Coding apparatus, decoding apparatus, coding method, decoding method and program

A coding apparatus comprising:

• symbol-string searching means for searching a predetermined search range of a data buffer used for holding input data for a state of matching a symbol sub-string serving as a coding object of said input data;
• internal-state holding means used for holding a predetermined internal state;
• matching-length coding means for assigning a matching-length code to a matching length representing the length of said symbol sub-string in a matching state detected by said symbol-string searching means as a result of a search process in an assignment process according to an internal state held by said internal-state holding means and then updating said internal state held by said internal-state holding means in accordance with said matching length;
• and
• symbol-string coding means for coding said symbol sub-string on the basis of the position of said symbol sub-string in a matching state detected by said symbol-string searching means as a result of a search process and on the basis of said matching-length code assigned by said matching-length coding means, wherein said matching-length coding means:
• assigns a code determined for a matching length as said matching-length code to said matching length in an assignment process independent of an internal state held by said internal-state holding means if said matching-length code is smaller than a predetermined threshold value;
• or
• assigns a code determined for a matching length as said matching-length code to said matching length in an assignment process dependent on an internal state held by said internal-state holding means and dependent on said matching length if said matching-length code is equal to or greater than said predetermined threshold value.

A coding apparatus comprising:

• symbol-string searching means for searching a predetermined search range of a data buffer used for holding input data for a state of matching a symbol sub-string serving as a coding object of said input data;
• internal-state holding means used for holding a predetermined internal state;
• matching-length coding means for assigning a matching-length code to a matching length representing the length of said symbol sub-string in a matching state detected by said symbol-string searching means as a result of a search process in an assignment process according to an internal state held by said internal-state holding means and then updating said internal state held by said internal-state holding means in accordance with said matching length;
• and
• symbol-string coding means for coding said symbol sub-string on the basis of the position of said symbol sub-string in a matching state detected by said symbol-string searching means as a result of a search process and on the basis of said matching-length code assigned by said matching-length coding means, said coding apparatus further having matching-length extension means for setting a relation between a matching length and a matching-length code to be assigned to said matching length as a relation according to an internal state held by said internal-state holding means, wherein said matching-length coding means:
• assigns a code determined for a matching length as said matching-length code to said matching length in an assignment process independent of an internal state held by said internal-state holding means if said matching-length code is smaller than a predetermined threshold value;
• or
• assigns a code determined by said matching-length extension means for a matching length to said matching length as said matching-length code if said matching-length code is equal to or greater than said predetermined threshold value.

A decoding apparatus comprising:

• a decoding buffer used for holding a symbol sub-string obtained as a result of a process to decode a code string;
• a code buffer used for holding said code string to be decoded;
• code acquisition means for acquiring symbol sub-string codes including the position of said symbol sub-string and including a matching-length code of said symbol sub-string from said code buffer;
• internal-state holding means used for holding a predetermined internal state;
• matching-length decoding means for decoding said matching-length code to generate a matching length represented by said matching-length code as a matching length representing the length of said symbol sub-string in a decoding process according to an internal state held by said internal-state holding means and then updating said internal state held by said internal-state holding means in accordance with said matching length;
• and
• symbol-string decoding means for decoding said symbol sub-string codes to generate said symbol sub-string represented by said symbol sub-string codes by referring to said decoding buffer in a decoding process according to said position of said symbol sub-string and according to said matching-length code of said symbol sub-string.

A compressed-program decompression apparatus comprising:

• a decompressed-program buffer used for holding a symbol sub-string obtained as a result of a process to decompress a compressed program embodied on a computer-readable media;
• a compressed-program buffer used for holding said compressed program to be decompressed;
• code acquisition means for acquiring symbol sub-string codes including the position of said symbol sub-string and including a matching-length code of said symbol sub-string from said compressed-program buffer;
• internal-state holding means used for holding a predetermined internal state;
• matching-length decoding means for decoding said matching-length code to generate a matching length representing the length of said symbol sub-string in a decoding process according to an internal state held by said internal-state holding means and then updating said internal state held by said internal-state holding means in accordance with said matching length;
• and
• symbol-string decoding means for decoding said symbol sub-string codes to generate said symbol sub-string represented by said symbol sub-string codes by referring to said decompressed-program buffer in a decoding process according to said position of said symbol sub-string and according to said matching-length code of said symbol sub-string.

A method of decoding a code string held in a code buffer in a code decoding process and storing a symbol sub-string obtained as a result of said code decoding process in a decoding buffer, said decoding method comprising:

• acquiring symbol sub-string codes including a relative address of said symbol sub-string and including a matching-length code of said symbol sub-string from said code buffer;
• decoding said matching-length code to generate a matching length representing the length of said symbol sub-string in a length decoding process according to a predetermined internal state;
• updating said internal state in accordance with said matching length obtained as a result of said length decoding process;
• and
• decoding said symbol sub-string codes to generate said symbol sub-string represented by said symbol sub-string codes by referring to said decoding buffer in a string decoding process according to said relative address of said symbol sub-string and according to said matching-length code of said symbol sub-string.

A computer program embodied in a computer-readable media for decoding a code string held in a code buffer in a code decoding process and storing a symbol sub-string obtained as a result of said code decoding process in a decoding buffer, said computer program comprising:

• acquiring symbol sub-string codes including a relative address of said symbol sub-string and including a matching-length code of said symbol sub-string from said code buffer;
• decoding said matching-length code to generate a matching length representing the length of said symbol sub-string in a length decoding process according to a predetermined internal state;
• updating said internal state in accordance with said matching length obtained as a result of said length decoding process;
• and
• decoding said symbol sub-string codes to generate said symbol sub-string represented by said symbol sub-string codes by referring to said decoding buffer in a string decoding process according to said relative address of said symbol sub-string and according to said matching-length code of said symbol sub-string.