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mmem.c

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00001 /*
00002  * Copyright (c) 2005, Swedish Institute of Computer Science
00003  * All rights reserved.
00004  *
00005  * Redistribution and use in source and binary forms, with or without
00006  * modification, are permitted provided that the following conditions
00007  * are met:
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 Institute nor the names of its contributors
00014  *    may be used to endorse or promote products derived from this software
00015  *    without specific prior written permission.
00016  *
00017  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
00018  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
00019  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
00020  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
00021  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
00022  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
00023  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
00024  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00025  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
00026  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00027  * SUCH DAMAGE.
00028  *
00029  * This file is part of the Contiki operating system.
00030  *
00031  * @(#)$Id: mmem.c,v 1.1 2006/06/17 22:41:18 adamdunkels Exp $
00032  */
00033 
00034 /**
00035  * \addtogroup mmem
00036  * @{
00037  */
00038 
00039 /**
00040  * \file
00041  *         Implementation of the managed memory allocator
00042  * \author
00043  *         Adam Dunkels <adam@sics.se>
00044  * 
00045  */
00046 
00047 
00048 #include "mmem.h"
00049 #include "list.h"
00050 
00051 #include <string.h>
00052 
00053 #define MMEM_SIZE 4096
00054 
00055 LIST(mmemlist);
00056 unsigned int avail_memory;
00057 static char memory[MMEM_SIZE];
00058 
00059 /*---------------------------------------------------------------------------*/
00060 /**
00061  * \brief      Allocate a managed memory block
00062  * \param m    A pointer to a struct mmem.
00063  * \param size The size of the requested memory block
00064  * \return     Non-zero if the memory could be allocated, zero if memory
00065  *             was not available.
00066  * \author     Adam Dunkels
00067  *
00068  *             This function allocates a chunk of managed memory. The
00069  *             memory allocated with this function must be deallocated
00070  *             using the mmem_free() function.
00071  *
00072  *             \note This function does NOT return a pointer to the
00073  *             allocated memory, but a pointer to a structure that
00074  *             contains information about the managed memory. The
00075  *             macro MMEM_PTR() is used to get a pointer to the
00076  *             allocated memory.
00077  *
00078  */
00079 int
00080 mmem_alloc(struct mmem *m, unsigned int size)
00081 {
00082   /* Check if we have enough memory left for this allocation. */
00083   if(avail_memory < size) {
00084     return 0;
00085   }
00086 
00087   /* We had enough memory so we add this memory block to the end of
00088      the list of allocated memory blocks. */
00089   list_add(mmemlist, m);
00090 
00091   /* Set up the pointer so that it points to the first available byte
00092      in the memory block. */
00093   m->ptr = &memory[MMEM_SIZE - avail_memory];
00094 
00095   /* Remember the size of this memory block. */
00096   m->size = size;
00097 
00098   /* Decrease the amount of available memory. */
00099   avail_memory -= size;
00100 
00101   /* Return non-zero to indicate that we were able to allocate
00102      memory. */
00103   return 1;
00104 }
00105 /*---------------------------------------------------------------------------*/
00106 /**
00107  * \brief      Deallocate a managed memory block
00108  * \param m    A pointer to the managed memory block
00109  * \author     Adam Dunkels
00110  *
00111  *             This function deallocates a managed memory block that
00112  *             previously has been allocated with mmem_alloc().
00113  *
00114  */
00115 void
00116 mmem_free(struct mmem *m)
00117 {
00118   struct mmem *n;
00119 
00120   if(m->next != NULL) {
00121     /* Compact the memory after the allocation that is to be removed
00122        by moving it downwards. */
00123     memmove(m->ptr, m->next->ptr,
00124             &memory[MMEM_SIZE - avail_memory] - (char *)m->next->ptr);
00125     
00126     /* Update all the memory pointers that points to memory that is
00127        after the allocation that is to be removed. */
00128     for(n = m->next; n != NULL; n = n->next) {
00129       n->ptr = (void *)((char *)n->ptr - m->size);
00130     }
00131   }
00132 
00133   avail_memory += m->size;
00134 
00135   /* Remove the memory block from the list. */
00136   list_remove(mmemlist, m);
00137 }
00138 /*---------------------------------------------------------------------------*/
00139 /**
00140  * \brief      Initialize the managed memory module
00141  * \author     Adam Dunkels
00142  *
00143  *             This function initializes the managed memory module and
00144  *             should be called before any other function from the
00145  *             module.
00146  *
00147  */
00148 void
00149 mmem_init(void)
00150 {
00151   list_init(mmemlist);
00152   avail_memory = MMEM_SIZE;
00153 }
00154 /*---------------------------------------------------------------------------*/
00155 
00156 /** @} */

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