path: root/src/H5HL.c

/*-------------------------------------------------------------------------
 * Copyright (C) 1997	National Center for Supercomputing Applications.
 *			All rights reserved.
 *
 *-------------------------------------------------------------------------
 *
 * Created:		H5HL.c
 *			Jul 16 1997
 *			Robb Matzke <matzke@llnl.gov>
 *
 * Purpose:		Heap functions for the local heaps used by symbol
 *			tables to store names (among other things).
 *
 * Modifications:
 *
 *	Robb Matzke, 5 Aug 1997
 *	Added calls to H5E.
 *
 *-------------------------------------------------------------------------
 */
#include <H5private.h>			/*library		  	*/
#include <H5ACprivate.h>		/*cache				*/
#include <H5Eprivate.h>			/*error handling	  	*/
#include <H5HLprivate.h>		/*self				*/
#include <H5MFprivate.h>		/*file memory management  	*/
#include <H5MMprivate.h>		/*core memory management  	*/

#define H5HL_FREE_NULL	1		/*end of free list on disk	*/
#define PABLO_MASK	H5HL_mask

typedef struct H5HL_free_t {
    size_t		offset;		/*offset of free block		*/
    size_t		size;		/*size of free block		*/
    struct H5HL_free_t	*prev;		/*previous entry in free list	*/
    struct H5HL_free_t	*next;		/*next entry in free list	*/
} H5HL_free_t;

typedef struct H5HL_t {
    intn		    dirty;
    haddr_t		    addr;	/*address of data		*/
    size_t		    disk_alloc;	/*data bytes allocated on disk	*/
    size_t		    mem_alloc;	/*data bytes allocated in mem	*/
    uint8		   *chunk;	/*the chunk, including header	*/
    H5HL_free_t		   *freelist;	/*the free list			*/
} H5HL_t;

/* PRIVATE PROTOTYPES */
static H5HL_t *H5HL_load(H5F_t *f, const haddr_t *addr, const void *udata1,
			 void *udata2);
static herr_t H5HL_flush(H5F_t *f, hbool_t dest, const haddr_t *addr,
			 H5HL_t *heap);

/*
 * H5HL inherits cache-like properties from H5AC
 */
static const H5AC_class_t H5AC_LHEAP[1] = {{
    H5AC_LHEAP_ID,
    (void *(*)(H5F_t*, const haddr_t*, const void*, void*))H5HL_load,
    (herr_t (*)(H5F_t*, hbool_t, const haddr_t*, void*))H5HL_flush,
}};

/* Interface initialization */
static intn interface_initialize_g = FALSE;
#define INTERFACE_INIT NULL


/*-------------------------------------------------------------------------
 * Function:	H5HL_create
 *
 * Purpose:	Creates a new heap data structure on disk and caches it
 *		in memory.  SIZE_HINT is a hint for the initial size of the
 *		data area of the heap.	If size hint is invalid then a
 *		reasonable (but probably not optimal) size will be chosen.
 *		If the heap ever has to grow, then REALLOC_HINT is the
 *		minimum amount by which the heap will grow.
 *
 * Return:	Success:	SUCCEED. The file address of new heap is
 *				returned through the ADDR argument.
 *
 *		Failure:	FAIL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 16 1997
 *
 * Modifications:
 *
 *	Robb Matzke, 5 Aug 1997
 *	Takes a flag that determines the type of heap that is
 *	created.
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5HL_create(H5F_t *f, size_t size_hint, haddr_t *addr/*out*/)
{
    H5HL_t	*heap = NULL;
    size_t	total_size;		/*total heap size on disk	*/

    FUNC_ENTER(H5HL_create, FAIL);

    /* check arguments */
    assert(f);
    assert(addr);

    if (size_hint && size_hint < H5HL_SIZEOF_FREE(f)) {
	size_hint = H5HL_SIZEOF_FREE(f);
    }
    size_hint = H5HL_ALIGN(size_hint);

    /* allocate file version */
    total_size = H5HL_SIZEOF_HDR(f) + size_hint;
    if (H5MF_alloc(f, H5MF_META, total_size, addr/*out*/) < 0) {
	HRETURN_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
		      "unable to allocate file memory");
    }

    /* allocate memory version */
    heap = H5MM_xcalloc(1, sizeof(H5HL_t));
    heap->addr = *addr;
    H5F_addr_inc(&(heap->addr), H5HL_SIZEOF_HDR(f));
    heap->disk_alloc = size_hint;
    heap->mem_alloc = size_hint;
    heap->chunk = H5MM_xcalloc(1, H5HL_SIZEOF_HDR(f) + size_hint);

    /* free list */
    if (size_hint) {
	heap->freelist = H5MM_xmalloc(sizeof(H5HL_free_t));
	heap->freelist->offset = 0;
	heap->freelist->size = size_hint;
	heap->freelist->prev = heap->freelist->next = NULL;
    } else {
	heap->freelist = NULL;
    }

    /* add to cache */
    heap->dirty = 1;
    if (H5AC_set(f, H5AC_LHEAP, addr, heap) < 0) {
	heap->chunk = H5MM_xfree(heap->chunk);
	heap->freelist = H5MM_xfree(heap->freelist);
	HRETURN_ERROR(H5E_HEAP, H5E_CANTINIT, FAIL,
		      "unable to cache heap");
    }
    FUNC_LEAVE(SUCCEED);
}

/*-------------------------------------------------------------------------
 * Function:	H5HL_load
 *
 * Purpose:	Loads a heap from disk.
 *
 * Return:	Success:	Ptr to a local heap memory data structure.
 *
 *		Failure:	NULL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 17 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static H5HL_t *
H5HL_load(H5F_t *f, const haddr_t *addr, const void *udata1, void *udata2)
{
    uint8		hdr[52];
    const uint8		*p = NULL;
    H5HL_t		*heap = NULL;
    H5HL_free_t		*fl = NULL, *tail = NULL;
    size_t		free_block = H5HL_FREE_NULL;
    H5HL_t		*ret_value = NULL;

    FUNC_ENTER(H5HL_load, NULL);

    /* check arguments */
    assert(f);
    assert(addr && H5F_addr_defined(addr));
    assert(H5HL_SIZEOF_HDR(f) <= sizeof hdr);
    assert(!udata1);
    assert(!udata2);

    if (H5F_block_read(f, addr, H5HL_SIZEOF_HDR(f), hdr) < 0) {
	HRETURN_ERROR(H5E_HEAP, H5E_READERROR, NULL,
		      "unable to read heap header");
    }
    p = hdr;
    heap = H5MM_xcalloc(1, sizeof(H5HL_t));

    /* magic number */
    if (HDmemcmp(hdr, H5HL_MAGIC, H5HL_SIZEOF_MAGIC)) {
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL,
		    "bad heap signature");
    }
    p += H5HL_SIZEOF_MAGIC;

    /* Reserved */
    p += 4;

    /* heap data size */
    H5F_decode_length(f, p, heap->disk_alloc);
    heap->mem_alloc = heap->disk_alloc;

    /* free list head */
    H5F_decode_length(f, p, free_block);
    if (free_block != H5HL_FREE_NULL && free_block >= heap->disk_alloc) {
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL,
		    "bad heap free list");
    }

    /* data */
    H5F_addr_decode(f, &p, &(heap->addr));
    heap->chunk = H5MM_xcalloc(1, H5HL_SIZEOF_HDR(f) + heap->mem_alloc);
    if (heap->disk_alloc &&
	H5F_block_read(f, &(heap->addr), heap->disk_alloc,
		       heap->chunk + H5HL_SIZEOF_HDR(f)) < 0) {
	HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL,
		    "unable to read heap data");
    }

    /* free list */
    while (H5HL_FREE_NULL != free_block) {
	if (free_block >= heap->disk_alloc) {
	    HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL,
			"bad heap free list");
	}
	fl = H5MM_xmalloc(sizeof(H5HL_free_t));
	fl->offset = free_block;
	fl->prev = tail;
	fl->next = NULL;
	if (tail) tail->next = fl;
	tail = fl;
	if (!heap->freelist) heap->freelist = fl;

	p = heap->chunk + H5HL_SIZEOF_HDR(f) + free_block;
	H5F_decode_length(f, p, free_block);
	H5F_decode_length(f, p, fl->size);

	if (fl->offset + fl->size > heap->disk_alloc) {
	    HGOTO_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL,
			"bad heap free list");
	}
    }

    ret_value = heap;

  done:
    if (!ret_value && heap) {
	heap->chunk = H5MM_xfree(heap->chunk);
	H5MM_xfree(heap);
	for (fl = heap->freelist; fl; fl = tail) {
	    tail = fl->next;
	    H5MM_xfree(fl);
	}
    }
    FUNC_LEAVE(ret_value);
}

/*-------------------------------------------------------------------------
 * Function:	H5HL_flush
 *
 * Purpose:	Flushes a heap from memory to disk if it's dirty.  Optionally
 *		deletes the heap from memory.
 *
 * Return:	Success:	SUCCEED
 *
 *		Failure:	FAIL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 17 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5HL_flush(H5F_t *f, hbool_t destroy, const haddr_t *addr, H5HL_t *heap)
{
    uint8	*p = heap->chunk;
    H5HL_free_t	*fl = heap->freelist;
    haddr_t	hdr_end_addr;

    FUNC_ENTER(H5HL_flush, FAIL);

    /* check arguments */
    assert(f);
    assert(addr && H5F_addr_defined(addr));
    assert(heap);

    if (heap->dirty) {
	/*
	 * If the heap grew larger than disk storage then move the
	 * data segment of the heap to a larger contiguous block of
	 * disk storage.
	 */
	if (heap->mem_alloc > heap->disk_alloc) {
	    haddr_t old_addr = heap->addr, new_addr;
	    if (H5MF_alloc(f, H5MF_META, heap->mem_alloc,
			   &new_addr/*out*/)<0) {
		HRETURN_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
			      "unable to allocate file space for heap");
	    }
	    heap->addr = new_addr;
	    H5MF_free(f, &old_addr, heap->disk_alloc);
	    H5E_clear(); /*don't really care if the free failed */
	    heap->disk_alloc = heap->mem_alloc;
	}

	/*
	 * Write the header.
	 */
	HDmemcpy(p, H5HL_MAGIC, H5HL_SIZEOF_MAGIC);
	p += H5HL_SIZEOF_MAGIC;
	*p++ = 0;	/*reserved*/
	*p++ = 0;	/*reserved*/
	*p++ = 0;	/*reserved*/
	*p++ = 0;	/*reserved*/
	H5F_encode_length(f, p, heap->mem_alloc);
	H5F_encode_length(f, p, fl ? fl->offset : H5HL_FREE_NULL);
	H5F_addr_encode(f, &p, &(heap->addr));

	/*
	 * Write the free list.
	 */
	while (fl) {
	    assert (fl->offset == H5HL_ALIGN (fl->offset));
	    p = heap->chunk + H5HL_SIZEOF_HDR(f) + fl->offset;
	    if (fl->next) {
		H5F_encode_length(f, p, fl->next->offset);
	    } else {
		H5F_encode_length(f, p, H5HL_FREE_NULL);
	    }
	    H5F_encode_length(f, p, fl->size);
	    fl = fl->next;
	}

	/*
	 * Copy buffer to disk.
	 */
	hdr_end_addr = *addr;
	H5F_addr_inc(&hdr_end_addr, H5HL_SIZEOF_HDR(f));
	if (H5F_addr_eq(&(heap->addr), &hdr_end_addr)) {
	    /* The header and data are contiguous */
	    if (H5F_block_write(f, addr, H5HL_SIZEOF_HDR(f) + heap->disk_alloc,
				heap->chunk) < 0) {
		HRETURN_ERROR(H5E_HEAP, H5E_WRITEERROR, FAIL,
			    "unable to write heap header and data to file");
	    }
	} else {
	    if (H5F_block_write(f, addr, H5HL_SIZEOF_HDR(f), heap->chunk)<0) {
		HRETURN_ERROR(H5E_HEAP, H5E_WRITEERROR, FAIL,
			      "unable to write heap header to file");
	    }
	    if (H5F_block_write(f, &(heap->addr), heap->disk_alloc,
				heap->chunk + H5HL_SIZEOF_HDR(f)) < 0) {
		HRETURN_ERROR(H5E_HEAP, H5E_WRITEERROR, FAIL,
			      "unable to write heap data to file");
	    }
	}

	heap->dirty = 0;
    }

    /*
     * Should we destroy the memory version?
     */
    if (destroy) {
	heap->chunk = H5MM_xfree(heap->chunk);
	while (heap->freelist) {
	    fl = heap->freelist;
	    heap->freelist = fl->next;
	    H5MM_xfree(fl);
	}
	H5MM_xfree(heap);
    }
    FUNC_LEAVE(SUCCEED);
}

/*-------------------------------------------------------------------------
 * Function:	H5HL_read
 *
 * Purpose:	Reads some object (or part of an object) from the heap
 *		whose address is ADDR in file F.  OFFSET is the byte offset
 *		from the beginning of the heap at which to begin reading
 *		and SIZE is the number of bytes to read.
 *
 *		If BUF is the null pointer then a buffer is allocated by
 *		this function.
 *
 *		Attempting to read past the end of an object may cause this
 *		function to fail.
 *
 * Return:	Success:	BUF (or the allocated buffer)
 *
 *		Failure:	NULL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 16 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
void *
H5HL_read(H5F_t *f, const haddr_t *addr, size_t offset, size_t size, void *buf)
{
    H5HL_t	*heap = NULL;

    FUNC_ENTER(H5HL_read, NULL);

    /* check arguments */
    assert(f);
    assert (addr && H5F_addr_defined(addr));

    if (NULL == (heap = H5AC_find(f, H5AC_LHEAP, addr, NULL, NULL))) {
	HRETURN_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL,
		      "unable to load heap");
    }
    assert(offset < heap->mem_alloc);
    assert(offset + size <= heap->mem_alloc);

    if (!buf) buf = H5MM_xmalloc(size);
    HDmemcpy(buf, heap->chunk + H5HL_SIZEOF_HDR(f) + offset, size);

    FUNC_LEAVE(buf);
}

/*-------------------------------------------------------------------------
 * Function:	H5HL_peek
 *
 * Purpose:	This function is a more efficient version of H5HL_read.
 *		Instead of copying a heap object into a caller-supplied
 *		buffer, this function returns a pointer directly into the
 *		cache where the heap is being held.  Thus, the return pointer
 *		is valid only until the next call to the cache.
 *
 *		The address of the heap is ADDR in file F.  OFFSET is the
 *		byte offset of the object from the beginning of the heap and
 *		may include an offset into the interior of the object.
 *
 * Return:	Success:	Ptr to the object.  The pointer points to
 *				a chunk of memory large enough to hold the
 *				object from the specified offset (usually
 *				the beginning of the object) to the end
 *				of the object.	Do not attempt to read past
 *				the end of the object.
 *
 *		Failure:	NULL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 16 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
const void *
H5HL_peek(H5F_t *f, const haddr_t *addr, size_t offset)
{
    H5HL_t		*heap = NULL;
    const void		*retval = NULL;

    FUNC_ENTER(H5HL_peek, NULL);

    /* check arguments */
    assert(f);
    assert(addr && H5F_addr_defined(addr));

    if (NULL == (heap = H5AC_find(f, H5AC_LHEAP, addr, NULL, NULL))) {
	HRETURN_ERROR(H5E_HEAP, H5E_CANTLOAD, NULL, "unable to load heap");
    }
    assert(offset < heap->mem_alloc);

    retval = heap->chunk + H5HL_SIZEOF_HDR(f) + offset;
    FUNC_LEAVE(retval);
}

/*-------------------------------------------------------------------------
 * Function:	H5HL_remove_free
 *
 * Purpose:	Removes free list element FL from the specified heap and
 *		frees it.
 *
 * Return:	NULL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 17 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static H5HL_free_t *
H5HL_remove_free(H5HL_t *heap, H5HL_free_t *fl)
{
    if (fl->prev) fl->prev->next = fl->next;
    if (fl->next) fl->next->prev = fl->prev;

    if (!fl->prev) heap->freelist = fl->next;
    return H5MM_xfree(fl);
}

/*-------------------------------------------------------------------------
 * Function:	H5HL_insert
 *
 * Purpose:	Inserts a new item into the heap.
 *
 * Return:	Success:	Offset of new item within heap.
 *
 *		Failure:	(size_t)(-1)
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 17 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
size_t
H5HL_insert(H5F_t *f, const haddr_t *addr, size_t buf_size, const void *buf)
{
    H5HL_t	*heap = NULL;
    H5HL_free_t	*fl = NULL, *max_fl = NULL;
    size_t	offset = 0;
    size_t	need_size, old_size, need_more;
    hbool_t	found;

    FUNC_ENTER(H5HL_insert, (size_t)(-1));

    /* check arguments */
    assert(f);
    assert(addr && H5F_addr_defined(addr));
    assert(buf_size > 0);
    assert(buf);

    if (NULL == (heap = H5AC_find(f, H5AC_LHEAP, addr, NULL, NULL))) {
	HRETURN_ERROR(H5E_HEAP, H5E_CANTLOAD, (size_t)(-1),
		      "unable to load heap");
    }
    heap->dirty += 1;

    /*
     * In order to keep the free list descriptors aligned on word boundaries,
     * whatever that might mean, we round the size up to the next multiple of
     * a word.
     */
    need_size = H5HL_ALIGN(buf_size);

    /*
     * Look for a free slot large enough for this object and which would
     * leave zero or at least H5G_SIZEOF_FREE bytes left over.
     */
    for (fl=heap->freelist, found=FALSE; fl; fl=fl->next) {
	if (fl->size > need_size &&
	    fl->size - need_size >= H5HL_SIZEOF_FREE(f)) {
	    /* a bigger free block was found */
	    offset = fl->offset;
	    fl->offset += need_size;
	    fl->size -= need_size;
	    assert (fl->offset==H5HL_ALIGN (fl->offset));
	    assert (fl->size==H5HL_ALIGN (fl->size));
	    found = TRUE;
	    break;
	} else if (fl->size == need_size) {
	    /* free block of exact size found */
	    offset = fl->offset;
	    fl = H5HL_remove_free(heap, fl);
	    found = TRUE;
	    break;
	} else if (!max_fl || max_fl->offset < fl->offset) {
	    /* use worst fit */
	    max_fl = fl;
	}
    }

    /*
     * If no free chunk was large enough, then allocate more space and
     * add it to the free list.	 If the heap ends with a free chunk, we
     * can extend that free chunk.  Otherwise we'll have to make another
     * free chunk.  If the heap must expand, we double its size.
     */
    if (found==FALSE) {
	need_more = MAX3(need_size, heap->mem_alloc, H5HL_SIZEOF_FREE(f));

	if (max_fl && max_fl->offset + max_fl->size == heap->mem_alloc) {
	    /*
	     * Increase the size of the maximum free block.
	     */
	    offset = max_fl->offset;
	    max_fl->offset += need_size;
	    max_fl->size += need_more - need_size;
	    assert (max_fl->offset==H5HL_ALIGN (max_fl->offset));
	    assert (max_fl->size==H5HL_ALIGN (max_fl->size));

	    if (max_fl->size < H5HL_SIZEOF_FREE(f)) {
#ifdef H5HL_DEBUG
		if (max_fl->size) {
		    fprintf(stderr, "H5HL: lost %lu bytes at line %d\n",
			    (unsigned long)(max_fl->size), __LINE__);
		}
#endif
		max_fl = H5HL_remove_free(heap, max_fl);
	    }
	} else {
	    /*
	     * Create a new free list element large enough that we can
	     * take some space out of it right away.
	     */
	    offset = heap->mem_alloc;
	    if (need_more - need_size >= H5HL_SIZEOF_FREE(f)) {
		fl = H5MM_xmalloc(sizeof(H5HL_free_t));
		fl->offset = heap->mem_alloc + need_size;
		fl->size = need_more - need_size;
		assert (fl->offset==H5HL_ALIGN (fl->offset));
		assert (fl->size==H5HL_ALIGN (fl->size));
		fl->prev = NULL;
		fl->next = heap->freelist;
		if (heap->freelist) heap->freelist->prev = fl;
		heap->freelist = fl;
#ifdef H5HL_DEBUG
	    } else if (need_more > need_size) {
		fprintf(stderr, "H5HL_insert: lost %lu bytes at line %d\n",
			(unsigned long)(need_more - need_size), __LINE__);
#endif
	    }
	}

#ifdef H5HL_DEBUG
	fprintf(stderr, "H5HL: resize mem buf from %lu to %lu bytes\n",
		(unsigned long)(heap->mem_alloc),
		(unsigned long)(heap->mem_alloc + need_more));
#endif
	old_size = heap->mem_alloc;
	heap->mem_alloc += need_more;
	heap->chunk = H5MM_xrealloc(heap->chunk,
				    H5HL_SIZEOF_HDR(f) + heap->mem_alloc);

	/* clear new section so junk doesn't appear in the file */
	HDmemset(heap->chunk + H5HL_SIZEOF_HDR(f) + old_size, 0, need_more);
    }
    /*
     * Copy the data into the heap
     */
    HDmemcpy(heap->chunk + H5HL_SIZEOF_HDR(f) + offset, buf, buf_size);
    FUNC_LEAVE(offset);
}

/*-------------------------------------------------------------------------
 * Function:	H5HL_write
 *
 * Purpose:	Writes (overwrites) the object (or part of object) stored
 *		in BUF to the heap at file address ADDR in file F.  The
 *		writing begins at byte offset OFFSET from the beginning of
 *		the heap and continues for SIZE bytes.
 *
 *		Do not partially write an object to create it;	the first
 *		write for an object must be for the entire object.
 *
 * Return:	Success:	SUCCEED
 *
 *		Failure:	FAIL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 16 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5HL_write(H5F_t *f, const haddr_t *addr, size_t offset, size_t size,
	  const void *buf)
{
    H5HL_t *heap = NULL;

    FUNC_ENTER(H5HL_write, FAIL);

    /* check arguments */
    assert(f);
    assert(addr && H5F_addr_defined(addr));
    assert(buf);
    assert (offset==H5HL_ALIGN (offset));

    if (NULL == (heap = H5AC_find(f, H5AC_LHEAP, addr, NULL, NULL))) {
	HRETURN_ERROR(H5E_HEAP, H5E_CANTLOAD, FAIL,
		      "unable to load heap");
    }
    assert(offset < heap->mem_alloc);
    assert(offset + size <= heap->mem_alloc);

    heap->dirty += 1;
    HDmemcpy(heap->chunk + H5HL_SIZEOF_HDR(f) + offset, buf, size);

    FUNC_LEAVE(SUCCEED);
}

/*-------------------------------------------------------------------------
 * Function:	H5HL_remove
 *
 * Purpose:	Removes an object or part of an object from the heap at
 *		address ADDR of file F.	 The object (or part) to remove
 *		begins at byte OFFSET from the beginning of the heap and
 *		continues for SIZE bytes.
 *
 *		Once part of an object is removed, one must not attempt
 *		to access that part.  Removing the beginning of an object
 *		results in the object OFFSET increasing by the amount
 *		truncated.  Removing the end of an object results in
 *		object truncation.  Removing the middle of an object results
 *		in two separate objects, one at the original offset and
 *		one at the first offset past the removed portion.
 *
 * Return:	Success:	SUCCEED
 *
 *		Failure:	FAIL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 16 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5HL_remove(H5F_t *f, const haddr_t *addr, size_t offset, size_t size)
{
    H5HL_t		*heap = NULL;
    H5HL_free_t		*fl = heap->freelist, *fl2 = NULL;

    FUNC_ENTER(H5HL_remove, FAIL);

    /* check arguments */
    assert(f);
    assert(addr && H5F_addr_defined(addr));
    assert(size > 0);
    assert (offset==H5HL_ALIGN (offset));
    size = H5HL_ALIGN (size);

    if (NULL == (heap = H5AC_find(f, H5AC_LHEAP, addr, NULL, NULL))) {
	HRETURN_ERROR(H5E_HEAP, H5E_CANTLOAD, FAIL,
		      "unable to load heap");
    }
    assert(offset < heap->mem_alloc);
    assert(offset + size <= heap->mem_alloc);

    heap->dirty += 1;

    /*
     * Check if this chunk can be prepended or appended to an already
     * free chunk.  It might also fall between two chunks in such a way
     * that all three chunks can be combined into one.
     */
    while (fl) {
	if (offset + size == fl->offset) {
	    fl->offset = offset;
	    fl->size += size;
	    assert (fl->offset==H5HL_ALIGN (fl->offset));
	    assert (fl->size==H5HL_ALIGN (fl->size));
	    fl2 = fl->next;
	    while (fl2) {
		if (fl2->offset + fl2->size == fl->offset) {
		    fl->offset = fl2->offset;
		    fl->size += fl2->size;
		    assert (fl->offset==H5HL_ALIGN (fl->offset));
		    assert (fl->size==H5HL_ALIGN (fl->size));
		    fl2 = H5HL_remove_free(heap, fl2);
		    HRETURN(SUCCEED);
		}
	    }
	    HRETURN(SUCCEED);

	} else if (fl->offset + fl->size == offset) {
	    fl->size += size;
	    fl2 = fl->next;
	    assert (fl->size==H5HL_ALIGN (fl->size));
	    while (fl2) {
		if (fl->offset + fl->size == fl2->offset) {
		    fl->size += fl2->size;
		    assert (fl->size==H5HL_ALIGN (fl->size));
		    fl2 = H5HL_remove_free(heap, fl2);
		    HRETURN(SUCCEED);
		}
	    }
	    HRETURN(SUCCEED);
	}
	fl = fl->next;
    }

    /*
     * The amount which is being removed must be large enough to
     * hold the free list data.	 If not, the freed chunk is forever
     * lost.
     */
    if (size < H5HL_SIZEOF_FREE(f)) {
#ifdef H5HL_DEBUG
	fprintf(stderr, "H5HL: lost %lu bytes\n", (unsigned long) size);
#endif
	HRETURN(SUCCEED);
    }
    /*
     * Add an entry to the free list.
     */
    fl = H5MM_xmalloc(sizeof(H5HL_free_t));
    fl->offset = offset;
    fl->size = size;
    assert (fl->offset==H5HL_ALIGN (fl->offset));
    assert (fl->size==H5HL_ALIGN (fl->size));
    fl->prev = NULL;
    fl->next = heap->freelist;
    if (heap->freelist) heap->freelist->prev = fl;
    heap->freelist = fl;

    FUNC_LEAVE(SUCCEED);
}

/*-------------------------------------------------------------------------
 * Function:	H5HL_debug
 *
 * Purpose:	Prints debugging information about a heap.
 *
 * Return:	Success:	SUCCEED
 *
 *		Failure:	FAIL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Aug  1 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5HL_debug(H5F_t *f, const haddr_t *addr, FILE * stream, intn indent,
	  intn fwidth)
{
    H5HL_t		*h = NULL;
    int			i, j, overlap;
    uint8		c;
    H5HL_free_t		*freelist = NULL;
    uint8		*marker = NULL;
    size_t		amount_free = 0;

    FUNC_ENTER(H5HL_debug, FAIL);

    /* check arguments */
    assert(f);
    assert(addr && H5F_addr_defined(addr));
    assert(stream);
    assert(indent >= 0);
    assert(fwidth >= 0);

    if (NULL == (h = H5AC_find(f, H5AC_LHEAP, addr, NULL, NULL))) {
	HRETURN_ERROR(H5E_HEAP, H5E_CANTLOAD, FAIL,
		      "unable to load heap");
    }
    fprintf(stream, "%*sHeap...\n", indent, "");
    fprintf(stream, "%*s%-*s %d\n", indent, "", fwidth,
	    "Dirty:",
	    (int) (h->dirty));
    fprintf(stream, "%*s%-*s %lu\n", indent, "", fwidth,
	    "Data bytes allocated on disk:",
	    (unsigned long) (h->disk_alloc));
    fprintf(stream, "%*s%-*s %lu\n", indent, "", fwidth,
	    "Data bytes allocated in core:",
	    (unsigned long) (h->mem_alloc));

    /*
     * Traverse the free list and check that all free blocks fall within
     * the heap and that no two free blocks point to the same region of
     * the heap.
     */
    marker = H5MM_xcalloc(h->mem_alloc, 1);
    for (freelist = h->freelist; freelist; freelist = freelist->next) {
	fprintf(stream, "%*s%-*s %8lu, %8lu\n", indent, "", fwidth,
		"Free Block (offset,size):",
		(unsigned long) (freelist->offset),
		(unsigned long) (freelist->size));
	if (freelist->offset + freelist->size > h->mem_alloc) {
	    fprintf(stream, "***THAT FREE BLOCK IS OUT OF BOUNDS!\n");
	} else {
	    for (i = overlap = 0; i < freelist->size; i++) {
		if (marker[freelist->offset + i])
		    overlap++;
		marker[freelist->offset + i] = 1;
	    }
	    if (overlap) {
		fprintf(stream, "***THAT FREE BLOCK OVERLAPPED A PREVIOUS "
			"ONE!\n");
	    } else {
		amount_free += freelist->size;
	    }
	}
    }

    if (h->mem_alloc) {
	fprintf(stream, "%*s%-*s %lu\n", indent, "", fwidth,
		"Percent of heap used:",
		(unsigned long) (100 * (h->mem_alloc - amount_free) /
				 h->mem_alloc));
    }
    /*
     * Print the data in a VMS-style octal dump.
     */
    fprintf(stream, "%*sData follows (`__' indicates free region)...\n",
	    indent, "");
    for (i = 0; i < h->disk_alloc; i += 16) {
	fprintf(stream, "%*s %8d: ", indent, "", i);
	for (j = 0; j < 16; j++) {
	    if (i + j < h->disk_alloc) {
		if (marker[i + j]) {
		    fprintf(stream, "__ ");
		} else {
		    c = h->chunk[H5HL_SIZEOF_HDR(f) + i + j];
		    fprintf(stream, "%02x ", c);
		}
	    } else {
		fprintf(stream, "   ");
	    }
	    if (7 == j)
		HDfputc(' ', stream);
	}

	for (j = 0; j < 16; j++) {
	    if (i + j < h->disk_alloc) {
		if (marker[i + j]) {
		    HDfputc(' ', stream);
		} else {
		    c = h->chunk[H5HL_SIZEOF_HDR(f) + i + j];
		    if (c > ' ' && c < '~')
			HDfputc(c, stream);
		    else
			HDfputc('.', stream);
		}
	    }
	}

	HDfputc('\n', stream);
    }

    H5MM_xfree(marker);
    FUNC_LEAVE(SUCCEED);
}