00 – Literal – uncompressed data upper 6 bits are used to store length (len-1) of data.The element type is encoded in the lower two bits of the first byte ( tag byte) of the element: The remaining bytes in the stream are encoded using one of four element types. The lower seven bits of each byte are used for data and the high bit is a flag to indicate the end of the length field. The first bytes of the stream are the length of uncompressed data, stored as a little-endian varint, which allows for use of a variable-length code. The format uses no entropy encoder, like Huffman tree or arithmetic encoder. Snappy encoding is not bit-oriented, but byte-oriented (only whole bytes are emitted or consumed from a stream). Snappy does not use inline assembler (except some optimizations ) and is portable. Decompression is tested to detect any errors in the compressed stream. It can be used in open-source projects like MariaDB ColumnStore, Cassandra, Couchbase, Hadoop, LevelDB, MongoDB, RocksDB, Lucene, Spark, and InfluxDB. Snappy is widely used in Google projects like Bigtable, MapReduce and in compressing data for Google's internal RPC systems. The compression ratio is 20–100% lower than gzip. Compression speed is 250 MB/s and decompression speed is 500 MB/s using a single core of a circa 2011 "Westmere" 2.26 GHz Core i7 processor running in 64-bit mode. It does not aim for maximum compression, or compatibility with any other compression library instead, it aims for very high speeds and reasonable compression. Snappy (previously known as Zippy) is a fast data compression and decompression library written in C++ by Google based on ideas from LZ77 and open-sourced in 2011.
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