Methods, devices and systems for a compressor and a decompressor for encoding and decoding data in the cache/memory/data transferring subsystem in a computer system or in a communication network are described herein. Example variable-length compressors and decompressors are able to: compress more densely when specific values occur in specific positions in a data block; to improve compression and decompression latency when specific values that appear frequently occur in a data block; to also improve decompression latency by recording the lengths of variable-length encoded values of a compressed data block. The compressor and decompressor are able to support compression and decompression of common compression scenarios that are used in combination with variable-length compression to improve compressibility in the cache/memory/data transferring subsystem in a computer system or in a communication network.