DATA COMPRESSION/DECOMPRESSION METHOD AND APPARATUS

A method and apparatus for compressing digital data uses data which has been previously compressed as a dictionary of substrings which may be replaced in an input data stream. The method and apparatus uses a hash table to take advantage of principles of locality and probability to solve the maximal matching substring problem inherent in this type of compressing apparatus, most of the time. The hash table consists of first-in, first-out (FIFO) collision chains of fixed, uniform numbers of pointers to substrings of data already compressed which potentially match an input substring. A link list is maintained for linking pointers to corresponding potentially matching strings. A companion decompressing method and apparatus receives compressed data from the compressing apparatus and expand that data back to its original form.