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