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.io_term && (*io_info.layout_ops.io_term)(fm) < 0)
        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down I/O op info")
    if (fm)
        fm = H5FL_FREE(H5D_chunk_map_t, fm);

    /* Shut down datatype info for operation */
    if (type_info_init && H5D__typeinfo_term(&type_info) < 0)
        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down type info")

    /* discard projected mem space if it was created */
    if (NULL != projected_mem_space)
        if (H5S_close(projected_mem_space) < 0)
            HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down projected memory dataspace")

    FUNC_LEAVE_NOAPI_TAG(ret_value)
} /* end H5D__read() */

/*-------------------------------------------------------------------------
 * Function:    H5D__write
 *
 * Purpose:    Writes (part of) a DATASET to a file from application memory
 *        BUF. See H5Dwrite() for complete details.
 *
 * Return:    Non-negative on success/Negative on failure
 *
 * Programmer:    Robb Matzke
 *        Thursday, December  4, 1997
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5D__write(H5D_t *dataset, hid_t mem_type_id, H5S_t *mem_space, H5S_t *file_space, const void *buf)
{
    H5D_chunk_map_t *fm = NULL;                   /* Chunk file<->memory mapping */
    H5D_io_info_t    io_info;                     /* Dataset I/O info     */
    H5D_type_info_t  type_info;                   /* Datatype info for operation */
    hbool_t          type_info_init      = FALSE; /* Whether the datatype info has been initialized */
    hbool_t          should_alloc_space  = FALSE; /* Whether or not to initialize dataset's storage */
    H5S_t *          projected_mem_space = NULL;  /* If not NULL, ptr to dataspace containing a     */
                                                  /* projection of the supplied mem_space to a new  */
                                                  /* dataspace with rank equal to that of           */
                                                  /* file_space.                                    */
                                                  /*                                                */
                                                  /* This field is only used if                     */
                                                  /* H5S_select_shape_same() returns TRUE when      */
                                                  /* comparing the mem_space and the data_space,    */
                                                  /* and the mem_space have different rank.         */
                                                  /*                                                */
                                                  /* Note that if this variable is used, the        */
                                                  /* projected mem space must be discarded at the   */
                                                  /* end of the function to avoid a memory leak.    */
    H5D_storage_t store;                          /* union of EFL and chunk pointer in file space */
    hsize_t       nelmts;                         /* total number of elmts    */
    hbool_t       io_op_init = FALSE;             /* Whether the I/O op has been initialized */
    char          fake_char;                      /* Temporary variable for NULL buffer pointers */
    herr_t        ret_value = SUCCEED;            /* Return value    */

    FUNC_ENTER_PACKAGE_TAG(dataset->oloc.addr)

    /* check args */
    HDassert(dataset && dataset->oloc.file);

    /* 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)
            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_INTENT(dataset->oloc.file) & H5F_ACC_RDWR))
        HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "no write intent on file")

    /* Set up datatype info for operation */
    if (H5D__typeinfo_init(dataset, mem_type_id, TRUE, &type_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up type info")
    type_info_init = TRUE;

    /* Various MPI based checks */
#ifdef H5_HAVE_PARALLEL
    if (H5F_HAS_FEATURE(dataset->oloc.file, H5FD_FEAT_HAS_MPI)) {
        /* If MPI based VFD is used, no VL or region reference 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_is_vl_storage(type_info.mem_type) > 0)
            HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL,
                        "Parallel IO does not support writing VL or region reference datatypes yet")
    } /* end if */
    else {
        H5FD_mpio_xfer_t io_xfer_mode; /* MPI I/O transfer mode */

        /* Get I/O transfer mode */
        if (H5CX_get_io_xfer_mode(&io_xfer_mode) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get MPI-I/O transfer mode")

        /* Collective access is not permissible without a MPI based VFD */
        if (io_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*/

    /* Initialize dataspace information */
    if (!file_space)
        file_space = dataset->shared->space;
    if (!mem_space)
        mem_space = file_space;

    nelmts = H5S_GET_SELECT_NPOINTS(mem_space);

    /* Make certain that the number of elements in each selection is the same */
    if (nelmts != H5S_GET_SELECT_NPOINTS(file_space))
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
                    "src and dest dataspaces have different number of elements selected")

    /* Check for a NULL buffer, after the H5S_ALL dataspace selection has been handled */
    if (NULL == buf) {
        /* Check for any elements selected (which is invalid) */
        if (nelmts > 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.
         */
        buf = &fake_char;
    } /* end if */

    /* Make sure that both selections have their extents set */
    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)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "memory dataspace does not have extent set")

    /* H5S_select_shape_same() has been modified to accept topologically
     * identical selections with different rank as having the same shape
     * (if the most rapidly changing coordinates match up), but the I/O
     * code still has difficulties with the notion.
     *
     * To solve this, we check to see if H5S_select_shape_same() returns
     * true, and if the ranks of the mem and file spaces are different.
     * If the are, construct a new mem space that is equivalent to the
     * old mem space, and use that instead.
     *
     * Note that in general, this requires us to touch up the memory buffer
     * as well.
     */
    if (TRUE == H5S_SELECT_SHAPE_SAME(mem_space, file_space) &&
        H5S_GET_EXTENT_NDIMS(mem_space) != H5S_GET_EXTENT_NDIMS(file_space)) {
        ptrdiff_t buf_adj = 0;

        /* Attempt to construct projected dataspace for memory dataspace */
        if (H5S_select_construct_projection(mem_space, &projected_mem_space,
                                            (unsigned)H5S_GET_EXTENT_NDIMS(file_space),
                                            type_info.src_type_size, &buf_adj) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to construct projected memory dataspace")
        HDassert(projected_mem_space);

        /* Adjust the buffer by the given amount */
        buf = (const void *)(((const uint8_t *)buf) + buf_adj);

        /* Switch to using projected memory dataspace & adjusted buffer */
        mem_space = projected_mem_space;
    } /* end if */

    /* Retrieve dataset properties */
    /* <none needed currently> */

    /* Set up I/O operation */
    io_info.op_type = H5D_IO_OP_WRITE;
    io_info.u.wbuf  = buf;
    if (H5D__ioinfo_init(dataset, &type_info, &store, &io_info) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to set up I/O operation")

    /* Allocate dataspace and initialize it if it hasn't been. */
    should_alloc_space = dataset->shared->dcpl_cache.efl.nused == 0 &&
                         !(*dataset->shared->layout.ops->is_space_alloc)(&dataset->shared->layout.storage);

    /*
     * If not using an MPI-based VFD, we only need to allocate
     * and initialize storage if there's a selection in the
     * dataset's dataspace. Otherwise, we always need to participate
     * in the storage allocation since this may use collective
     * operations and we will hang if we don't participate.
     */
    if (!H5F_HAS_FEATURE(dataset->oloc.file, H5FD_FEAT_HAS_MPI))
        should_alloc_space = should_alloc_space && (nelmts > 0);

    if (should_alloc_space) {
        hssize_t file_nelmts;    /* Number of elements in file dataset's dataspace */
        hbool_t  full_overwrite; /* Whether we are over-writing all the elements */

        /* Get the number of elements in file dataset's dataspace */
        if ((file_nelmts = H5S_GET_EXTENT_NPOINTS(file_space)) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_BADVALUE, FAIL, "can't retrieve number of elements in file dataset")

        /* Always allow fill values to be written if the dataset has a VL datatype */
        if (H5T_detect_class(dataset->shared->type, H5T_VLEN, FALSE))
            full_overwrite = FALSE;
        else
            full_overwrite = (hbool_t)((hsize_t)file_nelmts == nelmts ? TRUE : FALSE);

        /* Allocate storage */
        if (H5D__alloc_storage(&io_info, H5D_ALLOC_WRITE, full_overwrite, NULL) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to initialize storage")
    } /* end if */

    /* Allocate the chunk map */
    if (NULL == (fm = H5FL_CALLOC(H5D_chunk_map_t)))
        HGOTO_ERROR(H5E_DATASET, H5E_CANTALLOC, FAIL, "can't allocate chunk map")

    /* Call storage method's I/O initialization routine */
    if (io_info.layout_ops.io_init &&
        (*io_info.layout_ops.io_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, file_space, mem_space, &type_info) < 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
    /*
     * This was taken out because it can be called in a parallel program with
     * independent access, causing the metadata cache to get corrupted. Its been
     * disabled for all types of access (serial as well as parallel) to make the
     * modification time consistent for all programs. -QAK
     *
     * We should set a value in the dataset's shared information instead and flush
     * it to the file when the dataset is being closed. -QAK
     */
    /*
     * Update modification time.  We have to do this explicitly because
     * writing to a dataset doesn't necessarily change the object header.
     */
    if (H5O_touch(&(dataset->oloc), FALSE) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to update modification time")
#endif /* OLD_WAY */

done:
    /* Shut down the I/O op information */
    if (io_op_init && io_info.layout_ops.io_term && (*io_info.layout_ops.io_term)(fm) < 0)
        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down I/O op info")
    if (fm)
        fm = H5FL_FREE(H5D_chunk_map_t, fm);

    /* Shut down datatype info for operation */
    if (type_info_init && H5D__typeinfo_term(&type_info) < 0)
        HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down type info")

    /* discard projected mem space if it was created */
    if (NULL != projected_mem_space)
        if (H5S_close(projected_mem_space) < 0)
            HDONE_ERROR(H5E_DATASET, H5E_CANTCLOSEOBJ, FAIL, "unable to shut down projected memory dataspace")

    FUNC_LEAVE_NOAPI_TAG(ret_value)
} /* end H5D__write() */

/*-------------------------------------------------------------------------
 * Function:    H5D__ioinfo_init
 *
 * Purpose:    Routine for determining correct I/O operations for
 *              each I/O action.
 *
 * Return:    Non-negative on success/Negative on failure
 *
 * Programmer:    Quincey Koziol
 *        Thursday, September 30, 2004
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__ioinfo_init(H5D_t *dset, const H5D_type_info_t *type_info, H5D_storage_t *store, H5D_io_info_t *io_info)
{
    FUNC_ENTER_STATIC_NOERR

    /* check args */
    HDassert(dset);
    HDassert(dset->oloc.file);
    HDassert(type_info);
    HDassert(type_info->tpath);
    HDassert(io_info);

    /* Set up "normal" I/O fields */
    io_info->dset  = dset;
    io_info->store = store;

    /* Set I/O operations to initial values */
    io_info->layout_ops = *dset->shared->layout.ops;

    /* 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) {
        /*
         * 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.
         */
        io_info->io_ops.single_read  = H5D__select_read;
        io_info->io_ops.single_write = H5D__select_write;
    } /* end if */
    else {
        /*
         * This is the general case (type conversion, usually).
         */
        io_info->io_ops.single_read  = H5D__scatgath_read;
        io_info->io_ops.single_write = H5D__scatgath_write;
    } /* end else */

#ifdef H5_HAVE_PARALLEL
    /* Determine if the file was opened with an MPI VFD */
    io_info->using_mpi_vfd = H5F_HAS_FEATURE(dset->oloc.file, H5FD_FEAT_HAS_MPI);
#endif /* H5_HAVE_PARALLEL */

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5D__ioinfo_init() */

/*-------------------------------------------------------------------------
 * Function:    H5D__typeinfo_init
 *
 * Purpose:    Routine for determining correct datatype information for
 *              each I/O action.
 *
 * Return:    Non-negative on success/Negative on failure
 *
 * Programmer:    Quincey Koziol
 *        Tuesday, March  4, 2008
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__typeinfo_init(const H5D_t *dset, hid_t mem_type_id, hbool_t do_write, H5D_type_info_t *type_info)
{
    const H5T_t *     src_type;            /* Source datatype */
    const H5T_t *     dst_type;            /* Destination datatype */
    H5Z_data_xform_t *data_transform;      /* Data transform info */
    herr_t            ret_value = SUCCEED; /* Return value    */

    FUNC_ENTER_STATIC

    /* check args */
    HDassert(type_info);
    HDassert(dset);

    /* Patch the top level file pointer for dt->shared->u.vlen.f if needed */
    if (H5T_patch_vlen_file(dset->shared->type, dset->oloc.file) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTOPENOBJ, FAIL, "can't patch VL datatype file pointer")

    /* Initialize type info safely */
    HDmemset(type_info, 0, sizeof(*type_info));

    /* 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;

    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 */

    /* Locate the type conversion function and dataspace 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 == (type_info->tpath = H5T_path_find(src_type, dst_type)))
        HGOTO_ERROR(H5E_DATASET, H5E_UNSUPPORTED, FAIL, "unable to convert between src and dest datatype")

    /* Retrieve info from API context */
    if (H5CX_get_data_transform(&data_transform) < 0)
        HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get data transform info")

    /* 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(data_transform);
    if (type_info->is_xform_noop && type_info->is_conv_noop) {
        type_info->cmpd_subset = NULL;
        type_info->need_bkg    = H5T_BKG_NO;
    } /* end if */
    else {
        void *    tconv_buf;     /* Temporary conversion buffer pointer */
        void *    bkgr_buf;      /* Background conversion buffer pointer */
        size_t    max_temp_buf;  /* Maximum temporary buffer size */
        H5T_bkg_t bkgr_buf_type; /* Background buffer type */
        size_t    target_size;   /* Desired buffer size    */

        /* Get info from API context */
        if (H5CX_get_max_temp_buf(&max_temp_buf) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't retrieve max. temp. buf size")
        if (H5CX_get_tconv_buf(&tconv_buf) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't retrieve temp. conversion buffer pointer")
        if (H5CX_get_bkgr_buf(&bkgr_buf) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't retrieve background conversion buffer pointer")
        if (H5CX_get_bkgr_buf_type(&bkgr_buf_type) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't retrieve background buffer type")

        /* Check if the datatypes are compound subsets of one another */
        type_info->cmpd_subset = H5T_path_compound_subset(type_info->tpath);

        /* Check if we need a background buffer */
        if (do_write && H5T_detect_class(dset->shared->type, H5T_VLEN, FALSE))
            type_info->need_bkg = H5T_BKG_YES;
        else {
            H5T_bkg_t path_bkg; /* Type conversion's background info */

            if ((path_bkg = H5T_path_bkg(type_info->tpath))) {
                /* Retrieve the bkgr buffer property */
                type_info->need_bkg = 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 */

        /* Set up datatype conversion/background buffers */

        target_size = max_temp_buf;

        /* 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 */

            /* Detect if we have all default settings for buffers */
            default_buffer_info =
                (hbool_t)((H5D_TEMP_BUF_SIZE == max_temp_buf) && (NULL == tconv_buf) && (NULL == bkgr_buf));

            /* 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 */

        /* Compute the number of elements that will fit into buffer */
        type_info->request_nelmts = target_size / type_info->max_type_size;

        /* 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")

        /* 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.
         */
        if (NULL == (type_info->tconv_buf = (uint8_t *)tconv_buf)) {
            /* Allocate temporary buffer */
            if (NULL == (type_info->tconv_buf = H5FL_BLK_CALLOC(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 *)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 < max_temp_buf)
                bkg_size = 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 */
    }     /* end else */

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D__typeinfo_init() */

#ifdef H5_HAVE_PARALLEL

/*-------------------------------------------------------------------------
 * Function:    H5D__ioinfo_adjust
 *
 * Purpose:    Adjust operation's I/O info for any parallel I/O
 *
 * Return:    Non-negative on success/Negative on failure
 *
 * Programmer:    Quincey Koziol
 *        Thursday, March 27, 2008
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D__ioinfo_adjust(H5D_io_info_t *io_info, const H5D_t *dset, const H5S_t *file_space, const H5S_t *mem_space,
                   const H5D_type_info_t *type_info)
{
    herr_t ret_value = SUCCEED; /* Return value    */

    FUNC_ENTER_STATIC

    /* check args */
    HDassert(dset);
    HDassert(dset->oloc.file);
    HDassert(mem_space);
    HDassert(file_space);
    HDassert(type_info);
    HDassert(type_info->tpath);
    HDassert(io_info);

    /* Reset the actual io mode properties to the default values in case
     * the DXPL (if it's non-default) was previously used in a collective
     * I/O operation.
     */
    if (!H5CX_is_def_dxpl()) {
        H5CX_set_mpio_actual_chunk_opt(H5D_MPIO_NO_CHUNK_OPTIMIZATION);
        H5CX_set_mpio_actual_io_mode(H5D_MPIO_NO_COLLECTIVE);
    } /* end if */

    /* Make any parallel I/O adjustments */
    if (io_info->using_mpi_vfd) {
        H5FD_mpio_xfer_t xfer_mode; /* Parallel transfer for this request */
        htri_t           opt;       /* Flag whether a selection is optimizable */

        /* Get the original state of parallel I/O transfer mode */
        if (H5CX_get_io_xfer_mode(&xfer_mode) < 0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get MPI-I/O transfer mode")

        /* Get MPI communicator */
        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 */
        if ((opt = H5D__mpio_opt_possible(io_info, file_space, mem_space, type_info)) < 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) {
            /* 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 {
            /* Check if there are any filters in the pipeline. If there are,
             * we cannot break to independent I/O if this is a write operation
             * with multiple ranks involved; otherwise, there will be metadata
             * inconsistencies in the file.
             */
            if (io_info->op_type == H5D_IO_OP_WRITE && io_info->dset->shared->dcpl_cache.pline.nused > 0) {
                int comm_size = 0;

                /* Retrieve size of MPI communicator used for file */
                if ((comm_size = H5F_mpi_get_size(io_info->dset->oloc.file)) < 0)
                    HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "can't get MPI communicator size")

                if (comm_size > 1) {
                    char local_no_coll_cause_string[512];
                    char global_no_coll_cause_string[512];

                    if (H5D__mpio_get_no_coll_cause_strings(local_no_coll_cause_string, 512,
                                                            global_no_coll_cause_string, 512) < 0)
                        HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL,
                                    "can't get reasons for breaking collective I/O")

                    HGOTO_ERROR(H5E_IO, H5E_NO_INDEPENDENT, FAIL,
                                "Can't perform independent write with filters in pipeline.\n"
                                "    The following caused a break from collective I/O:\n"
                                "        Local causes: %s\n"
                                "        Global causes: %s",
                                local_no_coll_cause_string, global_no_coll_cause_string);
                }
            }

            /* 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
             */
            if (xfer_mode == H5FD_MPIO_COLLECTIVE) {
                /* Change the xfer_mode to independent for handling the I/O */
                if (H5CX_set_io_xfer_mode(H5FD_MPIO_INDEPENDENT) < 0)
                    HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set MPI-I/O transfer mode")
            } /* end if */
        }     /* end else */
    }         /* end if */

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D__ioinfo_adjust() */
#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_STATIC_NOERR

    /* 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() */