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/* $OpenBSD: alloc.c,v 1.6 2002/03/14 03:16:09 millert Exp $ */
/* $NetBSD: alloc.c,v 1.6 1997/02/04 18:36:33 thorpej Exp $ */
/*
* Copyright (c) 1997 Christopher G. Demetriou. All rights reserved.
* Copyright (c) 1996
* Matthias Drochner. All rights reserved.
* Copyright (c) 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)alloc.c 8.1 (Berkeley) 6/11/93
*
*
* Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
* All Rights Reserved.
*
* Author: Alessandro Forin
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
/*
* Dynamic memory allocator.
*
* Compile options:
*
* ALLOC_TRACE enable tracing of allocations/deallocations
*
* ALLOC_FIRST_FIT use a first-fit allocation algorithm, rather than
* the default best-fit algorithm.
*
* HEAP_LIMIT heap limit address (defaults to "no limit").
*
* HEAP_START start address of heap (defaults to '&end').
*
* DEBUG enable debugging sanity checks.
*/
#include <sys/param.h>
/*
* Each block actually has ALIGN(unsigned) + ALIGN(size) bytes allocated
* to it, as follows:
*
* 0 ... (sizeof(unsigned) - 1)
* allocated or unallocated: holds size of user-data part of block.
*
* sizeof(unsigned) ... (ALIGN(sizeof(unsigned)) - 1)
* allocated: unused
* unallocated: depends on packing of struct fl
*
* ALIGN(sizeof(unsigned)) ... (ALIGN(sizeof(unsigned)) + ALIGN(data size) - 1)
* allocated: user data
* unallocated: depends on packing of struct fl
*
* 'next' is only used when the block is unallocated (i.e. on the free list).
* However, note that ALIGN(sizeof(unsigned)) + ALIGN(data size) must
* be at least 'sizeof(struct fl)', so that blocks can be used as structures
* when on the free list.
*/
#include "stand.h"
struct fl {
unsigned size;
struct fl *next;
} *freelist = (struct fl *)0;
#ifdef HEAP_START
static char *top = (char *)HEAP_START;
#else
extern char end[];
static char *top = end;
#endif
void *
alloc(size)
unsigned size;
{
register struct fl **f = &freelist, **bestf = NULL;
#ifndef ALLOC_FIRST_FIT
unsigned bestsize = 0xffffffff; /* greater than any real size */
#endif
char *help;
int failed;
#ifdef ALLOC_TRACE
printf("alloc(%u)", size);
#endif
#ifdef ALLOC_FIRST_FIT
while (*f != (struct fl *)0 && (*f)->size < size)
f = &((*f)->next);
bestf = f;
failed = (*bestf == (struct fl *)0);
#else
/* scan freelist */
while (*f) {
if ((*f)->size >= size) {
if ((*f)->size == size) /* exact match */
goto found;
if ((*f)->size < bestsize) {
/* keep best fit */
bestf = f;
bestsize = (*f)->size;
}
}
f = &((*f)->next);
}
/* no match in freelist if bestsize unchanged */
failed = (bestsize == 0xffffffff);
#endif
if (failed) { /* nothing found */
/*
* allocate from heap, keep chunk len in
* first word
*/
help = top;
/* make _sure_ the region can hold a struct fl. */
if (size < ALIGN(sizeof (struct fl *)))
size = ALIGN(sizeof (struct fl *));
top += ALIGN(sizeof(unsigned)) + ALIGN(size);
#ifdef HEAP_LIMIT
if (top > (char *)HEAP_LIMIT)
panic("heap full (0x%lx+%u)", help, size);
#endif
*(unsigned *)help = ALIGN(size);
#ifdef ALLOC_TRACE
printf("=%p\n", help + ALIGN(sizeof(unsigned)));
#endif
return(help + ALIGN(sizeof(unsigned)));
}
/* we take the best fit */
f = bestf;
#ifndef ALLOC_FIRST_FIT
found:
#endif
/* remove from freelist */
help = (char *)*f;
*f = (*f)->next;
#ifdef ALLOC_TRACE
printf("=%p (origsize %u)\n", help + ALIGN(sizeof(unsigned)),
*(unsigned *)help);
#endif
return(help + ALIGN(sizeof(unsigned)));
}
void
free(ptr, size)
void *ptr;
unsigned size; /* only for consistence check */
{
register struct fl *f =
(struct fl *)((char *)ptr - ALIGN(sizeof(unsigned)));
#ifdef ALLOC_TRACE
printf("free(%p, %u) (origsize %u)\n", ptr, size, f->size);
#endif
#ifdef DEBUG
if (size > f->size)
printf("free %u bytes @%p, should be <=%u\n",
size, ptr, f->size);
#ifdef HEAP_START
if (ptr < (void *)HEAP_START)
#else
if (ptr < (void *)end)
#endif
printf("free: %lx before start of heap.\n", (u_long)ptr);
#ifdef HEAP_LIMIT
if (ptr > (void *)HEAP_LIMIT)
printf("free: %lx beyond end of heap.\n", (u_long)ptr);
#endif
#endif /* DEBUG */
/* put into freelist */
f->next = freelist;
freelist = f;
}
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