Function zstdDecompress

src/openrct2/core/Compression.cpp:224–275

    }

    bool zstdDecompress(IStream& source, uint64_t sourceLength, IStream& dest, uint64_t decompressLength)
    {
        if (sourceLength > source.GetLength() - source.GetPosition())
            throw IOException("Not Enough Data to Decompress");

        size_t ret;
        StreamReadBuffer sourceBuf(source, sourceLength, ZSTD_DStreamInSize());
        StreamWriteBuffer destBuf(dest, decompressLength, ZSTD_DStreamOutSize());

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

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

            do
            {
                if (!destBuf)
                {
                    LOG_ERROR("Decompressed data larger than expected");
                    return false;
                }

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

                ret = ZSTD_decompressStream(ctx.get(), &output, &input);
                if (ZSTD_isError(ret))
                {
                    LOG_ERROR("Failed to compress data with error: %s", ZSTD_getErrorName(ret));
                    return false;
                }

                destBuf.WriteBlockCommit(dest, output.pos);
            } while (input.pos < input.size || (!sourceBuf && ret > 0));
        } while (sourceBuf);

        if (destBuf)
        {
            LOG_ERROR("Decompressed data smaller than expected");
            return false;
        }

        return true;
    }
} // namespace OpenRCT2::Compression