Function zstdCompress

src/openrct2/core/Compression.cpp:153–222

    }

    bool zstdCompress(IStream& source, uint64_t sourceLength, IStream& dest, ZstdMetadata metadata, int16_t level)
    {
        if (sourceLength > source.GetLength() - source.GetPosition())
            throw IOException("Not Enough Data to Compress");

        StreamReadBuffer sourceBuf(source, sourceLength, ZSTD_CStreamInSize());
        StreamWriteBuffer destBuf(dest, zstdCompressBound(sourceLength), ZSTD_CStreamOutSize());
        unsigned metaFlags = static_cast<unsigned>(metadata);

        const auto deleter = [](ZSTD_CCtx* ptr) { ZSTD_freeCCtx(ptr); };
        std::unique_ptr<ZSTD_CCtx, decltype(deleter)> ctx(ZSTD_createCCtx(), deleter);
        if (ctx == nullptr)
        {
            LOG_ERROR("Failed to create zstd context");
            return false;
        }

        size_t ret = ZSTD_CCtx_setParameter(ctx.get(), ZSTD_c_compressionLevel, level);
        if (ZSTD_isError(ret))
        {
            LOG_ERROR("Failed to set compression level with error: %s", ZSTD_getErrorName(ret));
            return false;
        }
        // set options for content size (default on) and checksum (default off)
        ret = ZSTD_CCtx_setParameter(ctx.get(), ZSTD_c_contentSizeFlag, (metaFlags & 1) != 0);
        if (ZSTD_isError(ret))
        {
            LOG_ERROR("Failed to set content size flag with error: %s", ZSTD_getErrorName(ret));
            return false;
        }
        ret = ZSTD_CCtx_setParameter(ctx.get(), ZSTD_c_checksumFlag, (metaFlags & 2) != 0);
        if (ZSTD_isError(ret))
        {
            LOG_ERROR("Failed to set checksum flag with error: %s", ZSTD_getErrorName(ret));
            return false;
        }
        // unlike gzip, zstd puts the decompressed content size at the start of the file,
        // so we need to tell zstd how big the input is before we start compressing.
        ret = ZSTD_CCtx_setPledgedSrcSize(ctx.get(), sourceLength);
        if (ZSTD_isError(ret))
        {
            LOG_ERROR("Failed to set file length with error: %s", ZSTD_getErrorName(ret));
            return false;
        }

        do
        {
            auto readBlock = sourceBuf.ReadBlock(source);
            ZSTD_inBuffer input = { readBlock.first, readBlock.second, 0 };

            do
            {
                Guard::Assert(destBuf, "Compression Overruns Ouput Size");

                auto writeBlock = destBuf.WriteBlockStart();
                ZSTD_outBuffer output = { writeBlock.first, writeBlock.second, 0 };

                ret = ZSTD_compressStream2(ctx.get(), &output, &input, sourceBuf ? ZSTD_e_continue : ZSTD_e_end);