| 摘要 |
PURPOSE:To obtain a data compressor and a data expander in which a data string received sequentially is processed in real time and data are compressed/ expanded while keeping a high compression rate at all times. CONSTITUTION:The data compressor includes a data buffer 10, a dictionary buffer 12, a buffer update section 14, a coincidence length coding section 16, a position coding section 20, a sequence coding section 24 and a table update section 28. The coincidence length coding section 16 checks a character string in the data buffer 10 from the head and compares the character string with that in a dictionary, and encodes and outputs the coincident length. When a coincident character string is in existence in the dictionary, the position coding section 20 encodes an address in the dictionary and provides a coded address as an output. When no coincident character string is in existence in the dictionary, the sequence coding section 24 applies coding of a shorter bit length to a head character with a higher frequency of incidence. |
