memory_pool.c

00001 /*
00002  * Copyright (C) 2011 by Matthias Ringwald
00003  *
00004  * Redistribution and use in source and binary forms, with or without
00005  * modification, are permitted provided that the following conditions
00006  * are met:
00007  *
00008  * 1. Redistributions of source code must retain the above copyright
00009  *    notice, this list of conditions and the following disclaimer.
00010  * 2. Redistributions in binary form must reproduce the above copyright
00011  *    notice, this list of conditions and the following disclaimer in the
00012  *    documentation and/or other materials provided with the distribution.
00013  * 3. Neither the name of the copyright holders nor the names of
00014  *    contributors may be used to endorse or promote products derived
00015  *    from this software without specific prior written permission.
00016  *
00017  * THIS SOFTWARE IS PROVIDED BY MATTHIAS RINGWALD AND CONTRIBUTORS
00018  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00019  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00020  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
00021  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00022  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00023  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
00024  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
00025  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
00026  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
00027  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00028  * SUCH DAMAGE.
00029  *
00030  */
00031 
00032 /*
00033  *  memory_pool.c
00034  *
00035  *  Fixed-size block allocation
00036  *
00037  *  Free blocks are kept in singly linked list
00038  *
00039  */
00040 
00041 #include "btstack/memory_pool.h"
00042 #include <stddef.h>
00043 
00044 typedef struct node {
00045     struct node * next;
00046 } node_t;
00047 
00048 void memory_pool_create(memory_pool_t *pool, void * storage, int count, int block_size){
00049     node_t *free_blocks = (node_t*) pool;
00050     char   *mem_ptr = (char *) storage;
00051     int i;
00052     
00053     // create singly linked list of all available blocks
00054     free_blocks->next = NULL;
00055     for (i = 0 ; i < count ; i++){
00056         memory_pool_free(pool, mem_ptr);
00057         mem_ptr += block_size;
00058     }
00059 }
00060 
00061 void * memory_pool_get(memory_pool_t *pool){
00062     node_t *free_blocks = (node_t*) pool;
00063     
00064     if (!free_blocks->next) return NULL;
00065     
00066     // remove first
00067     node_t *node      = free_blocks->next;
00068     free_blocks->next = node->next;
00069     
00070     return (void*) node;
00071 }
00072 
00073 void memory_pool_free(memory_pool_t *pool, void * block){
00074     node_t *free_blocks = (node_t*) pool;
00075     node_t *node        = (node_t*) block;
00076     // add block as node to list
00077     node->next          = free_blocks->next;
00078     free_blocks->next   = node;
00079 }