Zlib.hpp

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/*
 *
 * ---
 *
 *  Copyright (C) 2020 Anselm Schmidt (ans[ät]ohai.su)
 *
 *  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 in addition to the terms of any
 *  licences already herein identified.
 *
 *  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 <https://www.gnu.org/licenses/>.
 *
 * ---
 *
 * Zlib.hpp
 *
 * Namespace for functions for zlib compression.
 *
 *  Created on: May 2, 2019
 *      Author: ans
 */

#ifndef DATA_ZLIB_HPP_
#define DATA_ZLIB_HPP_

#include "../../Main/Exception.hpp"

#include <zlib.h>

#include <array>    // std::array
#include <string>   // std::string

namespace crawlservpp::Data::Compression::Zlib {

    /*
     * DECLARATION
     */


    std::string compress(const std::string& content);
    std::string decompress(const std::string& compressedContent);


    inline constexpr auto bufferSize{65536};


    /*
     * CLASS FOR ZLIB EXCEPTIONS
     */


    MAIN_EXCEPTION_CLASS();

    /*
     * IMPLEMENTATION
     */


    inline std::string compress(const std::string& content) {
        if(content.empty()) {
            return "";
        }

        z_stream control{z_stream()};
        int returnValue{};
        std::array<char, bufferSize> buffer{};
        std::string result;

        result.reserve(content.size());

        if(deflateInit(&control, Z_BEST_COMPRESSION) != Z_OK) {
            throw Exception(
                    "Data::Compression::Zlib::compress():"
                    " Could not initialize zlib compression"
            );
        }

        control.next_in = reinterpret_cast<const Bytef *>(
                content.data()
        );
        control.avail_in = content.size();

        do {
            control.next_out = reinterpret_cast<Bytef *>(buffer.data());
            control.avail_out = buffer.size();

            returnValue = deflate(&control, Z_FINISH);

            if(result.size() < control.total_out) {
                result.append(buffer.data(), control.total_out - result.size());
            }
        }
        while(returnValue == Z_OK);

        deflateEnd(&control);

        if(returnValue != Z_STREAM_END) {
            throw Exception(
                    "Data::Compression::Zlib::compress():"
                    " zlib error: "
                    + std::string(control.msg)
            );
        }

        return result;
    }


    inline std::string decompress(const std::string& compressedContent) {
        if(compressedContent.empty()) {
            return "";
        }

        z_stream control{z_stream()};
        int returnValue{};
        std::array<char, bufferSize> buffer{};
        std::string result;

        if(inflateInit(&control) != Z_OK) {
            throw Exception(
                    "Data::Compression::Zlib::decompress():"
                    " Could not initialize zlib decompression"
            );
        }

        control.next_in = reinterpret_cast<const Bytef *>(
                compressedContent.data()
        );
        control.avail_in = compressedContent.size();

        do {
            control.next_out = reinterpret_cast<Bytef *>(buffer.data());
            control.avail_out = buffer.size();

            returnValue = inflate(&control, 0);

            if(result.size() < control.total_out) {
                result.append(buffer.data(), control.total_out - result.size());
            }
        }
        while(returnValue == Z_OK);

        inflateEnd(&control);

        if(returnValue != Z_STREAM_END) {
            throw Exception(
                    "Data::Compression::Zlib::decompress():"
                    " zlib error: "
                    + std::string(control.msg)
            );
        }

        return result;
    }

} /* namespace crawlservpp::Data::Compression::Zlib */

#endif /* DATA_ZLIB_HPP_ */