Equipment for LEMPEL-ZIV data compression with improved multiple dictionary management of associative memory in the memory, and methods

摘要

PURPOSE: To facilitate data compression and expansion by using a memory-based dictionary whose lossless type data compressing algorithm has finite size. ;CONSTITUTION: For the reduction of loss at the time of data compression due to the resetting of a dictionary, a stand-by dictionary is used to store a subset of encoded data items stored in a current dictionary before. In a 2nd embodiment, data are compressed and expanded according to the address positions of data items included in a dictionary generated in content addressable memory(CAM). In a 3rd embodiment, the minimum memory/high-compressing capacity technique of the stand-by dictionary is combined with a CAM circuit which has a high-speed encoding/decoding function for a single cycle per character. In a 4th embodiment selective overwriting and dictionary switching technique is used and all data items are usable to encode a character string at all times.;COPYRIGHT: (C)1995,JPO