usr/src/cmd/audio/utilities/zmalloc.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright (c) 1991-2001 by Sun Microsystems, Inc.
  24  * All rights reserved.
  25  */
  26
  27 #pragma ident   "%Z%%M% %I%     %E% SMI"
  28
  29 /*
  30  * zmalloc      - use mmap(2) to allocate memory from /dev/zero.
  31  * zfree        - use munmap(2) to unmap (free) memory.
  32  *
  33  * These functions should be better than malloc(3) for large memory allocation.
  34  */
  35
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <fcntl.h>
  39 #include <unistd.h>
  40 #include <sys/types.h>
  41 #include <sys/mman.h>
  42 #include <sys/stat.h>
  43
  44 #include <zmalloc.h>
  45
  46 /*
  47  * a utility structure to keep track of the (possibly) multiple mmaps
  48  * that we have done...
  49  */
  50 struct buffer_map {
  51         struct buffer_map *bm_next;
  52         char *bm_buffer;
  53         int bm_size;
  54 };
  55
  56 static  void *bm_empty = (void *) "";           /* special buffer */
  57 static  struct buffer_map *bm_list;             /* NULL by default */
  58
  59 static struct buffer_map *
  60 insert_bm(char *buf, size_t size)
  61 {
  62         struct buffer_map *bm;
  63
  64         bm = (struct buffer_map *)malloc(sizeof (struct buffer_map));
  65         bm->bm_buffer = buf;
  66         bm->bm_size = size;
  67         bm->bm_next = bm_list;
  68
  69         bm_list = bm;
  70
  71         return (bm_list);
  72 }
  73
  74 static size_t
  75 delete_bm(char *buf)
  76 {
  77         size_t size;
  78         register struct buffer_map *p_curr;
  79         register struct buffer_map *p_prev;
  80
  81         p_prev = NULL;
  82         p_curr = bm_list;
  83         while (p_curr != NULL) {
  84                 if (p_curr->bm_buffer == buf) {
  85                         if (p_prev == NULL)
  86                                 bm_list = p_curr->bm_next;
  87                         else
  88                                 p_prev->bm_next = p_curr->bm_next;
  89                         size = p_curr->bm_size;
  90                         free(p_curr);
  91                         return (size);
  92                 }
  93
  94                 p_prev = p_curr;
  95                 p_curr = p_curr->bm_next;
  96         }
  97         return (0);
  98 }
  99
 100 void *
 101 zmalloc(size_t size)
 102 {
 103         int     fd;
 104         caddr_t mbuf;
 105
 106         /* XXX - Special case: never allocate 0 bytes, use a special buffer */
 107         if (size == 0)
 108             return ((void *)NULL); /* return (bm_empty); */
 109
 110         if ((fd = open("/dev/zero", O_RDWR)) < 0) {
 111                 perror("/dev/zero");
 112                 return ((void *) NULL);
 113         }
 114
 115         mbuf = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
 116         (void) close(fd);
 117
 118         if (mbuf == (caddr_t)-1) {
 119                 perror("zmalloc: mmap");
 120                 return ((void *) NULL);
 121         }
 122
 123         (void) insert_bm(mbuf, size);
 124
 125         return ((void *) mbuf);
 126 }
 127
 128 void
 129 zfree(void* mbuf)
 130 {
 131         size_t size;
 132
 133         if (mbuf == bm_empty)
 134             return;
 135
 136         if (mbuf != NULL) {
 137                 if (size = delete_bm((caddr_t)mbuf)) {
 138                         if (munmap((char *)mbuf, size) < 0)
 139                             perror("zfree: munmap");
 140                 }
 141         }
 142 }