path: root/src/H5HLcache.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.     *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*-------------------------------------------------------------------------
 *
 * Created:		H5HLcache.c
 *			Feb  5 2008
 *			Quincey Koziol <koziol@hdfgroup.org>
 *
 * Purpose:		Implement local heap metadata cache methods.
 *
 *-------------------------------------------------------------------------
 */

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

#define H5HL_PACKAGE		/* Suppress error about including H5HLpkg */


/***********/
/* Headers */
/***********/
#include "H5private.h"		/* Generic Functions			*/
#include "H5Eprivate.h"		/* Error handling		  	*/
#include "H5HLpkg.h"		/* Local Heaps				*/
#include "H5MFprivate.h"	/* File memory management		*/
#include "H5WBprivate.h"        /* Wrapped Buffers                      */


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

#define H5HL_VERSION	0               /* Local heap collection version    */

/* Set the local heap size to speculatively read in */
/* (needs to be more than the local heap prefix size to work at all and
 *      should be larger than the default local heap size to save the
 *      extra I/O operations) */
#define H5HL_SPEC_READ_SIZE 512


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


/********************/
/* Package Typedefs */
/********************/


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

/* Metadata cache callbacks */
static herr_t H5HL__cache_prefix_get_load_size(const void *udata, size_t *image_len);
static void *H5HL__cache_prefix_deserialize(const void *image, size_t len,
    void *udata, hbool_t *dirty);
static herr_t H5HL__cache_prefix_image_len(const void *thing, 
    size_t *image_len, hbool_t *compressed_ptr, 
    size_t *compressed_image_len_ptr);
static herr_t H5HL__cache_prefix_serialize(const H5F_t *f, void *image,
    size_t len, void *thing); 
static herr_t H5HL__cache_prefix_free_icr(void *thing);

static herr_t H5HL__cache_datablock_get_load_size(const void *udata,
    size_t *image_len); 
static void *H5HL__cache_datablock_deserialize(const void *image, size_t len,
    void *udata, hbool_t *dirty); 
static herr_t H5HL__cache_datablock_image_len(const void *thing, 
    size_t *image_len, hbool_t *compressed_ptr, 
    size_t *compressed_image_len_ptr);
static herr_t H5HL__cache_datablock_serialize(const H5F_t *f, void *image,
    size_t len, void *thing); 
static herr_t H5HL__cache_datablock_free_icr(void *thing);


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

/* H5HL inherits cache-like properties from H5AC */
const H5AC_class_t H5AC_LHEAP_PRFX[1] = {{
    H5AC_LHEAP_PRFX_ID,                 /* Metadata client ID */
    "local heap prefix",                /* Metadata client name (for debugging) */
    H5FD_MEM_LHEAP,                     /* File space memory type for client */
    H5AC__CLASS_SPECULATIVE_LOAD_FLAG,  /* Client class behavior flags */
    H5HL__cache_prefix_get_load_size,   /* 'get_load_size' callback */
    H5HL__cache_prefix_deserialize,     /* 'deserialize' callback */
    H5HL__cache_prefix_image_len,       /* 'image_len' callback */
    NULL,                               /* 'pre_serialize' callback */
    H5HL__cache_prefix_serialize,       /* 'serialize' callback */
    NULL,                               /* 'notify' callback */
    H5HL__cache_prefix_free_icr,        /* 'free_icr' callback */
    NULL,                               /* 'clear' callback */
    NULL,                               /* 'fsf_size' callback */
}};

const H5AC_class_t H5AC_LHEAP_DBLK[1] = {{
    H5AC_LHEAP_DBLK_ID,                 /* Metadata client ID */
    "local heap datablock",             /* Metadata client name (for debugging) */
    H5FD_MEM_LHEAP,                     /* File space memory type for client */
    H5AC__CLASS_NO_FLAGS_SET,           /* Client class behavior flags */
    H5HL__cache_datablock_get_load_size,/* 'get_load_size' callback */
    H5HL__cache_datablock_deserialize,  /* 'deserialize' callback */
    H5HL__cache_datablock_image_len,    /* 'image_len' callback */
    NULL,                               /* 'pre_serialize' callback */
    H5HL__cache_datablock_serialize,    /* 'serialize' callback */
    NULL,                               /* 'notify' callback */
    H5HL__cache_datablock_free_icr,     /* 'free_icr' callback */
    NULL,                               /* 'clear' callback */
    NULL,                               /* 'fsf_size' callback */
}};


/*****************************/
/* Library Private Variables */
/*****************************/


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



/*-------------------------------------------------------------------------
 * Function:	H5HL__fl_deserialize
 *
 * Purpose:	Deserialize the free list for a heap data block
 *
 * Return:      Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		koziol@hdfgroup.org
 *		Oct 12 2008
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HL__fl_deserialize(H5HL_t *heap)
{
    H5HL_free_t *fl = NULL, *tail = NULL;      /* Heap free block nodes */
    hsize_t free_block;                 /* Offset of free block */
    herr_t ret_value = SUCCEED;         /* Return value */

    FUNC_ENTER_STATIC

    /* check arguments */
    HDassert(heap);
    HDassert(!heap->freelist);

    /* Build free list */
    free_block = heap->free_block;
    while(H5HL_FREE_NULL != free_block) {
        const uint8_t *image;           /* Pointer into image buffer */

        /* Sanity check */
        if(free_block >= heap->dblk_size)
            HGOTO_ERROR(H5E_HEAP, H5E_BADRANGE, FAIL, "bad heap free list")

        /* Allocate & initialize free list node */
        if(NULL == (fl = H5FL_MALLOC(H5HL_free_t)))
            HGOTO_ERROR(H5E_HEAP, H5E_CANTALLOC, FAIL, "memory allocation failed")
        fl->offset = (size_t)free_block;
        fl->prev = tail;
        fl->next = NULL;

        /* Decode offset of next free block */
        image = heap->dblk_image + free_block;
        H5F_DECODE_LENGTH_LEN(image, free_block, heap->sizeof_size);
        if(free_block == 0)
            HGOTO_ERROR(H5E_HEAP, H5E_BADVALUE, FAIL, "free block size is zero?")

        /* Decode length of this free block */
        H5F_DECODE_LENGTH_LEN(image, fl->size, heap->sizeof_size);
        if((fl->offset + fl->size) > heap->dblk_size)
            HGOTO_ERROR(H5E_HEAP, H5E_BADRANGE, FAIL, "bad heap free list")

        /* Append node onto list */
        if(tail)
            tail->next = fl;
        else
            heap->freelist = fl;
        tail = fl;
        fl = NULL;
    } /* end while */

done:
    if(ret_value < 0)
        if(fl)
            fl = H5FL_FREE(H5HL_free_t, fl);

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5HL__fl_deserialize() */


/*-------------------------------------------------------------------------
 * Function:	H5HL__fl_serialize
 *
 * Purpose:	Serialize the free list for a heap data block
 *
 * Return:	Success:	SUCCESS
 *		Failure:	FAIL
 *
 * Programmer:	Quincey Koziol
 *		koziol@hdfgroup.org
 *		Oct 12 2008
 *
 *-------------------------------------------------------------------------
 */
static void
H5HL__fl_serialize(const H5HL_t *heap)
{
    H5HL_free_t	*fl;                    /* Pointer to heap free list node */

    FUNC_ENTER_STATIC_NOERR

    /* check arguments */
    HDassert(heap);

    /* Serialize the free list into the heap data's image */
    for(fl = heap->freelist; fl; fl = fl->next) {
        uint8_t     *image;     /* Pointer into raw data buffer */

        HDassert(fl->offset == H5HL_ALIGN(fl->offset));
        image = heap->dblk_image + fl->offset;

        if(fl->next)
            H5F_ENCODE_LENGTH_LEN(image, fl->next->offset, heap->sizeof_size)
        else
            H5F_ENCODE_LENGTH_LEN(image, H5HL_FREE_NULL, heap->sizeof_size)

        H5F_ENCODE_LENGTH_LEN(image, fl->size, heap->sizeof_size)
    } /* end for */

    FUNC_LEAVE_NOAPI_VOID
} /* end H5HL__fl_serialize() */


/*-------------------------------------------------------------------------
 * Function:    H5HL__cache_prefix_get_load_size()
 *
 * Purpose:	Return the size of the buffer the metadata cache should 
 *		load from file and pass to the deserialize routine.
 *
 *		The version 2 metadata cache callbacks included a test to 
 *		ensure that the read did not pass the end of file, but this 
 *		functionality has been moved to H5C_load_entry().  Thus 
 *		all this function does is set *image_len equal to 
 *		H5HL_SPEC_READ_SIZE, leaving it to the metadata cache to 
 *		reduce the size of the read if appropriate.
 *
 * Return:      Success:        SUCCEED
 *              Failure:        FAIL
 *
 * Programmer:  John Mainzer
 *              6/21/14
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HL__cache_prefix_get_load_size(const void H5_ATTR_UNUSED *_udata, size_t *image_len)
{
    FUNC_ENTER_STATIC_NOERR

    HDassert(image_len);

    *image_len = H5HL_SPEC_READ_SIZE;

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5HL__cache_prefix_get_load_size() */


/*-------------------------------------------------------------------------
 * Function:    H5HL__cache_prefix_deserialize
 *
 * Purpose:	Given a buffer containing the on disk image of the local 
 *		heap prefix, deserialize it, load its contents into a newly allocated
 *		instance of H5HL_prfx_t, and return a pointer to the new instance.
 *
 * Return:      Success:        Pointer to in core representation
 *              Failure:        NULL
 *
 * Programmer:  John Mainzer
 *              6/21/14
 *
 *-------------------------------------------------------------------------
 */
static void *
H5HL__cache_prefix_deserialize(const void *_image, size_t len, void *_udata,
    hbool_t H5_ATTR_UNUSED *dirty)
{
    H5HL_t               *heap = NULL;  /* Local heap */
    H5HL_prfx_t          *prfx = NULL;  /* Heap prefix deserialized */
    const uint8_t        *image = (const uint8_t *)_image;      /* Pointer into decoding buffer */
    H5HL_cache_prfx_ud_t *udata = (H5HL_cache_prfx_ud_t *)_udata;       /* User data for callback */
    void                 *ret_value;    /* Return value */

    FUNC_ENTER_STATIC

    /* Check arguments */
    HDassert(image);
    HDassert(len > 0);
    HDassert(udata);
    HDassert(udata->sizeof_size > 0);
    HDassert(udata->sizeof_addr > 0);
    HDassert(udata->sizeof_prfx > 0);
    HDassert(H5F_addr_defined(udata->prfx_addr));
    HDassert(dirty);

    /* Check magic number */
    if(HDmemcmp(image, H5HL_MAGIC, (size_t)H5_SIZEOF_MAGIC)) 
        HGOTO_ERROR(H5E_HEAP, H5E_BADVALUE, NULL, "bad local heap signature")
    image += H5_SIZEOF_MAGIC;

    /* Version */
    if(H5HL_VERSION != *image++) 
        HGOTO_ERROR(H5E_HEAP, H5E_BADVALUE, NULL, "wrong version number in local heap")

    /* Reserved */
    image += 3;
    
    /* Allocate space in memory for the heap */
    if(NULL == (heap = H5HL_new(udata->sizeof_size, udata->sizeof_addr, udata->sizeof_prfx)))
        HGOTO_ERROR(H5E_HEAP, H5E_CANTALLOC, NULL, "can't allocate local heap structure")

    /* Allocate the heap prefix */
    if(NULL == (prfx = H5HL_prfx_new(heap)))
        HGOTO_ERROR(H5E_HEAP, H5E_CANTALLOC, NULL, "can't allocate local heap prefix")

    /* Store the prefix's address & length */
    heap->prfx_addr = udata->prfx_addr;
    heap->prfx_size = udata->sizeof_prfx;

    /* Heap data size */
    H5F_DECODE_LENGTH_LEN(image, heap->dblk_size, udata->sizeof_size);

    /* Free list head */
    H5F_DECODE_LENGTH_LEN(image, heap->free_block, udata->sizeof_size);

    if((heap->free_block != H5HL_FREE_NULL) && (heap->free_block >= heap->dblk_size))
        HGOTO_ERROR(H5E_HEAP, H5E_BADVALUE, NULL, "bad heap free list")

    /* Heap data address */
    H5F_addr_decode_len(udata->sizeof_addr, &image, &(heap->dblk_addr));

    /* Check if heap block exists */
    if(heap->dblk_size) {
        /* Check if heap data block is contiguous with header */
        if(H5F_addr_eq((heap->prfx_addr + heap->prfx_size), heap->dblk_addr)) {
            /* Note that the heap should be a single object in the cache */
            heap->single_cache_obj = TRUE;

            /* Check if the current buffer from the speculative read 
             * already has the heap data 
             */
            if(len >= (heap->prfx_size + heap->dblk_size)) {
                /* Allocate space for the heap data image */
                if(NULL == (heap->dblk_image = H5FL_BLK_MALLOC(lheap_chunk, heap->dblk_size)))
                    HGOTO_ERROR(H5E_HEAP, H5E_CANTALLOC, NULL, "memory allocation failed")

                /* Set image to the start of the data block.  This is necessary
                 * because there may be a gap between the used portion of the
                 * prefix and the data block due to alignment constraints. */
                image = ((const uint8_t *)_image) + heap->prfx_size;

                /* Copy the heap data from the speculative read buffer */
                HDmemcpy(heap->dblk_image, image, heap->dblk_size);

                /* Build free list */
                if(H5HL__fl_deserialize(heap) < 0)
                    HGOTO_ERROR(H5E_HEAP, H5E_CANTINIT, NULL, "can't initialize free list")
            } /* end if */
            else {
		/* the supplied buffer is too small -- We have already made note
                 * of the correct size, so simply return success.  H5C_load_entry()
                 * will notice the size discrepency, and re-try the load.
                 */

                /* Make certain that this is the first try ... */
                HDassert(!udata->made_attempt);

                /* ... and mark the udata so that we know that we have used up
                 * our first try.
                 */
                udata->made_attempt = TRUE;
	    } /* end else */
        } /* end if */
        else {
            /* Note that the heap should _NOT_ be a single 
             * object in the cache 
             */
            heap->single_cache_obj = FALSE;

	} /* end else */
    } /* end if */

    /* Set flag to indicate prefix from loaded from file */
    udata->loaded = TRUE;

    /* Set return value */
    ret_value = prfx;

done:
    /* Release the [possibly partially initialized] local heap on errors */
    if(!ret_value) {
        if(prfx) {
            if(H5HL_prfx_dest(prfx) < 0)
                HDONE_ERROR(H5E_HEAP, H5E_CANTRELEASE, NULL, "unable to destroy local heap prefix")
        } /* end if */
        else {
            if(heap && H5HL_dest(heap) < 0)
                HDONE_ERROR(H5E_HEAP, H5E_CANTRELEASE, NULL, "unable to destroy local heap")
        } /* end else */
    } /* end if */

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5HL__cache_prefix_deserialize() */


/*-------------------------------------------------------------------------
 * Function:    H5HL__cache_prefix_image_len
 *
 * Purpose:	Return the on disk image size of a local heap prefix to the 
 *		metadata cache via the image_len.
 *
 * Return:      Success:        SUCCEED
 *              Failure:        FAIL
 *
 * Programmer:  John Mainzer
 *              6/21/14
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HL__cache_prefix_image_len(const void *_thing, size_t *image_len,
    hbool_t H5_ATTR_UNUSED *compressed_ptr, size_t H5_ATTR_UNUSED *compressed_image_len_ptr)
{
    const H5HL_prfx_t *prfx = (const H5HL_prfx_t *)_thing;  /* Pointer to local heap prefix to query */

    FUNC_ENTER_STATIC_NOERR

    /* Check arguments */
    HDassert(prfx);
    HDassert(prfx->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
    HDassert(prfx->cache_info.type == H5AC_LHEAP_PRFX);
    HDassert(image_len);

    /* Set the prefix's size */
    *image_len = prfx->heap->prfx_size;

    /* If the heap is stored as a single object, add in the 
     * data block size also 
     */
    if(prfx->heap->single_cache_obj)
        *image_len += prfx->heap->dblk_size;


    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5HL__cache_prefix_image_len() */

/****************************************/
/* no H5HL_cache_prefix_pre_serialize() */
/****************************************/


/*-------------------------------------------------------------------------
 * Function:    H5HL__cache_prefix_serialize
 *
 * Purpose:	Given a pointer to an instance of H5HL_prfx_t and an 
 *		appropriately sized buffer, serialize the contents of the 
 *		instance for writing to disk, and copy the serialized data 
 *		into the buffer.
 *
 * Return:      Success:        SUCCEED
 *              Failure:        FAIL
 *
 * Programmer:  John Mainzer
 *              7/21/14
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HL__cache_prefix_serialize(const H5F_t *f, void *_image, size_t len,
    void *_thing)
{
    H5HL_prfx_t *prfx = (H5HL_prfx_t *)_thing;  /* Pointer to local heap prefix to query */
    H5HL_t      *heap;          /* Pointer to the local heap */
    uint8_t     *image = (uint8_t *)_image;     /* Pointer into image buffer */
    size_t       buf_size;      /* expected size of the image buffer */

    FUNC_ENTER_STATIC_NOERR

    /* Check arguments */
    HDassert(f);
    HDassert(image);
    HDassert(prfx);
    HDassert(prfx->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
    HDassert(prfx->cache_info.type == H5AC_LHEAP_PRFX);
    HDassert(H5F_addr_eq(prfx->cache_info.addr, prfx->heap->prfx_addr));
    HDassert(prfx->heap);

    /* Get the pointer to the heap */
    heap = prfx->heap;
    HDassert(heap);

    /* Compute the buffer size */
    buf_size = heap->prfx_size;
    if(heap->single_cache_obj)
        buf_size += heap->dblk_size;
    HDassert(len == buf_size);

    /* Update the free block value from the free list */
    heap->free_block = heap->freelist ? heap->freelist->offset : H5HL_FREE_NULL;

    /* Serialize the heap prefix */
    HDmemcpy(image, H5HL_MAGIC, (size_t)H5_SIZEOF_MAGIC);
    image += H5_SIZEOF_MAGIC;
    *image++ = H5HL_VERSION;
    *image++ = 0;       /*reserved*/
    *image++ = 0;       /*reserved*/
    *image++ = 0;       /*reserved*/
    H5F_ENCODE_LENGTH_LEN(image, heap->dblk_size, heap->sizeof_size);
    H5F_ENCODE_LENGTH_LEN(image, heap->free_block, heap->sizeof_size);
    H5F_addr_encode_len(heap->sizeof_addr, &image, heap->dblk_addr);

    /* Check if the local heap is a single object in cache */
    if(heap->single_cache_obj) {
        if((size_t)(image - (uint8_t *)_image) < heap->prfx_size) {
            size_t gap;         /* Size of gap between prefix and data block */

            /* Set image to the start of the data block.  This is necessary 
             * because there may be a gap between the used portion of 
             * the prefix and the data block due to alignment constraints. 
             */
            gap = heap->prfx_size - (size_t)(image - (uint8_t *)_image);
            HDmemset(image, 0, gap);
            image += gap;
        } /* end if */

        /* Serialize the free list into the heap data's image */
        H5HL__fl_serialize(heap);

        /* Copy the heap data block into the cache image */
        HDmemcpy(image, heap->dblk_image, heap->dblk_size);
    } /* end if */

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5HL__cache_prefix_serialize() */

/******************************************/
/* no H5HL_cache_prefix_notify() function */
/******************************************/


/*-------------------------------------------------------------------------
 * Function:    H5HL__cache_prefix_free_icr
 *
 * Purpose:	Free the supplied in core representation of a local heap 
 *		prefix.
 *
 *		Note that this function handles the partially initialize prefix 
 *		from a failed speculative load attempt.  See comments below for 
 *		details.
 *
 * Note:	The metadata cache sets the object's cache_info.magic to
 *		H5C__H5C_CACHE_ENTRY_T_BAD_MAGIC before calling a free_icr
 *		callback (checked in assert).
 *
 * Return:      Success:        SUCCEED
 *              Failure:        FAIL
 *
 * Programmer:  John Mainzer
 *              6/21/14
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HL__cache_prefix_free_icr(void *_thing)
{
    H5HL_prfx_t *prfx = (H5HL_prfx_t *)_thing;  /* Pointer to local heap prefix to query */
    herr_t       ret_value = SUCCEED;    /* Return value */

    FUNC_ENTER_STATIC

    /* Check arguments */
    HDassert(prfx);
    HDassert(prfx->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_BAD_MAGIC);
    HDassert(prfx->cache_info.type == H5AC_LHEAP_PRFX);
    HDassert(H5F_addr_eq(prfx->cache_info.addr, prfx->heap->prfx_addr));

    /* Destroy local heap prefix */
    if(H5HL_prfx_dest(prfx) < 0)
        HGOTO_ERROR(H5E_HEAP, H5E_CANTRELEASE, FAIL, "can't destroy local heap prefix")

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5HL__cache_prefix_free_icr() */


/*-------------------------------------------------------------------------
 * Function:    H5HL__cache_datablock_get_load_size()
 *
 * Purpose:	Tell the metadata cache how large a buffer to read from 
 *		file when loading a datablock.  In this case, we simply lookup
 *		the correct value in the user data, and return it in *image_len.
 *
 * Return:      Success:        SUCCEED
 *              Failure:        FAIL
 *
 * Programmer:  John Mainzer
 *              6/21/14
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HL__cache_datablock_get_load_size(const void *_udata, size_t *image_len)
{
    const H5HL_cache_dblk_ud_t *udata = (const H5HL_cache_dblk_ud_t *)_udata; /* User data for callback */

    FUNC_ENTER_STATIC_NOERR

    /* Check arguments */
    HDassert(udata);
    HDassert(udata->heap);
    HDassert(udata->heap->dblk_size > 0);
    HDassert(image_len);

    *image_len = udata->heap->dblk_size;

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5HL__cache_datablock_get_load_size() */


/*-------------------------------------------------------------------------
 * Function:    H5HL__cache_datablock_deserialize
 *
 * Purpose:	Given a buffer containing the on disk image of a local 
 *		heap data block, deserialize it, load its contents into a newly allocated
 *		instance of H5HL_dblk_t, and return a pointer to the new instance.
 *
 * Return:      Success:        Pointer to in core representation
 *              Failure:        NULL
 *
 * Programmer:  John Mainzer
 *              6/21/14
 *
 *-------------------------------------------------------------------------
 */
static void *
H5HL__cache_datablock_deserialize(const void *image, size_t len, void *_udata,
    hbool_t H5_ATTR_UNUSED *dirty)
{
    H5HL_dblk_t          *dblk = NULL;  /* Local heap data block deserialized */
    H5HL_cache_dblk_ud_t *udata = (H5HL_cache_dblk_ud_t *)_udata; /* User data for callback */
    void *                ret_value;    /* Return value */

    FUNC_ENTER_STATIC

    /* Check arguments */
    HDassert(image);
    HDassert(len > 0);
    HDassert(udata);
    HDassert(udata->heap);
    HDassert(udata->heap->dblk_size == len);
    HDassert(!udata->heap->single_cache_obj);
    HDassert(NULL == udata->heap->dblk);
    HDassert(dirty);

    /* Allocate space in memory for the heap data block */
    if(NULL == (dblk = H5HL_dblk_new(udata->heap)))
        HGOTO_ERROR(H5E_HEAP, H5E_CANTALLOC, NULL, "memory allocation failed")

    /* Check for heap still retaining image */
    if(NULL == udata->heap->dblk_image) {
        /* Allocate space for the heap data image */
        if(NULL == (udata->heap->dblk_image = H5FL_BLK_MALLOC(lheap_chunk, udata->heap->dblk_size)))
            HGOTO_ERROR(H5E_HEAP, H5E_CANTALLOC, NULL, "can't allocate data block image buffer")

        /* copy the datablock from the read buffer */
        HDmemcpy(udata->heap->dblk_image, image, len);

        /* Build free list */
        if(H5HL__fl_deserialize(udata->heap) < 0)
            HGOTO_ERROR(H5E_HEAP, H5E_CANTINIT, NULL, "can't initialize free list")
    } /* end if */

    /* Set flag to indicate data block from loaded from file */
    udata->loaded = TRUE;

    /* Set return value */
    ret_value = dblk;

done:
    /* Release the [possibly partially initialized] local heap on errors */
    if(!ret_value && dblk)
        if(H5HL_dblk_dest(dblk) < 0)
            HDONE_ERROR(H5E_HEAP, H5E_CANTRELEASE, NULL, "unable to destroy local heap data block")

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5HL__cache_datablock_deserialize() */


/*-------------------------------------------------------------------------
 * Function:    H5HL__cache_datablock_image_len
 *
 * Purpose:	Return the size of the on disk image of the datablock.
 *
 * Return:      Success:        SUCCEED
 *              Failure:        FAIL
 *
 * Programmer:  John Mainzer
 *              6/21/14
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HL__cache_datablock_image_len(const void *_thing, size_t *image_len,
    hbool_t H5_ATTR_UNUSED *compressed_ptr, size_t H5_ATTR_UNUSED *compressed_image_len_ptr)
{
    const H5HL_dblk_t *dblk = (const H5HL_dblk_t *)_thing;    /* Pointer to the local heap data block */

    FUNC_ENTER_STATIC_NOERR

    /* Check arguments */
    HDassert(dblk);
    HDassert(dblk->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
    HDassert(dblk->cache_info.type == H5AC_LHEAP_DBLK);
    HDassert(dblk->heap);
    HDassert(dblk->heap->dblk_size > 0);
    HDassert(image_len);

    *image_len = dblk->heap->dblk_size;

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5HL__cache_datablock_image_len() */

/*******************************************/
/* no H5HL_cache_datablock_pre_serialize() */
/*******************************************/


/*-------------------------------------------------------------------------
 * Function:    H5HL__cache_datablock_serialize
 *
 * Purpose:	Serialize the supplied datablock, and copy the serialized
 *		image into the supplied image buffer.
 *
 * Return:      Success:        SUCCEED
 *              Failure:        FAIL
 *
 * Programmer:  John Mainzer
 *              6/21/14
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HL__cache_datablock_serialize(const H5F_t *f, void *image, size_t len,
    void *_thing)
{
    H5HL_t      *heap;          /* Pointer to the local heap */
    H5HL_dblk_t *dblk = (H5HL_dblk_t *)_thing;  /* Pointer to the local heap data block */

    FUNC_ENTER_STATIC_NOERR

    /* Check arguments */
    HDassert(f);
    HDassert(image);
    HDassert(dblk);
    HDassert(dblk->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
    HDassert(dblk->cache_info.type == H5AC_LHEAP_DBLK);
    HDassert(dblk->heap);
    heap = dblk->heap;
    HDassert(heap->dblk_size == len);
    HDassert(!heap->single_cache_obj);

    /* Update the free block value from the free list */
    heap->free_block = heap->freelist ? heap->freelist->offset : H5HL_FREE_NULL;

    /* Serialize the free list into the heap data's image */
    H5HL__fl_serialize(heap);

    /* Copy the heap's data block into the cache's image */
    HDmemcpy(image, heap->dblk_image, heap->dblk_size);

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5HL__cache_datablock_serialize() */

/*********************************************/
/* no H5HL_cache_datablock_notify() function */
/*********************************************/


/*-------------------------------------------------------------------------
 * Function:    H5HL__cache_datablock_free_icr
 *
 * Purpose:	Free the in memory representation of the supplied local heap data block.
 *
 * Note:	The metadata cache sets the object's cache_info.magic to
 *		H5C__H5C_CACHE_ENTRY_T_BAD_MAGIC before calling a free_icr
 *		callback (checked in assert).
 *
 * Return:      Success:        SUCCEED
 *              Failure:        FAIL
 *
 * Programmer:  John Mainzer
 *              6/21/14
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HL__cache_datablock_free_icr(void *_thing)
{
    H5HL_dblk_t *dblk = (H5HL_dblk_t *)_thing; /* Pointer to the local heap data block */
    herr_t       ret_value = SUCCEED;    /* Return value */

    FUNC_ENTER_STATIC

    /* Check arguments */
    HDassert(dblk);
    HDassert(dblk->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_BAD_MAGIC);
    HDassert(dblk->cache_info.type == H5AC_LHEAP_DBLK);

    /* Destroy the data block */
    if(H5HL_dblk_dest(dblk) < 0)
        HGOTO_ERROR(H5E_HEAP, H5E_CANTFREE, FAIL, "unable to destroy local heap data block")

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5HL__cache_datablock_free_icr() */