JPH11306194A - Method for calculating hash value of character string and machine-readable recording medium where program for implementing same method is recorded - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calculating method for the hash value of a character string which is partial in the appearance frequency of the arrangement of characters. SOLUTION: This method includes a step 252 wherein a machine-readable table for uniquely relating a specific character string to a shorter character string after conversion is prepared, steps 256 and 268 wherein a character string appearing in a character string to be processed is converted to a corresponding character string by referring to the table by using a computer, and a step 260 wherein the hash value is calculated according to the character string to be processed which includes the converted character string by using the computer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of calculating a hash value for a character string, and more particularly, to a method of calculating the access history of a homepage or the like on the so-called Internet WWW (World Wide Web), by using the URL (U
The present invention relates to a method for efficiently calculating a hash value by using a computer when storing the hash value in a storage area determined using a hash value calculated from an H.niform Resource Locator.

[0002]

2. Description of the Related Art As a program for browsing a home page on the Internet WWW, a program called a browser is known. In order to browse a desired homepage using a browser, basically, the URL of the homepage is given to the browser. Usually, a browser accesses a predetermined resource on the Internet according to a given URL, and displays, for example, a homepage on a monitor of a computer on which the browser is operating.

[0003] The URL is a combination of the name of a server that manages a home page and the file name of the home page in the server with the name of a protocol used for access. For example, "http://www.sharp.co.
jp / sc / zaurus / index.html ”,“ htt
p: ”is the protocol name (http (hypert
ext transfer protocol)), “//www.sharp.co.jp” represents the server name, and “/sc/zaurus/index.html” represents the file name (including the file path). Is shown.

[0004] A server name usually includes a name (such as www or ftp) according to a service provided by the server, and
It consists of the domain name where the server exists. The domain name is a name (unique on the Internet) given to a partial network constituting a network (the Internet in this example). In the above example, “www” indicates a server that provides a www service according to the http protocol, and “sharp.co.jp” indicates a domain name.

By the way, when the number of computers connected to the Internet increases and the traffic on the Internet increases, there is a possibility that the communication speed decreases and good services cannot be provided. Also, from the point of view of individual users who use the browser, if they try to access the homepage once accessed and displayed again without a long interval, take the same time as the first time to download the homepage. Reaccessing is problematic in terms of response.

[0006] Therefore, a general browser saves the file of the homepage once accessed as a cache file together with the URL history in a storage device (typically, a fixed disk) of a computer on which the browser operates. ing. And again the same URL
Is given in the cache file,
A check is made to see if there is a match with L. If there is, the file in the cache file is accessed and displayed without accessing a remote server. Only when there is no match with the URL in the cache file, the URL on the Internet is accessed and displayed, and saved as a cache file.

By having a cache file, an increase in traffic on the Internet is prevented, and a user can obtain a good response. There are various methods for maintaining the contents of the cache file, but the details are not described in detail here because they are not directly related to the present invention.

There are various methods for storing a file on a fixed disk. Generally, when a certain URL is given, it is necessary to quickly search for a file corresponding to the URL. The method of accumulating the history of the cache file is naturally limited. For example, as a history, a set of the URL of each file and its storage address is simply stored in the history list in order, and each time a URL is given, the history list is checked from the beginning to determine whether there is a matching URL. The viewing method has a problem that as data increases, the average time required for the data increases. Therefore, conventionally, a method is generally employed in which a history list is divided into two stages using a hash value calculated from a URL of a file according to a predetermined calculation formula.

In this method, a hash value is calculated from a given URL. The calculation of the hash value is typically m
An od operation is used to classify URLs into a plurality of groups based on their hash values. For example, the characters Ui (i
= 1... N) represents the i-th character of the URL character string, and the variable SUM is calculated as follows.

It is assumed that SUM = 0 as an initial value. The following calculation is repeated for i = 1 to n.

[0011]

When the calculation is completed up to SUM = SUM × 5 + Ui i = n, the lower 32 bits of SUM are used as a hash code (hash value). By using only the lower 32 bits as a hash code, a mod operation is performed, and the URL is classified based on the hash code.

Each URL is allocated according to the hash code thus calculated. That is, the history list is a list of each hash code, and the URL having the hash code is linked to each hash code as a sublist. To each URL, a storage address of a file corresponding to the URL on a fixed disk is added.

Given a URL, the hash code is first calculated according to the above equation. Then, the sub list linked to the calculated hash code in the history list is traced, and the target URL is included in the sub list.
Checks if exists. If the URL exists, the fixed disk is accessed using the storage address assigned to the URL, and a target file is extracted and displayed. If not, the target URL is accessed on the Internet as if it does not exist in the history.

By using such a two-stage history list, character string comparison for URL search can be performed at most.
Since this is the number of elements of the sublist linked to one hash code, the number of comparisons is greatly reduced as compared with the case where the histories are sequentially stored.

[0015]

When such a classification using a hash is used, it is desirable that the number of URLs having the hash code value is equal for each hash code. However, it has been found that there is a problem that URLs are not uniformly classified even if a hash code is used. This is due to the following factors.

The URL is a combination of the protocol name, the server name, and the file name as described above. However, the types of protocols are limited and especially when accessed by a browser program, in most cases, ht
Since the tp protocol is used, almost all portions of the URL character string representing the protocol are "http: //". If the same character string is in the same part in the URL, the hash code obtained from this part will be the same when calculated according to the above equation.

In many cases, the head of the server name is usually fixed to a character string representing each service. For example, "www". Then, even in this part, no difference occurs in the calculation of the hash code.

Further, the URLs of data existing in the same domain are mostly the same, and there are many cases where only a part is different. In the first place, within the same domain, U
The domain name portion of the RL is the same. Also in this case, no difference occurs in the calculation of the hash code.

As a result, there is a bias in the arrangement of characters appearing in the character string of the URL.
There is a problem that the classification of L is also biased.

As described above, when the URL classification is biased, it is necessary to compare a given URL character string with a large number of URL character strings having the same hash code as the hash code calculated for the URL. . In this case, the character string is compared with the next URL character string only when a mismatch is found by sequentially comparing the character strings from the beginning. However, for example, URL character strings of data belonging to the same domain are mostly equal from the beginning, and different parts are often only the last few characters. In such a case, many characters from the beginning are compared. Since the difference is recognized only at the part near the end, it is necessary to repeat the comparison of each character many times for each URL character string. Therefore, when the variation due to the hash code is not performed efficiently, the search becomes inefficient because the number of URLs to be compared increases.

In order to avoid this, it is necessary to make the hash code for calculating the hash code more complicated so that the hash codes are efficiently dispersed. However, even in this case, it is not possible to solve the problem that a character string to be compared becomes longer when directly comparing in the same hash code. Further, if the function is complicated, the time required for the processing also becomes longer.

These problems are caused by the URL of the Internet.
The problem is not limited to browsers for caching data, but also occurs when data storage locations having similar properties are determined by hashing. When such hashing is performed, it is preferable that the memory area necessary for the hashing be saved as much as possible and that the hashing calculation can be performed at high speed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hash value calculation method for a character string, such as a URL, in which hashing can be efficiently performed on a character string in which the appearance frequency of a character sequence is biased. To provide.

[0024]

According to a first aspect of the present invention, there is provided a method of calculating a hash value for a character string to be processed in which a character sequence appears at an uneven frequency,
Preparing a machine-readable table for uniquely associating a specific character string with a shorter-length converted character string; and, using a computer, converting the character string appearing in the character string to be processed into a table. Referencing and converting to a corresponding converted character string; and using a computer to calculate a hash value based on the processing target character string including the converted character string.

The character string length after conversion is shorter than that before conversion. Therefore, the calculation of the hash value can be performed at high speed, and the capacity of the area for storing the character string can be reduced. If the hash values are the same, the character strings need to be directly compared. However, since the converted short character strings are to be compared, the comparison can be performed at high speed.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the step of preparing a table includes the step of preparing a character string to be processed that has appeared in the past in a computer. And, using a computer, totalizing the number of appearances and the character string length of each of the partial character strings of the processing target character string that appeared in the past. Based on the totaled number of appearances and the character string length, Among the partial character strings of the processing target character string that appeared in the above, select the partial character string that can most efficiently compress the processing target character string that appeared in the past when it was replaced with a predetermined character, and added it to the table And a step of recalculating the number of appearances in consideration of the selected partial character string, and repeating the step of adding until a predetermined condition is satisfied.

For a character string to be processed that has appeared in the past,
By compiling the number of appearances of the partial character string and the character string length, the compression amount obtained when each partial character string is replaced with a predetermined character string can be calculated. By selecting a character string to be listed in the table based on the amount of compression, the character string to be processed can be effectively compressed and a hash can be calculated.

A recording medium according to a third aspect of the present invention is a machine-readable recording medium storing a program for implementing a method of calculating a hash value for a character string to be processed in which a character sequence appears at an uneven frequency. Thereupon, the program includes a step of preparing a machine-readable table for uniquely associating a specific character string with a shorter-length converted character string, and converting the character string appearing in the processing target character string into a table. And converting to a corresponding converted character string, and calculating a hash value based on the processing target character string including the converted character string.

The length of the converted character string is shorter than that of the character string before conversion. Therefore, the calculation of the hash value can be performed at high speed, and the capacity of the area for storing the character string can be reduced.

According to a fourth aspect of the present invention, in the recording medium according to the third aspect, the step of preparing the table includes the step of preparing a character string to be processed that has appeared in the past; A step of totalizing the number of appearances and the character string length of each of the partial character strings of the processing target character string that appeared in the past, and the processing target character string that appeared in the past based on the totaled number of appearances and the character string length Selecting a partial character string capable of most efficiently compressing a processing target character string that appeared in the past when the character string is replaced with a predetermined character, and adding the selected partial character string to the table; Recalculating the number of appearances in consideration of the character string, and repeating the adding step until a predetermined condition is satisfied.

For a character string to be processed that has appeared in the past,
By compiling the number of appearances of the partial character string and the character string length, the compression amount obtained when each partial character string is replaced with a predetermined character string can be calculated. By selecting a character string to be included in the table based on the compression amount, the character string to be processed can be effectively compressed and the hash can be calculated.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] Referring to FIG. 1, a method according to a first embodiment of the present invention is a method for managing a cache file area 24 by a browser 20. The given URL is compressed according to a method described later, a hash calculation is performed on the compressed URL, and the compressed URL and its URL are compressed.
A hash record 42 consisting of a set of addresses of a cache file corresponding to L is stored in the hash memory 26
This is realized by the URL compression device 22 that performs a process of storing the URL in the hash area 40 calculated.
Although this embodiment describes management of URL access history by a browser, the present invention is not limited to this, and hashing is performed using a character string as a key, and records are stored or searched based on the hash value. It can be applied to the whole system.

The URL compression device 22 is actually realized by software executed on a computer.
A character string list 50, which is a table of character strings before and after replacement, used when replacing URLs; a list creation process 56 for constructing the character string list 50 based on the past access history file 46; The partial character string included in the URL given from the
, A character string replacement process 52 for replacing a shorter code with a predetermined code (a one-byte code in the present embodiment), and the character string replacement process 52 And a hash calculation processing 54 for maintaining and managing the hash memory 26 in accordance with the hash value obtained by the calculation.

Referring to FIG. 2, character string list 50 includes a character string to be replaced (left column) and a character string after replacement (right column), and includes 30 such sets. Things. In the example shown in FIG. 2, the character string “http: // www.” Is replaced with “1”, and the character string “http: //” is replaced with “2”.
And the character string “.co.jp. /” Is replaced with “3”, and so on.

Generally, an ordinary personal computer uses ASCII (American Standard Code for Informatio).
n Interchange) code. However, the characters actually used as characters are ASCII codes "3
2 "or more. Therefore, if codes 1 to 31 are used as codes after compression, a certain byte of the URL character string of a certain hash record 42 is replaced with the original URL.
It can be determined from the value of the code whether the character has been included in L or the code has been replaced by the character string replacement process 52. In this embodiment, 1 to 30 are used as codes after replacement.

FIG. 3 shows a URL character string before substitution of a character string using the character string list 50 (left column) and a URL character string after substitution.
An example with an L character string is shown. In FIG. 3, the portion of “http: // www.” In the character string in the left column matches the left column in the first line of the character string in FIG. According to FIG. 2, this string is AS
Replaced by "1" in the CII code. In the character string in the left column of FIG. 3, the last character string of “.co.jp /” is
In the table above, the value matches the left column of the third row, and the corresponding ASCII code is “3”. Therefore, `` http://www.sharp.co.
"jp /" is converted to "[1] sharp [3]" as shown in the right column of FIG. 3 (the code is indicated by square brackets).

After converting the partial character string into the corresponding ASCII code as much as possible with reference to the character string list 50 in this way, the hash calculation processing 54 is performed on the converted character string. Then, the URL is allocated to each hash area 40 according to the calculated hash code, and if the URL is stored, the replaced URL and the disk address of the corresponding cache file are stored in the hash area 40, and the corresponding URL is stored. In the case of searching the disk storage area of the cache file, the URL character string after the replacement is searched in the corresponding hash area 40, and the added disk address is returned to the browser 20.

By doing so, the following effects occur. First, since the hash calculation is performed on the URL after replacing the substring with the corresponding shorter code,
The character string to be subjected to hash calculation itself becomes shorter, and the calculation amount of hash calculation decreases. In particular, when a complicated hash calculation formula is selected in order to make variations in hash calculation more efficient, an increase in the amount of calculation can be suppressed. Therefore, the hash calculation can be further speeded up. Also, if you want to achieve the same variation,
Since the target character string is shortened, there is an effect that it is not necessary to use a complicated expression as a hash calculation expression.

Further, since the URL stored in the hash record 42 of the hash area 40 is a shorter character string after replacement, it is necessary to store a larger number of URLs in the hash area 40 having the same capacity. Can be. Alternatively, the capacity of the hash area 40 required to store the same number of URLs can be reduced. That is, the storage area for the hash area 40 can be effectively used.
Further, even when URL character strings must be compared in the same hash area 40, the length of the character string to be compared is short, so that the comparison can be performed at high speed.

As described above, the URL compression device 22 is actually realized by software executed on a computer such as a personal computer or a workstation. FIG. 4 shows the appearance of a computer that realizes a method of calculating a hash value for a character string. Referring to FIG. 4, this computer 120 has a CD-ROM (Compac
t Disc Read-Only Memory) Drive 144 and FD
(Flexible Disk) A computer main body 130 having a driving device 142, a monitor 148, and a printer 146.
, A keyboard 136, and a mouse 134.

FIG. 5 shows the configuration of the computer 120 in a block diagram form. As shown in FIG. 5, the computer main unit 130 includes an FD driving device 142 and a CD-R.
In addition to the OM drive device 144, a CPU 132 (Central Processing Unit), a memory 138, and a fixed disk 140 are connected to each other by a bus. CD-
The CD-ROM 152 is mounted on the ROM drive 144. The FD 150 is mounted on the FD driving device 142.

As described above, the method of calculating the hash value for this character string is based on computer hardware, C
This is realized by software executed by the PU 132. Generally, such software is a CD-RO
The CD-ROM drive 144 or the FD drive 1 is stored in a storage medium such as M152 or FD150 and distributed.
Fixed disk 1 read from the storage medium
40 temporarily stored. Further, the data is read from the fixed disk 140 to the memory 138 and executed by the CPU 132. The hardware itself of the computer shown in FIGS. 4 and 5 is general. Therefore, the most essential part of the present invention is the software stored in the storage medium such as the CD-ROM 152, the FD 150, and the fixed disk 140.

Since the operation of the computer itself shown in FIGS. 4 and 5 is well known, detailed description thereof will not be repeated here.

Referring to FIG. 6, the details of list creation processing 56 shown in FIG. 1 will be described. In the apparatus according to the present embodiment, a character string list 50 which is a table for uniquely associating a character string before replacement with a character string after replacement is created from the past access history file 46. This is because it is considered that the character string list 50 can be created so that the efficiency of the replacement of the character string of the URL is maximized by using the history. However, when the access history file 46 cannot be prepared, the character string list 50 may be manually created theoretically. Alternatively, a character string list 50 created from access histories at other sites may be used. String list 5
The character string list 50 may be prepared so that 0 can be replaced with short data as long as possible in a URL referred to by the browser 20 with relatively high frequency.

In this embodiment, the character string list 50 is used.
In order to prepare the character string list 50, the list creation processing 56 is performed based on the access history file 46 only once at the first time based on the access history file. You may try again. However, in this case, it is needless to say that the contents of the hash memory 26 created based on the character string list 50 before re-creation must be re-created according to the character string list 50 after re-creation.

Referring to FIG. 6, first, the number of appearances of the partial character strings in the URL is totaled for each partial character string (20).
0). At this time, not only the URL is used as a unit, but also the URL
The number of times each character string appears in the access history file 46, including the partial character strings included in L, is counted together with the length of each character string. Since the length of the partial character string to be totaled need only be longer than the length of the code after the replacement, in this embodiment, all the partial character strings of three or more characters are totaled. As a result of the tallying, the character string of three or more characters, the character string length of the character string, and the number of appearances of the character string in the access history file 46 are all totaled.

Subsequently, 0 is substituted for the variable i (202).
The variable i is a variable for counting the number of character strings listed in the character string list 50, and its initial value is substituted here.

Next, 1 is added to the variable i (204), and the value of the variable i is larger than a predetermined number (30 in the present embodiment) as the maximum number of character strings in the character string list 50. It is determined whether or not it is (206). If the judgment result is YES
If so, the process ends. If the determination result is NO, the control proceeds to step 208.

In step 208, a partial character string that provides the highest compression effect is selected from the tabulation table obtained in step 200. The compression effect is obtained, for example, according to the following equation.

[0050]

## EQU2 ## Total compressed length = (character string length-size after compression) .times. Number of appearances A partial character string having the largest total compressed length calculated in this way is selected in step 208 and added to the character string list 50 in step 210. I do. Then, this partial character string is deleted from the original tabulation table (212). For example, if the summary table is
Consider the case as shown in FIG. in this case,
The largest total compression length calculated according to the above equation is "http: // www" (total compression length = (10-
1) × 800 = 7200). Therefore, "http: // ww
"w" is added to the character string list 50 and deleted from the summary table.

At this time, since the partial character strings are deleted, the character strings included in the deleted partial character strings among the character strings in the original totaling table are also respectively included in the partial character strings. The number of appearances is subtracted by the number of occurrences of, and the summary table is recalculated (214). In the example shown in FIG. 7, "http: //" is a partial character string of "http: // www" and is listed in the table of FIG. "Http: // ww
Since the number of appearances of “w” was 800 according to FIG. 7,
The number of occurrences of “http: //” is 80 from the original “900”
It becomes “100” obtained by subtracting 0 (FIG. 8).

After recalculating the summary table in this manner, the control returns to step 204.
The steps up to 14 are repeated until the processing is completed by the judgment of step 206. Of course, if there is no character string remaining in the tally table during this process, the process may be terminated at that point.

Next, a process for storing a URL will be described with reference to FIG. First, the URL and the disk address of the cache file corresponding to the URL are received from the browser 20 (250). Next, the character string list 50 is read (252).

Hereinafter, whether or not there is a character string that matches each line of the character string list 50 will be compared from the beginning of the URL character string. First, in step 254, it is determined whether the character to be processed is the last character. If it is the last character, the above-described comparison ends, and control proceeds to step 260. Step 260 and subsequent steps will be described later.

If it is determined in step 254 that the character to be processed is not the last character, in step 256, any of the character strings starting with this character is displayed in the character string list 5.
It is determined whether any one of the character strings of 0 matches. If they do not match, the processing target is advanced to the next character, and control returns to step 254. If there is a match, the character string is replaced with a code indicated as corresponding to the character string in the character string list 50 (258). Thereafter, the processing target is advanced to the next character, and control returns to step 254. In this way, the character strings in the input URL are sequentially replaced with codes.

When the result of the determination in step 254 is YES, the input URLs to be replaced with the codes have been replaced, and are considerably shorter than the original URL length. In this case, step 260
Then, the URL in which the character string is converted into the code in this way
The hash is calculated based on The hash calculation formula in this case may be as described above, or may be more complicated in order to make variations more uniform. Since the URL character string to be calculated is shorter than the original URL character string, hash calculation can be performed at high speed. Therefore, even if the hash calculation is complicated, the processing speed does not increase unduly.

The hash area 40 in which the URL is to be stored is selected based on the hash code calculated in this manner, and the URL after the replacement as the last record in the area and the disk of the cache file corresponding to the URL are selected. The address is additionally stored (or updated) (262).

With reference to FIG.
Processing for searching the hash memory 26 in response to the input of L will be described. In FIG. 10, the same processes as those in FIG. 9 are denoted by the same step numbers. Since the processing performed in each of these steps is the same, the description will not be repeated here. FIG. 10 differs from FIG.
Instead of step 262, the hash area 40 determined according to the hash code is accessed to
Step of checking whether or not L exists (270)
And step 272 of performing a process of returning the disk address added to the URL to the browser 20 when the URL exists, and returning information indicating that the URL does not exist to the browser 20 when the URL does not exist. It is provided.

By the processing shown in FIG. 10, when the URL is present in the cache file area 24, the browser 20 can access the cache file according to the returned disk address. The UR
If L does not exist in the cache file area 24, the URL is accessed again via the Internet. [Second Embodiment] In the first embodiment described above, 1 to 30 are used as character codes after replacement. However, it is considered that the hash calculation can be made more efficient if a larger number of character strings can be replaced. Also in this case, it is desirable that a replacement character string common to all users can be determined and operated separately from what is set for each user. Therefore, in the second embodiment, the character string table for common replacement and the character string table for each user are separated. However, the software is the same as that in the first embodiment, except that these two types of character string lists are used. Therefore, only the details of the character string list will be described below.

FIG. 11 shows an example of a replacement character string list used in the second embodiment and commonly used by a plurality of users. FIG. 12 shows an example of a replacement character string list used for each user.

As described above, in a system using the ASCII code system, codes 0 to 31 are not usually used. Therefore, in the first embodiment, A
The SCII code was used as the replacement code. However, in this case, there are only 32 types of character codes that can be used as character codes after replacement, from 0 to 31 at the maximum.
This alone is not enough to define replacement strings for each user in addition to the common ones.

Therefore, in the second embodiment, as in the first embodiment, 1 to 30 are used as the post-replacement character codes of the common replacement character string list (see FIG. 11), and the characters for each user are used. In the column list, the ASCII code "31" is used as an escape code, and the code "31" and one byte thereafter are used to indicate the user-defined character code after replacement (see FIG. 12). By using the escape code in this manner, the range of the subsequent character codes is not limited, and therefore, the user-defined character string after replacement is changed from the code “31 + 0” to the code “31 + 255”.
Up to 256 types can be used, and efficient URL management can be performed according to the situation of the user.

FIG. 13 shows an example of a set of character strings before and after replacing the URL character string using the character string lists shown in FIGS. 11 and 12. The character string “http://www.sharp.co.jp” in the URL shown on the first line in the left column of FIG. 13 appears on the first line in the left column of FIG. The corresponding character code is "0", and an escape code "31" is required before it. The remaining character string “/index.html” in FIG. 13 appears in the last line of FIG. 11, and the corresponding character code is “30”. Moreover, in this case, no escape code is required. Therefore, "http: // w
ww.sharp.co.jp/index.html ”will be replaced with“ [31] [0] [30] ”. The result is shown in the right column of the first row in FIG.

The same applies to the second row in FIG. However, in this case, the character string “slab.tnr” cannot be replaced, and thus remains in the right column. Also in this case, since codes 1 to 31 which are not usually used are used as the replaced character strings, it is possible to distinguish the replaced character strings from the unreplaced character strings.

According to the second embodiment, the same effects as those of the first embodiment can be obtained, and the URL can be more flexibly managed according to the situation of the user. In addition, since the number of character codes that can be used as a character string after replacement increases, more efficient URL management can be performed. [Third Embodiment] In each of the first and second embodiments, an unused ASCII code is assigned to a character string after replacement.
However, the invention is not so limited. For example, as in the third embodiment, a two-digit number ("00" to "99") can be used as a character string after replacement. In other words, the character string before the replacement can be restored from the character string after the replacement (that is, the replacement character string and the code after the replacement are uniquely associated), and the character string length after the replacement is definitely shorter than that before the replacement. This means that any character string may be used as the character string after the replacement.

In the third embodiment, as shown in FIG. 14, a two-digit number is used as a character string after replacement. Each number itself is a commonly used ASCII
No change from the numbers in the code. In this case however,
It is necessary to distinguish between the two-digit number that is the character string after the replacement and the original number. Therefore, in the third embodiment, all original one-digit numbers are represented by two-digit numbers, and the upper one digit in that case is set to "0" (the right column in FIG. 14). reference). That is, the one-digit number is replaced with a two-digit number that is equal to the upper one digit but equal to the original digit with the lower one digit being “0”.

By defining such a rule, if a numeral is found in the character string after replacement, it is handled two digits at a time and the original character string is restored by referring to the right to left columns of FIG. can do.

FIG. 15 shows an example of replacement of a character string (URL) using the character string list shown in FIG. 1 in FIG.
Of the character strings shown in the left column of the line, "http: // www."
Is replaced with “10” from FIG. "Sharp" is "5
0 ". “.Co.jp /” is replaced with “12”. Therefore, the whole is “105012”.

In the character string shown in the left column of the second line of FIG. 15, “http://www.sharp.co.jp/” is replaced with “105012” as described above. Then "zaurus /
Cannot be replaced, but the subsequent "index"
To “13”, “0” to “00”, “.html”
Is also replaced by "14", respectively. Therefore, the whole is “105012zaurus / 13001”
4 ".

As described above, various methods are conceivable as to what to do with the character string after replacement. In essence, the replacement string should be such that the replacement replaces as many URLs as possible with the shortest possible string, and the original URL is definitely derived from such a replaced string. Should be determined.

In the third embodiment, since a one-digit number is replaced by a two-digit number, a character string may be partially long. However, for example, a very long character string that frequently appears can be replaced with only two digits, so that the URL character string can be shortened and compressed as a whole similarly to the first and second embodiments. it can. Since the hash calculation is performed on the URL thus compressed, the amount of calculation is small, the area of the hash memory is small, and the direct comparison of character strings in the case of the same hash code value is also possible. Since the target character string itself is short, it is possible to achieve an effect that high-speed operation can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a URL compression apparatus for implementing a method according to a first embodiment of the present invention, together with surrounding elements.

FIG. 2 is a diagram schematically showing a character string list 50;

FIG. 3 is a diagram schematically showing URLs before and after replacement.

FIG. 4 is an external view of the computer shown in FIG. 5;

FIG. 5 is a block diagram of a computer for realizing the method according to the first embodiment of the present invention.

FIG. 6 is a flowchart illustrating an outline of a list creation process 56;

FIG. 7 is a diagram schematically illustrating an example of an aggregation table before recalculation;

FIG. 8 is a diagram schematically illustrating an example of a tabulation table after recalculation.

FIG. 9 is a flowchart of a URL storage process.

FIG. 10 is a flowchart of a URL search process.

FIG. 11 is a diagram schematically showing a common character string replacement table used in the method according to the second embodiment of the present invention.

FIG. 12 is a diagram schematically illustrating a user-defined character string replacement table used in the method according to the second embodiment of the present invention;

FIG. 13 is a diagram schematically illustrating URLs before and after character string replacement by the method according to the second embodiment;

FIG. 14 is a diagram schematically showing a user-defined character string replacement table used in the method according to the third embodiment of the present invention.

FIG. 15 is a diagram schematically illustrating URLs before and after character string replacement by a method according to a third embodiment;

[Explanation of symbols]

 Reference Signs List 20 browser 22 URL compression device 24 cache file area 26 hash memory 46 access history 50 character string list 52 character string replacement processing 54 hash calculation processing 56 list creation processing

Claims (4)

[Claims] 1. A method for calculating a hash value for a character string to be processed in which a sequence of characters appears at a biased frequency, wherein a specific character string is uniquely associated with a converted character string having a shorter length. Preparing a machine-readable table of the following: using a computer, converting a character string appearing in the character string to be processed into a corresponding converted character string with reference to the table; Calculating a hash value based on the processing target character string including the converted character string. 2. The method according to claim 1, wherein the step of preparing the table includes a step of preparing, in a computer, a processing target character string that has appeared in the past, and the number of appearances of each of the partial character strings of the processing target character string that has appeared in the past. And summing the character string length using a computer.Based on the counted number of appearances and the character string length, replace with a predetermined character among the partial character strings of the processing target character string that appeared in the past. Selecting a partial character string capable of most efficiently compressing the processing target character string that appeared in the past and adding it to the table; and considering the selected partial character string, 2. The method for calculating a hash value for a character string according to claim 1, further comprising: recalculating the number of times, and repeating the adding step until a predetermined condition is satisfied. 3. A machine-readable recording medium recording a program for implementing a method of calculating a hash value for a character string to be processed in which a character sequence appears at a biased frequency, wherein the program comprises a specific character string Preparing a machine-readable table for uniquely associating a converted character string with a shorter-length converted character string; and converting a character string appearing in the processing target character string into a corresponding converted character string by referring to the table. A machine-readable record that records a program that implements a method of calculating a hash value for a character string, the method including a step of converting the character string into a string, and a step of calculating a hash value based on the processing target character string including the converted character string. Medium. 4. The step of preparing the table includes the steps of: preparing a processing target character string that has appeared in the past; and the number of appearances and the character string of each of the partial character strings of the processing target character string that has appeared in the past. Summing the length, and, based on the counted number of appearances and the character string length, among the partial character strings of the processing target character string that appeared in the past, when the character string was replaced with a predetermined character, the character string appeared in the past. Selecting a partial character string capable of most efficiently compressing the processing target character string and adding it to the table; recalculating the number of appearances in consideration of the selected partial character string; And a step of repeating the adding step until a predetermined condition is satisfied. The machine-readable program storing a program for implementing a hash value calculation method for a character string according to claim 3. Recording media.