memorypool.h

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * 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/>.
 *
 */

#ifndef COMMON_MEMORYPOOL_H
#define COMMON_MEMORYPOOL_H

#include "common/scummsys.h"
#include "common/array.h"


namespace Common {

class MemoryPool {
protected:
    MemoryPool(const MemoryPool&);
    MemoryPool& operator=(const MemoryPool&);

    struct Page {
        void *start;
        size_t numChunks;
    };

    const size_t    _chunkSize;
    Array<Page>     _pages;
    void            *_next;
    size_t          _chunksPerPage;

    void    allocPage();
    void    addPageToPool(const Page &page);
    bool    isPointerInPage(void *ptr, const Page &page);

public:
    explicit MemoryPool(size_t chunkSize);
    ~MemoryPool();

    void    *allocChunk();
    void    freeChunk(void *ptr);

    void    freeUnusedPages();

    size_t  getChunkSize() const { return _chunkSize; }
};

template<size_t CHUNK_SIZE, size_t NUM_INTERNAL_CHUNKS = 32>
class FixedSizeMemoryPool : public MemoryPool {
private:
    enum {
        REAL_CHUNK_SIZE = (CHUNK_SIZE + sizeof(void *) - 1) & (~(sizeof(void *) - 1))
    };

    byte    _storage[NUM_INTERNAL_CHUNKS * REAL_CHUNK_SIZE];
public:
    FixedSizeMemoryPool() : MemoryPool(CHUNK_SIZE) {
        assert(REAL_CHUNK_SIZE == _chunkSize);
        // Insert some static storage
        Page internalPage = { _storage, NUM_INTERNAL_CHUNKS };
        addPageToPool(internalPage);
    }
};

/*
 * This is the degenerate case of FixedSizeMemoryPool with 0 chunks.
 * It's a MemoryPool with static chunk size.
 * This is useful for ObjectPool users (HashMap)
 */
template<size_t CHUNK_SIZE>
class FixedSizeMemoryPool<CHUNK_SIZE, 0> : public MemoryPool {
public:
    FixedSizeMemoryPool() : MemoryPool(CHUNK_SIZE) {}
};

template<class T, size_t NUM_INTERNAL_CHUNKS = 32>
class ObjectPool : public FixedSizeMemoryPool<sizeof(T), NUM_INTERNAL_CHUNKS> {
public:
    void deleteChunk(T *ptr) {
        ptr->~T();
        this->freeChunk(ptr);
    }
};

} // End of namespace Common

inline void *operator new(size_t nbytes, Common::MemoryPool &pool) {
    assert(nbytes <= pool.getChunkSize());
    return pool.allocChunk();
}

inline void operator delete(void *p, Common::MemoryPool &pool) {
    pool.freeChunk(p);
}

#endif