path: root/src/H5H.c

/*-------------------------------------------------------------------------
 * Copyright (C) 1997	National Center for Supercomputing Applications.
 *                      All rights reserved.
 *
 *-------------------------------------------------------------------------
 *
 * Created:		H5H.c
 * 			Jul 16 1997
 * 			Robb Matzke <matzke@llnl.gov>
 *
 * Purpose:		Heap functions for the global small object heap
 *			and for local symbol table name heaps.
 *
 * Modifications:
 *
 * 	Robb Matzke, 5 Aug 1997
 *	Added calls to H5E.
 *
 *-------------------------------------------------------------------------
 */
#include <H5private.h>			/*library			*/
#include <H5ACprivate.h>		/*cache				*/
#include <H5Eprivate.h>			/*error handling		*/
#include <H5Hprivate.h>			/*self				*/
#include <H5MFprivate.h>		/*file memory management	*/
#include <H5MMprivate.h>		/*core memory management	*/

#define H5H_FREE_NULL	1		/*end of free list on disk	*/
#define PABLO_MASK	H5H_mask

typedef struct H5H_free_t {
   off_t	offset;			/*offset of free block		*/
   size_t	size;			/*size of free block		*/
   struct H5H_free_t *prev;		/*previous entry in free list	*/
   struct H5H_free_t *next;		/*next entry in free list	*/
} H5H_free_t;

typedef struct H5H_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	*/
   H5H_free_t	*freelist;		/*the free list			*/
} H5H_t;

/* PRIVATE PROTOTYPES */
static H5H_t *H5H_load (hdf5_file_t *f, haddr_t addr, const void *udata);
static herr_t H5H_flush (hdf5_file_t *f, hbool_t dest, haddr_t addr,
			 H5H_t *heap);

/*
 * H5H inherits cache-like properties from H5AC
 */
static const H5AC_class_t H5AC_HEAP[1] = {{
   (void*(*)(hdf5_file_t*,haddr_t,const void*))H5H_load,
   (herr_t(*)(hdf5_file_t*,hbool_t,haddr_t,void*))H5H_flush,
}};

/* Is the interface initialized? */
static intn interface_initialize_g = FALSE;


/*-------------------------------------------------------------------------
 * Function:	H5H_new
 *
 * 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:	File address of new heap.
 *
 *		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.
 *
 *-------------------------------------------------------------------------
 */
haddr_t
H5H_new (hdf5_file_t *f, H5H_type_t heap_type, size_t size_hint)
{
   H5H_t	*heap = NULL;
   size_t	total_size;		/*total heap size on disk	*/
   haddr_t	addr;			/*heap file address		*/

   FUNC_ENTER (H5H_new, NULL, FAIL);

   /* check arguments */
   assert (f);
   if (H5H_GLOBAL==heap_type) {
#ifndef NDEBUG
      fprintf (stderr, "H5H_new: a local heap is used as the global heap\n");
#endif
   }
   
   size_hint = MAX (0, size_hint);
   if (size_hint && size_hint<H5H_SIZEOF_FREE(f)) {
      size_hint = H5H_SIZEOF_FREE(f);
   }

   /* allocate file version */
   total_size = H5H_SIZEOF_HDR(f) + size_hint;
   if ((addr = H5MF_alloc (f, total_size))<0) {
      HRETURN_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL);
   }

   /* allocate memory version */
   heap = H5MM_xcalloc (1, sizeof(H5H_t));
   heap->addr = addr + H5H_SIZEOF_HDR(f);
   heap->disk_alloc = size_hint;
   heap->mem_alloc = size_hint;
   heap->chunk = H5MM_xcalloc (1, H5H_SIZEOF_HDR(f)+size_hint);

   /* free list */
   if (size_hint) {
      heap->freelist = H5MM_xmalloc (sizeof(H5H_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_HEAP, addr, heap)<0) {
      heap->chunk = H5MM_xfree (heap->chunk);
      heap->freelist = H5MM_xfree (heap->freelist);
      HRETURN_ERROR (H5E_HEAP, H5E_CANTINIT, FAIL);
   }

   FUNC_LEAVE (addr);
}


/*-------------------------------------------------------------------------
 * Function:	H5H_load
 *
 * Purpose:	Loads a heap from disk.
 *
 * Return:	Success:	Ptr to heap memory data structure.
 *
 *		Failure:	NULL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 17 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static H5H_t *
H5H_load (hdf5_file_t *f, haddr_t addr, const void *udata)
{
   uint8	hdr[20], *p;
   H5H_t	*heap=NULL;
   H5H_free_t	*fl=NULL, *tail=NULL;
   haddr_t	free_block=H5H_FREE_NULL;

   FUNC_ENTER (H5H_load, NULL, NULL);

   /* check arguments */
   assert (f);
   assert (addr>0);
   assert (H5H_SIZEOF_HDR(f) <= sizeof hdr);
   assert (!udata);

   if (H5F_block_read (f, addr, H5H_SIZEOF_HDR(f), hdr)<0) {
      HRETURN_ERROR (H5E_HEAP, H5E_READERROR, NULL);
   }
   p = hdr;
   heap = H5MM_xcalloc (1, sizeof(H5H_t));

   /* magic number */
   if (HDmemcmp (hdr, H5H_MAGIC, H5H_SIZEOF_MAGIC)) goto error;
   p += H5H_SIZEOF_MAGIC;

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

   /* free list head */
   H5F_decode_offset (f, p, free_block);
   if (-1!=free_block && (free_block<0 || free_block>=heap->disk_alloc)) {
      goto error;
   }

   /* data */
   H5F_decode_offset (f, p, heap->addr);
   heap->chunk = H5MM_xcalloc (1, H5H_SIZEOF_HDR(f) + heap->mem_alloc);
   if (heap->disk_alloc &&
       H5F_block_read (f, heap->addr, heap->disk_alloc,
		       heap->chunk + H5H_SIZEOF_HDR(f))<0) {
      goto error;
   }

   /* free list */
   while (H5H_FREE_NULL!=free_block) {
      if (free_block<0 || free_block>=heap->disk_alloc) goto error;
      fl = H5MM_xmalloc (sizeof (H5H_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 + H5H_SIZEOF_HDR(f) + free_block;
      H5F_decode_offset (f, p, free_block);
      H5F_decode_length (f, p, fl->size);

      if (fl->offset + fl->size > heap->disk_alloc) goto error;
   }

   FUNC_LEAVE (heap);


error:
   if (heap) {
      heap->chunk = H5MM_xfree (heap->chunk);
      H5MM_xfree (heap);
      for (fl=heap->freelist; fl; fl=tail) {
	 tail = fl->next;
	 H5MM_xfree (fl);
      }
   }
   HRETURN_ERROR (H5E_HEAP, H5E_CANTLOAD, NULL);
}


/*-------------------------------------------------------------------------
 * Function:	H5H_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
H5H_flush (hdf5_file_t *f, hbool_t destroy, haddr_t addr, H5H_t *heap)
{
   uint8	*p = heap->chunk;
   H5H_free_t	*fl = heap->freelist;

   FUNC_ENTER (H5H_flush, NULL, FAIL);

   /* check arguments */
   assert (f);
   assert (addr>0);
   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;
	 if ((heap->addr = H5MF_alloc (f, heap->mem_alloc))<0) {
	    HRETURN_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL);
	 }
	 H5MF_free (f, old_addr, heap->disk_alloc); /*don't care if fail*/
	 heap->disk_alloc = heap->mem_alloc;
      }

      /*
       * Write the header.
       */
      HDmemcpy (p, H5H_MAGIC, H5H_SIZEOF_MAGIC); p += H5H_SIZEOF_MAGIC;
      H5F_encode_length (f, p, heap->mem_alloc);
      H5F_encode_offset (f, p, fl?fl->offset:-1);
      H5F_encode_offset (f, p, heap->addr);

      /*
       * Write the free list.
       */
      while (fl) {
	 p = heap->chunk + H5H_SIZEOF_HDR(f) + fl->offset;
	 if (fl->next) {
	    H5F_encode_offset (f, p, fl->next->offset);
	 } else {
	    H5F_encode_offset (f, p, H5H_FREE_NULL);
	 }
	 H5F_encode_length (f, p, fl->size);
	 fl = fl->next;
      }

      /*
       * Copy buffer to disk.
       */
      if (heap->addr == addr + H5H_SIZEOF_HDR(f)) {
	 if (H5F_block_write (f, addr, H5H_SIZEOF_HDR(f)+heap->disk_alloc,
			      heap->chunk)<0) {
	    HRETURN_ERROR (H5E_HEAP, H5E_WRITEERROR, FAIL);
	 }
      } else {
	 if (H5F_block_write (f, addr, H5H_SIZEOF_HDR(f), heap->chunk)<0) {
	    HRETURN_ERROR (H5E_HEAP, H5E_WRITEERROR, FAIL);
	 }
	 if (H5F_block_write (f, heap->addr, heap->disk_alloc,
			      heap->chunk + H5H_SIZEOF_HDR(f))<0) {
	    HRETURN_ERROR (H5E_HEAP, H5E_WRITEERROR, FAIL);
	 }
      }

      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:	H5H_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.
 *
 *  		If the heap address ADDR is the constant H5H_GLOBAL then
 *		the address comes from the hdf5_file_t global heap field.
 *
 * Return:	Success:	BUF (or the allocated buffer)
 *
 *		Failure:	NULL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 16 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
void *
H5H_read (hdf5_file_t *f, haddr_t addr, off_t offset, size_t size, void *buf)
{
   H5H_t	*heap = NULL;

   FUNC_ENTER (H5H_read, NULL, NULL);

   /* check arguments */
   assert (f);
   if (H5H_GLOBAL==addr) addr = f->smallobj_off;
   assert (addr>0);
   assert (offset>=0);

   if (NULL==(heap=H5AC_find (f, H5AC_HEAP, addr, NULL))) {
      HRETURN_ERROR (H5E_HEAP, H5E_CANTLOAD, NULL);
   }
   assert (offset<heap->mem_alloc);
   assert (offset+size<=heap->mem_alloc);

   if (!buf) buf = H5MM_xmalloc (size);
   HDmemcpy (buf, heap->chunk+H5H_SIZEOF_HDR(f)+offset, size);

   FUNC_LEAVE (buf);
}


/*-------------------------------------------------------------------------
 * Function:	H5H_peek
 *
 * Purpose:	This function is a more efficient version of H5H_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.
 *
 *  		If the heap address ADDR is the constant H5H_GLOBAL then
 *		the address comes from the hdf5_file_t global heap field.
 *
 * 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 *
H5H_peek (hdf5_file_t *f, haddr_t addr, off_t offset)
{
   H5H_t	*heap = NULL;
   const void	*retval = NULL;

   FUNC_ENTER (H5H_peek, NULL, NULL);

   /* check arguments */
   assert (f);
   if (H5H_GLOBAL==addr) addr = f->smallobj_off;
   assert (addr>0);
   assert (offset>=0);

   if (NULL==(heap=H5AC_find (f, H5AC_HEAP, addr, NULL))) {
      HRETURN_ERROR (H5E_HEAP, H5E_CANTLOAD, NULL);
   }
   assert (offset<heap->mem_alloc);
   
   retval = heap->chunk+H5H_SIZEOF_HDR(f)+offset;
   FUNC_LEAVE (retval);
}


/*-------------------------------------------------------------------------
 * Function:	H5H_remove_free
 *
 * Purpose:	Removes free list element FL from the specified heap.
 *
 * Return:	void
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 17 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static void
H5H_remove_free (H5H_t *heap, H5H_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;
}


/*-------------------------------------------------------------------------
 * Function:	H5H_insert
 *
 * Purpose:	Inserts a new item into the heap.
 *
 *  		If the heap address ADDR is the constant H5H_GLOBAL then
 *		the address comes from the hdf5_file_t global heap field.
 *
 * Return:	Success:	Offset of new item within heap.
 *
 *		Failure:	FAIL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 17 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
off_t
H5H_insert (hdf5_file_t *f, haddr_t addr, size_t buf_size, const void *buf)
{
   H5H_t	*heap=NULL;
   H5H_free_t	*fl=NULL, *max_fl=NULL;
   off_t	offset = -1;
   size_t	need, old_size, need_more;
#ifndef NDEBUG
   static	nmessages = 0;
#endif

   FUNC_ENTER (H5H_insert, NULL, FAIL);

   /* check arguments */
   assert (f);
   if (H5H_GLOBAL==addr) addr = f->smallobj_off;
   assert (addr>0);
   assert (buf_size>0);
   assert (buf);

   /* allocate aligned file memory */
   need = buf_size;
   H5H_ALIGN (need);

   if (NULL==(heap=H5AC_find (f, H5AC_HEAP, addr, NULL))) {
      HRETURN_ERROR (H5E_HEAP, H5E_CANTLOAD, FAIL);
   }
   heap->dirty += 1;

   /*
    * 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; fl; fl=fl->next) {
      if (fl->size>need && fl->size-need>=H5H_SIZEOF_FREE(f)) {
	 offset = fl->offset;
	 fl->offset += need;
	 fl->size -= need;
	 break;
      } else if (fl->size==need) {
	 offset = fl->offset;
	 H5H_remove_free (heap, fl);
	 break;
      } else if (!max_fl || max_fl->offset < fl->offset) {
	 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 (offset<0) {

      need_more = MAX3 (need, heap->mem_alloc, H5H_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;
	 max_fl->size += need_more - need;

	 if (max_fl->size < H5H_SIZEOF_FREE(f)) {
#ifndef NDEBUG
	    if (max_fl->size) {
	       fprintf (stderr, "H5H_insert: lost %d bytes at line %d\n",
			max_fl->size, __LINE__);
	       if (0==nmessages++) {
		  fprintf (stderr, "Messages from H5H_insert() will go away "
			   "when assertions are turned off.\n");
	       }
	    }
#endif
	    H5H_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 >= H5H_SIZEOF_FREE(f)) {
	    fl = H5MM_xmalloc (sizeof(H5H_free_t));
	    fl->offset = heap->mem_alloc + need;
	    fl->size = need_more - need;
	    fl->prev = NULL;
	    fl->next = heap->freelist;
	    if (heap->freelist) heap->freelist->prev = fl;
	    heap->freelist = fl;
#ifndef NDEBUG
	 } else if (need_more>need) {
	    fprintf (stderr, "H5H_insert: lost %d bytes at line %d\n",
		     need_more-need, __LINE__);
	    if (0==nmessages++) {
	       fprintf (stderr, "Messages from H5H_insert() will go away "
			"when assertions are turned off.\n");
	    }
#endif
	 }
      }

#ifndef NDEBUG
      fprintf (stderr, "H5H_insert: resize mem buf from %lu to %lu bytes\n",
	       (unsigned long)(heap->mem_alloc),
	       (unsigned long)(heap->mem_alloc + need_more));
      if (0==nmessages++) {
	 fprintf (stderr, "Messages from H5H_insert() will go away "
		  "when assertions are turned off.\n");
      }
#endif
      old_size = heap->mem_alloc;
      heap->mem_alloc += need_more;
      heap->chunk = H5MM_xrealloc (heap->chunk,
				   H5H_SIZEOF_HDR(f)+heap->mem_alloc);

      /* clear new section so junk doesn't appear in the file */
      HDmemset (heap->chunk+H5H_SIZEOF_HDR(f)+old_size, 0, need_more);
   }

   /*
    * Copy the data into the heap
    */
   HDmemcpy (heap->chunk + H5H_SIZEOF_HDR(f) + offset, buf, buf_size);
   FUNC_LEAVE (offset);
}
   

/*-------------------------------------------------------------------------
 * Function:	H5H_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.
 *
 *  		If the heap address ADDR is the constant H5H_GLOBAL then
 *		the address comes from the hdf5_file_t global heap field.
 *
 * Return:	Success:	SUCCEED
 *
 *		Failure:	FAIL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 16 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5H_write (hdf5_file_t *f, haddr_t addr, off_t offset, size_t size,
	   const void *buf)
{
   H5H_t	*heap = NULL;

   FUNC_ENTER (H5H_write, NULL, FAIL);

   /* check arguments */
   assert (f);
   if (H5H_GLOBAL==addr) addr = f->smallobj_off;
   assert (addr>0);
   assert (offset>=0);
   assert (buf);

   if (NULL==(heap=H5AC_find (f, H5AC_HEAP, addr, NULL))) {
      HRETURN_ERROR (H5E_HEAP, H5E_CANTLOAD, FAIL);
   }
   assert (offset<heap->mem_alloc);
   assert (offset+size<=heap->mem_alloc);

   heap->dirty += 1;
   HDmemcpy (heap->chunk+H5H_SIZEOF_HDR(f)+offset, buf, size);

   FUNC_LEAVE (SUCCEED);
}


/*-------------------------------------------------------------------------
 * Function:	H5H_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.
 *
 *  		If the heap address ADDR is the constant H5H_GLOBAL then
 *		the address comes from the hdf5_file_t global heap field.
 *
 * Return:	Success:	SUCCEED
 *
 *		Failure:	FAIL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Jul 16 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5H_remove (hdf5_file_t *f, haddr_t addr, off_t offset, size_t size)
{
   H5H_t	*heap = NULL;
   H5H_free_t	*fl = heap->freelist, *fl2 = NULL;
#ifndef NDEBUG
   static int	nmessages = 0;
#endif

   FUNC_ENTER (H5H_remove, NULL, FAIL);

   /* check arguments */
   assert (f);
   if (H5H_GLOBAL==addr) addr = f->smallobj_off;
   assert (addr>0);
   assert (offset>=0);
   assert (size>0);

   if (NULL==(heap=H5AC_find (f, H5AC_HEAP, addr, NULL))) {
      HRETURN_ERROR (H5E_HEAP, H5E_CANTLOAD, FAIL);
   }
   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;
	 fl2 = fl->next;
	 while (fl2) {
	    if (fl2->offset + fl2->size == fl->offset) {
	       fl->offset = fl2->offset;
	       fl->size += fl2->size;
	       H5H_remove_free (heap, fl2);
	       HRETURN (SUCCEED);
	    }
	 }
	 HRETURN (SUCCEED);
	 
      } else if (fl->offset + fl->size == offset) {
	 fl->size += size;
	 fl2 = fl->next;
	 while (fl2) {
	    if (fl->offset + fl->size == fl2->offset) {
	       fl->size += fl2->size;
	       H5H_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 < H5H_SIZEOF_FREE(f)) {
#ifndef NDEBUG
      fprintf (stderr, "H5H_remove: lost %d bytes\n", size);
      if (0==nmessages++) {
	 fprintf (stderr, "Messages from H5H_remove() will go away "
		  "when assertions are turned off.\n");
      }
#endif
      HRETURN (SUCCEED);
   }

   /*
    * Add an entry to the free list.
    */
   fl = H5MM_xmalloc (sizeof(H5H_free_t));
   fl->offset = offset;
   fl->size = size;
   fl->prev = NULL;
   fl->next = heap->freelist;
   if (heap->freelist) heap->freelist->prev = fl;
   heap->freelist = fl;

   FUNC_LEAVE (SUCCEED);
}


/*-------------------------------------------------------------------------
 * Function:	H5H_debug
 *
 * Purpose:	Prints debugging information about a heap.
 *
 *  		If the heap address ADDR is the constant H5H_GLOBAL then
 *		the address comes from the hdf5_file_t global heap field.
 *
 * Return:	Success:	SUCCEED
 *
 *		Failure:	FAIL
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Aug  1 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5H_debug (hdf5_file_t *f, haddr_t addr, FILE *stream, intn indent,
	   intn fwidth)
{
   H5H_t	*h = NULL;
   int		i, j, overlap;
   uint8	c;
   H5H_free_t	*freelist=NULL;
   uint8	*marker = NULL;
   size_t	amount_free = 0;

   FUNC_ENTER (H5H_debug, NULL, FAIL);

   /* check arguments */
   assert (f);
   if (H5H_GLOBAL==addr) addr = f->smallobj_off;
   assert (addr>0);
   assert (stream);
   assert (indent>=0);
   assert (fwidth>=0);

   if (NULL==(h=H5AC_find (f, H5AC_HEAP, addr, NULL))) {
      HRETURN_ERROR (H5E_HEAP, H5E_CANTLOAD, FAIL);
   }

   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 %d\n", indent, "", fwidth,
	       "Percent of heap used:",
	       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[H5H_SIZEOF_HDR(f)+i+j];
	       fprintf (stream, "%02x ", c);
	    }
	 } else {
	    fprintf (stream, "   ");
	 }
	 if (7==j) fputc (' ', stream);
      }

      for (j=0; j<16; j++) {
	 if (i+j<h->disk_alloc) {
	    if (marker[i+j]) {
	       HDfputc (' ', stream);
	    } else {
	       c = h->chunk[H5H_SIZEOF_HDR(f)+i+j];
	       if (c>' ' && c<'~') HDfputc (c, stream);
	       else HDfputc ('.', stream);
	    }
	 }
      }

      fputc ('\n', stream);
   }
      
   H5MM_xfree (marker);
   FUNC_LEAVE (SUCCEED);
}