Compression method and decompression method

Abstract

A method includes: first setting a first and a second storage regions; first comparing a compression target data in a file with data in the first storage region; first creating a first compression code of the compression target data based on the data in the first storage region when a predetermined first consistency between the compression target data and the data in the first storage region is detected; second comparing the compression target data with data in the second storage region when the predetermined first consistency between the compression target data and the data in the first storage region is not detected, the compression target data being moved to the second storage region after the second comparing; and first storing the compression target data into the first storage region when a predetermined second consistency between the compression target data and the data in the second storage region is detected.

What is claimed is: 
     
         1 . A non-transitory storage medium storing a program for causing a computer to execute a process, the process comprising:
 first setting a first storage region and a second storage region in a memory;   first comparing a compression target data in a file with data in the first storage region;   first creating a first compression code of the compression target data based on the data in the first storage region when a predetermined first consistency between the compression target data and the data in the first storage region is detected;   second comparing the compression target data with data in the second storage region when the predetermined first consistency between the compression target data and the data in the first storage region is not detected, the compression target data being moved to the second storage region after the second comparing; and   first storing the compression target data into the first storage region when a predetermined second consistency between the compression target data and the data in the second storage region is detected.   
     
     
         2 . The storage medium according to  claim 1 , wherein
 the predetermined first consistency indicates that a data size of longest matching data between the compression target data and the data in the first storage region is greater than a predetermined first size.   
     
     
         3 . The storage medium according to  claim 1 , wherein the process further includes:
 second creating a second compression code of the compression target data based on the data in the second storage region when a predetermined second consistency between the compression target data and the data in the second storage region is detected based on the second comparing.   
     
     
         4 . The storage medium according to  claim 3 , wherein
 the predetermined second consistency indicates that a data size of longest matching data between the compression target data and the data in the second storage region is greater than a predetermined second size.   
     
     
         5 . The storage medium according to  claim 3 , wherein
 the first compression code and the second compression code are the same type of code and include an identifier indicating being created based on one of the first comparing and the second comparing.   
     
     
         6 . The storage medium according to  claim 5 , wherein the process further includes:
 third creating a third compression code of the compression target data based on a different type of coding process than a coding process of the first compression code and the second compression code when the predetermined second consistency between the compression target data and the data in the second storage region is not detected based on the second comparing.   
     
     
         7 . The storage medium according to  claim 6 , wherein
 the second comparing compares the compression target data with the data in the second storage region for a predetermined data unit, and   the third creating creates the third compression code based on the compression target data with the data unit.   
     
     
         8 . The storage medium according to  claim 1 , wherein
 the first compression code includes position information indicating a position in the first storage region of data portion longest matching with the compression target data among the data in the first storage region and length information indicating a matching length of the data portion.   
     
     
         9 . The storage medium according to  claim 3 , wherein
 the second compression code includes position information indicating a position in the second storage region of data portion longest matching with the compression target data among the data in the second storage region and length information indicating a matching length of the data portion.   
     
     
         10 . The storage medium according to  claim 1 , wherein
 the first setting sets the second storage region with a first size in the memory,   the first storing stores the compression target data into the first storage region according to position information indicating a position in the first storage region, the position information being updated according to a size of the compression target data, and   the process further includes:
 first changing a size of the second storage region from the first size to a second size smaller than the first size when a total size of data in the first storage region indicated by the position information exceeds a predetermined size. 
   
     
     
         11 . The storage medium according to  claim 10 , wherein the process further includes:
 the first changing includes deleting data stored foremost among data stored in the second storage region.   
     
     
         12 . The storage medium according to  claim 10 , wherein
 the first setting sets the first storage region with a third size in the memory,   the process further includes:
 second changing a size of the first storage region from the third size to a fourth size greater than the third size when the size of the second storage region is changed from the first size to the second size by the first changing. 
   
     
     
         13 . The storage medium according to  claim 1 , wherein
 the first setting sets the first storage region with a third size in the memory,   the first storing includes:
 storing the compression target data into the first storage region according to position information indicating a position in the first storage region, 
 updating the position information according to a size of the stored compression target data, and 
 controlling update of the position information to store the compression target data within the third size, and 
   the process further includes:
 counting a number of detecting the data in the first storage region that the predetermined first consistency with the compression target data is detected; and 
 second storing a stored data following the compression target data into the first storage region when the compression target data is overwritten the stored data in the first storage region with the number of detecting exceeds a predetermined number according to the position information. 
   
     
     
         14 . A non-transitory storage medium storing a program for causing a computer to execute a process decompressing a compressed file, the process comprising:
 reading a compressed data from the compressed file, the compressed file being created based on a first compression code, a second compression code and a third compression code by:
 first setting a first storage region and a second storage region in a first memory, 
 first comparing a compression target data in a file with data in the first storage region, 
 first creating the first compression code of the compression target data based on the data in the first storage region when a predetermined first consistency between the compression target data and the data in the first storage region is detected, 
 second comparing the compression target data with data in the second storage region when the predetermined first consistency between the compression target data and the data in the first storage region is not detected, the compression target data being moved to the second storage region after the second comparing, 
 when a predetermined second consistency between the compression target data and the data in the second storage region is detected, first storing the compression target data into the first storage region and second creating the second compression code of the compression target data based on the data in the second storage region, the first compression code and the second compression code are the same type of code and include an identifier indicating being created based on one of the first comparing and the second comparing, and 
 third creating the third compression code of the compression target data based on a different type of coding process than a coding process of the first compression code and the second compression code when the predetermined second consistency between the compression target data and the data in the second storage region is not detected based on the second comparing; 
 fourth creating a first decompression data based on data in a fourth storage region of a second memory according to the first compression code when it is determined that the read compressed data is the first compression code; 
 fifth creating a second decompression data based on data in a fifth storage region of the second memory according to the second compression code when it is determined that the read compressed data is the second compression code, the fifth storage region being a different storage region from the fourth storage region; 
 first updating the fourth storage region according to the second compression code and the second decompression data when the second decompression data is created by the fifth creating; 
 sixth creating a third decompression data from the read compressed data based on a decoding process corresponding to the coding process when it is determined that the read compressed data is the third compression code; and 
 third storing the third decompression data into the fourth storage region. 
   
     
     
         15 . A system comprising:
 a memory; and   a processor coupled to the memory and configured to execute a process including:
 first setting a first storage region and a second storage region in the memory, 
 first comparing a compression target data in a file with data in the first storage region, 
 first creating a first compression code of the compression target data based on the data in the first storage region when a predetermined first consistency between the compression target data and the data in the first storage region is detected, 
 second comparing the compression target data with data in the second storage region when the predetermined first consistency between the compression target data and the data in the first storage region is not detected, the compression target data being moved to the second storage region after the second comparing, and 
 first storing the compression target data into the first storage region when a predetermined second consistency between the compression target data and the data in the second storage region is detected. 
   
     
     
         16 . The system according to  claim 15 , wherein
 the process further includes:
 second creating a second compression code of the compression target data based on the data in the second storage region when a predetermined second consistency between the compression target data and the data in the second storage region is detected based on the second comparing, and 
 the first compression code and the second compression code are the same type of code and include an identifier indicating being created based on one of the first comparing and the second comparing. 
   
     
     
         17 . The system according to  claim 15 , wherein
 the first compression code includes position information indicating a position in the first storage region of data portion longest matching with the compression target data among the data in the first storage region and length information indicating a matching length of the data portion.   
     
     
         18 . The system according to  claim 15 , wherein
 the first setting sets the second storage region with a first size in the memory,   the first storing stores the compression target data into the first storage region according to position information indicating a position in the first storage region, the position information being updated according to a size of the compression target data, and   the process further includes:
 first changing a size of the second storage region from the first size to a second size smaller than the first size when a total size of data in the first storage region indicated by the position information exceeds a predetermined size. 
   
     
     
         19 . The system according to  claim 15 , wherein
 the first setting sets the first storage region with a third size in the memory,   the first storing includes:
 storing the compression target data into the first storage region according to position information indicating a position in the first storage region, 
 updating the position information according to a size of the stored compression target data, and 
 controlling update of the position information to store the compression target data within the third size, and 
   the process further includes:
 counting a number of detecting the data in the first storage region that the predetermined first consistency with the compression target data is detected; and 
 second storing a stored data following the compression target data into the first storage region when the compression target data is overwritten the stored data in the first storage region with the number of detecting exceeds a predetermined number according to the position information. 
   
     
     
         20 . A system comprising:
 a first memory; and   a processor coupled to the first memory and configured to execute a process including:
 reading a compressed data from a compressed file, the compressed file being created based on a first compression code, a second compression code and a third compression code by:
 first setting a first storage region and a second storage region in a second memory, 
 first comparing a compression target data in a file with data in the first storage region, 
 first creating the first compression code of the compression target data based on the data in the first storage region when a predetermined first consistency between the compression target data and the data in the first storage region is detected, 
 second comparing the compression target data with data in the second storage region when the predetermined first consistency between the compression target data and the data in the first storage region is not detected, the compression target data being moved to the second storage region after the second comparing, 
 when a predetermined second consistency between the compression target data and the data in the second storage region is detected, first storing the compression target data into the first storage region and second creating the second compression code of the compression target data based on the data in the second storage region, the first compression code and the second compression code are the same type of code and include an identifier indicating being created based on one of the first comparing and the second comparing, and 
 third creating the third compression code of the compression target data based on a different type of coding process than a coding process of the first compression code and the second compression code when the predetermined second consistency between the compression target data and the data in the second storage region is not detected based on the second comparing; 
 
   fourth creating a first decompression data based on data in a fourth storage region of the first memory according to the first compression code when it is determined that the read compressed data is the first compression code;   fifth creating a second decompression data based on data in a fifth storage region of the first memory according to the second compression code when it is determined that the read compressed data is the second compression code, the fifth storage region being a different storage region from the fourth storage region;   first updating the fourth storage region according to the second compression code and the second decompression data when the second decompression data is created by the fifth creating;   sixth creating a third decompression data from the read compressed data based on a decoding process corresponding to the coding process when it is determined that the read compressed data is the third compression code; and   third storing the third decompression data into the fourth storage region.