JPS61236224A - Method for compressing data - Google Patents

Abstract

PURPOSE:To restore a compression data in a short time by replacing a code string being compression object into a 1-byte control code and adding a 1-byte control code before a code representing non-compression object so as to record the result. CONSTITUTION:In taking 0s or spaces only consecutive for >=3bytes as a compression object, a control code 17 comprising 00 representing a non-compression object and a figure 2 representing a byte number are added to head 2-byte AB of a digital code string 11 and the result is recorded. Since the next code string 13 is a compression object, the string is replaced into a control code 19 comprised of 10 representing the compression of consecutive 0s and a figure 3 representing its byte number and the result is recorded. The final code string 15 is replaced into a control code 22 consisting of 01 representing the compression of consecutive spaces and of figure 4 representing the byte number and the result is recorded. The data compressed in this way is restored very easily in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a data compression method, and particularly to a data compression method suitable for restoration in a short time.

[Background of the invention]

As the amount of information increases, the capacity of memory devices for storing it increases. In order to avoid this, it is necessary to perform data compression, and various data compression methods have been proposed in the past (for example, Japanese Patent Laid-Open No. 75244/1983). However, when data is compressed, a problem arises in that it takes time to restore the compressed data to the original data.

[Purpose of the invention]

An object of the present invention is to provide a data compression method that can restore compressed data in a short time.

[Summary of the invention]

Some data, such as program data,
Many parts of the data (in the case of program data, 1/2
~1/3) is occupied by 0 or space. In such data, in the present invention, when there are three or more consecutive 0 or space bytes, this is converted into a first control code and compressed, and if the data is at risk of being compressed, a first control code is added before the consecutive data string. 2 control codes are added. The first control code consists of an identification code of 0 or space and a code indicating the number of bytes of the data to be compressed, and the second control code consists of a code indicating the object to be compressed and an indication of the number of bytes of the data string. It consists of a symbol. [Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of the principle of the data compression method according to this embodiment, where 11 indicates a digital code string before compression, and 16 indicates a digital code string after compression. In this compression method, only consecutive zeros or spaces of 3 or more bytes are subject to compression, and the other digital code strings are not compressed.The digital code string to be compressed is replaced with a 1-byte control code, and the digital code string to be The code string is recorded by adding a 1-byte control code to the front of the digital code string. The first 2 bytes "''AB'a12 of digital code string 11 are to be uncompressed, so the character identification code is 00 indicating that it is to be uncompressed, and the length code is digital code II'''AB''.
A control code 17 of number 2 indicating the number of bytes) is added and recorded (18).

The next digital code string "ooo" 13 is the compression target code "'
Since the compression target consists of 3 or more consecutive 0''' characters, the character identification code is "10" which indicates that consecutive 0's have been compressed.
The number 3 indicates the number of bytes with consecutive 0 length codes.
The control code 19 is replaced with the control code 19 and recorded. The next digital code string "CDE" 14 is to be uncompressed, so ""CD
A control code 20 is added in front of "E" and recorded (21).

The last digital code string 6 space space space space "14" indicates that the code space to be compressed is 4 or more consecutive bytes, so the length is 01" indicating that the character identification code has compressed a continuous space. The code is recorded by replacing it with a control encoder of number 4, which indicates the length of the space (the number of bytes).

FIG. 2 is a functional block diagram of an apparatus for compressing data and recording compressed data, and 1 and 3 are recording media for recording digital codes. 2 is a processing means for compressing the digital code on the recording medium 1 and recording it on the recording medium 3, and for restoring the compressed digital code on the recording medium 3 to the original digital code and recording it.

FIG. 3 is a flowchart of a data compression method executed by the processing means 2 shown in FIG. 1, and the compression procedure of the data compression shown in FIG. 1 will be explained according to this FIG.

First, the first 3-byte digital code string @ABO'' of the digital code string 11 is read (step 1O1), and the length code is set to 1 (step 102).Then, the digital code string ``ABO'' to be uncompressed is read. Read the next digital code string @BOO” (step 103゜114.13
4-135). Since this digital code string is not to be compressed, 1 is added to the length code to make it 2, and steps 136 and 137
), the next digital code string "000" 13 is read (steps 134, 135). Since this digital code string is to be compressed, the character identification code 'oo
'', a control code 17 with a length code of 2 is added, and the data 18
(Steps 134 to 136, 141, 142
).

Next, the digital code string "'ooo" is processed.

Set the length code to 1 and read the next digital code string "ooc" (Step 102) (Steps 103 to 105)
.

Since this digital code string is not to be compressed, the character identification code is set to 10'' indicating '0'' (step 111), and 2, the unadded length of consecutive 0s, is added to the length code (step 112). A control code 19 of 3 is recorded (step 113).

Next, read the digital code string "CDE" 14 2 bytes ahead (steps 125-126), and set the length code to 1 (step 102).The next digital code string "CDE" to be uncompressed Read the code string "'DE space" (steps 103, 114, 134-135) Since this digital code string is to be uncompressed, the length code is set to 1.
is added to 2 (steps 136-137), and the next digital code string "E space space" is read (134-137).
135). Since this digital code string is also to be uncompressed, add 1 to the length code to make it 3 (steps 136-137),
Next digital code string “Space Space Space”
(134-135). Since this digital code is to be compressed (step 136), a control code 20 with a character identification code of "00" indicating a character to be uncompressed and a length code of 3 is added before the digital code string "CDE" to be uncompressed. and record data 21 (steps 141-142)
.

Next, the digital code string "space space space" is processed. Set the length code to 1 and step 102
), reads the next digital code string "1 space space space" (steps 103, 114 to 116),
Add 1 to the length code to make it 2 (step 119). Since there is no digital code to read next (step 115)
, the character identification code is "+1" indicating 1 space (step 119), and the control code 22, which is 4 by adding 2, the unadded length of the length of the consecutive spaces to the length code (step 120), is recorded. At step 121), the process ends.

Next, a procedure for restoring the compressed and recorded digital code string 16 to the digital code string 11 will be explained using FIG.

First, the first byte of control code 17 is read (step 401). The character identification code of this control code 17 is ""oo
” (steps 402, 404), and since the length code is 2, it is identified as a non-compressible character, and a 2-byte digital code “AB” following the control code 17 is recorded (step 407). Next, the control code 19 after the digital code AE'' is read (step 401).
). The character identification code of this control code 19 is "10" (step 402) and the length code ' is 3, so it is identified that the digital code "'ON" is 3 consecutive bytes, and "AE
Record 3 bytes of 0 after “” (steps 402 to 40
3).

The next control code 20 has a character identification code of 00'' (steps 402, 404) and a length code of 6, so a 3-byte digital code string @CDE'' following the control code 2G is recorded. Next, the control code n after the digital code string "CDE" is read (steps 408, 401).

This control code n has a character identification code of 01” (step 4
02,404) Since the length code is 4, 9 spaces 1
It is recognized that 4 bytes are continuous, and 4 bytes of space are recorded after "CDE" (step 405). Since there is no control code following this control code n (step 406)
, ends the process.

〔Effect of the invention〕

According to the present invention, since the compressed data is limited to consecutive 0's and spaces, the control code can be shortened to 1 byte, and
Since the control code is added before the uncompressed data, the data restoration time is shortened.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of an embodiment of the method of the present invention, Fig. 2 is a functional block diagram of a data compression recording device, Fig. 3 is a flowchart showing the data compression procedure, and Fig. 4 is a flowchart showing the data restoration procedure. It is. 1... Uncompressed format digital code recording medium 2... Digital code compression/decompression processing means 3... Compressed format digital code recording medium 11... Uncompressed format digital code string 16... Compressed format digital code string

Claims (1)

[Claims] A data string of 1 or 3 consecutive bytes or more of 0 or space is to be compressed, and the data string is converted into a control code consisting of an identification code of 0 or space and a code representing the number of bytes of the data string, and A data compression method characterized in that a control code consisting of a code representing an object to be compressed and a code representing the number of bytes of the data is added in front of the data.