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/* Change the size of a block allocated by `malloc'.
Copyright 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
Written May 1989 by Mike Haertel.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.
The author may be reached (Email) at the address mike@ai.mit.edu,
or (US mail) as Mike Haertel c/o Free Software Foundation. */
#ifndef _MALLOC_INTERNAL
#define _MALLOC_INTERNAL
#include <malloc.h>
#endif
#define min(A, B) ((A) < (B) ? (A) : (B))
/* Debugging hook for realloc. */
__ptr_t (*__realloc_hook) __P ((__ptr_t __ptr, size_t __size));
/* Resize the given region to the new size, returning a pointer
to the (possibly moved) region. This is optimized for speed;
some benchmarks seem to indicate that greater compactness is
achieved by unconditionally allocating and copying to a
new region. This module has incestuous knowledge of the
internals of both free and malloc. */
__ptr_t
realloc (ptr, size)
__ptr_t ptr;
size_t size;
{
__ptr_t result;
int type;
size_t block, blocks, oldlimit;
if (size == 0)
{
free (ptr);
return malloc (0);
}
else if (ptr == NULL)
return malloc (size);
if (__realloc_hook != NULL)
return (*__realloc_hook) (ptr, size);
block = BLOCK (ptr);
type = _heapinfo[block].busy.type;
switch (type)
{
case 0:
/* Maybe reallocate a large block to a small fragment. */
if (size <= BLOCKSIZE / 2)
{
result = malloc (size);
if (result != NULL)
{
memcpy (result, ptr, size);
free (ptr);
return result;
}
}
/* The new size is a large allocation as well;
see if we can hold it in place. */
blocks = BLOCKIFY (size);
if (blocks < _heapinfo[block].busy.info.size)
{
/* The new size is smaller; return
excess memory to the free list. */
_heapinfo[block + blocks].busy.type = 0;
_heapinfo[block + blocks].busy.info.size
= _heapinfo[block].busy.info.size - blocks;
_heapinfo[block].busy.info.size = blocks;
free (ADDRESS (block + blocks));
result = ptr;
}
else if (blocks == _heapinfo[block].busy.info.size)
/* No size change necessary. */
result = ptr;
else
{
/* Won't fit, so allocate a new region that will.
Free the old region first in case there is sufficient
adjacent free space to grow without moving. */
blocks = _heapinfo[block].busy.info.size;
/* Prevent free from actually returning memory to the system. */
oldlimit = _heaplimit;
_heaplimit = 0;
free (ptr);
_heaplimit = oldlimit;
result = malloc (size);
if (result == NULL)
{
/* Now we're really in trouble. We have to unfree
the thing we just freed. Unfortunately it might
have been coalesced with its neighbors. */
if (_heapindex == block)
(void) malloc (blocks * BLOCKSIZE);
else
{
__ptr_t previous = malloc ((block - _heapindex) * BLOCKSIZE);
(void) malloc (blocks * BLOCKSIZE);
free (previous);
}
return NULL;
}
if (ptr != result)
memmove (result, ptr, blocks * BLOCKSIZE);
}
break;
default:
/* Old size is a fragment; type is logarithm
to base two of the fragment size. */
if (size > (size_t) (1 << (type - 1)) && size <= (size_t) (1 << type))
/* The new size is the same kind of fragment. */
result = ptr;
else
{
/* The new size is different; allocate a new space,
and copy the lesser of the new size and the old. */
result = malloc (size);
if (result == NULL)
return NULL;
memcpy (result, ptr, min (size, (size_t) 1 << type));
free (ptr);
}
break;
}
return result;
}
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