adamdunkels | a2f3c42 | 2004-09-12 20:24:53 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2004, Swedish Institute of Computer Science. |
| 3 | * All rights reserved. |
| 4 | * |
| 5 | * Redistribution and use in source and binary forms, with or without |
| 6 | * modification, are permitted provided that the following conditions |
| 7 | * are met: |
| 8 | * 1. Redistributions of source code must retain the above copyright |
| 9 | * notice, this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer in the |
| 12 | * documentation and/or other materials provided with the distribution. |
| 13 | * 3. Neither the name of the Institute nor the names of its contributors |
| 14 | * may be used to endorse or promote products derived from this software |
| 15 | * without specific prior written permission. |
| 16 | * |
| 17 | * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND |
| 18 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE |
| 21 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 22 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 23 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 24 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 25 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 26 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 27 | * SUCH DAMAGE. |
| 28 | * |
| 29 | * This file is part of the Contiki operating system. |
| 30 | * |
| 31 | * Author: Adam Dunkels <adam@sics.se> |
| 32 | * |
| 33 | * $Id: memb.c,v 1.5 2004/09/12 20:24:55 adamdunkels Exp $ |
| 34 | */ |
adamdunkels | 25adfdf | 2003-10-14 11:14:54 +0000 | [diff] [blame] | 35 | /** |
adamdunkels | 01f657c | 2004-03-18 21:07:00 +0000 | [diff] [blame] | 36 | * \defgroup memb Memory block management functions |
adamdunkels | 25adfdf | 2003-10-14 11:14:54 +0000 | [diff] [blame] | 37 | * |
| 38 | * The memory block allocation routines provide a simple yet powerful |
| 39 | * set of functions for managing a set of memory blocks of fixed |
| 40 | * size. A set of memory blocks is statically declared with the |
| 41 | * MEMB() macro. Memory blocks are allocated from the declared |
| 42 | * memory by the memb_alloc() function, and are deallocated with the |
| 43 | * memb_free() function. |
| 44 | * |
| 45 | * \note Because of namespace clashes only one MEMB() can be |
| 46 | * declared per C module, and the name scope of a MEMB() memory |
| 47 | * block is local to each C module. |
| 48 | * |
| 49 | * The following example shows how to declare and use a memory block |
| 50 | * called "cmem" which has 8 chunks of memory with each memory chunk |
| 51 | * being 20 bytes large. |
| 52 | * |
| 53 | \code |
adamdunkels | 01f657c | 2004-03-18 21:07:00 +0000 | [diff] [blame] | 54 | #include "memb.h" |
| 55 | |
adamdunkels | 25adfdf | 2003-10-14 11:14:54 +0000 | [diff] [blame] | 56 | MEMB(cmem, 20, 8); |
| 57 | |
| 58 | int main(int argc, char *argv[]) { |
| 59 | char *ptr; |
| 60 | |
| 61 | memb_init(&cmem); |
| 62 | |
| 63 | ptr = memb_alloc(&cmem); |
| 64 | |
| 65 | if(ptr != NULL) { |
| 66 | do_something(ptr); |
| 67 | } else { |
| 68 | printf("Could not allocate memory.\n"); |
| 69 | } |
| 70 | |
adamdunkels | 01f657c | 2004-03-18 21:07:00 +0000 | [diff] [blame] | 71 | if(memb_free(&cmem, ptr) == 0) { |
adamdunkels | 25adfdf | 2003-10-14 11:14:54 +0000 | [diff] [blame] | 72 | printf("Deallocation succeeded.\n"); |
| 73 | } |
| 74 | } |
| 75 | \endcode |
adamdunkels | 01f657c | 2004-03-18 21:07:00 +0000 | [diff] [blame] | 76 | * |
| 77 | * @{ |
adamdunkels | 25adfdf | 2003-10-14 11:14:54 +0000 | [diff] [blame] | 78 | */ |
| 79 | |
adamdunkels | 01f657c | 2004-03-18 21:07:00 +0000 | [diff] [blame] | 80 | /** |
| 81 | * \file |
| 82 | * Memory block allocation routines. |
| 83 | * \author Adam Dunkels <adam@sics.se> |
| 84 | */ |
adamdunkels | 25adfdf | 2003-10-14 11:14:54 +0000 | [diff] [blame] | 85 | #include <string.h> |
| 86 | |
| 87 | #include "memb.h" |
| 88 | |
| 89 | /*------------------------------------------------------------------------------*/ |
| 90 | /** |
| 91 | * Initialize a memory block that was declared with MEMB(). |
| 92 | * |
| 93 | * \param m A memory block previosly declared with MEMB(). |
| 94 | */ |
| 95 | /*------------------------------------------------------------------------------*/ |
| 96 | void |
| 97 | memb_init(struct memb_blocks *m) |
| 98 | { |
adamdunkels | 9e15ad7 | 2004-02-16 20:48:13 +0000 | [diff] [blame] | 99 | memset(m->mem, 0, (m->size + 1) * m->num); |
adamdunkels | 25adfdf | 2003-10-14 11:14:54 +0000 | [diff] [blame] | 100 | } |
| 101 | /*------------------------------------------------------------------------------*/ |
| 102 | /** |
| 103 | * Allocate a memory block from a block of memory declared with MEMB(). |
| 104 | * |
| 105 | * \param m A memory block previosly declared with MEMB(). |
| 106 | */ |
| 107 | /*------------------------------------------------------------------------------*/ |
| 108 | char * |
| 109 | memb_alloc(struct memb_blocks *m) |
| 110 | { |
| 111 | int i; |
| 112 | char *ptr; |
| 113 | |
| 114 | ptr = m->mem; |
| 115 | for(i = 0; i < m->num; ++i) { |
| 116 | if(*ptr == 0) { |
| 117 | /* If this block was unused, we increase the reference count to |
| 118 | indicate that it now is used and return a pointer to the |
| 119 | first byte following the reference counter. */ |
| 120 | ++*ptr; |
| 121 | return ptr + 1; |
| 122 | } |
| 123 | ptr += m->size + 1; |
| 124 | } |
| 125 | |
| 126 | /* No free block was found, so we return NULL to indicate failure to |
| 127 | allocate block. */ |
| 128 | return NULL; |
| 129 | } |
| 130 | /*------------------------------------------------------------------------------*/ |
| 131 | /** |
| 132 | * Deallocate a memory block from a memory block previously declared |
| 133 | * with MEMB(). |
| 134 | * |
| 135 | * \param m m A memory block previosly declared with MEMB(). |
| 136 | * |
| 137 | * \param ptr A pointer to the memory block that is to be deallocated. |
| 138 | * |
| 139 | * \return The new reference count for the memory block (should be 0 |
| 140 | * if successfully deallocated) or -1 if the pointer "ptr" did not |
| 141 | * point to a legal memory block. |
| 142 | */ |
| 143 | /*------------------------------------------------------------------------------*/ |
| 144 | char |
adamdunkels | 01f657c | 2004-03-18 21:07:00 +0000 | [diff] [blame] | 145 | memb_free(struct memb_blocks *m, void *ptr) |
adamdunkels | 25adfdf | 2003-10-14 11:14:54 +0000 | [diff] [blame] | 146 | { |
| 147 | int i; |
| 148 | char *ptr2; |
| 149 | |
| 150 | /* Walk through the list of blocks and try to find the block to |
| 151 | which the pointer "ptr" points to. */ |
| 152 | ptr2 = m->mem; |
| 153 | for(i = 0; i < m->num; ++i) { |
| 154 | |
adamdunkels | 01f657c | 2004-03-18 21:07:00 +0000 | [diff] [blame] | 155 | if(ptr2 == (char *)ptr - 1) { |
adamdunkels | 25adfdf | 2003-10-14 11:14:54 +0000 | [diff] [blame] | 156 | /* We've found to block to which "ptr" points so we decrease the |
| 157 | reference count and return the new value of it. */ |
| 158 | return --*ptr2; |
| 159 | } |
| 160 | ptr2 += m->size + 1; |
| 161 | } |
| 162 | return -1; |
| 163 | } |
| 164 | /*------------------------------------------------------------------------------*/ |
| 165 | /** |
| 166 | * Increase the reference count for a memory chunk. |
| 167 | * |
| 168 | * \note No sanity checks are currently made. |
| 169 | * |
| 170 | * \param m m A memory block previosly declared with MEMB(). |
| 171 | * |
| 172 | * \param ptr A pointer to the memory chunk for which the reference |
| 173 | * count should be increased. |
| 174 | * |
| 175 | * \return The new reference count. |
| 176 | */ |
| 177 | /*------------------------------------------------------------------------------*/ |
| 178 | char |
| 179 | memb_ref(struct memb_blocks *m, char *ptr) |
| 180 | { |
| 181 | return ++*(ptr - 1); |
| 182 | } |
| 183 | /*------------------------------------------------------------------------------*/ |
| 184 | |
adamdunkels | 01f657c | 2004-03-18 21:07:00 +0000 | [diff] [blame] | 185 | /** @} */ |