Method of and an apparatus for compressing/decompressing data

摘要

The present invention relates to a method of and an apparatus for compressing/decompressing data, to improve the compression ratio of sliding-dictionary-type Ziv-Lempel codes. A sliding-dictionary-type data compression method finds a matching character string in a coding character string and in a coded character string stored in a dictionary 101. According to the length of the matching character string, the method chooses a raw data mode that codes the matching character string that must consist of a single character as it is, or a reproduction mode that codes the position and length in the dictionary 101 of the matching character string. The method allocates consecutive numbers to different codes to be prepared under the raw data mode and reproduction mode. The method relates any code prepared under one of the raw data mode and reproduction mode to a corresponding one of the consecutive numbers, codes the number according to a code book, and rearranges the code book to shorten the length of the code of the number.