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/*
* libc/stdlib/malloc/memalign.c -- memalign (`aligned malloc') function
*
* Copyright (C) 2002 NEC Corporation
* Copyright (C) 2002 Miles Bader <miles@gnu.org>
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License. See the file COPYING.LIB in the main
* directory of this archive for more details.
*
* Written by Miles Bader <miles@gnu.org>
*/
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include "malloc.h"
#include "heap.h"
#define MAX(x,y) ((x) > (y) ? (x) : (y))
/*
______________________ TOTAL _________________________
/ \
+---------------+-------------------------+--------------+
| | | |
+---------------+-------------------------+--------------+
\____ INIT ____/ \______ RETURNED _______/ \____ END ___/
*/
void *memalign (size_t alignment, size_t size);
void *
memalign (size_t alignment, size_t size)
{
void *mem, *base;
unsigned long tot_addr, tot_end_addr, addr, end_addr;
struct heap_free_area **heap = &__malloc_heap;
/* Make SIZE something we like. */
size = HEAP_ADJUST_SIZE (size);
/* Use malloc to do the initial allocation, since it deals with getting
system memory. We over-allocate enough to be sure that we'll get
enough memory to hold a properly aligned block of size SIZE,
_somewhere_ in the result. */
mem = malloc (size + 2 * alignment);
if (! mem)
/* Allocation failed, we can't do anything. */
return 0;
if (alignment < MALLOC_ALIGNMENT)
return mem;
/* Remember the base-address, of the allocation, although we normally
use the user-address for calculations, since that's where the
alignment matters. */
base = MALLOC_BASE (mem);
/* The bounds of the initial allocation. */
tot_addr = (unsigned long)mem;
tot_end_addr = (unsigned long)base + MALLOC_SIZE (mem);
/* Find a likely place inside MEM with the right alignment. */
addr = MALLOC_ROUND_UP (tot_addr, alignment);
/* Unless TOT_ADDR was already aligned correctly, we need to return the
initial part of MEM to the heap. */
if (addr != tot_addr)
{
size_t init_size = addr - tot_addr;
/* Ensure that memory returned to the heap is large enough. */
if (init_size < HEAP_MIN_SIZE)
{
addr = MALLOC_ROUND_UP (tot_addr + HEAP_MIN_SIZE, alignment);
init_size = addr - tot_addr;
}
__heap_free (heap, base, init_size);
/* Remember that we've freed the initial part of MEM. */
base += init_size;
}
/* Return the end part of MEM to the heap, unless it's too small. */
end_addr = addr + size;
if (end_addr + MALLOC_REALLOC_MIN_FREE_SIZE < tot_end_addr)
__heap_free (heap, (void *)end_addr, tot_end_addr - end_addr);
else
/* We didn't free the end, so include it in the size. */
end_addr = tot_end_addr;
return MALLOC_SETUP (base, end_addr - (unsigned long)base);
}
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