File content as of revision 22:a0b1d0e6d237:

/*
 mempool.cpp - sleek implementation of a memory pool
 Copyright (c) 2013 Norbert Truchsess <norbert.truchsess@t-online.de>
 All rights reserved.

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "MemPool.h"
#include <string.h>

#define POOLOFFSET  1

struct memblock MemPool::    blocks[MEMPOOL_NUM_MEMBLOCKS + 1];

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void MemPool::init() {
    memset(&blocks[0], 0, sizeof(blocks));
    blocks[POOLSTART].begin = MEMPOOL_STARTADDRESS;
    blocks[POOLSTART].size = 0;
    blocks[POOLSTART].nextblock = NOBLOCK;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
memhandle MemPool::allocBlock(memaddress size) {
    memblock*   best = NULL;
    memhandle   cur = POOLSTART;
    memblock*   block = &blocks[POOLSTART];
    memaddress  bestsize = MEMPOOL_SIZE + 1;

    do {
        memhandle   next = block->nextblock;
        memaddress  freesize = (next == NOBLOCK ? blocks[POOLSTART].begin + MEMPOOL_SIZE : blocks[next].begin) -
            block->begin -
            block->size;
        if (freesize == size) {
            best = &blocks[cur];
            goto found;
        }

        if (freesize > size && freesize < bestsize) {
            bestsize = freesize;
            best = &blocks[cur];
        }

        if (next == NOBLOCK) {
            if (best)
                goto found;
            else
                goto collect;
        }

        block = &blocks[next];
        cur = next;
    } while (true);

collect:
    {
        cur = POOLSTART;
        block = &blocks[POOLSTART];

        memhandle   next;
        while ((next = block->nextblock) != NOBLOCK) {
            memaddress      dest = block->begin + block->size;
            memblock*       nextblock = &blocks[next];
            memaddress*     src = &nextblock->begin;
            if (dest != *src)
            {
#ifdef MEMPOOL_MEMBLOCK_MV
                MEMPOOL_MEMBLOCK_MV(dest, *src, nextblock->size);
#endif
                *src = dest;
            }

            block = nextblock;
        }

        if (blocks[POOLSTART].begin + MEMPOOL_SIZE - block->begin - block->size >= size)
            best = block;
        else
            goto notfound;
    }

found:
    {
        block = &blocks[POOLOFFSET];
        for (cur = POOLOFFSET; cur < MEMPOOL_NUM_MEMBLOCKS + POOLOFFSET; cur++) {
            if (block->size) {
                block++;
                continue;
            }

            memaddress  address = best->begin + best->size;
#ifdef MEMBLOCK_ALLOC
            MEMBLOCK_ALLOC(address, size);
#endif
            block->begin = address;
            block->size = size;
            block->nextblock = best->nextblock;
            best->nextblock = cur;
            return cur;
        }
    }

notfound:
    return NOBLOCK;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void MemPool::freeBlock(memhandle handle) {
    if (handle == NOBLOCK)
        return;

    memblock*   b = &blocks[POOLSTART];

    do {
        memhandle   next = b->nextblock;
        if (next == handle) {
            memblock*   f = &blocks[next];
#ifdef MEMBLOCK_FREE
            MEMBLOCK_FREE(f->begin, f->size);
#endif
            b->nextblock = f->nextblock;
            f->size = 0;
            f->nextblock = NOBLOCK;
            return;
        }

        if (next == NOBLOCK)
            return;
        b = &blocks[next];
    } while (true);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void MemPool::resizeBlock(memhandle handle, memaddress position) {
    memblock*   block = &blocks[handle];
    block->begin += position;
    block->size -= position;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void MemPool::resizeBlock(memhandle handle, memaddress position, memaddress size) {
    memblock*   block = &blocks[handle];
    block->begin += position;
    block->size = size;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
memaddress MemPool::blockSize(memhandle handle) {
    return blocks[handle].size;
}