/* $NetBSD: free.c,v 1.1.1.1 2016/01/13 21:42:18 christos Exp $ */
/* Free a block of memory allocated by `malloc'.
Copyright 1990, 1991, 1992, 1994 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
[email protected],
or (US mail) as Mike Haertel c/o Free Software Foundation. */
#ifndef _MALLOC_INTERNAL
#define _MALLOC_INTERNAL
#include <malloc.h>
#endif
/* Debugging hook for free. */
void (*__free_hook) __P ((__ptr_t __ptr));
/* List of blocks allocated by memalign. */
struct alignlist *_aligned_blocks = NULL;
/* Return memory to the heap.
Like `free' but don't call a __free_hook if there is one. */
void
_free_internal (ptr)
__ptr_t ptr;
{
int type;
__malloc_size_t block, blocks;
register __malloc_size_t i;
struct list *prev, *next;
block = BLOCK (ptr);
type = _heapinfo[block].busy.type;
switch (type)
{
case 0:
/* Get as many statistics as early as we can. */
--_chunks_used;
_bytes_used -= _heapinfo[block].busy.info.size * BLOCKSIZE;
_bytes_free += _heapinfo[block].busy.info.size * BLOCKSIZE;
/* Find the free cluster previous to this one in the free list.
Start searching at the last block referenced; this may benefit
programs with locality of allocation. */
i = _heapindex;
if (i > block)
while (i > block)
i = _heapinfo[i].free.prev;
else
{
do
i = _heapinfo[i].free.next;
while (i > 0 && i < block);
i = _heapinfo[i].free.prev;
}
/* Determine how to link this block into the free list. */
if (block == i + _heapinfo[i].free.size)
{
/* Coalesce this block with its predecessor. */
_heapinfo[i].free.size += _heapinfo[block].busy.info.size;
block = i;
}
else
{
/* Really link this block back into the free list. */
_heapinfo[block].free.size = _heapinfo[block].busy.info.size;
_heapinfo[block].free.next = _heapinfo[i].free.next;
_heapinfo[block].free.prev = i;
_heapinfo[i].free.next = block;
_heapinfo[_heapinfo[block].free.next].free.prev = block;
++_chunks_free;
}
/* Now that the block is linked in, see if we can coalesce it
with its successor (by deleting its successor from the list
and adding in its size). */
if (block + _heapinfo[block].free.size == _heapinfo[block].free.next)
{
_heapinfo[block].free.size
+= _heapinfo[_heapinfo[block].free.next].free.size;
_heapinfo[block].free.next
= _heapinfo[_heapinfo[block].free.next].free.next;
_heapinfo[_heapinfo[block].free.next].free.prev = block;
--_chunks_free;
}
/* Now see if we can return stuff to the system. */
blocks = _heapinfo[block].free.size;
if (blocks >= FINAL_FREE_BLOCKS && block + blocks == _heaplimit
&& (*__morecore) (0) == ADDRESS (block + blocks))
{
register __malloc_size_t bytes = blocks * BLOCKSIZE;
_heaplimit -= blocks;
(*__morecore) (-bytes);
_heapinfo[_heapinfo[block].free.prev].free.next
= _heapinfo[block].free.next;
_heapinfo[_heapinfo[block].free.next].free.prev
= _heapinfo[block].free.prev;
block = _heapinfo[block].free.prev;
--_chunks_free;
_bytes_free -= bytes;
}
/* Set the next search to begin at this block. */
_heapindex = block;
break;
default:
/* Do some of the statistics. */
--_chunks_used;
_bytes_used -= 1 << type;
++_chunks_free;
_bytes_free += 1 << type;
/* Get the address of the first free fragment in this block. */
prev = (struct list *) ((char *) ADDRESS (block) +
(_heapinfo[block].busy.info.frag.first << type));
if (_heapinfo[block].busy.info.frag.nfree == (BLOCKSIZE >> type) - 1)
{
/* If all fragments of this block are free, remove them
from the fragment list and free the whole block. */
next = prev;
for (i = 1; i < (__malloc_size_t) (BLOCKSIZE >> type); ++i)
next = next->next;
prev->prev->next = next;
if (next != NULL)
next->prev = prev->prev;
_heapinfo[block].busy.type = 0;
_heapinfo[block].busy.info.size = 1;
/* Keep the statistics accurate. */
++_chunks_used;
_bytes_used += BLOCKSIZE;
_chunks_free -= BLOCKSIZE >> type;
_bytes_free -= BLOCKSIZE;
free (ADDRESS (block));
}
else if (_heapinfo[block].busy.info.frag.nfree != 0)
{
/* If some fragments of this block are free, link this
fragment into the fragment list after the first free
fragment of this block. */
next = (struct list *) ptr;
next->next = prev->next;
next->prev = prev;
prev->next = next;
if (next->next != NULL)
next->next->prev = next;
++_heapinfo[block].busy.info.frag.nfree;
}
else
{
/* No fragments of this block are free, so link this
fragment into the fragment list and announce that
it is the first free fragment of this block. */
prev = (struct list *) ptr;
_heapinfo[block].busy.info.frag.nfree = 1;
_heapinfo[block].busy.info.frag.first = (unsigned long int)
((unsigned long int) ((char *) ptr - (char *) NULL)
% BLOCKSIZE >> type);
prev->next = _fraghead[type].next;
prev->prev = &_fraghead[type];
prev->prev->next = prev;
if (prev->next != NULL)
prev->next->prev = prev;
}
break;
}
}
/* Return memory to the heap. */
void
free (ptr)
__ptr_t ptr;
{
register struct alignlist *l;
if (ptr == NULL)
return;
for (l = _aligned_blocks; l != NULL; l = l->next)
if (l->aligned == ptr)
{
l->aligned = NULL; /* Mark the slot in the list as free. */
ptr = l->exact;
break;
}
if (__free_hook != NULL)
(*__free_hook) (ptr);
else
_free_internal (ptr);
}
