Abstract: A class of lossless data compression algorithms use a memory-based dictionary of finite size to facilitate the compression and decompression of data. To reduce the loss in data compression caused by dictionary resets, a standby dictionary is used to store a subset of encoded data entries previously stored in a current dictionary. In a second aspect of the invention, data is compressed/decompressed according to the address location of data entries contained within a dictionary built in a content addressable memory (CAM). In a third aspect of the invention, the minimum memory/high compression capacity of the standby dictionary scheme is combined with the fast single-cycle per character encoding/decoding capacity of the CAM circuit. The circuit uses multiple dictionaries within the storage locations of a CAM to reduce the amount of memory required to provide a high data compression ratio.

Abstract: A class of lossless data compression algorithms use a RAM-based dictionary to facilitate the compression and decompression of data. The dictionary is initialized or reset at various events, such as data file boundaries, or at specific compression ratio thresholds. The average time to perform the dictionary reset is decreased by using a dictionary reset optimizer (12) to reset the dictionary without writing the DICT.sub.-- VALID fields (19) of all dictionary locations (1,2,3, . . . L) immediately upon each reset. The DICT.sub.-- VALID field in static RAM (16) is set up as an N-bit field and the optimizer includes a counter (20) for generating an N-bit DICT.sub.-- NUMBER field (22) under control of a controller (24) responsive to reset signals. During operation to compress/decompress data after a reset, the DICT.sub.-- VALID field of a dictionary location is compared to the current DICT.sub.-- NUMBER (1). If their values are equal, the DICT.sub.-- ENTRY field (18) in such location is deemed valid.

Abstract: A logic circuit in an integrated circuit implementation of an adaptive data compression algorithm which uses a RAM to store dictionary entries. The logic circuit generates predetermined codewords for single-character strings without accessing the dictionary. The logic circuit also generates single-character strings for corresponding codewords without accessing the dictionary.