path: root/src/H5HFcache.c

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * 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://hdf.ncsa.uiuc.edu/HDF5/doc/Copyright.html.  If you do not have     *
 * access to either file, you may request a copy from hdfhelp@ncsa.uiuc.edu. *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*-------------------------------------------------------------------------
 *
 * Created:		H5HFcache.c
 *			Feb 24 2006
 *			Quincey Koziol <koziol@ncsa.uiuc.edu>
 *
 * Purpose:		Implement fractal heap metadata cache methods.
 *
 *-------------------------------------------------------------------------
 */

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

#define H5HF_PACKAGE		/*suppress error about including H5HFpkg  */

/***********/
/* Headers */
/***********/
#include "H5private.h"		/* Generic Functions			*/
#include "H5HFpkg.h"		/* Fractal heaps			*/
#include "H5Eprivate.h"		/* Error handling		  	*/
#include "H5Vprivate.h"		/* Vectors and arrays 			*/

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

/* Fractal heap format version #'s */
#define H5HF_HDR_VERSION        0               /* Header */
#define H5HF_DBLOCK_VERSION     0               /* Direct block */

/* Size of free space description in an absolute managed direct block */
#define H5HF_MAN_ABS_FREE_NODE_SIZE(d) (2 * (d)->blk_off_size)


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

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

/* Metadata cache callbacks */
static H5HF_t *H5HF_cache_hdr_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void *_type, void *udata);
static herr_t H5HF_cache_hdr_flush(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5HF_t *fh);
static herr_t H5HF_cache_hdr_clear(H5F_t *f, H5HF_t *fh, hbool_t destroy);
static herr_t H5HF_cache_hdr_size(const H5F_t *f, const H5HF_t *fh, size_t *size_ptr);
static H5HF_direct_t *H5HF_cache_dblock_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void *_type, void *udata);
static herr_t H5HF_cache_dblock_flush(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5HF_direct_t *dblock);
static herr_t H5HF_cache_dblock_clear(H5F_t *f, H5HF_direct_t *dblock, hbool_t destroy);
static herr_t H5HF_cache_dblock_size(const H5F_t *f, const H5HF_direct_t *dblock, size_t *size_ptr);

/* Local encode/decode routines */
static herr_t H5HF_dtable_encode(H5F_t *f, uint8_t **pp, const H5HF_dtable_param_t *dt_param);
static herr_t H5HF_dtable_decode(H5F_t *f, const uint8_t **pp, H5HF_dtable_param_t *dt_param);

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

/* H5HF header inherits cache-like properties from H5AC */
const H5AC_class_t H5AC_FHEAP_HDR[1] = {{
    H5AC_FHEAP_HDR_ID,
    (H5AC_load_func_t)H5HF_cache_hdr_load,
    (H5AC_flush_func_t)H5HF_cache_hdr_flush,
    (H5AC_dest_func_t)H5HF_cache_hdr_dest,
    (H5AC_clear_func_t)H5HF_cache_hdr_clear,
    (H5AC_size_func_t)H5HF_cache_hdr_size,
}};

/* H5HF direct block inherits cache-like properties from H5AC */
const H5AC_class_t H5AC_FHEAP_DBLOCK[1] = {{
    H5AC_FHEAP_DBLOCK_ID,
    (H5AC_load_func_t)H5HF_cache_dblock_load,
    (H5AC_flush_func_t)H5HF_cache_dblock_flush,
    (H5AC_dest_func_t)H5HF_cache_dblock_dest,
    (H5AC_clear_func_t)H5HF_cache_dblock_clear,
    (H5AC_size_func_t)H5HF_cache_dblock_size,
}};

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


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

/* Declare a free list to manage heap header data to/from disk */
H5FL_BLK_DEFINE_STATIC(header_block);

/* Declare a free list to manage heap direct block data to/from disk */
H5FL_BLK_DEFINE(direct_block);



/*-------------------------------------------------------------------------
 * Function:	H5HF_dtable_decode
 *
 * Purpose:	Decodes the metadata for a doubling table
 *
 * Return:	Success:	Pointer to a new fractal heap
 *
 *		Failure:	NULL
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 27 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HF_dtable_decode(H5F_t *f, const uint8_t **pp, H5HF_dtable_param_t *dt_param)
{
    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5HF_dtable_decode)

    /* Check arguments */
    HDassert(f);
    HDassert(pp && *pp);
    HDassert(dt_param);

    /* Table width */
    UINT16DECODE(*pp, dt_param->cparam.width);

    /* Starting block size */
    H5F_DECODE_LENGTH(f, *pp, dt_param->cparam.start_block_size);

    /* Maximum direct block size */
    H5F_DECODE_LENGTH(f, *pp, dt_param->cparam.max_direct_size);

    /* Maximum heap size (as # of bits) */
    UINT16DECODE(*pp, dt_param->cparam.max_index);

    /* Starting # of rows in root indirect block */
    UINT16DECODE(*pp, dt_param->cparam.start_root_rows);

    /* Address of table */
    H5F_addr_decode(f, pp, &(dt_param->table_addr));

    /* Current # of rows in root indirect block */
    UINT16DECODE(*pp, dt_param->curr_root_rows);

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5HF_dtable_decode() */


/*-------------------------------------------------------------------------
 * Function:	H5HF_dtable_encode
 *
 * Purpose:	Encodes the metadata for a doubling table
 *
 * Return:	Success:	Pointer to a new fractal heap
 *
 *		Failure:	NULL
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 27 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HF_dtable_encode(H5F_t *f, uint8_t **pp, const H5HF_dtable_param_t *dt_param)
{
    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5HF_dtable_encode)

    /* Check arguments */
    HDassert(f);
    HDassert(pp && *pp);
    HDassert(dt_param);

    /* Table width */
    UINT16ENCODE(*pp, dt_param->cparam.width);

    /* Starting block size */
    H5F_ENCODE_LENGTH(f, *pp, dt_param->cparam.start_block_size);

    /* Maximum direct block size */
    H5F_ENCODE_LENGTH(f, *pp, dt_param->cparam.max_direct_size);

    /* Maximum heap size (as # of bits) */
    UINT16ENCODE(*pp, dt_param->cparam.max_index);

    /* Starting # of rows in root indirect block */
    UINT16ENCODE(*pp, dt_param->cparam.start_root_rows);

    /* Address of table */
    H5F_addr_encode(f, pp, dt_param->table_addr);

    /* Current # of rows in root indirect block */
    UINT16ENCODE(*pp, dt_param->curr_root_rows);

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5HF_dtable_encode() */


/*-------------------------------------------------------------------------
 * Function:	H5HF_cache_hdr_load
 *
 * Purpose:	Loads a fractal heap header from the disk.
 *
 * Return:	Success:	Pointer to a new fractal heap
 *
 *		Failure:	NULL
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 24 2006
 *
 *-------------------------------------------------------------------------
 */
static H5HF_t *
H5HF_cache_hdr_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED *udata1, void UNUSED *udata2)
{
    H5HF_t		*fh = NULL;     /* Fractal heap info */
    H5HF_shared_t       *shared = NULL; /* Shared fractal heap information */
    size_t		size;           /* Header size */
    uint8_t		*buf = NULL;    /* Temporary buffer */
    const uint8_t	*p;             /* Pointer into raw data buffer */
    uint32_t            metadata_chksum;        /* Metadata checksum value */
    H5HF_t		*ret_value;     /* Return value */

    FUNC_ENTER_NOAPI(H5HF_cache_hdr_load, NULL)

    /* Check arguments */
    HDassert(f);
    HDassert(H5F_addr_defined(addr));

    /* Allocate space for the fractal heap data structure */
    if(NULL == (fh = H5FL_MALLOC(H5HF_t)))
	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
    HDmemset(&fh->cache_info, 0, sizeof(H5AC_info_t));

    /* Allocate & basic initialization for the shared info struct */
    if(NULL == (shared = H5HF_shared_alloc(f)))
	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "can't allocate space for shared heap info")
    shared->heap_addr = addr;

    /* Compute the size of the fractal heap header on disk */
    size = H5HF_HEADER_SIZE(f);

    /* Allocate temporary buffer */
    if((buf = H5FL_BLK_MALLOC(header_block, size)) == NULL)
        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")

    /* Read header from disk */
    if(H5F_block_read(f, H5FD_MEM_FHEAP_HDR, addr, size, dxpl_id, buf) < 0)
	HGOTO_ERROR(H5E_HEAP, H5E_READERROR, NULL, "can't read fractal heap header")

    p = buf;

    /* Magic number */
    if(HDmemcmp(p, H5HF_HDR_MAGIC, H5HF_SIZEOF_MAGIC))
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "wrong fractal heap header signature")
    p += H5HF_SIZEOF_MAGIC;

    /* Version */
    if(*p++ != H5HF_HDR_VERSION)
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "wrong fractal heap header version")

    /* Metadata flags (unused, currently) */
/* XXX: Plan out metadata flags (including "read-only duplicate" feature) */
    if(*p++ != 0)
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "unknown metadata flag in fractal heap header")

    /* Metadata checksum (unused, currently) */
    UINT32DECODE(p, metadata_chksum);
/* XXX: Verify checksum */
    if(metadata_chksum != 0)
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "incorrect metadata checksum for fractal heap header")

    /* Heap address mapping */
    shared->addrmap = *p++;
    HDassert(H5HF_ABSOLUTE == 0);
    if(shared->addrmap > H5HF_MAPPED)
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "incorrect fractal heap address mapping")

    /* Min. size of standalone objects */
    UINT32DECODE(p, shared->standalone_size);

    /* Length of fixed-length objects in heap */
    UINT32DECODE(p, shared->fixed_len_size);

    /* Size of ref. count for objects in heap */
    shared->ref_count_size = *p++;

    /* Managed objects' doubling-table info */
    if(H5HF_dtable_decode(shared->f, &p, &(shared->man_dtable_info)) < 0)
        HGOTO_ERROR(H5E_HEAP, H5E_CANTENCODE, NULL, "unable to encode managed obj. doubling table info")

    HDassert((size_t)(p - buf) == size);

    /* Make shared heap info reference counted */
    if(H5HF_shared_own(fh, shared) < 0)
	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "can't create ref-count wrapper for shared fractal heap info")

    /* Set return value */
    ret_value = fh;

done:
    if(buf)
        H5FL_BLK_FREE(header_block, buf);
    if(!ret_value && fh)
        (void)H5HF_cache_hdr_dest(f, fh);

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5HF_cache_hdr_load() */ /*lint !e818 Can't make udata a pointer to const */


/*-------------------------------------------------------------------------
 * Function:	H5HF_cache_hdr_flush
 *
 * Purpose:	Flushes a dirty fractal heap header to disk.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 24 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HF_cache_hdr_flush(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5HF_t *fh)
{
    H5HF_shared_t *shared;              /* Shared fractal heap information */
    herr_t      ret_value = SUCCEED;    /* Return value */

    FUNC_ENTER_NOAPI(H5HF_cache_hdr_flush, FAIL)

    /* check arguments */
    HDassert(f);
    HDassert(H5F_addr_defined(addr));
    HDassert(fh);

    /* Get the pointer to the shared heap info */
    shared = H5RC_GET_OBJ(fh->shared);
    HDassert(shared);

    if(fh->cache_info.is_dirty) {
        uint8_t	*buf = NULL;        /* Temporary raw data buffer */
        uint8_t *p;                 /* Pointer into raw data buffer */
        size_t	size;               /* Header size on disk */

        /* Compute the size of the heap header on disk */
        size = H5HF_HEADER_SIZE(f);

        /* Allocate temporary buffer */
        if((buf = H5FL_BLK_MALLOC(header_block, size)) == NULL)
            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")

        p = buf;

        /* Magic number */
        HDmemcpy(p, H5HF_HDR_MAGIC, H5HF_SIZEOF_MAGIC);
        p += H5HF_SIZEOF_MAGIC;

        /* Version # */
        *p++ = H5HF_HDR_VERSION;

        /* Metadata status flags */
/* XXX: Set this? */
        *p++ = 0;

        /* Metadata checksum */
/* XXX: Set this!  (After all the metadata is in the buffer) */
        HDmemset(p, 0, 4);
        p += 4;

        /* Heap address mapping */
        *p++ = shared->addrmap;

        /* Min. size of standalone objects */
        UINT32ENCODE(p, shared->standalone_size);

        /* Size of fixed-length objects in heap */
        UINT32ENCODE(p, shared->fixed_len_size);

        /* Size of ref. count for objects in heap */
        *p++ = shared->ref_count_size;

        /* Managed objects' doubling-table info */
        if(H5HF_dtable_encode(shared->f, &p, &(shared->man_dtable_info)) < 0)
	    HGOTO_ERROR(H5E_HEAP, H5E_CANTENCODE, FAIL, "unable to encode managed obj. doubling table info")

	/* Write the heap header. */
        HDassert((size_t)(p - buf) == size);
	if(H5F_block_write(f, H5FD_MEM_FHEAP_HDR, addr, size, dxpl_id, buf) < 0)
	    HGOTO_ERROR(H5E_HEAP, H5E_CANTFLUSH, FAIL, "unable to save fractal heap header to disk")

        H5FL_BLK_FREE(header_block, buf);

	fh->cache_info.is_dirty = FALSE;
    } /* end if */

    if(destroy)
        if(H5HF_cache_hdr_dest(f, fh) < 0)
	    HGOTO_ERROR(H5E_HEAP, H5E_CANTFREE, FAIL, "unable to destroy fractal heap header")

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* H5HF_cache_hdr_flush() */


/*-------------------------------------------------------------------------
 * Function:	H5HF_cache_hdr_dest
 *
 * Purpose:	Destroys a fractal heap header in memory.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 24 2006
 *
 *-------------------------------------------------------------------------
 */
/* ARGSUSED */
herr_t
H5HF_cache_hdr_dest(H5F_t UNUSED *f, H5HF_t *fh)
{
    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5HF_cache_hdr_dest)

    /*
     * Check arguments.
     */
    HDassert(fh);

    /* Decrement reference count on shared fractal heap info */
    if(fh->shared)
        H5RC_DEC(fh->shared);

    /* Free fractal heap header info */
    H5FL_FREE(H5HF_t, fh);

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5HF_cache_hdr_dest() */


/*-------------------------------------------------------------------------
 * Function:	H5HF_cache_hdr_clear
 *
 * Purpose:	Mark a fractal heap header in memory as non-dirty.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 24 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HF_cache_hdr_clear(H5F_t *f, H5HF_t *fh, hbool_t destroy)
{
    herr_t ret_value = SUCCEED;         /* Return value */

    FUNC_ENTER_NOAPI_NOINIT(H5HF_cache_hdr_clear)

    /*
     * Check arguments.
     */
    HDassert(fh);

    /* Reset the dirty flag.  */
    fh->cache_info.is_dirty = FALSE;

    if(destroy)
        if(H5HF_cache_hdr_dest(f, fh) < 0)
	    HGOTO_ERROR(H5E_HEAP, H5E_CANTFREE, FAIL, "unable to destroy fractal heap header")

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5HF_cache_hdr_clear() */


/*-------------------------------------------------------------------------
 * Function:	H5HF_cache_hdr_size
 *
 * Purpose:	Compute the size in bytes of a fractal heap header
 *		on disk, and return it in *size_ptr.  On failure,
 *		the value of *size_ptr is undefined.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 24 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HF_cache_hdr_size(const H5F_t *f, const H5HF_t UNUSED *fh, size_t *size_ptr)
{
    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5HF_cache_hdr_size)

    /* check arguments */
    HDassert(f);
    HDassert(size_ptr);

    /* Set size value */
    *size_ptr = H5HF_HEADER_SIZE(f);

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* H5HF_cache_hdr_size() */


/*-------------------------------------------------------------------------
 * Function:	H5HF_cache_dblock_load
 *
 * Purpose:	Loads a fractal heap direct block from the disk.
 *
 * Return:	Success:	Pointer to a new fractal heap direct block
 *
 *		Failure:	NULL
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 27 2006
 *
 *-------------------------------------------------------------------------
 */
static H5HF_direct_t *
H5HF_cache_dblock_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void *_size, void *_fh_shared)
{
    const size_t        *size = (const size_t *)_size;         /* Size of block */
    H5RC_t 		*fh_shared = (H5RC_t *)_fh_shared;     /* Shared heap information */
    H5HF_shared_t       *shared = NULL; /* Shared fractal heap information */
    H5HF_direct_t	*dblock = NULL; /* Direct block info */
    uint8_t		*buf = NULL;    /* Temporary buffer */
    const uint8_t	*p;             /* Pointer into raw data buffer */
    haddr_t             heap_addr;      /* Address of heap header in the file */
    uint32_t            metadata_chksum;        /* Metadata checksum value */
    H5HF_direct_t	*ret_value;     /* Return value */

    FUNC_ENTER_NOAPI(H5HF_cache_dblock_load, NULL)

    /* Check arguments */
    HDassert(f);
    HDassert(H5F_addr_defined(addr));
    HDassert(fh_shared);

    /* Allocate space for the fractal heap direct block */
    if(NULL == (dblock = H5FL_MALLOC(H5HF_direct_t)))
	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
    HDmemset(&dblock->cache_info, 0, sizeof(H5AC_info_t));

    /* Share common heap information */
    dblock->shared = fh_shared;
    H5RC_INC(dblock->shared);

    /* Get the pointer to the shared heap info */
    shared = H5RC_GET_OBJ(dblock->shared);
    HDassert(shared);

    /* Set block's internal information */
    dblock->size = *size;
    dblock->blk_off_size = H5HF_SIZEOF_OFFSET_LEN(dblock->size);
    dblock->free_list = NULL;

    /* Allocate block buffer */
/* XXX: Change to using free-list factories */
    if((buf = H5FL_BLK_MALLOC(direct_block, (size_t)dblock->size)) == NULL)
        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")

    /* Read header from disk */
    if(H5F_block_read(f, H5FD_MEM_FHEAP_HDR, addr, (size_t)dblock->size, dxpl_id, buf) < 0)
	HGOTO_ERROR(H5E_HEAP, H5E_READERROR, NULL, "can't read fractal heap direct block")

    p = buf;

    /* Magic number */
    if(HDmemcmp(p, H5HF_DBLOCK_MAGIC, H5HF_SIZEOF_MAGIC))
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "wrong fractal heap direct block signature")
    p += H5HF_SIZEOF_MAGIC;

    /* Version */
    if(*p++ != H5HF_DBLOCK_VERSION)
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "wrong fractal heap direct block version")

    /* Metadata flags (unused, currently) */
/* XXX: Plan out metadata flags (including "read-only duplicate" feature) */
    if(*p++ != 0)
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "unknown metadata flag in fractal heap direct block")

    /* Metadata checksum (unused, currently) */
    UINT32DECODE(p, metadata_chksum);
/* XXX: Verify checksum */
    if(metadata_chksum != 0)
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "incorrect metadata checksum for fractal heap direct block")

    /* Address of heap that owns this block (skip) */
    H5F_addr_decode(f, &p, &heap_addr);
    if(H5F_addr_ne(heap_addr, shared->heap_addr))
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "incorrect heap header address for direct block")
    
    /* Offset of heap within the heap's address space */
    UINT64DECODE_VAR(p, dblock->block_off, shared->heap_off_size);

    /* Total free space in block */
    UINT64DECODE_VAR(p, dblock->blk_free_space, dblock->blk_off_size);

    /* Offset of free list head */
    /* (Defer deserializing the whole free list until we actually need to modify it) */
    UINT64DECODE_VAR(p, dblock->free_list_head, dblock->blk_off_size);

    /* Keep pointer to block buffer */
    dblock->blk = buf;

    /* Set return value */
    ret_value = dblock;

done:
    if(!ret_value && dblock)
        (void)H5HF_cache_dblock_dest(f, dblock);

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5HF_cache_dblock_load() */


/*-------------------------------------------------------------------------
 * Function:	H5HF_cache_dblock_flush
 *
 * Purpose:	Flushes a dirty fractal heap direct block to disk.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 27 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HF_cache_dblock_flush(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5HF_direct_t *dblock)
{
    herr_t      ret_value = SUCCEED;    /* Return value */

    FUNC_ENTER_NOAPI(H5HF_cache_dblock_flush, FAIL)

    /* check arguments */
    HDassert(f);
    HDassert(H5F_addr_defined(addr));
    HDassert(dblock);

    if(dblock->cache_info.is_dirty) {
        H5HF_shared_t *shared;      /* Shared fractal heap information */
        uint8_t *p;                 /* Pointer into raw data buffer */

        /* Get the pointer to the shared heap info */
        shared = H5RC_GET_OBJ(dblock->shared);
        HDassert(shared);

        p = dblock->blk;

        /* Magic number */
        HDmemcpy(p, H5HF_DBLOCK_MAGIC, H5HF_SIZEOF_MAGIC);
        p += H5HF_SIZEOF_MAGIC;

        /* Version # */
        *p++ = H5HF_DBLOCK_VERSION;

        /* Metadata status flags */
/* XXX: Set this? */
        *p++ = 0;

        /* Metadata checksum */
/* XXX: Set this!  (After all the metadata is in the buffer) */
        HDmemset(p, 0, 4);
        p += 4;

        /* Address of heap header for heap which owns this block */
        H5F_addr_encode(f, &p, shared->heap_addr);

        /* Offset of block in heap */
        UINT64ENCODE_VAR(p, dblock->block_off, shared->heap_off_size);

        /* Check for (currently) unsupported address mapping */
        if(shared->addrmap != H5HF_ABSOLUTE)
            HGOTO_ERROR(H5E_HEAP, H5E_UNSUPPORTED, FAIL, "encoding mapped direct blocks not supported currently")

        /* Total free space in block */
        UINT64ENCODE_VAR(p, dblock->blk_free_space, dblock->blk_off_size);

        /* Offset of free list head */
        UINT64ENCODE_VAR(p, dblock->free_list_head, dblock->blk_off_size);

        /* Sanity check */
        HDassert((size_t)(p - dblock->blk) == H5HF_MAN_ABS_DIRECT_OVERHEAD_DBLOCK(shared, dblock));

        /* Check for dirty free list */
        if(dblock->free_list && dblock->free_list->dirty) {
            H5HF_direct_free_node_t *node;      /* Pointer to free list node for block */

            /* Loop over all free list blocks, updating their data */
            node = dblock->free_list->first;
            while(node) {
                /* Find first node which has enough room to describe free space */
                while(node && node->size < H5HF_MAN_ABS_FREE_NODE_SIZE(dblock))
                    node = node->next;

                /* Check for free space node to encode */
                if(node) {
                    H5HF_direct_free_node_t *next_node; /* Pointer to next free list node for block */

                    /* Probe ahead for next node that is large enough to encode free space description */
                    next_node = node->next;
                    while(next_node && next_node->size < H5HF_MAN_ABS_FREE_NODE_SIZE(dblock))
                        next_node = next_node->next;

                    /* Encode information for this node on free list */
                    p = dblock->blk + node->my_offset;
                    UINT64ENCODE_VAR(p, node->size, dblock->blk_off_size);
                    UINT64ENCODE_VAR(p, (next_node ? next_node->my_offset : 0), dblock->blk_off_size);

                    /* Advance to next node */
                    node = node->next;
                } /* end if */

            } /* end while */

            /* Reset the free list dirty flag */
            dblock->free_list->dirty = FALSE;
        } /* end if */

	/* Write the heap header. */
	if(H5F_block_write(f, H5FD_MEM_FHEAP_HDR, addr, (size_t)dblock->size, dxpl_id, dblock->blk) < 0)
	    HGOTO_ERROR(H5E_HEAP, H5E_CANTFLUSH, FAIL, "unable to save fractal heap direct block to disk")

	dblock->cache_info.is_dirty = FALSE;
    } /* end if */

    if(destroy)
        if(H5HF_cache_dblock_dest(f, dblock) < 0)
	    HGOTO_ERROR(H5E_HEAP, H5E_CANTFREE, FAIL, "unable to destroy fractal heap direct block")

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* H5HF_cache_dblock_flush() */


/*-------------------------------------------------------------------------
 * Function:	H5HF_cache_dblock_dest
 *
 * Purpose:	Destroys a fractal heap direct block in memory.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 27 2006
 *
 *-------------------------------------------------------------------------
 */
/* ARGSUSED */
herr_t
H5HF_cache_dblock_dest(H5F_t UNUSED *f, H5HF_direct_t *dblock)
{
    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5HF_cache_dblock_dest)

    /*
     * Check arguments.
     */
    HDassert(dblock);

    /* Decrement reference count on shared fractal heap info */
    if(dblock->shared)
        H5RC_DEC(dblock->shared);

    /* Check for free list & free it, if necessary */
    if(dblock->free_list) {
        H5HF_direct_free_node_t *node; /* Pointer to free list node for block */

        /* Walk through list, freeing the nodes */
        node = dblock->free_list->first;
        while(node) {
            H5HF_direct_free_node_t *last_node; /* Pointer to last free list node for block */

            /* Advance to next node */
            last_node = node;
            node = node->next;

            /* Release the last node */
            H5FL_FREE(H5HF_direct_free_node_t, last_node);
        } /* end while */

        /* Release the free list head */
        H5FL_FREE(H5HF_direct_free_head_t, dblock->free_list);
    } /* end if */

    /* Free block's buffer */
    H5FL_BLK_FREE(direct_block, dblock->blk);

    /* Free fractal heap direct block info */
    H5FL_FREE(H5HF_direct_t, dblock);

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* end H5HF_cache_dblock_dest() */


/*-------------------------------------------------------------------------
 * Function:	H5HF_cache_dblock_clear
 *
 * Purpose:	Mark a fractal heap direct block in memory as non-dirty.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 27 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HF_cache_dblock_clear(H5F_t *f, H5HF_direct_t *dblock, hbool_t destroy)
{
    herr_t ret_value = SUCCEED;         /* Return value */

    FUNC_ENTER_NOAPI_NOINIT(H5HF_cache_dblock_clear)

    /*
     * Check arguments.
     */
    HDassert(dblock);

    /* Reset the free list dirty flag */
    dblock->free_list->dirty = FALSE;

    /* Reset the dirty flag.  */
    dblock->cache_info.is_dirty = FALSE;

    if(destroy)
        if(H5HF_cache_dblock_dest(f, dblock) < 0)
	    HGOTO_ERROR(H5E_HEAP, H5E_CANTFREE, FAIL, "unable to destroy fractal heap direct block")

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5HF_cache_dblock_clear() */


/*-------------------------------------------------------------------------
 * Function:	H5HF_cache_block_size
 *
 * Purpose:	Compute the size in bytes of a fractal heap direct block
 *		on disk, and return it in *size_ptr.  On failure,
 *		the value of *size_ptr is undefined.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Feb 24 2006
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HF_cache_dblock_size(const H5F_t UNUSED *f, const H5HF_direct_t *dblock, size_t *size_ptr)
{
    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5HF_cache_dblock_size)

    /* check arguments */
    HDassert(dblock);
    HDassert(size_ptr);

    /* Set size value */
    *size_ptr = dblock->size;

    FUNC_LEAVE_NOAPI(SUCCEED)
} /* H5HF_cache_dblock_size() */