Data coding method, data decoding method, data compression apparatus, and data decompression apparatus

A data compression apparatus, comprising:

• obtaining means for obtaining a character one after another from a compression target;
• first coding means for outputting a code corresponding to the character obtained by said obtaining means;
• first controlling means for instructing said first coding means to stop functioning when the character obtained by said obtaining means and a predetermined number of characters that have recently been used by said first coding means are identical;
• judging means, which functions when said first coding means does not function, for judging whether the character obtained by said obtaining means is identical with a continuative character, wherein said continuative character is the last character encoded by said first coding means;
• second coding means for outputting a code corresponding to a run-length, which is a number of characters that have been judged to be identical with the continuative character, when said judging means judges that the character is not identical with the continuative character;
• and
• second controlling means for instructing said first coding means to start functioning when said second coding means outputs the code.

A data decompression apparatus, comprising:

• first decoding means for outputting a character corresponding to a code in a decompression target;
• first controlling means for instructing said first decoding means to stop functioning when a predetermined number of characters that have consecutively been outputted by said first decoding means are identical;
• second decoding means, which functions when said first decoding means does not function, for decoding a code following the code used by said first decoding means and outputting characters identical with the predetermined number of the characters and equal in number to the decoded code produced by the second decoding means;
• and
• second controlling means for instructing said first decoding means start functioning when said second decoding means outputs the characters.

A data compression apparatus, comprising:

• an obtaining section obtaining a character one after another from a compression target;
• a first coding section outputting a code corresponding to the character obtained in the obtaining section when the character obtained by the obtaining section and a predetermined number of characters that have been consecutively obtained in the past in the obtaining section are not identical;
• and
• a second coding section for counting a number of characters obtained in the obtaining section, while the character obtained in the obtaining section and a predetermined number of characters that have been consecutively obtained in the past in the obtaining section are identical, and outputting a code corresponding to the number of characters counted, when the character obtained in the obtaining section is not identical with the predetermined number of characters.