Method decompress

src/Compression/CompressedReadBufferBase.cpp:294–313

}

void CompressedReadBufferBase::decompress(BufferBase::Buffer & to, size_t size_decompressed, size_t size_compressed_without_checksum)
{
    readHeaderAndGetCodec(compressed_buffer, size_decompressed, codec, allow_different_codecs, external_data);

    if (codec->isNone())
    {
        /// Shortcut for NONE codec to avoid extra memcpy.
        /// We doing it by changing the buffer `to` to point to existing uncompressed data.

        UInt8 header_size = ICompressionCodec::getHeaderSize();
        if (size_compressed_without_checksum < header_size)
            throw Exception(external_data ? ErrorCodes::CANNOT_DECOMPRESS : ErrorCodes::CORRUPTED_DATA,
                "Can't decompress data: the compressed data size ({}, this should include header size) is less than the header size ({})",
                    size_compressed_without_checksum, static_cast<size_t>(header_size));

        to = BufferBase::Buffer(compressed_buffer + header_size, compressed_buffer + size_compressed_without_checksum);
    }
    else
        codec->decompress(compressed_buffer, static_cast<UInt32>(size_compressed_without_checksum), to.begin());
}

void CompressedReadBufferBase::addDiagnostics(Exception & e) const
{