319 lines
9.1 KiB
C
319 lines
9.1 KiB
C
/* Memory allocator `malloc'.
|
|
Copyright 1990, 1991, 1992, 1993 Free Software Foundation
|
|
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
|
|
|
|
/* How to really get more memory. */
|
|
__ptr_t (*__morecore) __P ((ptrdiff_t __size)) = __default_morecore;
|
|
|
|
/* Debugging hook for `malloc'. */
|
|
__ptr_t (*__malloc_hook) __P ((size_t __size));
|
|
|
|
/* Pointer to the base of the first block. */
|
|
char *_heapbase;
|
|
|
|
/* Block information table. Allocated with align/__free (not malloc/free). */
|
|
malloc_info *_heapinfo;
|
|
|
|
/* Number of info entries. */
|
|
static size_t heapsize;
|
|
|
|
/* Search index in the info table. */
|
|
size_t _heapindex;
|
|
|
|
/* Limit of valid info table indices. */
|
|
size_t _heaplimit;
|
|
|
|
/* Free lists for each fragment size. */
|
|
struct list _fraghead[BLOCKLOG];
|
|
|
|
/* Instrumentation. */
|
|
size_t _chunks_used;
|
|
size_t _bytes_used;
|
|
size_t _chunks_free;
|
|
size_t _bytes_free;
|
|
|
|
/* Are you experienced? */
|
|
int __malloc_initialized;
|
|
|
|
void (*__after_morecore_hook) __P ((void));
|
|
|
|
/* Aligned allocation. */
|
|
static __ptr_t align __P ((size_t));
|
|
static __ptr_t
|
|
align (size)
|
|
size_t size;
|
|
{
|
|
__ptr_t result;
|
|
unsigned long int adj;
|
|
|
|
result = (*__morecore) (size);
|
|
adj = (unsigned long int) ((unsigned long int) ((char *) result -
|
|
(char *) NULL)) % BLOCKSIZE;
|
|
if (adj != 0)
|
|
{
|
|
adj = BLOCKSIZE - adj;
|
|
(void) (*__morecore) (adj);
|
|
result = (char *) result + adj;
|
|
}
|
|
|
|
if (__after_morecore_hook)
|
|
(*__after_morecore_hook) ();
|
|
|
|
return result;
|
|
}
|
|
|
|
/* Set everything up and remember that we have. */
|
|
static int initialize __P ((void));
|
|
static int
|
|
initialize ()
|
|
{
|
|
heapsize = HEAP / BLOCKSIZE;
|
|
_heapinfo = (malloc_info *) align (heapsize * sizeof (malloc_info));
|
|
if (_heapinfo == NULL)
|
|
return 0;
|
|
memset (_heapinfo, 0, heapsize * sizeof (malloc_info));
|
|
_heapinfo[0].free.size = 0;
|
|
_heapinfo[0].free.next = _heapinfo[0].free.prev = 0;
|
|
_heapindex = 0;
|
|
_heapbase = (char *) _heapinfo;
|
|
__malloc_initialized = 1;
|
|
return 1;
|
|
}
|
|
|
|
/* Get neatly aligned memory, initializing or
|
|
growing the heap info table as necessary. */
|
|
static __ptr_t morecore __P ((size_t));
|
|
static __ptr_t
|
|
morecore (size)
|
|
size_t size;
|
|
{
|
|
__ptr_t result;
|
|
malloc_info *newinfo, *oldinfo;
|
|
size_t newsize;
|
|
|
|
result = align (size);
|
|
if (result == NULL)
|
|
return NULL;
|
|
|
|
/* Check if we need to grow the info table. */
|
|
if ((size_t) BLOCK ((char *) result + size) > heapsize)
|
|
{
|
|
newsize = heapsize;
|
|
while ((size_t) BLOCK ((char *) result + size) > newsize)
|
|
newsize *= 2;
|
|
newinfo = (malloc_info *) align (newsize * sizeof (malloc_info));
|
|
if (newinfo == NULL)
|
|
{
|
|
(*__morecore) (-size);
|
|
return NULL;
|
|
}
|
|
memset (newinfo, 0, newsize * sizeof (malloc_info));
|
|
memcpy (newinfo, _heapinfo, heapsize * sizeof (malloc_info));
|
|
oldinfo = _heapinfo;
|
|
newinfo[BLOCK (oldinfo)].busy.type = 0;
|
|
newinfo[BLOCK (oldinfo)].busy.info.size
|
|
= BLOCKIFY (heapsize * sizeof (malloc_info));
|
|
_heapinfo = newinfo;
|
|
_free_internal (oldinfo);
|
|
heapsize = newsize;
|
|
}
|
|
|
|
_heaplimit = BLOCK ((char *) result + size);
|
|
return result;
|
|
}
|
|
|
|
/* Allocate memory from the heap. */
|
|
__ptr_t
|
|
malloc (size)
|
|
size_t size;
|
|
{
|
|
__ptr_t result;
|
|
size_t block, blocks, lastblocks, start;
|
|
register size_t i;
|
|
struct list *next;
|
|
|
|
/* ANSI C allows `malloc (0)' to either return NULL, or to return a
|
|
valid address you can realloc and free (though not dereference).
|
|
|
|
It turns out that some extant code (sunrpc, at least Ultrix's version)
|
|
expects `malloc (0)' to return non-NULL and breaks otherwise.
|
|
Be compatible. */
|
|
|
|
#if 0
|
|
if (size == 0)
|
|
return NULL;
|
|
#endif
|
|
|
|
if (__malloc_hook != NULL)
|
|
return (*__malloc_hook) (size);
|
|
|
|
if (!__malloc_initialized)
|
|
if (!initialize ())
|
|
return NULL;
|
|
|
|
if (size < sizeof (struct list))
|
|
size = sizeof (struct list);
|
|
|
|
/* Determine the allocation policy based on the request size. */
|
|
if (size <= BLOCKSIZE / 2)
|
|
{
|
|
/* Small allocation to receive a fragment of a block.
|
|
Determine the logarithm to base two of the fragment size. */
|
|
register size_t log = 1;
|
|
--size;
|
|
while ((size /= 2) != 0)
|
|
++log;
|
|
|
|
/* Look in the fragment lists for a
|
|
free fragment of the desired size. */
|
|
next = _fraghead[log].next;
|
|
if (next != NULL)
|
|
{
|
|
/* There are free fragments of this size.
|
|
Pop a fragment out of the fragment list and return it.
|
|
Update the block's nfree and first counters. */
|
|
result = (__ptr_t) next;
|
|
next->prev->next = next->next;
|
|
if (next->next != NULL)
|
|
next->next->prev = next->prev;
|
|
block = BLOCK (result);
|
|
if (--_heapinfo[block].busy.info.frag.nfree != 0)
|
|
_heapinfo[block].busy.info.frag.first = (unsigned long int)
|
|
((unsigned long int) ((char *) next->next - (char *) NULL)
|
|
% BLOCKSIZE) >> log;
|
|
|
|
/* Update the statistics. */
|
|
++_chunks_used;
|
|
_bytes_used += 1 << log;
|
|
--_chunks_free;
|
|
_bytes_free -= 1 << log;
|
|
}
|
|
else
|
|
{
|
|
/* No free fragments of the desired size, so get a new block
|
|
and break it into fragments, returning the first. */
|
|
result = malloc (BLOCKSIZE);
|
|
if (result == NULL)
|
|
return NULL;
|
|
|
|
/* Link all fragments but the first into the free list. */
|
|
for (i = 1; i < (size_t) (BLOCKSIZE >> log); ++i)
|
|
{
|
|
next = (struct list *) ((char *) result + (i << log));
|
|
next->next = _fraghead[log].next;
|
|
next->prev = &_fraghead[log];
|
|
next->prev->next = next;
|
|
if (next->next != NULL)
|
|
next->next->prev = next;
|
|
}
|
|
|
|
/* Initialize the nfree and first counters for this block. */
|
|
block = BLOCK (result);
|
|
_heapinfo[block].busy.type = log;
|
|
_heapinfo[block].busy.info.frag.nfree = i - 1;
|
|
_heapinfo[block].busy.info.frag.first = i - 1;
|
|
|
|
_chunks_free += (BLOCKSIZE >> log) - 1;
|
|
_bytes_free += BLOCKSIZE - (1 << log);
|
|
_bytes_used -= BLOCKSIZE - (1 << log);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* Large allocation to receive one or more blocks.
|
|
Search the free list in a circle starting at the last place visited.
|
|
If we loop completely around without finding a large enough
|
|
space we will have to get more memory from the system. */
|
|
blocks = BLOCKIFY (size);
|
|
start = block = _heapindex;
|
|
while (_heapinfo[block].free.size < blocks)
|
|
{
|
|
block = _heapinfo[block].free.next;
|
|
if (block == start)
|
|
{
|
|
/* Need to get more from the system. Check to see if
|
|
the new core will be contiguous with the final free
|
|
block; if so we don't need to get as much. */
|
|
block = _heapinfo[0].free.prev;
|
|
lastblocks = _heapinfo[block].free.size;
|
|
if (_heaplimit != 0 && block + lastblocks == _heaplimit &&
|
|
(*__morecore) (0) == ADDRESS (block + lastblocks) &&
|
|
(morecore ((blocks - lastblocks) * BLOCKSIZE)) != NULL)
|
|
{
|
|
_heapinfo[block].free.size = blocks;
|
|
_bytes_free += (blocks - lastblocks) * BLOCKSIZE;
|
|
continue;
|
|
}
|
|
result = morecore (blocks * BLOCKSIZE);
|
|
if (result == NULL)
|
|
return NULL;
|
|
block = BLOCK (result);
|
|
_heapinfo[block].busy.type = 0;
|
|
_heapinfo[block].busy.info.size = blocks;
|
|
++_chunks_used;
|
|
_bytes_used += blocks * BLOCKSIZE;
|
|
return result;
|
|
}
|
|
}
|
|
|
|
/* At this point we have found a suitable free list entry.
|
|
Figure out how to remove what we need from the list. */
|
|
result = ADDRESS (block);
|
|
if (_heapinfo[block].free.size > blocks)
|
|
{
|
|
/* The block we found has a bit left over,
|
|
so relink the tail end back into the free list. */
|
|
_heapinfo[block + blocks].free.size
|
|
= _heapinfo[block].free.size - blocks;
|
|
_heapinfo[block + blocks].free.next
|
|
= _heapinfo[block].free.next;
|
|
_heapinfo[block + blocks].free.prev
|
|
= _heapinfo[block].free.prev;
|
|
_heapinfo[_heapinfo[block].free.prev].free.next
|
|
= _heapinfo[_heapinfo[block].free.next].free.prev
|
|
= _heapindex = block + blocks;
|
|
}
|
|
else
|
|
{
|
|
/* The block exactly matches our requirements,
|
|
so just remove it from the list. */
|
|
_heapinfo[_heapinfo[block].free.next].free.prev
|
|
= _heapinfo[block].free.prev;
|
|
_heapinfo[_heapinfo[block].free.prev].free.next
|
|
= _heapindex = _heapinfo[block].free.next;
|
|
--_chunks_free;
|
|
}
|
|
|
|
_heapinfo[block].busy.type = 0;
|
|
_heapinfo[block].busy.info.size = blocks;
|
|
++_chunks_used;
|
|
_bytes_used += blocks * BLOCKSIZE;
|
|
_bytes_free -= blocks * BLOCKSIZE;
|
|
}
|
|
|
|
return result;
|
|
}
|