Differential data forming method, program, recording medium, and apparatus

• US 20030163496A1
• Filed: 10/07/2002
• Published: 08/28/2003
• Est. Priority Date: 02/28/2002
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Terazono, Kohei, Okada, Yoshiyuki
• Granted Patent: US 7,908,250 B2
• Time in Patent Office: Days
• US Class Current: 707/204
• CPC Class Codes: G06F 11/1458 Management of the backup or restore process
• CPC Class Codes: G06F 16/178 Techniques for file synchronisation in file systems

Abstract

Two new and old files are sequentially compared from heads of the files on a predetermined data unit basis. If a data coincidence is discriminated, transfer information showing a position and a data length of the old file is output. If a data dissidence is discriminated by the sequential comparison, the old file is searched in both forward and backward directions from a data position where the dissidence has been discriminated in the old file, thereby searching a portion which coincides with data of the new file. If the coincident portion can be searched, shift information up to the coincident portion on the old file is output. If the coincident portion cannot be searched, new data is added to transfer replacement information showing a length of data of the dissident portion of the old file at a position until the coincident portion can be searched, and the resultant transfer replacement information is output.

Claims

1. A differential data forming method comprising:

a comparing step wherein two new and old files are sequentially compared from heads of the files on a predetermined data unit basis;

a transfer information forming step wherein if a coincidence of the data is determined by said sequential comparison, transfer information showing a position and a data length of the old file is output;

a searching step wherein if a dissidence of the data is determined by said sequential comparison, the old file is searched in both forward and backward directions from a data position where the dissidence has been determined on the old file, thereby searching a portion which coincides with the data of the new file;

a shift information forming step wherein if the coincident portion can be searched in said searching step, shift information up to the coincident portion on the old file is output; and

a replacement information forming step wherein if the coincident portion cannot be searched in said searching step, new data is added to transfer replacement information showing a data length of the dissident portion of the old file at a position until the coincident portion can be searched and resultant transfer replacement information is output.

2. A method according to claim 1, wherein in said searching step, when a portion of the old file which coincides with the data of the new file and continuous coincident portions of a predetermined number (n) or more of data subsequent to said coincident portion are searched, it is determined that the data coincides.

3. A method according to claim 1, wherein in said searching step, when a portion of the old file which coincides with the data of the new file and coincident portions of a predetermined number (y) or more of data distributed among a predetermined number (x) of data subsequent to said coincident portion are searched, it is determined that the data coincides.

4. A method according to claim 1, wherein in said shift information forming step, a shifting direction in which a forward position on said old file is set to a negative direction and a backward position on said old file is set to a positive direction and a shift length showing a length of data up to the coincident portion on the old file are output as said shift information.

5. A method according to claim 1, wherein in said searching step, if a structure of the file is that of a program file written by an n-bit code, the search is performed every other (n) bits in both forward and backward directions from the position of the data which was determined to be dissident in the old file, thereby searching the portion which coincides with the data in the new file.

6. A method according to claim 1, wherein in said replacement information forming step, when differential data between the old data and the new data coincides with differential data of replacement information formed in the past, the new data is not added but transfer replacement information showing the same as a past differential pattern or updating pattern is output.

7. A method according to claim 1, wherein in said replacement information forming step, if the coincident portion cannot be searched in said searching step due to the insertion of the new data in the new file, said new data is added to the transfer replacement information showing the data length of the dissident portion of the old file at a position until the coincident portion can be searched and the resultant transfer replacement information is output.

8. A method according to claim 1, wherein in said shift information forming step, if the coincident portion with the data of the new file cannot be searched in said searching step due to deletion of the data in the old file, shift information showing a shifting direction and the shift amount up to the backward coincident portion on the old file is formed.

9. A program for forming differential data, wherein said program allows a computer to execute:

a comparing step wherein two new and old files are sequentially compared from heads of the files on a predetermined data unit basis;

a transfer information forming step wherein if a coincidence of the data is determined by said sequential comparison, transfer information showing a position and a data length of the old file is output;

a searching step wherein if a dissidence of the data is determined by said sequential comparison, the old file is searched in both forward and backward directions from a data position where the dissidence has been determined on the old file, thereby searching a portion which coincides with the data of the new file;

a shift information forming step wherein if the coincident portion can be searched in said searching step, shift information up to the coincident portion on the old file is output; and

a replacement information forming step wherein if the coincident portion cannot be searched in said searching step, new data is added to transfer replacement information showing a data length of the dissident portion of the old file at a position until the coincident portion can be searched and resultant transfer replacement information is output.

10. A program according to claim 9, wherein in said searching step, when a portion of the old file which coincides with the data of the new file and continuous coincident portions of a predetermined number (n) or more of data subsequent to said coincident portion are searched, it is determined that the data coincides.

11. A program according to claim 9, wherein in said searching step, when a portion of the old file which coincides with the data of the new file and coincident portions of a predetermined number (y) or more of data distributed among a predetermined number (x) of data subsequent to said coincident portion are searched, it is determined that the data coincides.

12. A program according to claim 9, wherein in said shift information forming step, a shifting direction in which a forward position on said old file is set to a negative direction and a backward position on said old file is set to a positive direction and a shift length showing a length of data up to the coincident portion on the old file are output as said shift information.

13. A program according to claim 9, wherein in said searching step, if a structure of the file is that of a program file written by an n-bit code, the search is performed every other (n) bits in both forward and backward directions from the position of the data which was determined to be dissident in the old file, thereby searching the portion which coincides with the data in the new file.

14. A program according to claim 9, wherein in said replacement information forming step, when differential data between the old data and the new data coincides with differential data of replacement information formed in the past, the new data is not added but transfer replacement information showing the same as a past differential pattern or updating pattern is output.

15. A program according to claim 9, wherein in said replacement information forming step, if the coincident portion cannot be searched in said searching step due to the insertion of the new data in the new file, said new data is added to the transfer replacement information showing the data length of the dissident portion of the old file at a position until the coincident portion can be searched and the resultant transfer replacement information is output.

16. A program according to claim 9, wherein in said shift information forming step, if the coincident portion with the data of the new file cannot be searched in said searching step due to deletion of the data in the old file, shift information showing a shifting direction and the shift amount up to the backward coincident portion on the old file is formed.

17. A computer-readable recording medium which stores a program for forming differential data, wherein said program allows a computer to execute:

a comparing step wherein two new and old files are sequentially compared from heads of the files on a predetermined data unit basis;

a transfer information forming step wherein if a coincidence of the data is determined by said sequential comparison, transfer information showing a position and a data length of the old file is output;

a searching step wherein if a dissidence of the data is determined by said sequential comparison, the old file is searched in both forward and backward directions from a data position where the dissidence has been determined on the old file, thereby searching a portion which coincides with the data of the new file;

.

a shift information forming step wherein if the coincident portion can be searched in said searching step, shift information up to the coincident portion on the old file is output; and

a replacement information forming step wherein if the coincident portion cannot be searched in said searching step, new data is added to transfer replacement information showing a data length of the dissident portion of the old file at a position until the coincident portion can be searched and resultant transfer replacement information is output.

18. A differential data forming apparatus comprising:

a data comparing unit which sequentially compares two new and old files from heads of the files on a predetermined data unit basis;

a transfer information forming unit which, if a coincidence of the data is determined by said data comparing unit, outputs transfer information showing a position and a data length of the old file;

a coincident portion search unit which, if a dissidence of the data is determined by said data comparing unit, searches the old file in both forward and backward directions from a data position where the dissidence has been determined on the old file, thereby searching a portion which coincides with the data of the new file;

a shift information forming unit which, if the coincident portion can be searched by said coincident portion search unit, outputs shift information up to the coincident portion on the old file; and

a replacement information forming unit which, if the coincident portion cannot be searched by said coincident portion search unit, adds new data to transfer replacement information showing a data length of the dissident portion of the old file at a position until the coincident portion can be searched and outputs resultant transfer replacement information.