JP2009266128A - Data comparison device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data comparison device for outputting difference information by comparing files in a short period of time or within a desired period of time even when the size of a target data file is large. <P>SOLUTION: A coincident part retrieving part sequentially compares a first coincident place retrieval target word obtained by skipping words included in a first data string for a predetermined first selection interval at a time with a second coincident place retrieval target word obtained by skipping words included in a second data string for a predetermined second selection interval at a time to find a coincident place. A common part retrieving part compares the first data string with the second data string about words located before and after the first data string and the second data string, respectively on the basis of a word of the coincident place detected by the coincident place retrieving part and detects a range where both the data strings are coincident. A difference information outputting part outputs difference information between the first data string and the second data string on the basis of range information of a common part detected by the common part retrieving part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a data comparison apparatus that compares data and outputs difference information, and a program thereof.

  In the software development stage, file editing such as function improvement and bug correction frequently occurs. At this time, when a new file is created by editing a certain file, a tool that compares the old and new two files and outputs a difference is used to represent the editing location, represented by diff of UNIX (registered trademark). It is done. In the case of such changes by file editing, since there are generally few changes, the difference data size is small. If you need to keep information about both the old and new files, saving the storage space is better if you leave the files before the change and the difference files that represent the differences between them, rather than physically leaving both of them. Such a difference output tool is often used for generating a difference file.

  As an algorithm for generating a difference file, it has been required to reduce the size of the difference data as much as possible. Typical algorithms for this include LCS (Longest Common Subsequence) or SED (Shortest Edit Distance).

  Also, Non-Patent Document 1 describes an algorithm for speeding up based on this concept. Non-Patent Document 2 describes bdiff, which uses a suffix tree instead of LCS or SED as a differential search algorithm and simultaneously reduces data size by performing data compression.

  The invention described in Patent Document 1 divides one file into a certain block size and obtains the checksum of each block in substantially the same manner as the rsync algorithm (Non-Patent Document 3). The checksum of the block having the same block size is obtained from the head of the other file, and a search is performed for a block having the same checksum in the other file. If the same block is not found, the block is shifted backward by 1 byte to obtain a checksum, and the same search is performed. This is repeated thereafter. When the same block is found in the search process, the checksums are compared between the blocks shifted backward by the block size in both files to determine whether or not they are the same. In this way, the comparison of character units and block units is combined to increase the speed.

In the invention described in Patent Document 2, the LCS of two files is searched, and the two files are logically divided back and forth with the LCS as a boundary. The divided files are similarly searched for LCS and divided, and this operation is hierarchically repeated until the LCS becomes shorter than a predetermined length. In the present invention, the LCS portion is divided back and forth to limit the search range, thereby increasing the speed.
EUGENE W. MYERS, “An O (ND) difference algorithm and its variations”, Algorithmica, 1986, Vol. 1, No. 2, pp. 251-266. Walter F. Tichy, “The string-to-string correction problem with block moves”, ACM Transactions on Computer Systems, 1984, volume 2, issue 4, pp.309-321. Andrew Tridgell, Paul Mackerras, “The rsync algorithm”, [Search April 5, 2008], Internet <URL: http://rsync.samba.org/tech_report/> JP-A-2005-173726 Special table 2005-525641

  However, any of the above-described methods belonging to the background art is an algorithm on the premise that the difference between two files to be compared is small. Therefore, although the result can be output in a short time when the difference is very small, there is a problem that it takes a relatively long time when the difference is large. In particular, this problem of time is significant when comparing large files.

  Also, in the method belonging to the background art, the processing time for comparing the files and obtaining the difference depends on the file size and the difference size, and the processing cannot be completed within the desired time. It was.

  The present invention has been made based on the above problem recognition, and an object thereof is to provide a data comparison device and a program for comparing files in a relatively short time and outputting difference information. Another object of the present invention is to allow these data comparison devices and programs to finish processing within a desired time regardless of the file size.

  [1] One aspect of the present invention for solving the above-described problem is a data comparison device that compares a first data string and a second data string each consisting of a plurality of words, and is included in the first data string The first matching point search target word obtained by skipping the word by a predetermined first selection interval (the first selection interval is an integer of 1 or more) and the word included in the second data string A matching part search unit that sequentially compares the second matching part search target words obtained by skipping each second selection interval (the second selection interval is an integer equal to or greater than 1) to search for a part where both match, Comparison between the first data string and the second data string with respect to words preceding and following the first data string and the second data string, respectively, based on the word of the matching part detected by the matching part search unit Do A common part search unit that detects a matching range as a common part range, and based on information on the common part range detected by the common part search unit, the first data string and the second data string And a difference information output unit for outputting difference information between them.

According to this configuration, the matching part search unit sets only the first matching part search target word obtained by skipping the first data string by a predetermined first selection interval as a comparison target. Similarly, only the second matching portion search target word obtained by skipping the predetermined second selection interval among the words in the second data string is set as a comparison target. Therefore, the number of comparisons can be reduced compared to the case where all words are to be compared. That is, the processing time is short. In addition, the common part search unit compares the values between the first data string and the second data string with respect to the consecutive words before and after the matching part detected by the matching part search unit. The range of common parts including The difference information output unit can output the difference information between the first data string and the second data string in accordance with the information on the range of the common part obtained by the common part search unit. Note that the information of the range of the common part and the difference information are equivalent to each other as information.
Further, according to this configuration, the first selection interval and the second selection interval can be set as appropriate. The number of matching portion search target words is approximately equal to the number of each data string (number of words) divided by this selection interval. Therefore, the value of the word is determined by setting the first selection interval and the second selection interval. The number of comparisons can be changed. That is, even if the size of the first data row or the second data row is enormous, the first selection interval and the second selection interval are set so that the desired number of comparisons (and thus the desired processing time) is achieved. It can be set and the price is only a partial loss of matching opportunities.
The first selection interval and the second selection interval may be arbitrary integers of 1 or more, but the effect of the present invention that the processing time is shortened is greater when these numerical values are relatively large. For example, if at least one of the first selection interval and the second selection interval is 2 or more, the processing time can be shortened. If the first selection interval and the second selection interval are each 10 or more, the processing time can be further shortened. When the first selection interval and the second selection interval are each 100 or more, the processing time can be further shortened. The larger these values are, the shorter the processing time can be, but the length of the common part that is guaranteed to be detected becomes longer. (Shorter common parts may not be detected). How to set these intervals will be described later.

  [2] Further, according to an aspect of the present invention, in the data comparison apparatus, the greatest common divisor between the first selection interval and the second selection interval is 1.

  With this configuration, the first match location search target word and the second match location search target word gradually shift. Therefore, even if the position of the common part (the number of words from the head position of each data string) is shifted between the first data string and the second data string, if the common part is large, the matching portion search target words overlap. There is a high possibility that the location exists. That is, the possibility of detecting the coincidence portion increases. In addition, when the number of words in the common part is equal to or greater than the least common multiple of the first selection interval and the second selection interval, a coincident portion can be detected without fail.

  [3] Further, according to one aspect of the present invention, in the data comparison apparatus described above, the ordered processing unit that sorts the values of the first matching portion search target words and writes the resulting order information in the order information storage unit The match location search unit reads the sequence information from the sequence information storage unit, so that the second match location search target word needs to be compared with the first match location search target word. It is characterized by searching for a place where both match with each other.

With this configuration, since the matching part search unit can use the order information, it is not necessary to compare a certain second matching part search target word with all the first matching part search target words. By comparing, it is sufficient to compare with a limited number of first matching part search target words. That is, the comparison with the first matching point search target word can be performed efficiently. Therefore, the total number of comparisons can be reduced, and therefore the overall processing time can be shortened.
Also, in principle, the number of first matching part search target words can be a logarithmic order comparison count. That is, the greater the number of first matching portion search target words (the greater the number of words in the first data string), the greater the effect of time reduction by this configuration.

  [4] Further, according to an aspect of the present invention, in the data comparison apparatus, the word included in the first data string and the second data string may be compared with a predetermined size of the comparison target data that is the source of these data strings. It has a hash value obtained by applying a hash function to the data of the block divided into two.

  With this configuration, unless the block data in the original data match, the possibility that the values of the words included in the first data string and the second data string coincide by chance is very small. That is, the possibility that the values of the first and second matching part search target words will accidentally become the same even though it is not a common part is very small. That is, high accuracy in data comparison can be obtained without comparing the original data itself.

  [5] Further, according to one aspect of the present invention, there is provided a program for causing a computer to execute a process of comparing a first data string and a second data string each including a plurality of words, and the program included in the first data string A first matching point search target word obtained by skipping a word by a predetermined first selection interval (the first selection interval is an integer of 1 or more) and the word included in the second data string are set to a predetermined second A matching part search process for sequentially comparing the second matching part search target words obtained by skipping the selection intervals (the second selection interval is an integer of 1 or more) to find a matching part, and the matching part Comparing between the first data string and the second data string with respect to words preceding and following the first data string and the second data string, respectively, based on the matching word detected in the search process And performing a common part search process for detecting a range in which both coincide with each other as a common part range, and information on the range of the common part detected in the common part search process, and the first data string and the second data string. And a difference information output process for outputting difference information between and the computer.

  According to the present invention, a common part of two data strings can be detected at high speed. That is, the process of outputting the difference between the two data strings can be speeded up. Further, the number of comparison processing between words can be controlled by appropriately setting parameters (first selection interval and second selection interval). That is, even when the data string size is large, the processing time can be suppressed to a desired level. That is, it is possible to determine that two completely different data strings are completely different within a preset time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As a process for obtaining the difference data, as in the method described in the background art, the data comparison apparatus can perform a common part between two given data strings (if there are a plurality of common parts, The common part) is found, and the part excluding the common part is set as difference data. Therefore, in the embodiment described below, a process for searching for a common part of two data strings can be performed at high speed.

  Conventional methods have focused on reducing the amount of difference data by finding as many common parts as possible. On the other hand, an object of the embodiment of the present invention is to compare two data strings having a very large number of words and output the difference at high speed. Further, when comparing completely different data strings, it is possible to determine at high speed that there is no common part. Instead, the data amount of the difference does not necessarily need to be the minimum, and a basic strategy is that a short common part may be missed. Here, the word is one piece of data. The length of the word may be about 1 byte (= 8 bits), but in the present embodiment, a word having a length of about 4 bytes to 64 bytes is typically assumed. Further, it may be a word having a length exceeding 64 bytes.

  Each word constituting the data string is, for example, a value returned by the hash function. With a good hash function, it is very unlikely that the returned hash values will coincide by chance unless the original data to which the hash function is applied is identical.

[First Embodiment]
FIG. 1 is a block diagram showing a functional configuration of the data comparison apparatus according to the first embodiment of the present invention. As shown in the figure, the data comparison device 1 includes a common part search unit 3, a matching part search unit 4, a difference information output unit 5, a control unit 6, data files 10A, 10B, 20A, and 20B, and hash data. And a generation unit 15.

The matching part search unit 4 is directed to a data string after the position indicated by the comparison pointers of the data strings A and B received from the control unit 6 according to an instruction from the control unit 6, and a word included in the data string A described later is selected. Matching part search target word obtained by skipping by a predetermined first selection interval (n _A ) and match obtained by skipping a word included in the data string B by a predetermined second selection interval (n _B ) It has a function of sequentially comparing the location search target words to find a location where both match. The comparison pointers for the data strings A and B at the coincident part are returned to the control unit 6. If there is no match, the comparison pointer for the data string B is set at the end of the data string B, and the comparison pointer for the data strings A and B is returned to the control unit 6.

  The common part search unit 3 starts from the comparison pointers of the data strings A and B received from the control unit 6 in accordance with an instruction from the control unit 6, and the data sequence based on the word of the matching part detected by the matching part search unit 4 For words that precede and follow A and data string B, respectively, a comparison is made between data string A and data string B, and a range in which both match is detected as a common part range. The range of the comparison pointers for the data strings A and B in the common part is output to the difference information output unit 5, and the comparison pointer for the data strings A and B immediately after the range of the common part is returned to the control unit 6.

  The difference information output unit 5 has a function of outputting difference information between the data string A and the data string B according to an instruction from the control unit 6 based on the information on the range of the common part detected by the common part search unit 3. Have.

  Further, the control unit 6 controls the execution of the matching part search unit 4, the common part search unit 3, and the difference information output unit 5. Specifically, the comparison pointers of the data string A and the data string B are initialized, the common part search unit 3 is executed using the current position of the comparison pointer, and the data string A immediately after the common part is processed. And the comparison pointer of B are received, and it is determined whether or not the comparison pointer points to the end of the data string. If the pointer does not reach the end, the current position of the comparison pointer is used for the matching part search unit 4. The process is executed to receive the comparison pointers of the data strings A and B at the coincidence portion, and by determining whether the comparison pointer points to the end of the data row, the common portion 3 and the coincidence portion search unit are sequentially 4 is controlled so that processing can be performed. Further, when the pointer points to the end (that is, when the matching part search and the common part search are all finished), the difference information output unit 5 is caused to execute the process.

The data files 20A and 20B are two data files to which the data comparison device 1 is to perform comparison processing. The data files 10A and 10B (comparison target data) are two different data files.
The hash data generation unit 15 has a function of calculating a predetermined hash function. The hash data generation unit 15 applies the hash function based on the data file 10A to generate the data file 20A, and the same based on the data file 10B. A data file 20B is generated by applying a hash function. The hash function to be used may be appropriately selected. For example, MD5, SHA, HAVAL, checksum, CRC (cyclic redundancy code), or the like can be used.
The data files 10A, 10B, 20A, and 20B are stored in a recording medium such as a semiconductor memory or a hard disk device (HDD).

  FIG. 2 is a schematic diagram showing the relationship between the data files 10A and 20A. As shown in the figure, the data files 10A and 20A are both sequential files.

Data file 10A includes M _A number of blocks having a predetermined length. As an example, the block size is 4 kbytes (1 kbyte is 1024 bytes). In this example, the length of the entire data file 10A is 4k × M _A (bytes). In this figure, the data value of each block is expressed as B (0), B (1), B (2),..., B (M _A −1) in order from the first block. . The value of M _A may be any value. For example, if M _A = 1048576 (= 2 ^ 20), the length of the entire data file 10A is 4 GB (gigabytes). The block length is not limited to 4 kbytes, and may be any size.

The data file 20A is data generated by the hash data generation unit 15 based on the data file 10A. Data file 20A, the word (in this case, one word is set to 16 bytes) contains _{M A} number of. That is, the entire length of the data file 20A is 16 × M _A (bytes). Each word corresponds to the block of the data file 10A and the order thereof is also stored. For example, based on the first block B (0) of the data file 10A, the hash data generation unit 15 applies a hash function, and the value h (B (0)) obtained as a result is the first word of the data file 20A. Stored. The next block B (1) of the data file 10A corresponds to the value h (B (1)) of the next word of the data file 20A. In the same manner, the last block B (M _A −1) of the data file 10A corresponds to the last word value h (B (M _A −1)) of the data file 20A. Note that the word length is not limited to 16 bytes, but may be any size. The values returned by hash functions that are generally used at present are 16 bytes (= 128 bits), 20 bytes (= 160 bits), and 28 bytes. (= 224 bits), 32 bytes (= 256 bits), 48 bytes (= 384 bits), 64 bytes (= 512 bits), and the like. Based on the word length of the data file 20A and the like, a hash function to be used is selected and used.

  While the relationship between the data files 10A and 20A has been described above with reference to the drawings, the same applies to the relationship between the data files 10B and 20B. However, the length of the data file 10A and the length of the data file 10B may be different.

  Next, a method and procedure for processing in which the data comparison device 1 compares the data files 20A and 20B will be described.

FIG. 3 is a schematic diagram showing an outline of processing for finding a common part between the data files 20A and 20B mainly by the functions of the common part search unit 3 and the matching part search unit 4 in the data comparison device 1. is there. In this figure, data sequence A (first data row) represents the data of the data file 20A, the number of words that the data sequence A contains is N _A word (N _A is an integer of 1 or more). In the data string A, the match location search target word 51A or 52A (first match location) searched by the match location search unit 4 for every n _A words (n _A is an integer of 1 or more, first selection interval) from the beginning. Search word) exists. These matching part search target words 51A or 52A are each shown by a unique hatching pattern in the figure. In other words, the data string A includes N _A / n _A (in this case, the remainder of division is rounded up) matching point search target words. Similarly, the data sequence B (second data column) represents the data of the data file 20B, the number of words that the data sequence B contains is N _B word (N _B is an integer of 1 or more). In the data string B, the match location search target word 51B or 52B (second match location) searched by the match location search unit 4 for every n _B words (n _B is an integer of 1 or more, second selection interval) from the beginning. Search word) exists. These matching part search target words 51B or 52B are each shown by a unique hatching pattern in the figure. In other words, the data string B includes N _B / n _B (in this case, the remainder of division is rounded up) matching portion search target words.
Note that the processing speed can be increased by setting at least one of n _A and n _B to 2 or more.

  In the example of the data string shown in the figure, the range shown as the common part of the data strings A and B is a range in which the values of all the words included in the range completely match between the data strings A and B. is there. That is, this common part is a range to be detected by the common part search unit 3. Accordingly, among the above-described matching portion search target words, the matching portion search target words 52A and 52B included in this common portion have the same value. Note that the word position of the common part in the data string A (the number of words from the beginning of the data string A to the point immediately before the common part) and the word position of the common part in the data string B (similar) are not necessarily the same. There is no need.

  The common part search unit 3 and the coincidence part search unit 4 cooperate to detect a common part between the data strings A and B according to the procedure described later under the control of the control unit 6. At that time, the matching part search unit 4 compares only the matching part search target word (51A, 52A) included in the data string A and the matching part search target word (51B, 52B) included in the data string B. And In addition, the matching part search unit 4 skips words other than the matching part search target word (words in a portion without hatching in this figure) without being compared.

At this time, it is preferable to set the greatest common divisor of n _A and n _B to be 1, and to determine the matching portion search word accordingly. By making the greatest common divisor of n _A and n _B equal to 1, the matching point search target words of the data string A and the data string B are shifted little by little in the processing described below. The possibility of being able to be increased. In addition, when the number of words in the common part is greater than or equal to the least common multiple of n _A and n _B , a coincident part can be detected without fail.
Note that it is not essential to set the greatest common divisor of n _A and n _B to be 1. However, if this is not done, there is a possibility that a matching portion cannot be detected. For example, in the simplest case, when n _A = n _B = 2, the common part is the 0th to 9th words of the data string A and the 1st to 10th words of the data string B. Even if the data string A and the data string B are both shifted by one word, the matching portion search target word is the even word (0th word, 2nd word, 4th word,...). ), And a matching portion included in the common part cannot be detected.

  The matching part search unit 4 compares each of the matching part search target words included in the data string B with each of the matching part search target words included in the data string A. As a result of the comparison, when the matching part search unit 4 finds a matching word, the common part search unit 3 moves forward (from the location toward the beginning of the entire data string) and backward (from the entire data string). Are scanned one word at a time, and the beginning and end of a range (common part) where the values of both data strings are the same are searched. In this way, the range of the common part including the matching word found by the matching part search unit 4 is determined.

After the common part range is determined by the common part search unit 3, the above operation is repeated from the next word of the common part to the end of the data string. When the greatest common divisor of n _A and n _B is 1, there is always a coincidence place of both data string A and data B somewhere in the common part having a size of (n _A × n _B ) words or more. Since the search target word is included, a common part having a size of (n _A × n _B ) words or more can always be found by the processing procedure as described above.

Further, when the processing procedure as described above is taken, even when the data string A and the data string B are completely different, even when both the matching part search target words do not match, the matching part search unit 4 , at _{most, (n a / n a)} × (n B / n B) may be carried out comparison processing times. That is, even when comparing large data strings, the value of n _A and n _B is appropriately set to sacrifice the opportunity to detect a coincidence, but the number of comparison processes In other words, the processing time required for the comparison process between data strings can be suppressed within a predetermined range.

In this case, in other words, when the sizes N _A and N _{B of} the data string are given, the minimum value of the length of the common part to be found ((n _A × n _B ) words) and the number of searches (that is, search for matching points) The number of comparison processes (N _A / n _A ) × (N _B / n _B ), that is, (N _A × N _B ) / (n _A × n _B )) is inversely proportional. That is, when the minimum value of the length of the common part to be detected is a constant value, the maximum number of searches is almost the same regardless of the individual values of n _A and n _B. If n _A and n _B are set to relatively large values (if n _A × n _{B is set} to a relatively large value), the number of comparisons can be reduced, but the probability of missing a common part (possibility of failure to detect) Will increase. Conversely, if n _A and n _B are set to relatively small values (if n _A × n _{B is set} to a relatively small value), the probability of missing a common portion decreases, but the number of comparisons increases. Therefore, according to the method of the present embodiment, n _A and n _B can be appropriately set according to the required conditions such as the maximum search time and the minimum value of the common part length to be found.

  FIG. 4 is a flowchart showing a processing procedure for differential output by the data comparison device 1. Hereinafter, the detailed processing procedure of the data comparison device 1 will be described with reference to this flowchart.

  First, in step S61, the data comparison apparatus 1 performs an initialization process. In this initialization process, the data files 20A and 20B are opened, and the pointers of the words to be compared (comparison pointers) are set at the heads of the data strings A and B, respectively.

The initialization process includes a process of setting parameters n _A and n _B to appropriate values. The setting procedure of this parameter differs depending on the implementation conditions.

When the minimum value L of the common part to be found is set as a reference, n _A is set to an arbitrary positive integer value not exceeding L. n _B is a relatively prime to _{n A} and maximum setting a positive integer not exceeding L / _{n A.} In such a setting, since n _A × n _B ≦ L, a common portion having a size of L words or more can always be detected.

On the other hand, to set the value of _{n A} and _{n B} relative to the upper limit C of the comparison _{number, (N A / n A)} × (N B / n B) ≦ C to meet the _{n A} and _{n B} to Select a value. This is because, even if the data strings A and B are completely different, the number of times that the matching point search target words of both are compared brute force is at most (N _A / n _A ) × (N _B / This is because n _B ).

As a specific example, _{n A} is a positive integer not less than _(N A / C). Further, _{n B} is relatively prime to _{n A,} and is the smallest positive integer not less than _{(N A × N B) /} (n A × C). At this time, (N _A / n _A ) × (N _B / n _B ) ≦ C. That is, the total number of comparisons is C or less.

  Next, in step S62, the common part search unit 3 searches the range of the common part. Specifically, first, the values of the words indicated by the comparison pointers on the respective data strings are compared to determine whether or not they match. At this time, the comparison pointer points to the current matching point search target word of each data string. If the result of the determination is that they do not match, the process of this step is terminated and the process proceeds to the next step. If they match as a result of the above determination, the values of the words pointed to by both comparison pointers are sequentially compared while shifting both comparison pointers one by one in the forward direction of the data string. Then, the comparison pointer is advanced in the forward direction until one of the comparison pointers reaches the head of the data string or the word values do not match. In this way, the head position of the common part is searched. Next, return the comparison pointer to the first position (the position of the current matching point search target word), and similarly compare the word values of both data strings while shifting the comparison pointer backward one by one. By doing so, the end position of the common part is searched. When the current position of the search target word is a part of the common part, the head position and the tail position of the common part are obtained in this way. That is, the range of the common part is determined. The common part search unit 3 passes the information on the start position and the end position of the common part to the control unit 6.

  In step S63, the control unit 6 determines that the comparison pointers for both the data strings A and B are the end of the file (here, the end of the file is further after the last word of the data string). It is determined whether or not. When at least one of the comparison pointers is at the end of the file (when all the comparisons of the matching point search target words to be compared have been completed) (step S63: YES), the loop from step S62 to S65 is exited, and step S66 is completed. Proceed to As a result of the determination, if the comparison pointer is not at the end (if there is still a combination of matching point search target words to be compared) (step S63: NO), the process proceeds to the next step S64.

At the time of proceeding to the next step S64, the comparison pointers of the data strings of both A and B point to the next word of the common part which has been searched immediately before and the range is fixed. That is, the comparison pointer points to a position outside the common part searched immediately before. In this step, if necessary, the comparison pointer is advanced to the position of the next matching point search target word of each data string, and then the matching part search unit 4 searches for a matching part of the data strings A and B therefrom. Search for the target word and find the matching part. In the present embodiment, the matching part search unit 4 fixes the comparison pointer for the data string B and compares the matching part search target words pointed to by the comparison pointers for the data strings A and B while matching the set of matching words. The position pointed to by the comparison pointer in the data string A is sequentially advanced by n _A words until the data is found. When the comparison pointer of the data string A reaches the end, the comparison pointer of the data string A is temporarily returned to the original position (the destination to be restored is after the common part when there is a common part searched immediately before). In addition, the position of the first matching part search target word among them, or the position of the first matching part search target word in the data string A if there is no common part searched immediately before), and for comparison for the data string B The position pointing to the pointer is advanced by n _B words (that is, the next matching point search target word of the data string B is pointed), and the matching string search word of the data string B is the data string A in the same manner as above. The comparison is repeated while sequentially moving the comparison pointers. The processing in this step ends when the comparison of the remaining matching point search target words is completed for all the pairs or when matching words are detected during the sequential comparison.

Next, in step S65, the control unit 6 determines whether or not the pointer of the data string B points to the end.
The case where the pointer of the data string B points to the end refers to the case where the word matching part is not found in the matching part search process in step S64. In this case (step S65: YES), the process exits the loop from step S62 to S65 and proceeds to step S66.
On the other hand, the case where the pointer of the data string B does not point to the end is a case where a matching part is found in the matching part search process in step S64. In this case, the data strings A and B are detected. Each comparison pointer points to a matching point search target word having a matching value. In this case (step S65: NO), the process proceeds to step S62.

  If the determination result in step S65 is “NO” and the process proceeds to step S62, the common part as described above is processed as the process in step S62 based on the position indicated by the current comparison pointer. Perform a range search.

  As described above, the control shifts to step S66 when it is determined “YES” in either step S63 or S65, that is, all of the comparisons between the matching portion search target words included in the data strings A and B are all performed. This is the case. In step S66, the difference information output unit 5 performs difference information output processing. The difference information output at this time is, for example, information on data (word arrangement) included in the data string A and not included in the data string B, and included in the data string A but included in the data string B. It is expressed as data information that is not available. Such difference information is created based on the information on the range of the common part obtained by the common part search unit 3 in step S62 (information on the start position and the end position of each common part) from the memory. Can do. In addition, the information in the range of the common part itself is equivalent to the difference information as information. The information of the common part range itself, or the information of the common part range and the information that can be created from the data string A and the data string B can be expressed in various patterns. Information.

FIG. 5 is a schematic diagram showing an outline of the above-described series of processing using an example of a simple data string. Since the example shown in the drawing is for explanation, N _A = N _B = 16 and the length of each data string is shortened. In addition, since n _A = 2 is set for the data string A, the matching portion search target word (51A or 52A) exists every two words. In addition, since n _B = 3 is set for the data string B, the matching portion search target word (51B or 52B) exists every three words. In this example, the common part is the 6th to 11th words of the data string A and the 8th to 13th words of the data string B. The common part has a size of 6 words. is there. Therefore, of the illustrated matching part search target words, the tenth matching part search target word 52A in the data string A and the twelfth matching part search target word 52B in the data string B have the same value.

Hereinafter, description will be made with reference to the flowchart of FIG. 4 and the schematic diagram of FIG.
First, in the initialization process in step S61, the comparison pointers for the data strings A and B are set to the 0th word of each data string. In addition, parameters are set as n _A = 2 and n _B = 3.
Next, in the process of searching for the range of the common part in step S62, the values of the matching portion search target words pointed to by the respective comparison pointers are compared. In this case, since the values of the 0th word of the data string A and the 0th word of the data string B pointed to by the current comparison pointer are not the same, they do not match even if they are compared, and the process of this step ends here. To do.
In the determination in step S63, since neither of the data strings A and B is at the end of the data string (step S63: NO), the process proceeds to step S64.

In the next step S64, a matching point search target word is selected every three words (n _B words) from the current position of the comparison pointer of the data string B (pointing to the 0th word), and each matching point is selected. The search target words are sequentially compared with the matching point search target words in the data string A (from the 0th word, every 2 words (n _A words)). Until the 0th word, the 3rd word, the 6th word, and the 9th word of the data string B are sequentially compared, there is no match with the matching portion search target word of the data string A. If the comparison is further continued, the value of the 12th word (matching part search target word 52B) of the data string B matches the value of the tenth word (matching part search target word 52A) of the data string A. Since the coincidence portion has been detected, the processing in step S64 is completed.

  In step S65, at this time, the comparison pointer of the data string A points to the position of the tenth word, and the comparison pointer of the data string B points to the position of the twelfth word. That is, since the comparison pointer of the data string B is not the end of the data string (step S65: NO), the process returns to step S62.

In the processing of the next step S62, using the 10th word of the data string A and the 12th word of the data string B as a base point, search for a word that matches both by moving the pointer forward and backward one word at a time. To do. As a result, the beginning position of the common part is the sixth word of the data string A, that is, the eighth word of the data string B, and the end position of the common part is the eleventh word of the data string A, that is, the 13th word of the data string B. It turns out that it is the word.
In the determination of the next step S63, since the comparison pointer of the data string A points to the position of the 12th word and the comparison pointer of the data string B points to the position of the 14th word at this time, that is, the data string Since the comparison pointer for B is not the end of the data string (step S63: NO), the process proceeds to the next step S64.

  Again, in step S64, a search is made for a place where the words match. At this time, the comparison pointer of the data string B points to the position of the 14th word, but the matching point search target word is selected every 3 words from the current position of the comparison pointer (the 14th word). Note that the position of the comparison pointer is the first word (15 words) of the match target search words originally planned after the immediately preceding common part (from the 8th word to the 13th word of the data string B). It is also possible to select a matching portion search target word every three words after moving to the position of (eye). In any case, in the example shown in the figure, the match of the search target word between the data strings A and B is not detected. When the comparison pointer of the data string B reaches the end of the data, the process of this step is finished.

In the next step S65, since the pointer of the data string B has reached the end (step S65: YES), the process goes out of the loop and proceeds to step S66.
In step S66, the difference information is output, and the process of the entire flowchart ends.

[Second Embodiment]
FIG. 6 is a block diagram showing a functional configuration of the data comparison device 2 according to the second embodiment of the present invention. As shown in the figure, the data comparison device 2 includes a common part search unit 3, a matching part search unit 24, an ordered processing unit 31, an order information storage unit 32, a difference information output unit 5, and a control unit 6. The data files 10A, 10B, 20A and 20B, and the hash data generation unit 15 are configured.
This second embodiment is intended to further speed up the processing. In the following, description of the same parts as in the first embodiment will be omitted, and description will be made focusing on the configuration, processing procedure, and the like unique to this embodiment.

  In the present embodiment, means for further speeding up the processing is as follows. That is, in this embodiment, the matching point search target words of one of the two data strings (here, for convenience of explanation, the data string A) are sorted in the order of their values (ascending order or descending order). (Sequence) and search for matching points using the order information obtained as a result of sorting.

  More specifically, the ordering processing unit 31 sorts by the value of the matching part search target word included in the data string A, and orders the order information of the matching part search target word regarding the data string A obtained as a result. It has a function of writing in the information storage unit 32.

  In addition, the order information storage unit 32 holds order information regarding the value of the matching part search target word included in the data string A. Specifically, for example, index information for the data string A is held by a B-Tree (balance tree) structure. Thereby, since the order information can be held without changing the order of the data string A itself, it is possible to determine at high speed whether there is a word that matches the matching portion search target word of the data string A.

  Since the matching part search unit 24 can obtain the order of the values of the matching part search target words included in the data string A by reading the order information from the order information storage unit 32, It has a function of comparing a certain matching part search target word included with only the words that need to be compared among the matching part search target words included in the data string A, and searching for a part where both match. In other words, the matching part search unit 24 of the present embodiment does not need to compare the matching part search target words of the data strings A and B brute force, and for a certain matching part search target word included in the data string B, for example, It is only necessary to compare with a matching point search target word included in the data string A in a binary tree.

In order to sort the data string A only once, it is necessary to perform word comparison of at most (N _A / n _A ) log ₂ (N _A / n _A ) times. Further, once sorted, the matching point search target word for each data string B is compared with the matching point search target word of the data string A by approximately log ₂ (N _A / n _A ) comparisons. It can be confirmed that a match can be detected or that it does not match any match location search target word in the data string A. That is, since there are (N _B / n _B ) matching portion search target words in the data string B, the total number of comparisons is (N _B / n _B ) log ₂ (N _A / n _A ). Therefore, when these are combined, in the case of the present embodiment, even when the data string A and the data string B are completely different data strings, the maximum is ((N _A / n _A ) + (N _B / n _B )) × log ₂ (N _A / n _A ) comparisons may be performed. Unlike the case of the first embodiment, in the case of this embodiment, the maximum number of comparisons depends on the values of n _A and n _B even if the minimum value of the common portion to be found is a constant value. According to the arithmetic and geometric mean theorem, the maximum number of comparisons can be minimized by selecting n _A and n _B where the values of N _A / n _A and N _B / n _B are approximately the same. be able to.

  FIG. 7 is a flowchart showing a procedure of data comparison processing by the data comparison device 2 of the present embodiment. Hereinafter, it demonstrates along this flowchart.

First, the initialization process in step S81 is the same as the process in step S61 described in the first embodiment. However, how to determine the values for setting the value of n _A and n _B relative to the upper limit C of the number of comparisons are as follows. That is, ((N _A / n _A ) + (N _B / n _B )) × log ₂ (N _A / n _A ) ≦ C is satisfied, and N _A / n _A and N _B / n _B are satisfied as described above. values to select the value of n _a and n _B to a value of about the same.
As a specific example, _{n A} is the smallest positive integer that satisfies _{2 × (N A / n A} ) × log 2 (N A / n A) ≦ C. Further, _{n B} is relatively prime to _{n A,} and is a positive integer satisfying _{n B ≧ N B / N A} × n A. Incidentally, by selecting the smallest integer number of satisfying such conditions n _B, in a predetermined number of comparisons constraint, it is possible to increase the possibility of detecting the common portions.

The process of searching for the range of the common part in step S82 is the same as the process of step S62 of the first embodiment.
The determination process in step S83 is the same as the process in step S63 of the first embodiment.

  Next, in step S84, the matching part search unit 24 determines whether or not the data string A has been sorted (that is, whether or not the order information of the data string A has already been written in the order information storage unit 32). judge. If it has been sorted (step S84: YES), it is not necessary to perform further sorting, so step S85 is skipped and the process proceeds directly to step S86. If it has not been sorted (step S84: NO), the process proceeds to step S85 to perform the sort process.

At step S85, the the ordering processor 31, based on the parameter n _A determined above, the matching points searched word data sequence A, (which may be a descending) sort (ordering) in ascending order of the value processing To do. The sorting process itself is performed by a procedure using existing technology. Then, the ordering processing unit 31 obtains the order information obtained as a result (for example, index information to the matching portion search target word of the data string A expressed in the B-Tree structure. The word position in the column A is used))) is written in the order information storage unit 32.
Note that this sort processing may be performed in, for example, the initialization processing in step S81 instead of being executed in this portion.
Regardless of which part of the sort process is performed, it is not necessary to perform the sort process again after the second loop from step S82 to S87, and the order information is read from the order information storage unit 32 and used. Just do it.

In step S86, the matching part search unit 24 compares the matching part search target words of the data strings A and B to search for a matching part. In this case, in the present embodiment, matching point detecting unit 24, while utilizing the sequence information storage unit 32 reads the order information, for one of the matching locations searched word data sequence B, log 2 _{(N A} / N _A ) About comparison processing is performed. That is, the branches are selected while sequentially comparing the values from the root node of the B-Tree structure, and the matching part search target words in the data string A are searched for the matching words.
That is, the matching part search unit 24 selects a comparison word for every n _B words from the data string after the comparison pointer of the data string B at that time, and sorts the data string A sorted for all comparison words. Is compared with a comparison target word to determine whether there is a matching word.
The point that search processing is performed until a matching word is found is the same as step S64 of the first embodiment.

The determination process in step S87 is the same as the process in step S65 of the first embodiment.
The difference information output process in step S88 is the same as the process in step S66 of the first embodiment.

[Third Embodiment]
FIG. 8 is a block diagram showing a functional configuration of a data comparison apparatus 1A according to the third embodiment of the present invention. In the first embodiment, the data comparison device 1 includes the data files 10A and 10B and the hash data generation unit 15. The data comparison apparatus 1A according to the present embodiment does not have these, and as shown in FIG. 8, the common part search unit 3, the matching part search unit 4, the difference information output unit 5, the control unit 6, and the data file It is composed of 20A and 20B. Similar to the first embodiment, the data files 20A and 20B are data strings composed of words having a predetermined length. The data files 20A and 20B are files having a data string given from the outside. The operations of the common part search unit 3, the matching part search unit 4, the difference information output unit 5, and the control unit 6 are the same as those in the first embodiment.

[Fourth Embodiment]
FIG. 9 is a block diagram showing a functional configuration of a data comparison device 2A according to the fourth embodiment of the present invention. In the second embodiment, the data comparison device 2 includes the data files 10A and 10B and the hash data generation unit 15. The data comparison device 2A according to the present embodiment does not have these, and as shown in FIG. 9, the common part search unit 3, the matching part search unit 24, the ordered processing unit 31, the order information storage unit 32, It comprises a difference information output unit 5, a control unit 6, and data files 20A and 20B. Similar to the second embodiment, the data files 20A and 20B are data strings composed of words of a predetermined length. The data files 20A and 20B are files having a data string given from the outside. The operations of the common part search unit 3, the matching part search unit 24, the ordered processing unit 31, the order information storage unit 32, the difference information output unit 5, the control unit 6, and the like are the same as in the second embodiment. It is.

<< Application example >>
Here, application examples of the above-described embodiments will be described with reference to FIG. 1 showing the configuration of the first embodiment as a representative.

  In this application example, the data files 10A and 10B are moving image content files each having a size of about several gigabytes to several tens of gigabytes. The data files 10A and 10B are managed in units of blocks by the file system, and the size of one block is, for example, 4 kbytes (4096 bytes). That is, the data files 10A and 10B are each composed of several million to several tens of millions of blocks.

  The data files 10A and 10B are edited in units of blocks. In other words, the editing operations for the data files 10A and 10B are insertion of a block, deletion of a block, and change of a value closed in the block. The file system separately developed by the inventors of the present invention provides an application program interface (API) for inserting and deleting data having an integral multiple of the block size. When using such a file system, for example, by devising on the application program side, even when inserting or deleting in the middle of a position that is not a block boundary, data misalignment due to insertion / deletion is possible. Can be prevented from spreading across block boundaries. A detailed description of the file system itself is omitted here.

The data file 20A is a file that holds the hash value of the data file 10A. The hash data generation unit 15 applies a predetermined hash function based on the value of the data (length 4 kbytes) of each block included in the data file 10A, thereby obtaining a predetermined length (for example, 16 bytes (= 128 bits). )) Hash value. The hash value corresponds to each word of the data file 20A.
The relationship between the data files 20B and 10B is the same as the relationship between the data files 20A and 10A described above.
That is, the size of the data files 20A and 20B is not limited to this, but is typically several million to tens of millions of words. That is, when 1 word = 16 bytes, the sizes of the data files 20A and 20B are about several tens of megabytes to several hundreds of megabytes, respectively. It is very time consuming and inefficient to find a common part by comparing such large files with conventional techniques.

By the way, due to the nature of the hash function, unless the original data match at all, the probability that the hash values will coincide is very small. For example, when the length of the hash value is 128 bits and the hash function is sufficiently good, the probability that two hash values having different original data coincide by chance is ^2-128 . That is, as long as the data files 20A and 20B each have a size of several million words to several tens of millions of words, the hash values of the data files 20A and 20B are as long as the original data (block data included in the data files 10A and 10B) are different. The probability is small enough to ignore the chance of coincidence. In other words, when the hash values match, the possibility of matching the original data is high enough.

The purpose of this application example is to obtain the difference information between the data files 20A and 20B in a short time, but the further purpose is to determine which block the data files 10A and 10B have. It is to grasp if there is a short-term comparison process. When editing a video content file managed by the file system described above and saving multiple versions of the video content file as a result, it is difficult and time-consuming to grasp the difference between the multiple versions. Although it is an operation, using this application example, it is possible to grasp the difference between the plates in a short time (or within the desired time) instead of sacrificing the accuracy of common part detection. A big merit is obtained.
The processing for generating the data files 20A and 20B based on the data files 10A and 10B is performed in advance when the file is saved.

  Note that all or part of the functions of the data comparison apparatus in the above-described embodiment may be realized by a computer. In that case, it is realized by recording a program for realizing each function described in the above embodiment on a computer-readable recording medium, causing the computer system to read and execute the program recorded on the recording medium. May be. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible disk, a magneto-optical disk, a portable medium such as a ROM, a flash memory, and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” dynamically holds a program for a short time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. It is also possible to include those that hold a program for a certain time, such as a volatile memory inside a computer system serving as a server or client in that case. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  For example, the order information storage unit 32 of the second embodiment stores the order information using data of the B-Tree structure, but the data structure to be used is not limited to the B-Tree and uses a general tree structure. May be. In addition, a data value of each word and an index to the data string A (a value indicating the word number in the data string A) are used as elements, and an array sorted by the value of each word is used as a data structure. May be. In any case, the number of comparisons can be reduced by using the order information as compared with the brute force comparison.

  The present invention can be used for managing large data files. For example, it can be used for version management of moving image content files.

It is the block diagram which showed the function structure of the data comparison apparatus by the 1st Embodiment of this invention. In the embodiment, it is the schematic which shows the relationship between the data file 10A (original data) and the data file 20A (hash value data). It is the schematic which shows the outline | summary of the process of a matching location search and a common part search in the data comparison apparatus by the embodiment. It is a flowchart which shows the procedure of the process for determination of a common partial range and difference information output by the embodiment. It is the schematic for demonstrating the example of the data comparison by the embodiment. It is the block diagram which showed the function structure of the data comparison apparatus by the 2nd Embodiment of this invention. It is the flowchart which showed the processing procedure of the data comparison by the same embodiment. It is the block diagram which showed the function structure of the data comparison apparatus by the 3rd Embodiment of this invention. It is the block diagram which showed the function structure of the data comparison apparatus by the 4th Embodiment of this invention.

Explanation of symbols

1, 1A, 2, 2A Data comparison device 3 Common part search unit (common part search process)
4 Matching part search part (matching part search process)
5 Difference information output part (Difference information output process)
6 Control unit 10A, 10B Data file (comparison target data)
15 Hash data generation unit 20A, 20B Data file 24 Matched part search unit 31 Ordered processing unit (ordered processing process)
32 Order information storage unit

Claims (5)

A data comparison device for comparing a first data string and a second data string each consisting of a plurality of words,
A first matching point search target word obtained by skipping the word included in the first data string by a predetermined first selection interval (the first selection interval is an integer of 1 or more); and the second data string A second matching point search target word obtained by skipping the included words by a predetermined second selection interval (the second selection interval is an integer of 1 or more) is sequentially compared to search for a point where both match. A matching point search section;
Based on the word of the coincidence portion detected by the coincidence portion search unit, between the first data row and the second data row, the words that are connected before and after the first data row and the second data row, respectively. A common part search unit that performs a comparison and detects a range in which both match as a common part range;
A difference information output unit that outputs difference information between the first data string and the second data string based on information on a range of the common part detected by the common part search unit;
A data comparison device comprising: The data comparison device according to claim 1,
The greatest common divisor of the first selection interval and the second selection interval is 1.
A data comparison apparatus characterized by that. In the data comparison device according to claim 1 or 2,
Sorting the values of the first match location search target word, further comprising an ordering processing unit for writing the order information obtained as a result to the order information storage unit,
The matching part search unit compares the second matching part search target word with only the first matching part search target word that needs to be compared by reading the order information from the order information storage unit, Find a place where they match,
A data comparison apparatus characterized by that. In the data comparison device according to any one of claims 1 to 3,
The word included in the first data string and the second data string is a hash value obtained by applying a hash function to block data obtained by dividing the comparison target data that is the source of each data string into a predetermined size. Having
A data comparison apparatus characterized by that. A program for causing a computer to execute a process of comparing a first data string and a second data string each consisting of a plurality of words,
A first matching point search target word obtained by skipping the word included in the first data string by a predetermined first selection interval (the first selection interval is an integer of 1 or more); and the second data string A second matching point search target word obtained by skipping the included words by a predetermined second selection interval (the second selection interval is an integer of 1 or more) is sequentially compared to search for a point where both match. The matching point search process,
Based on the word of the matching part detected in the matching part search process, the word connected before and after the first data string and the second data string, respectively, between the first data string and the second data string. A common part search process in which comparison is performed and a range in which both coincide with each other is detected as a common part range;
A difference information output process for outputting difference information between the first data string and the second data string based on information on a range of the common part detected in the common part search process;
A program for causing a computer to execute the process.

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