block_collection_cache.h

// -*- mode: c++; tab-width: 4; indent-tabs-mode: t; c-file-style: "stroustrup"; -*-
// vi:set ts=4 sts=4 sw=4 noet cino+=(0 :
// Copyright 2014, 2015, The TPIE development team
// 
// This file is part of TPIE.
// 
// TPIE is free software: you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License as published by the
// Free Software Foundation, either version 3 of the License, or (at your
// option) any later version.
// 
// TPIE 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 Lesser General Public
// License for more details.
// 
// You should have received a copy of the GNU Lesser General Public License
// along with TPIE.  If not, see <http://www.gnu.org/licenses/>


#ifndef _TPIE_BLOCKS_BLOCK_COLLECTION_CACHE_H
#define _TPIE_BLOCKS_BLOCK_COLLECTION_CACHE_H

#include <tpie/tpie.h>
#include <tpie/tpie_assert.h>
#include <tpie/file_accessor/file_accessor.h>
#include <tpie/blocks/block.h>
#include <tpie/blocks/block_collection.h>
#include <list>
#include <map>

namespace tpie {

namespace blocks {

class block_collection_cache {
private:
    struct position_comparator {
        bool operator()(const block_handle & a, const block_handle & b) const {
            return a.position < b.position;
        }
    };

    typedef std::list<block_handle> block_list_t;

    struct block_information_t {
        block_information_t() {}

        block_information_t(block * pointer, block_list_t::iterator iterator, bool dirty)
            : pointer(pointer)
            , iterator(iterator)
            , dirty(dirty)
        {}

        block * pointer;
        block_list_t::iterator iterator;
        bool dirty;
    };

    typedef std::map<block_handle, block_information_t, position_comparator> block_map_t;
public:
    block_collection_cache(std::string fileName, memory_size_type blockSize, memory_size_type maxSize, bool writeable);

    ~block_collection_cache();


    block_handle get_free_block();

    void free_block(block_handle handle);

private:
    // make space for a new block in the cache
    void prepare_cache();

    void add_to_cache(block_handle handle, block * b, bool dirty);

    // Register that item is now the most recently used one.
    void used(block_information_t& item);

public:
    block * read_block(block_handle handle);

    void write_block(block_handle handle);

private:
    block_collection m_collection;
    block_list_t m_blockList;
    block_map_t m_blockMap;
    memory_size_type m_curSize;
    memory_size_type m_maxSize;
    memory_size_type m_blockSize;
};

} // blocks namespace

}  //  tpie namespace

#endif // _TPIE_BLOCKS_BLOCK_COLLECTION_CACHE_H