JP3186530B2 - How to compress and expand computer data - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for storing computer data in an external storage medium such as a magnetic disk or a magnetic tape, or a method for transferring data between computers, and more particularly to a method for compressing data for improving storage efficiency and transfer efficiency. It relates to a decompression method.

[0002]

A conventional data compression / expansion method is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 5-260097 and 3-162134. When the same code of 1 byte or 2 bytes repeatedly appears in the communication data, the same code in the data is repeated with the control code indicating compression, the count byte indicating the number of times the same code is repeated, and the repeated code. This is a continuous character compression process in which the data is compressed by representing a portion that appears repeatedly, and when decompression is performed, when the compression control code is detected, the same code count byte is repeated to restore the original data.

In addition, since the same code is repeatedly determined in order of one byte or two bytes, the use of the computer central processing unit is increased and the effect of data compression is offset. was there.

As described above, the conventional data compression / expansion method focuses on continuous character compression in a record. Depending on the type of data, only a low-efficiency compression ratio can be obtained. Since the method for determining the appearance of continuous characters is performed by the data sequential search method, the load on the CPU of the computer is increased. Therefore, the applicable range is narrowed.

In general, the data compression / decompression process requires a high CPU usage rate because data is sequentially searched for characters.
Therefore, if the compression ratio is not increased significantly, useless computer resources are used, and the object of reducing computer running costs cannot be achieved.

The present invention solves such a problem, and in order to increase the data compression rate, compression means taking into account the characteristic that data is redundant also between records, two consecutive steps, the same character between records It is an object of the present invention to provide a data compression / expansion method having efficient character search means for performing column determination, means for preventing duplication of compressed data, and the like.

That is, the method of compressing computer data according to the first aspect of the present invention is characterized in that there is data redundancy not only within the same record but also between different records in order to improve the data compression rate. It is an object of the present invention to provide a data compression method of computer data in consideration of the above.

The computer data compression method according to the first aspect of the present invention includes efficient character search means for performing the same character string determination between continuous characters and records in two stages in order to improve the efficiency of data compression processing. An object of the present invention is to provide a data compression method for computer data.

Further, claim 2 , claim 3 , and claim 4
The object of the present invention is to provide a computer data compression method including means for preventing double compression of compressed data.

[0010]

[0011]

According to a first aspect of the present invention, there is provided a computer data compression method for compressing data to be stored in an external storage medium of a computer before storing the data in the external storage medium by an external instruction parameter. A compression method and a data compression method for compressing communication data in a data transfer process between computers before data transfer using an externally designated parameter, wherein a first compression process for compressing the same character string between different records is performed. And performing a second compression process of compressing a continuous character string in the same record.

[0012] The step of performing a pre-Symbol first compression process,
Determining the same character string between records in a plurality of bytes as a first step, and determining the same character string between records in a byte as a second step if the results of the determination do not match; Compressing the same character string when the same character string exists as a result of the processing, the step of performing the second compression processing includes, A step of performing a determination; and a step of determining a continuous character string in the same record in byte units as a second step if the result of the determination does not match. Compressing the continuous character string.

[0013] The method of compressing computer data according to claim 2 is a method of compressing computer data according to claim 1, of 1 second of data was performed first compression processing or the second compression The method further includes a step of adding a predetermined code to a plurality of leading bytes of the record.

According to a third aspect of the present invention, there is provided the computer data compression method according to the second aspect , wherein the first plurality of bytes of the first data to be compressed is determined. If the code is not the predetermined code, a compression process is executed, and if the code is the predetermined code, the compression process is stopped.

According to a fourth aspect of the present invention, there is provided the computer data compression method according to the third aspect , wherein the plurality of bytes are four bytes, and the predetermined code is ALL "1F". It is characterized by the following.

[0016]

[0017]

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, an embodiment of the compression method will be described.
With reference to FIG. 1, in the method of compressing computer data according to claims 1 to 5 of the present application, arguments when reading a compression processing program from an application program requesting data compression processing will be described. In the compression process, the compression process is requested by designating the inter-record compression process, the necessity category (C1) of the continuous character compression process, and the data to be compressed (C5) according to the data characteristics.

Referring to FIG. 3, claims 1 to 1 of the present application will be described.
A block flowchart showing a processing procedure of a main routine of a compression processing program in the computer data compression method described in 4 will be described. Necessity of compression processing specified by application program (C
1), inter-record compression processing (S3 to S5), continuous character compression processing (S7 to S9), and both compression processing (S1 to S5)
0 to S15) are repeated until the end of the data (C5) to be compressed. In the main routine of the compression processing program,
3 byte check (S3 or S
If 10) is continuous character compression, a 4-byte check (S
7 or S13), a subroutine for inter-record compression / continuous character compression is called when the number of stored digits of the compression control code (described later in FIGS. 6 and 7) is larger, and compression processing is performed. In the inter-record compression / consecutive character compression subroutine, if there is no match in the inter-record / consecutive character comparison, the process returns to the main routine, and the character is transferred to the output buffer (C6) in a compressed format.

At the beginning of the main routine of the compression processing program, it is determined whether the compression processing is the first compression processing (S30). If the processing is the first processing, the first four bytes of data (C5) to be compressed are ALL. It is determined whether it is “1F” (S3
1). If ALL is "1F", double compression is performed, error processing (S33) is performed, and the processing ends. ALL
If it is not "1F", it is normal, so ALL "1F" (4 bytes) indicating compressed data is transferred to the output buffer (C6). It should be noted that "1F" is data that does not exist much in ordinary data, and that even if it is treated as a binary number, if there are 4 bytes, there will be almost no continuous characters of "1F" as data. ing.

Referring to FIG. 4 and FIG. 5, a block flowchart showing a processing procedure of an inter-record compression processing subroutine and a continuous character compression processing subroutine in the computer data compression method according to claims 1 to 4 of the present application. Will be described. In order to suppress the usage rate of the computer central processing unit in the comparison in the compression processing, a 10-byte check (S17) in the inter-record compression processing and a 5-byte check (S24) in the continuous character compression processing are first compared with a large number of digits. If they do not match, a one-byte check is performed (S20 and S27). When the one-byte check indicates a mismatch, the output processing (S22 and S29) of the compressed character, the compression control code, and the number of compressed characters to the output buffer (ARG-6) is performed. The purpose of first determining the same character string and the continuous character string in a plurality of bytes is to reduce the number of times the same character string and the continuous character string are determined, but 5 bytes and 10 bytes are values based on empirical values. In the performance evaluation result of the compression processing, the CPU performance is improved. If this value is too large, the result will be inconsistent in the determination of the same character string or continuous character string, and the determination processing will be performed on a byte-by-byte basis, and the effect of reducing the number of determinations cannot be obtained.

Referring to FIG. 6 and FIG. 7, an outline of the inter-record compression subroutine and the continuous character compression subroutine in the computer data compression method according to the first to fourth aspects of the present invention will be described. 6 and 7 provide a supplementary description of the block flowcharts of FIGS. 4 and 5.

FIGS. 6 and 7 also serve as explanatory diagrams of a compression control code storage method. In the case of inter-record compression, a compression control code (1 digit), two digits of the number of compressed characters (1 digit), and continuous character compression are used. Is composed of three digits: a compressed character (one digit), a compression control code (one digit), and the number of compressed characters (one digit).

The outline of the inter-record compression processing will be described with reference to the data of the n-th record and the (n + 1) -th record shown in FIG. First, the first three bytes are compared in (1),
Since they match in (2), compression between records is performed. (3)
The first 10 bytes are compared with each other, and since they do not match in (4), a 1-byte check is performed. In (5), a mismatch occurs in the second one-byte check, and in (6), an inter-record compression control code and ("1E" 4) representing the number of characters are output.
In (7), continuous character compression processing is performed from the fifth byte. 5
Compare 4 bytes from the byte. Since they did not match in (8), a one-byte check is performed, and in (9), no match occurs in the fourth one-byte check. Since neither inter-record compression nor continuous character compression can be performed in (10), ddd is directly transferred to the output buffer. Note that the same processing as (1) to (10) is performed for the hii of 8 to 10 bytes. Return to the process of (1) in (11) and return to the top 3
The bytes are compared, and since they match in (12), compression between records is performed. In (13), the 10th byte from the 11th byte is compared.
Compare bytes. Since they did not match in (15), 21
Check 1 byte from the byte, 1 in (16)
A mismatch occurs at the tenth byte check. (17) represents the inter-record compression control code and the number of characters (“1E” 1
9) is output. At (18), the same determination is made for the remaining one byte, and the result is output without compressing one byte. The reason why the three bytes are compared first is that the compression effect between the records cannot be obtained unless the storage method of the inter-record compression control code and the number of digits is two bytes or more.

With reference to FIG. 8, a special process at the time of compression will be described. Compression control code ("1E" or "1F")
When the compressed data and the compressed data match, it is impossible to determine the control code in the decompression process. Therefore, the determination can be made by inserting an auxiliary code (“0C”). That is, the compression control code (“1E”, “1F”) and the auxiliary code (“0
C "), the data is output with an auxiliary code (" 0C ") added one byte before. Referring to FIG. 9, in the inter-record compression processing and the continuous character compression processing, A description will be given of a control code storage method in the case where the number of compressed characters exceeds the maximum number of stored characters (one digit) of 255. One compression is performed in units of 255 bytes, and a case of compression exceeding 255 bytes. Is output in units of 255 bytes.

Next, an embodiment of the decompression method will be described.
Referring to FIG. 2, in the process of elongation computer data, it will be described argument when calling the decompression processing program from the application program requesting the data decompression processing. A decompression process is requested by specifying a decompression condition (E1), data to be decompressed (E5), and the like.

[0028] With reference to FIGS. 10 and 11 describes a procedure of the decompression process the main routine in extension method co Npyu <br/> Tadeta. Data to be expanded (E
5) to search for the compression control code (“1E” or “1E”).
F "), and an inter-record decompression process and a continuous character decompression process are performed.

Referring to FIG. 10, the inter-record decompression process will be described. When the compression control code "1E" appears, the decompression process is performed using the following method. That is,
When the compression control code is detected, the next one byte is recognized as the number of characters in the binary expression. Next, the number of characters is output from all records (ARG-4) to the output buffer (ARG-6).
Transfer to

Referring to FIG. 11, the continuous character decompression process will be described. When the compression control code "1F" appears, the decompression process is performed using the following method. That is,
When the compression control code is detected, the next one byte is recognized as the number of characters in the binary expression. Next, at this point, the character (compressed character) output to the output buffer (ARG-6) last is recognized. Next, the number of characters and the compressed characters are transferred to the output buffer (ARG-6).

With reference to FIG. 12, special items of the decompression process will be described. When the supplementary code (“0C”) is detected in the continuous character decompression process and the character transfer process, the character is skipped and the next character is treated as data. However,
The auxiliary code ("0C") is skipped only once.

[0032]

As described above, the computer data compression method according to claim 1 of the present application performs the same character compression processing between different records in addition to the conventional continuous character compression processing within the same record. Can significantly increase the compression ratio of computer data. Therefore, effective use of computer resources (central processing unit, magnetic disk, data communication equipment) can be achieved, and cost can be reduced.

[0033] According to the method of compressing computer data according to claim 1, the method of searching the computer data to be compressed in stages, to provide a method of compressing computer data to perform efficient compression Can be.

[0034] Further, claim 2 , claim 3 , and claim 4
According to the method for compressing computer data described in ( 1 ), in addition to the effect of the invention described in claim 1 , it is possible to provide a method for compressing computer data that prevents double compression.

[0035] According to or computer method decompressed data, and decompresses the data compressed by the compression method computer data according to any one of claims 1 to 4, can be restored to the original data . Therefore, it is possible to restore the original compressed data for use.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of arguments when a compression processing program is called from an application program in an embodiment.

FIG. 2 is an explanatory diagram of arguments when a decompression processing program is called from an application program in the embodiment.

FIG. 3 is a block flowchart showing a processing procedure of a main routine of a compression processing program in the embodiment.

FIG. 4 is a block flowchart showing a processing procedure of an inter-record compression processing subroutine in the embodiment.

FIG. 5 is a block flowchart showing a processing procedure of a continuous character compression processing subroutine in the embodiment.

FIG. 6 is an explanatory diagram of an outline of processing contents of an inter-record compression processing subroutine and a storage method of an inter-record compression control code in the embodiment.

FIG. 7 is an explanatory diagram of an outline of processing contents of a continuous character compression processing subroutine and a storage method of a continuous character compression control code in the embodiment.

FIG. 8 is an explanatory diagram of special treatment in compression processing and character transfer processing in the embodiment.

FIG. 9 is an explanatory diagram of a control code storage method when the number of compressed characters exceeds 255 in the embodiment.

FIG. 10 is an explanatory diagram relating to an inter-record decompression process in the embodiment.

FIG. 11 is a diagram illustrating a continuous character decompression process according to the embodiment.

FIG. 12 is an explanatory diagram of a special treatment of a decompression process in the embodiment.

Claims (4)

(57) [Claims] Claims: 1. An external storage medium for a computer.
Data is transferred to the external storage medium by an external instruction parameter.
A data compression method for compressing data before storing
Externally instruct communication data in data transfer processing between data
Data compression method to compress before data transfer by parameter
Method for compressing the same character string between different records
And a second compression for compressing a continuous character string in the same record.
Performing the first compression processing , wherein the step of performing the first compression processing includes, as a first step, a step of determining the same character string between records in units of a plurality of bytes; and a step of determining the same if the result of the determination does not match. A second step of determining the same character string between records as a two-step unit and compressing the same character string if the same character string exists as a result of the determination; The first step is a step of determining a continuous character string in the same record in a unit of a plurality of bytes as a first step. performing a determination, and step that said continuous string of the determination is to compress the continuous string when the presence of including computer data Shrinkage method. 2. A method according to claim 1, further comprising the step of adding a predetermined code to the beginning multibyte first compression processing or the second 1 of the record of the data subjected to compression processing
3. The method for compressing computer data according to item 1. 3. A first plurality of bytes of data to be subjected to a compression process are determined. If the first plurality of bytes is not the predetermined code, the compression process is executed. If the first code is the predetermined code, the compression process is performed. 3. The method according to claim 2 , further comprising the step of:
3. The method for compressing computer data according to item 1. 4. The computer data compression method according to claim 3 , wherein the plurality of bytes are four bytes, and the predetermined code is ALL “1F”.