JPH0621827A - Data compressor and its method - Google Patents

Abstract

PURPOSE:To compress efficiently data of consecutive same characters such as consecutive characters of Japanese data in 2-byte codes. CONSTITUTION:A compression pre-processing section 12 converts and processes data with same consecutive characters into a sum/subtraction modulo of adjacent data or exclusive OR data as the compression preprocessing and converts it into data consecutive in the unit of bytes. Compression data 14 comprising a special character representing the compression degree, repetitive character data and repetitive number of times of the characters are obtained from a compression post-processing section 13 when some characters are consecutive by taking one-byte character of the consecutive data from the compression pre-processing section 12 as one unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data compression apparatus and method for compressing repeated characters of data consisting of 2 bytes and having consecutive identical characters such as Japanese data.

[0002]

2. Description of the Related Art In the conventional data compression method of this type, when several characters are consecutive with one byte character as one unit, a special character indicating the compression of this character, repeated character data, and repeated character data are used. The data was reduced by converting it to the number of times.

FIG. 5 shows the configuration of a conventional data compression apparatus. In FIG. 5, compressed data 1 is supplied to a compression processing section 2 and subjected to compression processing to obtain compressed data 3.
FIG. 6 shows the conversion processing procedure in FIG. In FIG. 6, first, the character counter Cc and the repeat counter Cr are set to 0 (step (indicated by S in the drawing)).
60, 61). One character is read from the original data (step 62). Thereafter, the character counter Cc is incremented by 1 (step 63). The value of the character counter Cc is compared with the read character (step 64). In the first cycle, this comparison is always true, and the read character is stored in the buffer to see if the original data consists of four or more repeated characters (step 6).
5). In the second and subsequent cycles, the character read from the original data is compared with the character stored in the buffer (step 66). If the original character is equal to the stored character, four or more same characters are repeated, so compression is performed. When the character is equal to the stored character, the repeat counter Cr is incremented by 1 (step 67), and another character is read from the original data.
If the current character is not equal to the stored character, the repeat counter Cc is compared with 4 (step 68). If the number is less, the compression is not performed because only three characters are repeated (step 69). In this way, when the repetition counter is 4 or more, the compression format is created and the compressed data string shown in FIG. 7 is obtained.

[0004]

With this conventional data compression method, it is possible to reduce the data size when the same character appears consecutively in a data string consisting of 1-byte code characters such as ASCII code. However, in a data string composed of 2-byte code characters such as a shift JIS code, even if the same character appears consecutively, the adjacent 1-byte data is not equal, so there is a problem that the data size cannot be reduced. It was

The present invention solves the problems in the prior art as described above, and a data compression apparatus and a data compression apparatus capable of efficiently compressing data in which the same character continues, for example, consecutive characters of Japanese data of 2-byte code. The purpose is to provide the method.

[0006]

In order to achieve the above object, the data compression apparatus according to the present invention of claim 1 is a pre-compression process for data in which the same character is continuous. In the case where the pre-compression processing means for converting into data and converting it into continuous data in byte units, and a case where several characters are continuous with one byte character of continuous data from the pre-compression processing means as one unit, The special character indicating the compression, the repeated character data, and the post-compression processing means for obtaining the compressed data converted into the number of repetitions are provided.

Further, in the data compression method according to the present invention, the data size is reduced as compared with the case of repeating the same character by converting the special character indicating the compression of data in which the same character is continuous, the repeated character data, and the number of repetitions. It is a data compression method, and as a pre-processing of data compression,
The addition / subtraction modulo or exclusive OR of the adjacent bytes is taken, and the repeated character of the data in which the same character continues is repeated in byte units to be determined as a character.

In the first or second aspect of the present invention, the repeated character of the data in which the same character is continuous is the continuous character of the Japanese data of 2-byte code.

[0009]

According to the data compression apparatus and method of the present invention having the above-mentioned structure, the data is converted into addition / subtraction modulo of adjacent data or exclusive OR data as pre-compression processing of data in which the same character continues, and in byte units. Data that is converted into continuous data once and the same character is continuous,
For example, consecutive characters of 2-byte code Japanese data are efficiently compressed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a data compression apparatus and method of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the embodiment. In FIG. 1, a pre-compression processing unit 12 to which compressed data 10 of Japanese data of 2-byte code such as shift JIS code is input, and thereafter, several characters are consecutive with one byte character as one unit. In this case, the special character indicating the compression of the special character, the repeated character data, and the post-compression processing unit 13 for converting into the number of repetitions are included. , The number of repetitions and the compressed data 14 are obtained.

Next, the operation of the configuration of this embodiment will be described. The compressed data 10 is 2-byte code Japanese data such as shift JIS code, for example. The Japanese data is converted by the pre-compression processing unit 12 and then converted by the post-compression processing unit 13 to obtain compressed data 14.

FIG. 2 shows a detailed processing procedure in the pre-compression processing unit 12. In FIG. 2, first, two memories for storing character data are initialized (step 20). One byte is read from the compressed data and stored in the memory 2 (step 21). This reading is judged (step 2
2) If the processing has not ended after the elapse of a predetermined time, the processing ends. If the end is Yes, the exclusive OR of the memory 1 and the memory 2 is executed, and the operation result is output (steps 23 and 24). After that, the memory 1 is updated with the contents of the memory 2 and the loop for reading the compressed data again is repeated (step 25). Through the above conversion processing, data that is not continuous in byte units is converted into continuous data.

Next, when the compressed data is restored, as shown in FIG.
The post-processing is performed subsequent to the above processing. FIG. 3 shows a processing procedure for restoring this compressed data. In FIG. 3, first, two memories for storing character data are initialized (step 30). One byte is read from the compressed data and stored in the memory 2 (step 31). This reading is judged (step 32), and if it is not completed after the elapse of a predetermined time, the process is ended. If the end is Yes, the exclusive OR of the memory 1 and the memory 2 is executed, and the operation result is output (steps 33 and 34). Then, the calculation result is transferred to the memory 1 (step 35).

By performing the above conversion, it is possible to convert data that is not continuous in byte units into continuous data as shown in FIG. 4A is the compressed data 10 input to the pre-compression processing unit 12, and FIG. 4B is the data string output from the pre-compression processing unit 12 after the pre-compression processing. FIG. 4C shows the target compressed data 14 output from the post-compression processing unit 13, which is converted into special characters indicating compression, continuous repeated character data, and the number of repetitions.

[0015]

As described above, according to the data compression apparatus and method of the present invention, as a pre-compression process of data in which the same character is continuous, conversion processing of adjacent data into addition / subtraction modulo or exclusive OR data is performed, and the data is converted into bytes. Since the data is once converted into continuous data in units, it is possible to efficiently compress data in which the same character is continuous, for example, continuous characters of 2-byte code Japanese data.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a data compression apparatus and method according to the present invention.

FIG. 2 is a flowchart showing a processing procedure in a pre-compression processing unit shown in FIG.

FIG. 3 is a flowchart showing a processing procedure for decompressing compressed data in the embodiment.

FIG. 4 is a diagram for explaining the operation of the embodiment and showing a target compressed data content.

FIG. 5 is a block diagram showing a configuration of a conventional data compression device.

FIG. 6 is a flowchart showing a conversion processing procedure in the configuration of FIG.

FIG. 7 is a diagram showing a compressed data string by conventional processing.

[Explanation of symbols]

 10 compressed data 12 pre-compression processing unit 13 post-compression processing unit 14 compressed data

Claims (3)

[Claims] 1. Pre-compression processing means for converting data to add / subtract modulo or exclusive OR data of adjacent data and converting into continuous data in byte units as pre-compression processing for data in which the same character continues, and said pre-compression. When several characters are continuous with one byte character of continuous data from the processing means as one unit, special characters indicating compression of the characters, repeated character data, and compressed data converted into the number of repetitions are generated. A data compression apparatus comprising: post-compression processing means for obtaining. 2. A data compression method for converting a special character indicating the compression of data in which the same character is continuous, repeated character data, and the number of repetitions to reduce the data size when repeating the same character. As a pre-processing of the data compression, an addition / subtraction modulo or exclusive OR of adjacent bytes is taken, and a repeated character of data in which the same character is continuous is repeated in byte units to be determined as a character. 3. The data compression apparatus according to claim 1, or the data compression method according to claim 2, wherein the repeated character of data in which the same character is continuous is a continuous character of Japanese data of 2-byte code. .