stream_position.h

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// -*- mode: c++; tab-width: 4; indent-tabs-mode: t; eval: (progn (c-set-style "stroustrup") (c-set-offset 'innamespace 0)); -*-
// vi:set ts=4 sts=4 sw=4 noet :
// Copyright 2013, 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_COMPRESSED_STREAM_POSITION_H
#define TPIE_COMPRESSED_STREAM_POSITION_H


#include <tpie/compressed/predeclare.h>

namespace tpie {

// IMPLEMENTATION NOTES
//
// A stream position is the tuple `(read_offset, offset)`.
//
// For compressed streams, the stream block begins with a header at byte
// position `read_offset`.  After the block header, the items follow.
//
// For uncompressed streams, `read_offset` is zero and the item position
// in the stream is determined solely by `offset`.
//
// Thus, the first item in the stream has the position tuple `(0, 0)`.
class stream_position {
private:
    friend class compressed_stream_base;
    template <typename T>
    friend class file_stream;

    uint64_t m_readOffset;
    uint64_t m_offset;

public:
    static stream_position beginning() {
        return stream_position(0, 0);
    }

    static stream_position end() {
        return stream_position(
            std::numeric_limits<uint64_t>::max() - 1,
            std::numeric_limits<uint64_t>::max() - 1);
    }

    stream_position()
        : m_readOffset(std::numeric_limits<uint64_t>::max())
        , m_offset(std::numeric_limits<uint64_t>::max())
    {
    }

private:
    stream_position(stream_size_type readOffset,
                    stream_size_type offset)
        : m_readOffset(readOffset)
        , m_offset(offset)
    {
    }

    stream_size_type read_offset() const {
        return m_readOffset;
    }

public:
    stream_size_type offset() const {
        return m_offset;
    }

private:
    void advance_items(memory_size_type offset) {
        m_offset += offset;
    }

    void advance_item() {
        advance_items(1);
    }

public:
    bool operator==(const stream_position & other) const {
        return m_readOffset == other.m_readOffset
            && m_offset == other.m_offset;
    }

    bool operator!=(const stream_position & other) const {
        return !(*this == other);
    }

    bool operator<(const stream_position & other) const {
        return (m_offset != other.m_offset)
            ? (m_offset < other.m_offset)
            : (m_readOffset < other.m_readOffset);
    }

    friend std::ostream & operator<<(std::ostream & s, const stream_position & p) {
        return s << "(" << p.read_offset() << "," << p.offset() << ")";
    }
};

} // namespace tpie

#endif // TPIE_COMPRESSED_STREAM_POSITION_H