moduled_adaptor.hh

/*
 * Copyright (C) Flamewing 2016 <flamewing.sonic@gmail.com>
 *
 *
 * This program 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 2.1 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with main.c; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor Boston, MA 02110-1301,  USA
 */

#ifndef LIB_MODULED_ADAPTOR_HH
#define LIB_MODULED_ADAPTOR_HH

#include <mdcomp/bigendian_io.hh>

#include <limits>
#include <sstream>
#include <vector>

template <
        typename Format, size_t DefaultModuleSize, size_t DefaultModulePadding>
class ModuledAdaptor {
public:
    enum {
        ModuleSize    = DefaultModuleSize,
        ModulePadding = DefaultModulePadding
    };
    static size_t PadMaskBits;
    static bool   moduled_decode(
              std::istream& Src, std::iostream& Dst,
              size_t ModulePadding = DefaultModulePadding);

    static bool moduled_encode(
            std::istream& Src, std::ostream& Dst,
            size_t ModulePadding = DefaultModulePadding);
};

template <
        typename Format, size_t DefaultModuleSize, size_t DefaultModulePadding>
bool ModuledAdaptor<Format, DefaultModuleSize, DefaultModulePadding>::
        moduled_decode(
                std::istream& Src, std::iostream& Dst,
                size_t const ModulePadding) {
    int64_t const     FullSize = BigEndian::Read2(Src);
    std::stringstream in(std::ios::in | std::ios::out | std::ios::binary);
    in << Src.rdbuf();

    // Pad to even length, for safety.
    if ((in.tellp() % 2) != 0) {
        in.put(0);
    }

    in.seekg(0);
    size_t const PadMask = ModulePadding - 1;

    while (true) {
        Format::decode(in, Dst);
        if (Dst.tellp() >= FullSize) {
            break;
        }

        // Skip padding between modules
        size_t const paddingEnd = (size_t(in.tellg()) + PadMask) & ~PadMask;
        in.seekg(paddingEnd);
    }

    return true;
}

template <
        typename Format, size_t DefaultModuleSize, size_t DefaultModulePadding>
bool ModuledAdaptor<Format, DefaultModuleSize, DefaultModulePadding>::
        moduled_encode(
                std::istream& Src, std::ostream& Dst,
                size_t const ModulePadding) {
    size_t Location = Src.tellg();
    Src.ignore(std::numeric_limits<std::streamsize>::max());
    size_t FullSize = Src.gcount();
    Src.seekg(Location);
    std::vector<uint8_t> data;
    data.resize(FullSize);
    auto ptr = data.cbegin();
    Src.read(reinterpret_cast<char*>(&(data.front())), data.size());

    size_t const PadMask = ModulePadding - 1;

    BigEndian::Write2(Dst, FullSize);
    std::stringstream sout(std::ios::in | std::ios::out | std::ios::binary);

    while (FullSize > ModuleSize) {
        // We want to manage internal padding for all modules but the last.
        PadMaskBits = 8 * ModulePadding - 1U;
        Format::encode(sout, &(*ptr), ModuleSize);
        FullSize -= ModuleSize;
        ptr += ModuleSize;

        // Padding between modules
        int64_t const paddingEnd = (size_t(sout.tellp()) + PadMask) & ~PadMask;
        for (; sout.tellp() < paddingEnd; sout.put(0)) {
        }
    }

    PadMaskBits = 7U;
    Format::encode(sout, &(*ptr), FullSize);

    // Pad to even size.
    Dst << sout.rdbuf();
    if ((Dst.tellp() % 2) != 0) {
        Dst.put(0);
    }
    return true;
}

#endif    // LIB_MODULED_ADAPTOR_HH