nes-proj/core/lib/mmem.c

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/*
* Copyright (c) 2005, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
* @(#)$Id: mmem.c,v 1.1 2006/06/17 22:41:18 adamdunkels Exp $
*/
/**
* \addtogroup mmem
* @{
*/
/**
* \file
* Implementation of the managed memory allocator
* \author
* Adam Dunkels <adam@sics.se>
*
*/
#include "mmem.h"
#include "list.h"
#include <string.h>
#define MMEM_SIZE 4096
LIST(mmemlist);
unsigned int avail_memory;
static char memory[MMEM_SIZE];
/*---------------------------------------------------------------------------*/
/**
* \brief Allocate a managed memory block
* \param m A pointer to a struct mmem.
* \param size The size of the requested memory block
* \return Non-zero if the memory could be allocated, zero if memory
* was not available.
* \author Adam Dunkels
*
* This function allocates a chunk of managed memory. The
* memory allocated with this function must be deallocated
* using the mmem_free() function.
*
* \note This function does NOT return a pointer to the
* allocated memory, but a pointer to a structure that
* contains information about the managed memory. The
* macro MMEM_PTR() is used to get a pointer to the
* allocated memory.
*
*/
int
mmem_alloc(struct mmem *m, unsigned int size)
{
/* Check if we have enough memory left for this allocation. */
if(avail_memory < size) {
return 0;
}
/* We had enough memory so we add this memory block to the end of
the list of allocated memory blocks. */
list_add(mmemlist, m);
/* Set up the pointer so that it points to the first available byte
in the memory block. */
m->ptr = &memory[MMEM_SIZE - avail_memory];
/* Remember the size of this memory block. */
m->size = size;
/* Decrease the amount of available memory. */
avail_memory -= size;
/* Return non-zero to indicate that we were able to allocate
memory. */
return 1;
}
/*---------------------------------------------------------------------------*/
/**
* \brief Deallocate a managed memory block
* \param m A pointer to the managed memory block
* \author Adam Dunkels
*
* This function deallocates a managed memory block that
* previously has been allocated with mmem_alloc().
*
*/
void
mmem_free(struct mmem *m)
{
struct mmem *n;
if(m->next != NULL) {
/* Compact the memory after the allocation that is to be removed
by moving it downwards. */
memmove(m->ptr, m->next->ptr,
&memory[MMEM_SIZE - avail_memory] - (char *)m->next->ptr);
/* Update all the memory pointers that points to memory that is
after the allocation that is to be removed. */
for(n = m->next; n != NULL; n = n->next) {
n->ptr = (void *)((char *)n->ptr - m->size);
}
}
avail_memory += m->size;
/* Remove the memory block from the list. */
list_remove(mmemlist, m);
}
/*---------------------------------------------------------------------------*/
/**
* \brief Initialize the managed memory module
* \author Adam Dunkels
*
* This function initializes the managed memory module and
* should be called before any other function from the
* module.
*
*/
void
mmem_init(void)
{
list_init(mmemlist);
avail_memory = MMEM_SIZE;
}
/*---------------------------------------------------------------------------*/
/** @} */