path: root/src/H5Dcontig.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 files COPYING and Copyright.html.  COPYING can be found at the root   *
 * of the source code distribution tree; Copyright.html can be found at the  *
 * root level of an installed copy of the electronic HDF5 document set and   *
 * is linked from the top-level documents page.  It can also be found at     *
 * http://hdfgroup.org/HDF5/doc/Copyright.html.  If you do not have          *
 * access to either file, you may request a copy from help@hdfgroup.org.     *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*
 * Programmer: 	Quincey Koziol <koziol@ncsa.uiuc.edu>
 *	       	Thursday, September 28, 2000
 *
 * Purpose:
 *      Contiguous dataset I/O functions. These routines are similar to
 *      the H5D_istore_* routines and really only an abstract way of dealing
 *      with the data sieve buffer from H5F_seq_read/write.
 */

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

#define H5D_PACKAGE		/*suppress error about including H5Dpkg	  */


/***********/
/* Headers */
/***********/
#include "H5private.h"		/* Generic Functions			*/
#include "H5Dpkg.h"		/* Dataset functions			*/
#include "H5Eprivate.h"		/* Error handling		  	*/
#include "H5Fprivate.h"		/* Files				*/
#include "H5FDprivate.h"	/* File drivers				*/
#include "H5FLprivate.h"	/* Free Lists                           */
#include "H5Iprivate.h"		/* IDs			  		*/
#include "H5MFprivate.h"	/* File memory management		*/
#include "H5Oprivate.h"		/* Object headers		  	*/
#include "H5Pprivate.h"		/* Property lists			*/
#include "H5Sprivate.h"		/* Dataspace functions			*/
#include "H5Vprivate.h"		/* Vector and array functions		*/

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

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

/********************/
/* Local Prototypes */
/********************/
static herr_t H5D_contig_write(H5D_t *dset, const H5D_dxpl_cache_t *dxpl_cache,
    hid_t dxpl_id, const H5D_storage_t *store, hsize_t offset, size_t size, const void *buf);

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

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

/* Declare a PQ free list to manage the sieve buffer information */
H5FL_BLK_DEFINE(sieve_buf);

/* Declare the free list to manage blocks of non-zero fill-value data */
H5FL_BLK_DEFINE_STATIC(non_zero_fill);

/* Declare the free list to manage blocks of zero fill-value data */
H5FL_BLK_DEFINE_STATIC(zero_fill);

/* Declare a free list to manage blocks of type conversion data */
H5FL_BLK_EXTERN(type_conv);


/*-------------------------------------------------------------------------
 * Function:	H5D_contig_create
 *
 * Purpose:	Allocate file space for a contiguously stored dataset
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		April 19, 2003
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5D_contig_create(H5F_t *f, hid_t dxpl_id, H5O_layout_t *layout /*out */ )
{
    herr_t ret_value=SUCCEED;   /* Return value */

    FUNC_ENTER_NOAPI(H5D_contig_create, FAIL)

    /* check args */
    assert(f);
    assert(layout);

    /* Allocate space for the contiguous data */
    if (HADDR_UNDEF==(layout->u.contig.addr=H5MF_alloc(f, H5FD_MEM_DRAW, dxpl_id, layout->u.contig.size)))
        HGOTO_ERROR (H5E_IO, H5E_NOSPACE, FAIL, "unable to reserve file space")

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D_contig_create */


/*-------------------------------------------------------------------------
 * Function:	H5D_contig_fill
 *
 * Purpose:	Write fill values to a contiguously stored dataset.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		August 22, 2002
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5D_contig_fill(H5D_t *dset, hid_t dxpl_id)
{
    H5D_storage_t store;                /* Union of storage info for dataset */
    H5D_dxpl_cache_t _dxpl_cache;       /* Data transfer property cache buffer */
    H5D_dxpl_cache_t *dxpl_cache = &_dxpl_cache;   /* Data transfer property cache */
    hssize_t    snpoints;       /* Number of points in space (for error checking) */
    size_t      npoints;        /* Number of points in space */
    size_t      ptsperbuf;      /* Maximum # of points which fit in the buffer */
    size_t      elmt_size;      /* Size of each element */
    size_t	bufsize = H5D_XFER_MAX_TEMP_BUF_DEF; /* Size of buffer to write */
    hsize_t	offset;         /* Offset of dataset */
    void       *buf = NULL;     /* Buffer for fill value writing */
#ifdef H5_HAVE_PARALLEL
    MPI_Comm	mpi_comm = MPI_COMM_NULL;	/* MPI communicator for file */
    int         mpi_rank = (-1); /* This process's rank  */
    int         mpi_code;       /* MPI return code */
    hbool_t     blocks_written = FALSE; /* Flag to indicate that chunk was actually written */
    hbool_t     using_mpi = FALSE;      /* Flag to indicate that the file is being accessed with an MPI-capable file driver */
#endif /* H5_HAVE_PARALLEL */
    htri_t      non_zero_fill_f = (-1); /* Indicate that a non-zero fill-value was used */
    H5T_path_t *fill_to_mem_tpath;      /* Datatype conversion path for converting the fill value to the memory buffer */
    H5T_path_t *mem_to_dset_tpath;      /* Datatype conversion path for converting the memory buffer to the dataset elements */
    uint8_t    *bkg_buf = NULL;         /* Background conversion buffer */
    H5T_t      *mem_type = NULL;        /* Pointer to memory datatype */
    size_t      mem_type_size, file_type_size;       /* Size of datatype in memory and on disk */
    hid_t       mem_tid = (-1);         /* Memory version of disk datatype */
    size_t      bkg_buf_size;           /* Size of background buffer */
    hbool_t     has_vlen_fill_type = FALSE;  /* Whether the datatype for the fill value has a variable-length component */
    herr_t	ret_value = SUCCEED;	/* Return value */

    FUNC_ENTER_NOAPI(H5D_contig_fill, FAIL)

    /* Check args */
    HDassert(TRUE == H5P_isa_class(dxpl_id, H5P_DATASET_XFER));
    HDassert(dset && H5D_CONTIGUOUS == dset->shared->layout.type);
    HDassert(H5F_addr_defined(dset->shared->layout.u.contig.addr));
    HDassert(dset->shared->layout.u.contig.size > 0);
    HDassert(dset->shared->space);
    HDassert(dset->shared->type);

#ifdef H5_HAVE_PARALLEL
    /* Retrieve MPI parameters */
    if(IS_H5FD_MPI(dset->ent.file)) {
        /* Get the MPI communicator */
        if (MPI_COMM_NULL == (mpi_comm=H5F_mpi_get_comm(dset->ent.file)))
            HGOTO_ERROR(H5E_INTERNAL, H5E_MPI, FAIL, "Can't retrieve MPI communicator")

        /* Get the MPI rank */
        if ((mpi_rank=H5F_mpi_get_rank(dset->ent.file))<0)
            HGOTO_ERROR(H5E_INTERNAL, H5E_MPI, FAIL, "Can't retrieve MPI rank")

        /* Set the MPI-capable file driver flag */
        using_mpi = TRUE;

        /* Fill the DXPL cache values for later use */
        if (H5D_get_dxpl_cache(H5AC_ind_dxpl_id,&dxpl_cache)<0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't fill dxpl cache")
    } /* end if */
    else {
#endif  /* H5_HAVE_PARALLEL */
        /* Fill the DXPL cache values for later use */
        if (H5D_get_dxpl_cache(dxpl_id,&dxpl_cache)<0)
            HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't fill dxpl cache")
#ifdef H5_HAVE_PARALLEL
    } /* end else */
#endif  /* H5_HAVE_PARALLEL */

    /* Initialize storage info for this dataset */
    store.contig.dset_addr = dset->shared->layout.u.contig.addr;
    store.contig.dset_size = dset->shared->layout.u.contig.size;

    /* Get the number of elements in the dataset's dataspace */
    snpoints = H5S_GET_EXTENT_NPOINTS(dset->shared->space);
    HDassert(snpoints >= 0);
    H5_ASSIGN_OVERFLOW(npoints, snpoints, hssize_t, size_t);

    /* Fill the buffer with the user's fill value */
    if(dset->shared->fill.buf) {
        /* Indicate that a non-zero fill buffer will be used */
        non_zero_fill_f = TRUE;

        /* Detect whether the datatype has a VL component */
        has_vlen_fill_type = H5T_detect_class(dset->shared->type, H5T_VLEN);

        /* If necessary, convert fill value datatypes (which copies VL components, etc.) */
        if(has_vlen_fill_type) {
            /* Create temporary datatype for conversion operation */
            if(NULL == (mem_type = H5T_copy(dset->shared->type, H5T_COPY_REOPEN)))
                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCOPY, FAIL, "unable to copy file datatype")
            if((mem_tid = H5I_register(H5I_DATATYPE, mem_type)) < 0)
                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTREGISTER, FAIL, "unable to register memory datatype")

            /* Retrieve sizes of memory & file datatypes */
            mem_type_size = H5T_get_size(mem_type);
            HDassert(mem_type_size > 0);
            file_type_size = H5T_get_size(dset->shared->type);
            HDassert(file_type_size == dset->shared->fill.size);

            /* If fill value is not library default, use it to set the element size */
            elmt_size = MAX(mem_type_size, file_type_size);

            /* Compute the number of elements that fit within a buffer to write */
            ptsperbuf = MIN(npoints, MAX(1, bufsize / elmt_size));
            bufsize = MAX(bufsize, ptsperbuf * elmt_size);

            /* Allocate temporary buffer */
            if(NULL == (buf = H5FL_BLK_MALLOC(non_zero_fill, bufsize)))
                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for fill buffer")

            /* Get the datatype conversion path for this operation */
            if(NULL == (fill_to_mem_tpath = H5T_path_find(dset->shared->type, mem_type, NULL, NULL, dxpl_id)))
                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to convert between src and dst datatypes")

            /* Get the inverse datatype conversion path for this operation */
            if(NULL == (mem_to_dset_tpath = H5T_path_find(mem_type, dset->shared->type, NULL, NULL, dxpl_id)))
                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to convert between src and dst datatypes")

            /* Check if we need to allocate a background buffer */
            if(H5T_path_bkg(fill_to_mem_tpath) || H5T_path_bkg(mem_to_dset_tpath)) {
                /* Check for inverse datatype conversion needing a background buffer */
                /* (do this first, since it needs a larger buffer) */
                if(H5T_path_bkg(mem_to_dset_tpath))
                    bkg_buf_size = ptsperbuf * elmt_size;
                else
                    bkg_buf_size = elmt_size;

                /* Allocate the background buffer */
                if(NULL == (bkg_buf = H5FL_BLK_MALLOC(type_conv, bkg_buf_size)))
                    HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
            } /* end if */
        } /* end if */
        else {
            /* If fill value is not library default, use it to set the element size */
            elmt_size = dset->shared->fill.size;

            /* Compute the number of elements that fit within a buffer to write */
            ptsperbuf = MIN(npoints, MAX(1, bufsize / elmt_size));
            bufsize = MAX(bufsize, ptsperbuf * elmt_size);

            /* Allocate temporary buffer */
            if(NULL == (buf = H5FL_BLK_MALLOC(non_zero_fill, bufsize)))
                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for fill buffer")

            /* Replicate the fill value into the cached buffer */
            H5V_array_fill(buf, dset->shared->fill.buf, elmt_size, ptsperbuf);
        } /* end else */
    } /* end if */
    else {      /* Fill the buffer with the default fill value */
        htri_t buf_avail = H5FL_BLK_AVAIL(zero_fill, bufsize);  /* Check if there is an already zeroed out buffer available */
        HDassert(buf_avail != FAIL);

        /* Allocate temporary buffer (zeroing it if no buffer is available) */
        if(!buf_avail)
            buf = H5FL_BLK_CALLOC(zero_fill, bufsize);
        else
            buf = H5FL_BLK_MALLOC(zero_fill, bufsize);
        if(buf == NULL)
            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for fill buffer")

        /* Retrieve size of elements */
        elmt_size = H5T_get_size(dset->shared->type);
        HDassert(elmt_size > 0);

        /* Compute the number of elements that fit within a buffer to write */
        ptsperbuf = MIN(npoints, MAX(1, bufsize / elmt_size));

        /* Indicate that a zero fill buffer was used */
        non_zero_fill_f = FALSE;
    } /* end else */

    /* Start at the beginning of the dataset */
    offset = 0;

    /*
     * Fill the entire current extent with the fill value.  We can do
     * this quite efficiently by making sure we copy the fill value
     * in relatively large pieces.
     */

    /* Loop through writing the fill value to the dataset */
    while(npoints > 0) {
        size_t curr_points;     /* Number of elements to write on this iteration of the loop */
        size_t size;            /* Size of buffer to write */
        
        /* Compute # of elements and buffer size to write for this iteration */
        curr_points = MIN(ptsperbuf, npoints);
        size = curr_points * elmt_size;

        /* Check for VL datatype & non-default fill value */
        if(has_vlen_fill_type) {
            /* Make a copy of the (disk-based) fill value into the buffer */
            HDmemcpy(buf, dset->shared->fill.buf, file_type_size);

            /* Reset first element of background buffer, if necessary */
            if(H5T_path_bkg(fill_to_mem_tpath))
                HDmemset(bkg_buf, 0, elmt_size);

            /* Type convert the dataset buffer, to copy any VL components */
            if(H5T_convert(fill_to_mem_tpath, dset->shared->type_id, mem_tid, (size_t)1, (size_t)0, (size_t)0, buf, bkg_buf, dxpl_id) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_CANTCONVERT, FAIL, "data type conversion failed")

            /* Replicate the fill value into the cached buffer */
            H5V_array_fill(buf, buf, mem_type_size, curr_points);

            /* Reset the entire background buffer, if necessary */
            if(H5T_path_bkg(mem_to_dset_tpath))
                HDmemset(bkg_buf, 0, bkg_buf_size);

            /* Type convert the dataset buffer, to copy any VL components */
            if(H5T_convert(mem_to_dset_tpath, mem_tid, dset->shared->type_id, curr_points, (size_t)0, (size_t)0, buf, bkg_buf, dxpl_id) < 0)
                HGOTO_ERROR(H5E_DATASET, H5E_CANTCONVERT, FAIL, "data type conversion failed")
        } /* end if */

#ifdef H5_HAVE_PARALLEL
            /* Check if this file is accessed with an MPI-capable file driver */
            if(using_mpi) {
                /* Write the chunks out from only one process */
                /* !! Use the internal "independent" DXPL!! -QAK */
                if(H5_PAR_META_WRITE==mpi_rank) {
                    if (H5D_contig_write(dset, dxpl_cache, H5AC_ind_dxpl_id, &store, offset, size, buf)<0)
                        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to write fill value to dataset")
                } /* end if */

                /* Indicate that blocks are being written */
                blocks_written = TRUE;
            } /* end if */
            else {
#endif /* H5_HAVE_PARALLEL */
                H5_CHECK_OVERFLOW(size,size_t,hsize_t);
                if (H5D_contig_write(dset, dxpl_cache, dxpl_id, &store, offset, size, buf)<0)
                    HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to write fill value to dataset")
#ifdef H5_HAVE_PARALLEL
            } /* end else */
#endif /* H5_HAVE_PARALLEL */

          npoints -= curr_points;
          offset += size;
      } /* end while */

#ifdef H5_HAVE_PARALLEL
    /* Only need to block at the barrier if we actually wrote fill values */
    /* And if we are using an MPI-capable file driver */
    if(using_mpi && blocks_written) {
        /* Wait at barrier to avoid race conditions where some processes are
         * still writing out fill values and other processes race ahead to data
         * in, getting bogus data.
         */
        if (MPI_SUCCESS != (mpi_code=MPI_Barrier(mpi_comm)))
            HMPI_GOTO_ERROR(FAIL, "MPI_Barrier failed", mpi_code)
    } /* end if */
#endif /* H5_HAVE_PARALLEL */

done:
    /* Free the buffer for fill values */
    if(buf) {
        HDassert(non_zero_fill_f >= 0);
        if(non_zero_fill_f)
            H5FL_BLK_FREE(non_zero_fill, buf);
        else
            H5FL_BLK_FREE(zero_fill, buf);
    } /* end if */

    /* Free other resources for vlen fill values */
    if(has_vlen_fill_type) {
        if(mem_tid > 0)
            H5I_dec_ref(mem_tid);
        else if(mem_type)
            H5T_close(mem_type);
        if(bkg_buf)
            H5FL_BLK_FREE(type_conv, bkg_buf);
    } /* end if */

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D_contig_fill() */


/*-------------------------------------------------------------------------
 * Function:	H5D_contig_delete
 *
 * Purpose:	Delete the file space for a contiguously stored dataset
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		March 20, 2003
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5D_contig_delete(H5F_t *f, hid_t dxpl_id, const struct H5O_layout_t *layout)
{
    herr_t ret_value=SUCCEED;   /* Return value */

    FUNC_ENTER_NOAPI(H5D_contig_delete, FAIL)

    /* check args */
    assert(f);
    assert(layout);

    /* Free the file space for the chunk */
    if (H5MF_xfree(f, H5FD_MEM_DRAW, dxpl_id, layout->u.contig.addr, layout->u.contig.size)<0)
        HGOTO_ERROR(H5E_OHDR, H5E_CANTFREE, FAIL, "unable to free object header")

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5D_contig_delete */


/*-------------------------------------------------------------------------
 * Function:	H5D_contig_get_addr
 *
 * Purpose:	Get the offset of the contiguous data on disk
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		June  2, 2004
 *
 *-------------------------------------------------------------------------
 */
haddr_t
H5D_contig_get_addr(const H5D_t *dset)
{
    FUNC_ENTER_NOAPI_NOFUNC(H5D_contig_get_addr)

    /* check args */
    assert(dset);
    assert(dset->shared->layout.type==H5D_CONTIGUOUS);

    FUNC_LEAVE_NOAPI(dset->shared->layout.u.contig.addr)
} /* end H5D_contig_get_addr */


/*-------------------------------------------------------------------------
 * Function:	H5D_contig_write
 *
 * Purpose:	Writes some data from a dataset into a buffer.
 *		The data is contiguous.	 The address is relative to the base
 *		address for the file.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *              Thursday, September 28, 2000
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5D_contig_write(H5D_t *dset, const H5D_dxpl_cache_t *dxpl_cache,
    hid_t dxpl_id, const H5D_storage_t *store,
    hsize_t offset, size_t size, const void *buf)
{
    H5D_io_info_t io_info;      /* Dataset I/O info */
    hsize_t dset_off=offset;    /* Offset in dataset */
    size_t dset_len=size;       /* Length in dataset */
    size_t dset_curr_seq=0;     /* "Current sequence" in dataset */
    hsize_t mem_off=0;          /* Offset in memory */
    size_t mem_len=size;        /* Length in memory */
    size_t mem_curr_seq=0;      /* "Current sequence" in memory */
    herr_t ret_value=SUCCEED;   /* Return value */

    FUNC_ENTER_NOAPI(H5D_contig_write, FAIL)

    assert (dset);
    assert (dxpl_cache);
    assert (store);
    assert (buf);

    H5D_BUILD_IO_INFO(&io_info,dset,dxpl_cache,dxpl_id,store);
    if (H5D_contig_writevv(&io_info,
            1, &dset_curr_seq, &dset_len, &dset_off, 1, &mem_curr_seq, &mem_len, &mem_off, buf)<0)
        HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "vector write failed")

done:
    FUNC_LEAVE_NOAPI(ret_value)
}   /* end H5D_contig_write() */


/*-------------------------------------------------------------------------
 * Function:	H5D_contig_readvv
 *
 * Purpose:	Reads some data vectors from a dataset into a buffer.
 *		The data is contiguous.	 The address is the start of the dataset,
 *              relative to the base address for the file and the offsets and
 *              sequence lengths are in bytes.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *              Friday, May 3, 2001
 *
 * Notes:
 *      Offsets in the sequences must be monotonically increasing
 *
 *-------------------------------------------------------------------------
 */
ssize_t
H5D_contig_readvv(const H5D_io_info_t *io_info,
    size_t dset_max_nseq, size_t *dset_curr_seq, size_t dset_len_arr[], hsize_t dset_offset_arr[],
    size_t mem_max_nseq, size_t *mem_curr_seq, size_t mem_len_arr[], hsize_t mem_offset_arr[],
    void *_buf)
{
    H5F_t *file=io_info->dset->ent.file;        /* File for dataset */
    H5D_rdcdc_t *dset_contig=&(io_info->dset->shared->cache.contig); /* Cached information about contiguous data */
    const H5D_contig_storage_t *store_contig=&(io_info->store->contig);    /* Contiguous storage info for this I/O operation */
    unsigned char *buf=(unsigned char *)_buf;   /* Pointer to buffer to fill */
    haddr_t addr;               /* Actual address to read */
    size_t total_size=0;        /* Total size of sequence in bytes */
    size_t size;                /* Size of sequence in bytes */
    size_t u;                   /* Counting variable */
    size_t v;                   /* Counting variable */
    ssize_t ret_value;          /* Return value */

    FUNC_ENTER_NOAPI(H5D_contig_readvv, FAIL)

    /* Check args */
    assert(io_info);
    assert(io_info->dset);
    assert(io_info->store);
    assert(buf);

    /* Check if data sieving is enabled */
    if(H5F_HAS_FEATURE(file,H5FD_FEAT_DATA_SIEVE)) {
        haddr_t sieve_start=HADDR_UNDEF, sieve_end=HADDR_UNDEF;     /* Start & end locations of sieve buffer */
        haddr_t contig_end;             /* End locations of block to write */
        size_t sieve_size=(size_t)-1;   /* size of sieve buffer */
        haddr_t abs_eoa;	        /* Absolute end of file address		*/
        haddr_t rel_eoa;	        /* Relative end of file address		*/
        hsize_t max_data;               /* Actual maximum size of data to cache */

        /* Set offsets in sequence lists */
        u=*dset_curr_seq;
        v=*mem_curr_seq;

        /* Stash local copies of these value */
        if(dset_contig->sieve_buf!=NULL) {
            sieve_start=dset_contig->sieve_loc;
            sieve_size=dset_contig->sieve_size;
            sieve_end=sieve_start+sieve_size;
        } /* end if */

        /* Works through sequences as fast as possible */
        for(; u<dset_max_nseq && v<mem_max_nseq; ) {
            /* Choose smallest buffer to write */
            if(mem_len_arr[v]<dset_len_arr[u])
                size=mem_len_arr[v];
            else
                size=dset_len_arr[u];

            /* Compute offset on disk */
            addr=store_contig->dset_addr+dset_offset_arr[u];

            /* Compute offset in memory */
            buf = (unsigned char *)_buf + mem_offset_arr[v];

            /* Check if the sieve buffer is allocated yet */
            if(dset_contig->sieve_buf==NULL) {
                /* Check if we can actually hold the I/O request in the sieve buffer */
                if(size>dset_contig->sieve_buf_size) {
                    if (H5F_block_read(file, H5FD_MEM_DRAW, addr, size, io_info->dxpl_id, buf)<0)
                        HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "block read failed")
                } /* end if */
                else {
                    /* Allocate room for the data sieve buffer */
                    if (NULL==(dset_contig->sieve_buf=H5FL_BLK_MALLOC(sieve_buf,dset_contig->sieve_buf_size)))
                        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")

                    /* Determine the new sieve buffer size & location */
                    dset_contig->sieve_loc=addr;

                    /* Make certain we don't read off the end of the file */
                    if (HADDR_UNDEF==(abs_eoa=H5F_get_eoa(file)))
                        HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "unable to determine file size")

                    /* Adjust absolute EOA address to relative EOA address */
                    rel_eoa=abs_eoa-H5F_get_base_addr(file);

                    /* Set up the buffer parameters */
                    max_data=store_contig->dset_size-dset_offset_arr[u];

                    /* Compute the size of the sieve buffer */
                    H5_ASSIGN_OVERFLOW(dset_contig->sieve_size,MIN3(rel_eoa-dset_contig->sieve_loc,max_data,dset_contig->sieve_buf_size),hsize_t,size_t);

                    /* Read the new sieve buffer */
                    if (H5F_block_read(file, H5FD_MEM_DRAW, dset_contig->sieve_loc, dset_contig->sieve_size, io_info->dxpl_id, dset_contig->sieve_buf)<0)
                        HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "block read failed")

                    /* Grab the data out of the buffer (must be first piece of data in buffer ) */
                    HDmemcpy(buf,dset_contig->sieve_buf,size);

                    /* Reset sieve buffer dirty flag */
                    dset_contig->sieve_dirty=0;

                    /* Stash local copies of these value */
                    sieve_start=dset_contig->sieve_loc;
                    sieve_size=dset_contig->sieve_size;
                    sieve_end=sieve_start+sieve_size;
                } /* end else */
            } /* end if */
            else {
                /* Compute end of sequence to retrieve */
                contig_end=addr+size-1;

                /* If entire read is within the sieve buffer, read it from the buffer */
                if(addr>=sieve_start && contig_end<sieve_end) {
                    unsigned char *base_sieve_buf=dset_contig->sieve_buf+(addr-sieve_start);

                    /* Grab the data out of the buffer */
                    HDmemcpy(buf,base_sieve_buf,size);
                } /* end if */
                /* Entire request is not within this data sieve buffer */
                else {
                    /* Check if we can actually hold the I/O request in the sieve buffer */
                    if(size>dset_contig->sieve_buf_size) {
                        /* Check for any overlap with the current sieve buffer */
                        if((sieve_start>=addr && sieve_start<(contig_end+1))
                                || ((sieve_end-1)>=addr && (sieve_end-1)<(contig_end+1))) {
                            /* Flush the sieve buffer, if it's dirty */
                            if(dset_contig->sieve_dirty) {
                                /* Write to file */
                                if (H5F_block_write(file, H5FD_MEM_DRAW, sieve_start, sieve_size, io_info->dxpl_id, dset_contig->sieve_buf)<0)
                                    HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "block write failed")

                                /* Reset sieve buffer dirty flag */
                                dset_contig->sieve_dirty=0;
                            } /* end if */
                        } /* end if */

                        /* Read directly into the user's buffer */
                        if (H5F_block_read(file, H5FD_MEM_DRAW, addr, size, io_info->dxpl_id, buf)<0)
                            HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "block read failed")
                    } /* end if */
                    /* Element size fits within the buffer size */
                    else {
                        /* Flush the sieve buffer if it's dirty */
                        if(dset_contig->sieve_dirty) {
                            /* Write to file */
                            if (H5F_block_write(file, H5FD_MEM_DRAW, sieve_start, sieve_size, io_info->dxpl_id, dset_contig->sieve_buf)<0)
                                HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "block write failed")

                            /* Reset sieve buffer dirty flag */
                            dset_contig->sieve_dirty=0;
                        } /* end if */

                        /* Determine the new sieve buffer size & location */
                        dset_contig->sieve_loc=addr;

                        /* Make certain we don't read off the end of the file */
                        if (HADDR_UNDEF==(abs_eoa=H5F_get_eoa(file)))
                            HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "unable to determine file size")

                        /* Adjust absolute EOA address to relative EOA address */
                        rel_eoa=abs_eoa-H5F_get_base_addr(file);

                        /* Only need this when resizing sieve buffer */
                        max_data=store_contig->dset_size-dset_offset_arr[u];

                        /* Compute the size of the sieve buffer */
                        /* Don't read off the end of the file, don't read past the end of the data element and don't read more than the buffer size */
                        H5_ASSIGN_OVERFLOW(dset_contig->sieve_size,MIN3(rel_eoa-dset_contig->sieve_loc,max_data,dset_contig->sieve_buf_size),hsize_t,size_t);

                        /* Update local copies of sieve information */
                        sieve_start=dset_contig->sieve_loc;
                        sieve_size=dset_contig->sieve_size;
                        sieve_end=sieve_start+sieve_size;

                        /* Read the new sieve buffer */
                        if (H5F_block_read(file, H5FD_MEM_DRAW, dset_contig->sieve_loc, dset_contig->sieve_size, io_info->dxpl_id, dset_contig->sieve_buf)<0)
                            HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "block read failed")

                        /* Grab the data out of the buffer (must be first piece of data in buffer ) */
                        HDmemcpy(buf,dset_contig->sieve_buf,size);

                        /* Reset sieve buffer dirty flag */
                        dset_contig->sieve_dirty=0;
                    } /* end else */
                } /* end else */
            } /* end else */

            /* Update memory information */
            mem_len_arr[v]-=size;
            mem_offset_arr[v]+=size;
            if(mem_len_arr[v]==0)
                v++;

            /* Update file information */
            dset_len_arr[u]-=size;
            dset_offset_arr[u]+=size;
            if(dset_len_arr[u]==0)
                u++;

            /* Increment number of bytes copied */
            total_size+=size;
        } /* end for */
    } /* end if */
    else {
        /* Work through all the sequences */
        for(u=*dset_curr_seq, v=*mem_curr_seq; u<dset_max_nseq && v<mem_max_nseq; ) {
            /* Choose smallest buffer to write */
            if(mem_len_arr[v]<dset_len_arr[u])
                size=mem_len_arr[v];
            else
                size=dset_len_arr[u];

            /* Compute offset on disk */
            addr=store_contig->dset_addr+dset_offset_arr[u];

            /* Compute offset in memory */
            buf = (unsigned char *)_buf + mem_offset_arr[v];

            /* Write data */
            if (H5F_block_read(file, H5FD_MEM_DRAW, addr, size, io_info->dxpl_id, buf)<0)
                HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "block write failed")

            /* Update memory information */
            mem_len_arr[v]-=size;
            mem_offset_arr[v]+=size;
            if(mem_len_arr[v]==0)
                v++;

            /* Update file information */
            dset_len_arr[u]-=size;
            dset_offset_arr[u]+=size;
            if(dset_len_arr[u]==0)
                u++;

            /* Increment number of bytes copied */
            total_size+=size;
        } /* end for */
    } /* end else */

    /* Update current sequence vectors */
    *dset_curr_seq=u;
    *mem_curr_seq=v;

    /* Set return value */
    H5_ASSIGN_OVERFLOW(ret_value,total_size,size_t,ssize_t);

done:
    FUNC_LEAVE_NOAPI(ret_value)
}   /* end H5D_contig_readvv() */


/*-------------------------------------------------------------------------
 * Function:	H5D_contig_writevv
 *
 * Purpose:	Writes some data vectors into a dataset from vectors into a
 *              buffer.  The address is the start of the dataset,
 *              relative to the base address for the file and the offsets and
 *              sequence lengths are in bytes.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *              Friday, May 2, 2003
 *
 * Notes:
 *      Offsets in the sequences must be monotonically increasing
 *
 *-------------------------------------------------------------------------
 */
ssize_t
H5D_contig_writevv(const H5D_io_info_t *io_info,
    size_t dset_max_nseq, size_t *dset_curr_seq, size_t dset_len_arr[], hsize_t dset_offset_arr[],
    size_t mem_max_nseq, size_t *mem_curr_seq, size_t mem_len_arr[], hsize_t mem_offset_arr[],
    const void *_buf)
{
    H5F_t *file=io_info->dset->ent.file;        /* File for dataset */
    H5D_rdcdc_t *dset_contig=&(io_info->dset->shared->cache.contig); /* Cached information about contiguous data */
    const H5D_contig_storage_t *store_contig=&(io_info->store->contig);    /* Contiguous storage info for this I/O operation */
    const unsigned char *buf=(const unsigned char *)_buf;      /* Pointer to buffer to fill */
    haddr_t addr;               /* Actual address to read */
    size_t total_size=0;        /* Size of sequence in bytes */
    size_t size;                /* Size of sequence in bytes */
    size_t u;                   /* Counting variable */
    size_t v;                   /* Counting variable */
    ssize_t ret_value;          /* Return value */

    FUNC_ENTER_NOAPI(H5D_contig_writevv, FAIL)

    /* Check args */
    assert(io_info);
    assert(io_info->dset);
    assert(io_info->store);
    assert(buf);

    /* Check if data sieving is enabled */
    if(H5F_HAS_FEATURE(file,H5FD_FEAT_DATA_SIEVE)) {
        haddr_t sieve_start=HADDR_UNDEF, sieve_end=HADDR_UNDEF;     /* Start & end locations of sieve buffer */
        haddr_t contig_end;             /* End locations of block to write */
        size_t sieve_size=(size_t)-1;   /* size of sieve buffer */
        haddr_t abs_eoa;	        /* Absolute end of file address		*/
        haddr_t rel_eoa;	        /* Relative end of file address		*/
        hsize_t max_data;               /* Actual maximum size of data to cache */

        /* Set offsets in sequence lists */
        u=*dset_curr_seq;
        v=*mem_curr_seq;

        /* Stash local copies of these values */
        if(dset_contig->sieve_buf!=NULL) {
            sieve_start=dset_contig->sieve_loc;
            sieve_size=dset_contig->sieve_size;
            sieve_end=sieve_start+sieve_size;
        } /* end if */

        /* Works through sequences as fast as possible */
        for(; u<dset_max_nseq && v<mem_max_nseq; ) {
            /* Choose smallest buffer to write */
            if(mem_len_arr[v]<dset_len_arr[u])
                size=mem_len_arr[v];
            else
                size=dset_len_arr[u];

            /* Compute offset on disk */
            addr=store_contig->dset_addr+dset_offset_arr[u];

            /* Compute offset in memory */
            buf = (const unsigned char *)_buf + mem_offset_arr[v];

            /* No data sieve buffer yet, go allocate one */
            if(dset_contig->sieve_buf==NULL) {
                /* Check if we can actually hold the I/O request in the sieve buffer */
                if(size>dset_contig->sieve_buf_size) {
                    if (H5F_block_write(file, H5FD_MEM_DRAW, addr, size, io_info->dxpl_id, buf)<0)
                        HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "block write failed")
                } /* end if */
                else {
                    /* Allocate room for the data sieve buffer */
                    if (NULL==(dset_contig->sieve_buf=H5FL_BLK_MALLOC(sieve_buf,dset_contig->sieve_buf_size)))
                        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
#ifdef H5_CLEAR_MEMORY
if(dset_contig->sieve_size > size)
    HDmemset(dset_contig->sieve_buf + size, 0, (dset_contig->sieve_size - size));
#endif /* H5_CLEAR_MEMORY */

                    /* Determine the new sieve buffer size & location */
                    dset_contig->sieve_loc=addr;

                    /* Make certain we don't read off the end of the file */
                    if (HADDR_UNDEF==(abs_eoa=H5F_get_eoa(file)))
                        HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "unable to determine file size")

                    /* Adjust absolute EOA address to relative EOA address */
                    rel_eoa=abs_eoa-H5F_get_base_addr(file);

                    /* Set up the buffer parameters */
                    max_data=store_contig->dset_size-dset_offset_arr[u];

                    /* Compute the size of the sieve buffer */
                    H5_ASSIGN_OVERFLOW(dset_contig->sieve_size,MIN3(rel_eoa-dset_contig->sieve_loc,max_data,dset_contig->sieve_buf_size),hsize_t,size_t);

                    /* Check if there is any point in reading the data from the file */
                    if(dset_contig->sieve_size>size) {
                        /* Read the new sieve buffer */
                        if (H5F_block_read(file, H5FD_MEM_DRAW, dset_contig->sieve_loc, dset_contig->sieve_size, io_info->dxpl_id, dset_contig->sieve_buf)<0)
                            HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "block read failed")
                    } /* end if */

                    /* Grab the data out of the buffer (must be first piece of data in buffer ) */
                    HDmemcpy(dset_contig->sieve_buf,buf,size);

                    /* Set sieve buffer dirty flag */
                    dset_contig->sieve_dirty=1;

                    /* Stash local copies of these values */
                    sieve_start=dset_contig->sieve_loc;
                    sieve_size=dset_contig->sieve_size;
                    sieve_end=sieve_start+sieve_size;
                } /* end else */
            } /* end if */
            else {
                /* Compute end of sequence to retrieve */
                contig_end=addr+size-1;

                /* If entire write is within the sieve buffer, write it to the buffer */
                if(addr>=sieve_start && contig_end<sieve_end) {
                    unsigned char *base_sieve_buf=dset_contig->sieve_buf+(addr-sieve_start);

                    /* Put the data into the sieve buffer */
                    HDmemcpy(base_sieve_buf,buf,size);

                    /* Set sieve buffer dirty flag */
                    dset_contig->sieve_dirty=1;
                } /* end if */
                /* Entire request is not within this data sieve buffer */
                else {
                    /* Check if we can actually hold the I/O request in the sieve buffer */
                    if(size>dset_contig->sieve_buf_size) {
                        /* Check for any overlap with the current sieve buffer */
                        if((sieve_start>=addr && sieve_start<(contig_end+1))
                                || ((sieve_end-1)>=addr && (sieve_end-1)<(contig_end+1))) {
                            /* Flush the sieve buffer, if it's dirty */
                            if(dset_contig->sieve_dirty) {
                                /* Write to file */
                                if (H5F_block_write(file, H5FD_MEM_DRAW, sieve_start, sieve_size, io_info->dxpl_id, dset_contig->sieve_buf)<0)
                                    HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "block write failed")

                                /* Reset sieve buffer dirty flag */
                                dset_contig->sieve_dirty=0;
                            } /* end if */

                            /* Force the sieve buffer to be re-read the next time */
                            dset_contig->sieve_loc=HADDR_UNDEF;
                            dset_contig->sieve_size=0;
                        } /* end if */

                        /* Write directly from the user's buffer */
                        if (H5F_block_write(file, H5FD_MEM_DRAW, addr, size, io_info->dxpl_id, buf)<0)
                            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "block write failed")
                    } /* end if */
                    /* Element size fits within the buffer size */
                    else {
                        /* Check if it is possible to (exactly) prepend or append to existing (dirty) sieve buffer */
                        if(((addr+size)==sieve_start || addr==sieve_end) &&
                                (size+sieve_size)<=dset_contig->sieve_buf_size &&
                                dset_contig->sieve_dirty) {
                            /* Prepend to existing sieve buffer */
                            if((addr+size)==sieve_start) {
                                /* Move existing sieve information to correct location */
                                HDmemmove(dset_contig->sieve_buf+size,dset_contig->sieve_buf,dset_contig->sieve_size);

                                /* Copy in new information (must be first in sieve buffer) */
                                HDmemcpy(dset_contig->sieve_buf,buf,size);

                                /* Adjust sieve location */
                                dset_contig->sieve_loc=addr;

                            } /* end if */
                            /* Append to existing sieve buffer */
                            else {
                                /* Copy in new information */
                                HDmemcpy(dset_contig->sieve_buf+sieve_size,buf,size);
                            } /* end else */

                            /* Adjust sieve size */
                            dset_contig->sieve_size += size;

                            /* Update local copies of sieve information */
                            sieve_start=dset_contig->sieve_loc;
                            sieve_size=dset_contig->sieve_size;
                            sieve_end=sieve_start+sieve_size;
                        } /* end if */
                        /* Can't add the new data onto the existing sieve buffer */
                        else {
                            /* Flush the sieve buffer if it's dirty */
                            if(dset_contig->sieve_dirty) {
                                /* Write to file */
                                if (H5F_block_write(file, H5FD_MEM_DRAW, sieve_start, sieve_size, io_info->dxpl_id, dset_contig->sieve_buf)<0)
                                    HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "block write failed")

                                /* Reset sieve buffer dirty flag */
                                dset_contig->sieve_dirty=0;
                            } /* end if */

                            /* Determine the new sieve buffer size & location */
                            dset_contig->sieve_loc=addr;

                            /* Make certain we don't read off the end of the file */
                            if (HADDR_UNDEF==(abs_eoa=H5F_get_eoa(file)))
                                HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "unable to determine file size")

                            /* Adjust absolute EOA address to relative EOA address */
                            rel_eoa=abs_eoa-H5F_get_base_addr(file);

                            /* Only need this when resizing sieve buffer */
                            max_data=store_contig->dset_size-dset_offset_arr[u];

                            /* Compute the size of the sieve buffer */
                            /* Don't read off the end of the file, don't read past the end of the data element and don't read more than the buffer size */
                            H5_ASSIGN_OVERFLOW(dset_contig->sieve_size,MIN3(rel_eoa-dset_contig->sieve_loc,max_data,dset_contig->sieve_buf_size),hsize_t,size_t);

                            /* Update local copies of sieve information */
                            sieve_start=dset_contig->sieve_loc;
                            sieve_size=dset_contig->sieve_size;
                            sieve_end=sieve_start+sieve_size;

                            /* Check if there is any point in reading the data from the file */
                            if(dset_contig->sieve_size>size) {
                                /* Read the new sieve buffer */
                                if (H5F_block_read(file, H5FD_MEM_DRAW, dset_contig->sieve_loc, dset_contig->sieve_size, io_info->dxpl_id, dset_contig->sieve_buf)<0)
                                    HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "block read failed")
                            } /* end if */

                            /* Grab the data out of the buffer (must be first piece of data in buffer ) */
                            HDmemcpy(dset_contig->sieve_buf,buf,size);

                            /* Set sieve buffer dirty flag */
                            dset_contig->sieve_dirty=1;
                        } /* end else */
                    } /* end else */
                } /* end else */
            } /* end else */

            /* Update memory information */
            mem_len_arr[v]-=size;
            mem_offset_arr[v]+=size;
            if(mem_len_arr[v]==0)
                v++;

            /* Update file information */
            dset_len_arr[u]-=size;
            dset_offset_arr[u]+=size;
            if(dset_len_arr[u]==0)
                u++;

            /* Increment number of bytes copied */
            total_size+=size;
        } /* end for */
    } /* end if */
    else {
        /* Work through all the sequences */
        for(u=*dset_curr_seq, v=*mem_curr_seq; u<dset_max_nseq && v<mem_max_nseq; ) {
            /* Choose smallest buffer to write */
            if(mem_len_arr[v]<dset_len_arr[u])
                size=mem_len_arr[v];
            else
                size=dset_len_arr[u];

            /* Compute offset on disk */
            addr=store_contig->dset_addr+dset_offset_arr[u];

            /* Compute offset in memory */
            buf = (const unsigned char *)_buf + mem_offset_arr[v];

            /* Write data */
            if (H5F_block_write(file, H5FD_MEM_DRAW, addr, size, io_info->dxpl_id, buf)<0)
                HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "block write failed")

            /* Update memory information */
            mem_len_arr[v]-=size;
            mem_offset_arr[v]+=size;
            if(mem_len_arr[v]==0)
                v++;

            /* Update file information */
            dset_len_arr[u]-=size;
            dset_offset_arr[u]+=size;
            if(dset_len_arr[u]==0)
                u++;

            /* Increment number of bytes copied */
            total_size+=size;
        } /* end for */
    } /* end else */

    /* Update current sequence vectors */
    *dset_curr_seq=u;
    *mem_curr_seq=v;

    /* Set return value */
    H5_ASSIGN_OVERFLOW(ret_value,total_size,size_t,ssize_t);

done:
    FUNC_LEAVE_NOAPI(ret_value)
}   /* end H5D_contig_writevv() */