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Data compression using hashing

  • US 5,371,499 A
  • Filed: 10/23/1992
  • Issued: 12/06/1994
  • Est. Priority Date: 02/28/1992
  • Status: Expired due to Fees
First Claim
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1. A method of compressing a stream of input data into a compressed stream of output data comprising:

  • (a) maintaining multiple hash tables, each respectively for a different data subblock size, and each hash table having entries having respective hash keys,(b) hashing a string of input characters of the input data for each of the different data subblock sizes to obtain the hash keys, and using these hash keys to address hash table entries containing hash information to facilitate location of string matches,(c) hashing, for each of the subblock sizes, subsequent strings of data and searching for a match of prior strings related to the information addressed by hash keys in at least one of the hashing tables, and(d) if a hash match occurs in at least one hash table, outputting the subsequent occurrence of the string as compressed data, and if a hash match for each of the subblocks does not occur in any hash table, outputting at least the first character of an input subblock as uncompressed data.

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