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1325 |
phoenix |
/*
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* libc/stdlib/malloc/memalign.c -- memalign (`aligned malloc') function
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*
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* Copyright (C) 2002 NEC Corporation
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* Copyright (C) 2002 Miles Bader <miles@gnu.org>
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License. See the file COPYING.LIB in the main
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* directory of this archive for more details.
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*
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* Written by Miles Bader <miles@gnu.org>
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*/
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/mman.h>
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#include "malloc.h"
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#include "heap.h"
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#define MAX(x,y) ((x) > (y) ? (x) : (y))
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/*
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______________________ TOTAL _________________________
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/ \
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+---------------+-------------------------+--------------+
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| | | |
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+---------------+-------------------------+--------------+
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\____ INIT ____/ \______ RETURNED _______/ \____ END ___/
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*/
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void *
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memalign (size_t alignment, size_t size)
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{
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void *mem, *base;
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unsigned long tot_addr, tot_end_addr, addr, end_addr;
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struct heap *heap = &__malloc_heap;
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/* Make SIZE something we like. */
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size = HEAP_ADJUST_SIZE (size);
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/* Use malloc to do the initial allocation, since it deals with getting
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system memory. We over-allocate enough to be sure that we'll get
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enough memory to hold a properly aligned block of size SIZE,
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_somewhere_ in the result. */
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mem = malloc (size + 2 * alignment);
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if (! mem)
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/* Allocation failed, we can't do anything. */
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return 0;
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if (alignment < MALLOC_ALIGNMENT)
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return mem;
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/* Remember the base-address, of the allocation, although we normally
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use the user-address for calculations, since that's where the
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alignment matters. */
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base = MALLOC_BASE (mem);
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/* The bounds of the initial allocation. */
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tot_addr = (unsigned long)mem;
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tot_end_addr = (unsigned long)base + MALLOC_SIZE (mem);
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/* Find a likely place inside MEM with the right alignment. */
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addr = MALLOC_ROUND_UP (tot_addr, alignment);
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/* Unless TOT_ADDR was already aligned correctly, we need to return the
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initial part of MEM to the heap. */
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if (addr != tot_addr)
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{
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size_t init_size = addr - tot_addr;
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/* Ensure that memory returned to the heap is large enough. */
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if (init_size < HEAP_MIN_SIZE)
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{
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addr = MALLOC_ROUND_UP (tot_addr + HEAP_MIN_SIZE, alignment);
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init_size = addr - tot_addr;
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}
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__heap_free (heap, base, init_size);
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/* Remember that we've freed the initial part of MEM. */
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base += init_size;
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}
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/* Return the end part of MEM to the heap, unless it's too small. */
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end_addr = addr + size;
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if (end_addr + MALLOC_REALLOC_MIN_FREE_SIZE < tot_end_addr)
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__heap_free (heap, (void *)end_addr, tot_end_addr - end_addr);
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else
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/* We didn't free the end, so include it in the size. */
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end_addr = tot_end_addr;
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return MALLOC_SETUP (base, end_addr - (unsigned long)base);
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}
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