MultiMC5/api/logic/GZip.cpp

#include "GZip.h"
#include <zlib.h>
#include <QByteArray>

bool GZip::unzip(const QByteArray &compressedBytes, QByteArray &uncompressedBytes)
{
    if (compressedBytes.size() == 0)
    {
        uncompressedBytes = compressedBytes;
        return true;
    }

    unsigned uncompLength = compressedBytes.size();
    uncompressedBytes.clear();
    uncompressedBytes.resize(uncompLength);

    z_stream strm;
    memset(&strm, 0, sizeof(strm));
    strm.next_in = (Bytef *)compressedBytes.data();
    strm.avail_in = compressedBytes.size();

    bool done = false;

    if (inflateInit2(&strm, (16 + MAX_WBITS)) != Z_OK)
    {
        return false;
    }

    int err = Z_OK;

    while (!done)
    {
        // If our output buffer is too small
        if (strm.total_out >= uncompLength)
        {
            uncompressedBytes.resize(uncompLength * 2);
            uncompLength *= 2;
        }

        strm.next_out = (Bytef *)(uncompressedBytes.data() + strm.total_out);
        strm.avail_out = uncompLength - strm.total_out;

        // Inflate another chunk.
        err = inflate(&strm, Z_SYNC_FLUSH);
        if (err == Z_STREAM_END)
            done = true;
        else if (err != Z_OK)
        {
            break;
        }
    }

    if (inflateEnd(&strm) != Z_OK || !done)
    {
        return false;
    }

    uncompressedBytes.resize(strm.total_out);
    return true;
}

bool GZip::zip(const QByteArray &uncompressedBytes, QByteArray &compressedBytes)
{
    if (uncompressedBytes.size() == 0)
    {
        compressedBytes = uncompressedBytes;
        return true;
    }

    unsigned compLength = std::min(uncompressedBytes.size(), 16);
    compressedBytes.clear();
    compressedBytes.resize(compLength);

    z_stream zs;
    memset(&zs, 0, sizeof(zs));

    if (deflateInit2(&zs, Z_DEFAULT_COMPRESSION, Z_DEFLATED, (16 + MAX_WBITS), 8, Z_DEFAULT_STRATEGY) != Z_OK)
    {
        return false;
    }

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

    int ret;
    compressedBytes.resize(uncompressedBytes.size());

    unsigned offset = 0;
    unsigned temp = 0;
    do
    {
        auto remaining = compressedBytes.size() - offset;
        if(remaining < 1)
        {
            compressedBytes.resize(compressedBytes.size() * 2);
        }
        zs.next_out = (Bytef *) (compressedBytes.data() + offset);
        temp = zs.avail_out = compressedBytes.size() - offset;
        ret = deflate(&zs, Z_FINISH);
        offset += temp - zs.avail_out;
    } while (ret == Z_OK);

    compressedBytes.resize(offset);

    if (deflateEnd(&zs) != Z_OK)
    {
        return false;
    }

    if (ret != Z_STREAM_END)
    {
        return false;
    }
    return true;
}