Data compression and decompression methods, data compression device, and data decompression device

A data decompression method comprising:

• causing a decompression apparatus to perform processing of registering a symbol in a second table and outputting the symbol, the second table having the same data structure as that of a first table included in a compression apparatus by the same method as a method of registering the symbol in the compression apparatus in a case where the decompression apparatus has received index data indicating non-compression and the symbol which are transmitted from the compression apparatus, and processing of reading and outputting the symbol registered in an entry in the second table indicated by positional information indicating a position of an entry having the symbol registered therein in the first table in a case where the decompression apparatus has received index data indicating compression and the positional information,
• wherein the positional information is represented by a first number of bits, which is a least number of bits capable of representing positional information of an entry in use in the first table, the first number of bits being calculated based on information indicating usage conditions of the plurality of entries of the first table in a case where the compression apparatus outputs the index data indicating compression and the positional information, and
• the decompression apparatus extracts the positional information from a bit sequence transmitted from the compression apparatus and input to the decompression apparatus using a second number of bits which is a least number of bits capable of representing positional information of an entry in use in the second table, the second number of bits being calculated by the same calculation method as a method of calculating the first number of bits based on information indicating usage conditions of the plurality of entries of the second table in a case where the decompression apparatus has received the index data indicating non-compression and the symbol and has registered the symbol in the second table.

A data decompression apparatus comprising:

• a decompressor that performs processing of registering a symbol in a second table and outputting the symbol, the second table having the same data structure as that of a first table included in a compression apparatus by the same method as a method of registering the symbol in the compression apparatus in a case where index data indicating non-compression and the symbol which are transmitted from the compression apparatus have been received, and processing of reading and outputting the symbol registered in an entry in the second table indicated by positional information indicating a position of an entry having the symbol registered therein in the first table in a case where index data indicating compression and the positional information have been received,
• wherein the positional information is represented by a first number of bits, which is a least number of bits capable of representing positional information of an entry in use in the first table, the first number of bits being calculated based on information indicating usage conditions of the plurality of entries of the first table in a case where the compression apparatus outputs the index data indicating compression and the positional information, and
• the decompressor extracts the positional information from a bit sequence transmitted from the compression apparatus and input to the decompression apparatus using a second number of bits which is a least number of bits capable of representing positional information of an entry in use in the second table, the second number of bits being calculated by the same calculation method as a method of calculating the first number of bits based on information indicating usage conditions of the plurality of entries of the second table in a case where the index data indicating non-compression and the symbol have been received and the symbol has been registered in the second table.

A non-transitory storage medium storing a program causing a computer to execute processing of registering a symbol in a second table and outputting the symbol, the second table having the same data structure as that of a first table included in a compression apparatus by the same method as a method of registering the symbol in the compression apparatus in a case where index data indicating non-compression and the symbol which are transmitted from the compression apparatus have been received, and processing of reading and outputting the symbol registered in an entry in the second table indicated by positional information, which indicates a position of an entry having the symbol registered therein in the first table and of which a size changes depending on usage conditions of the first table, in a case where the decompression apparatus has received index data indicating compression and the positional information,

• wherein the positional information is represented by a first number of bits, which is a least number of bits capable of representing positional information of an entry in use in the first table, the first number of bits being calculated based on information indicating usage conditions of the plurality of entries of the first table in a case where the compression apparatus outputs the index data indicating compression and the positional information, and
• the positional information is extracted from a bit sequence transmitted from the compression apparatus and input to the decompression apparatus using a second number of bits which is a least number of bits capable of representing positional information of an entry in use in the second table, the second number of bits being calculated by the same calculation method as a method of calculating the first number of bits based on information indicating usage conditions of the plurality of entries of the second table in a case where the index data indicating non-compression and the symbol have been received and the symbol has been registered in the second table.