audio/utilities/zmalloc.c

	zmalloc.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 1991-2001 by Sun Microsystems, Inc.
 * All rights reserved.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * zmalloc  - use mmap(2) to allocate memory from /dev/zero.
 * zfree    - use munmap(2) to unmap (free) memory.
 *
 * These functions should be better than malloc(3) for large memory allocation.
 */

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include <zmalloc.h>

/*
 * a utility structure to keep track of the (possibly) multiple mmaps
 * that we have done...
 */
struct buffer_map {
    struct buffer_map *bm_next;
    char *bm_buffer;
    int bm_size;
};

static  void *bm_empty = (void *) "";       /* special buffer */
static  struct buffer_map *bm_list;     /* NULL by default */

static struct buffer_map *
insert_bm(char *buf, size_t size)
{
    struct buffer_map *bm;

    bm = (struct buffer_map *)malloc(sizeof (struct buffer_map));
    bm->bm_buffer = buf;
    bm->bm_size = size;
    bm->bm_next = bm_list;

    bm_list = bm;

    return (bm_list);
}

static size_t
delete_bm(char *buf)
{
    size_t size;
    register struct buffer_map *p_curr;
    register struct buffer_map *p_prev;

    p_prev = NULL;
    p_curr = bm_list;
    while (p_curr != NULL) {
        if (p_curr->bm_buffer == buf) {
            if (p_prev == NULL)
                bm_list = p_curr->bm_next;
            else
                p_prev->bm_next = p_curr->bm_next;
            size = p_curr->bm_size;
            free(p_curr);
            return (size);
        }

        p_prev = p_curr;
        p_curr = p_curr->bm_next;
    }
    return (0);
}

void *
zmalloc(size_t size)
{
    int fd;
    caddr_t mbuf;

    /* XXX - Special case: never allocate 0 bytes, use a special buffer */
    if (size == 0)
        return ((void *)NULL); /* return (bm_empty); */

    if ((fd = open("/dev/zero", O_RDWR)) < 0) {
        perror("/dev/zero");
        return ((void *) NULL);
    }

    mbuf = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    (void) close(fd);

    if (mbuf == (caddr_t)-1) {
        perror("zmalloc: mmap");
        return ((void *) NULL);
    }

    (void) insert_bm(mbuf, size);

    return ((void *) mbuf);
}

void
zfree(void* mbuf)
{
    size_t size;

    if (mbuf == bm_empty)
        return;

    if (mbuf != NULL) {
        if (size = delete_bm((caddr_t)mbuf)) {
            if (munmap((char *)mbuf, size) < 0)
                perror("zfree: munmap");
        }
    }
}