Compression method and decompression method

Patent metadata

Field	Value
Publication number	US-9496895-B2
Application number	US-201514742257-A
Country	US
Kind code	B2
Filing date	Jun 17, 2015
Priority date	Dec 19, 2012
Publication date	Nov 15, 2016
Grant date	Nov 15, 2016

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.

First claim

What is claimed is:

1. A method comprising:
first setting a first storage region and a second storage region in a memory;
first comparing, by a first processor, a compression target data in a file with data in the first storage region;
first creating, by the first processor, 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, by the first processor, 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;
first storing, by the first processor, 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; and
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, 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.

2. The method according to claim 1 , 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.

3. The method according to claim 1 , further comprising:
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.

4. The method according to claim 3 , 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.

5. The method according to claim 1 , 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.

6. The method according to claim 3 , wherein
a compression file corresponding to the file is created based on the first compression code, the second compression code and the third compression code,
the method further comprising:
reading a compressed data from the compression file;
fourth creating a first decompression data based on data in a fourth storage region 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 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.

7. A method comprising:
first setting a first storage region and a second storage region in a memory;
first comparing, by a first processor, a compression target data in a file with data in the first storage region;
first creating, by the first processor, 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, by the first processor, 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, by the first processor, 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, wherein
the first compression code includes position information indicating a position in the first storage region of a 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.

8. The method according to claim 7 , 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.

9. A method comprising:
first setting a first storage region and a second storage region in a memory;
first comparing, by a first processor, a compression target data in a file with data in the first storage region;
first creating, by the first processor, 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, by the first processor, 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, by the first processor, 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, wherein
the first setting sets the second storage region with a first size in the memory, and
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,
the method further comprising:
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.

10. The method according to claim 9 , wherein
the first changing includes deleting data stored foremost among data stored in the second storage region.

11. The method according to claim 9 , wherein
the first setting sets the first storage region with

Assignees

• Fujitsu Ltd

Inventors

• Kataoka Masahiro
• Suzuki Yasuhiro
• Yamamoto Kohshi

Classifications

• H03M7/60 Primary

  General implementation details not specific to a particular type of compression · CPC title

• H03M7/40

  Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code · CPC title

• H03M7/3086 Primary

  employing a sliding window, e.g. LZ77 · CPC title