core/lib/mmem.c

   1 /*
   2  * Copyright (c) 2005, 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  * @(#)$Id: mmem.c,v 1.2 2006/12/22 17:14:06 barner Exp $
  32  */
  33
  34 /**
  35  * \addtogroup mmem
  36  * @{
  37  */
  38
  39 /**
  40  * \file
  41  *         Implementation of the managed memory allocator
  42  * \author
  43  *         Adam Dunkels <adam@sics.se>
  44  *
  45  */
  46
  47
  48 #include "mmem.h"
  49 #include "list.h"
  50 #include "contiki-conf.h"
  51 #include <string.h>
  52
  53 #ifdef MMEM_CONF_SIZE
  54 #define MMEM_SIZE MMEM_CONF_SIZE
  55 #else
  56 #define MMEM_SIZE 4096
  57 #endif
  58
  59 LIST(mmemlist);
  60 unsigned int avail_memory;
  61 static char memory[MMEM_SIZE];
  62
  63 /*---------------------------------------------------------------------------*/
  64 /**
  65  * \brief      Allocate a managed memory block
  66  * \param m    A pointer to a struct mmem.
  67  * \param size The size of the requested memory block
  68  * \return     Non-zero if the memory could be allocated, zero if memory
  69  *             was not available.
  70  * \author     Adam Dunkels
  71  *
  72  *             This function allocates a chunk of managed memory. The
  73  *             memory allocated with this function must be deallocated
  74  *             using the mmem_free() function.
  75  *
  76  *             \note This function does NOT return a pointer to the
  77  *             allocated memory, but a pointer to a structure that
  78  *             contains information about the managed memory. The
  79  *             macro MMEM_PTR() is used to get a pointer to the
  80  *             allocated memory.
  81  *
  82  */
  83 int
  84 mmem_alloc(struct mmem *m, unsigned int size)
  85 {
  86   /* Check if we have enough memory left for this allocation. */
  87   if(avail_memory < size) {
  88     return 0;
  89   }
  90
  91   /* We had enough memory so we add this memory block to the end of
  92      the list of allocated memory blocks. */
  93   list_add(mmemlist, m);
  94
  95   /* Set up the pointer so that it points to the first available byte
  96      in the memory block. */
  97   m->ptr = &memory[MMEM_SIZE - avail_memory];
  98
  99   /* Remember the size of this memory block. */
 100   m->size = size;
 101
 102   /* Decrease the amount of available memory. */
 103   avail_memory -= size;
 104
 105   /* Return non-zero to indicate that we were able to allocate
 106      memory. */
 107   return 1;
 108 }
 109 /*---------------------------------------------------------------------------*/
 110 /**
 111  * \brief      Deallocate a managed memory block
 112  * \param m    A pointer to the managed memory block
 113  * \author     Adam Dunkels
 114  *
 115  *             This function deallocates a managed memory block that
 116  *             previously has been allocated with mmem_alloc().
 117  *
 118  */
 119 void
 120 mmem_free(struct mmem *m)
 121 {
 122   struct mmem *n;
 123
 124   if(m->next != NULL) {
 125     /* Compact the memory after the allocation that is to be removed
 126        by moving it downwards. */
 127     memmove(m->ptr, m->next->ptr,
 128             &memory[MMEM_SIZE - avail_memory] - (char *)m->next->ptr);
 129
 130     /* Update all the memory pointers that points to memory that is
 131        after the allocation that is to be removed. */
 132     for(n = m->next; n != NULL; n = n->next) {
 133       n->ptr = (void *)((char *)n->ptr - m->size);
 134     }
 135   }
 136
 137   avail_memory += m->size;
 138
 139   /* Remove the memory block from the list. */
 140   list_remove(mmemlist, m);
 141 }
 142 /*---------------------------------------------------------------------------*/
 143 /**
 144  * \brief      Initialize the managed memory module
 145  * \author     Adam Dunkels
 146  *
 147  *             This function initializes the managed memory module and
 148  *             should be called before any other function from the
 149  *             module.
 150  *
 151  */
 152 void
 153 mmem_init(void)
 154 {
 155   list_init(mmemlist);
 156   avail_memory = MMEM_SIZE;
 157 }
 158 /*---------------------------------------------------------------------------*/
 159
 160 /** @} */