Compression.cpp

#include "Compression.h"
#include "Logger.h"

#include <zlib.h>
#include <stdexcept>

using namespace std;

string Compression::gzip(const string& data)
{
    z_stream zs{};
    
    if (deflateInit2(
            &zs,
            Z_DEFAULT_COMPRESSION,
            Z_DEFLATED,
            15 + 16,          // gzip header
            8,
            Z_DEFAULT_STRATEGY) != Z_OK)
    {
        Logger::error("Compression failed");
        throw runtime_error("deflateInit2 failed");
    }

    zs.next_in = (Bytef*)data.data();
    zs.avail_in = data.size();

    string output;

    char buffer[32768];

    int ret;

    do
    {
        zs.next_out = (Bytef*)buffer;
        zs.avail_out = sizeof(buffer);

        ret = deflate(&zs, Z_FINISH);

        output.append(
            buffer,
            sizeof(buffer) - zs.avail_out);

    } while(ret == Z_OK);

    deflateEnd(&zs);

    if(ret != Z_STREAM_END)
    {
        Logger::error("Compression failed");
        throw runtime_error("gzip failed");
    }

    Logger::debug("Compression statistics: original size=" + to_string(data.size()) + ", compressed size=" + to_string(output.size()));

    return output;
}