JPH0563583A - Data compression and decoding method and backup method in electronic exchange using said method - Google Patents

Abstract

PURPOSE:To suppress a load imposed on the system to be sufficiently small and to reduce a required backup file capacity by adopting the data compression method in which the property of an electronic exchange is taken notice of such that most of data being backup object for each byte are zero so as to compress the content of a main memory to be stored in a backup file resulting in offering the very simple compression method. CONSTITUTION:When the content of a main memory is saved in a backup file, data in the main memory are divided into byte by byte and single data or consecutive n-byte data whose content is zero such as data 12,14 are converted into data 13,15 in 9-bit length having a value of 256+n. Data in 1-byte whose content is not 0 but as data 10 are converted into data 11 in 9-bit length. Data in 256-byte whose content is consecutive zero as data 16 are converted into data 17 in 9-bit length having value of 256+n.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data compression and decompression method and a backup method in an electronic exchange using these methods.

[0002]

2. Description of the Related Art Generally, in an electronic exchange, the contents of a main memory are saved in a backup file on an external storage device as a countermeasure against a failure, and the contents of the backup file are loaded into the main memory as needed. By doing so, the contents of the main memory can be restored.

Conventionally, the contents of the main memory are saved in the backup file with the same values as the above saving.

[0004]

Conventionally, the above-mentioned backup method has been adopted, and since the contents of the main memory are saved in the backup file as they are, there is an advantage that it is sufficient to load them as they are. However, on the other hand, there are the following problems.

Since the contents of the main memory are output to the external storage device as they are, the capacity of the external storage device must be increased with the increase in the size of the replacement software in recent years, which causes a high system cost.

The time for reading and writing the backup file becomes longer as the file capacity increases.

The present invention has been made in view of such circumstances, and an object thereof is to reduce the capacity of an external storage device required for backup and the time required for reading and writing the same.

[0008]

In order to achieve such an object, the present invention performs data compression and decompression. However, complicated data compression and decompression methods are overloaded, especially when run online.
Not preferable.

Therefore, in the present invention, attention is paid to the characteristics of the contents of the main memory to be saved in the electronic exchange, and a data compression method that can obtain a certain compression ratio by a simple method is adopted. That is, the software file on the main memory of the electronic exchange is composed of a huge amount of station data in addition to the program, and most of the station data frequently have a value of 0 for each byte. Therefore, a certain degree of compression ratio can be obtained by a simple method of compressing only the 0 pattern.

That is, in the present invention, the data to be compressed is sequentially divided into 1-byte units, and continuous n-byte data having a value of 0 is converted into 9-bit length data having a value of 256 + n to obtain a numerical value other than 0. Data is compressed by converting 1-byte data having i into 9-bit data having a value of i.

It should be noted that non-contiguous 1-byte data having a value of 0 is converted to 9-bit data having a value of 0, as well as being converted to 9-bit data having a value of 256 + 1. May be. Further, when the maximum value of n is 256, the data of n = 256 may be converted into the data of the 9-bit length having the value of 256.

In the restoration, the data to be restored is divided into 9-bit data in order, and 9-bit data having a value n of 256 or more is converted into continuous data of n-256 bytes having a value of 0. This is performed by converting 9-bit length data having a value i of less than 256 into 8-bit length data having a value of i.

When the maximum value of n is 256, n
= 256 data is converted into 256-byte continuous data having a value of 0.

When the data in the main memory of the electronic exchange is stored in the backup file on the external storage device, the data is compressed and stored by the above-mentioned data compression method, and when the data is loaded into the main memory. The data is restored by the above data restoration method.

[0015]

When the numerical value i other than 0 is continuous or when the data having the value of 0 appears in units of 1 byte, the number of bits after data compression increases from 8 bits to 9 bits, so the number of bits increases. However, as described above, most of the station data often occur when the value of each byte is 0, so at the place where data with a value of 0 continues for n bytes, they are collectively 9 bits. As a result, the overall compression rate is increased.

[0016]

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

Referring to FIG. 1, an electronic exchange 1 to which the present invention is applied has a main memory 3, a compression means 4 and a decompression means 5.
And an input / output unit 6, and the backup file 2 is provided on an external storage device such as a magnetic disk device.

In FIG. 1, when the contents of the main memory 3 are saved in the backup file 2, the main memory 3
Is compressed by the compression means 4 and stored in the backup file 2 through the input / output means 6.

On the other hand, when the contents saved in the backup file 2 are loaded into the main memory 3, the contents of the backup file 2 input through the input / output means 6 are restored to the original format by the restoring means 5, and the main memory 3 is restored.
Stored in.

FIG. 2 is an explanatory view of the compression method of the compression means 4, and shows what kind of bit string 8-bit data is compressed.

A numerical value i (i is 1 to 25) as shown in FIG.
The 8-bit data 10 having 5) is converted to 9-bit data such as the data 11 in which the most significant bit is added with 1-bit 0.

The 8-bit data 12 and 14 having the numerical value 0 as shown in FIGS. 2B and 2C are 9-bit length data 13 and 15 having a value of 256 + n according to the number of consecutive bytes n. Is converted to.

That is, as shown in FIG. 2 (c), when 8-bit data having a numerical value of 0 continues for n bytes, the data is collectively converted into 9-bit data 15 having a value of 256 + n. FIG. 2B shows a case where the 8-bit data 12 having the numerical value 0 appears independently, and in this case, n = 1, and the data 13 is converted into 9-bit data 13 having a value of 256 + 1 = 257.

Here, the numerical value of 256 indicates that the value of the most significant 1 bit of the 9-bit string is 1.

Note that 25-bit 8-bit data having a numerical value of 0
If 6 bytes continue, n = 256, so the value is 8
It cannot be expressed in bit length. Therefore, in the present embodiment, as shown in FIG. 2D, the data 16 in which 256-byte continuous 8-bit data having a numerical value 0 is simply 25
It is adapted to be converted into data 17 having a value of 6 and having a length of 9 bits.

Here, in the cases of FIGS. 2A and 2B, since the 8-bit data is converted to 9 bits, the data amount increases, but in the cases of FIGS. 2C and 2D, 2 bytes. 256 bytes of data are compressed to 9 bits. As described above, since the station data included in the main memory 3 has a high probability of consecutive bytes having a value of 0, a remarkable compression effect is obtained as a whole, and the data amount is about half to 2/3 in the trial calculation. ..

FIG. 3 is a flow chart showing the procedure of the compression method of the compression means 4, and FIG. 4 is a flow chart showing the procedure of the decompression method of the decompression means 5.

First, the detailed procedure of the compression method will be described with reference to FIG.

First, in the first step 101, CN
Initialize T to 0. Here, CNT is a variable that holds the number of bytes in which 0 continuously appears.

Next, at step 102, 1 byte is extracted from the beginning of the file before compression, that is, the contents to be backed up in the main memory 3 in FIG. 1, and the value is set as C.

Next, in step 103, it is determined whether or not the uncompressed file has been read to the end, that is, step 102.
It is determined whether the data taken out in step EOF is EOF.

If it is not the end of the file, step 10
In 4, it is determined whether or not C reflecting the value extracted in step 102 is 0.

If C is 0, 1 is added to the value of CNT in step 105, and it is judged in step 106 whether the value of C has reached 256. If not, the next 8 bits are processed. Return to step 102. On the other hand, if the value of CNT has reached 256, a 9-bit value 256 is output in step 107, the value of CNT is reset to 0 in step 108, and the process returns to step 102.

In step 104, step 102
If C reflecting the value fetched in step 3 is not 0, if it is confirmed in step 121 that the current value of CNT is 0, in step 123 the value C having a 9-bit length is output, and the process proceeds to step 108. To do. Also, step 12
If it is confirmed that the current CNT value is not 0 in 1,
In step 122, a 9-bit length value (256 + CNT) for a continuous 8-bit string of 0s is output, and then the process proceeds to step 123, in which the non-zero C is output in 9-bit length.

If it is determined in step 103 that the end of the file has been reached, steps 111, 11
In step 2, as in steps 121 and 122, a continuous 8-bit string of 0s is converted into a 9-bit length and output, and then the process ends.

Next, the detailed procedure of the restoration method will be described with reference to FIG.

First, in the first step 201, 9 bits are read from the backup file 2 and the value is set as C.

Next, in step 202, it is checked whether or not the backup file 2 has been read to the end, and if it has been read to the end, the processing ends.

If it is not the end of the backup file 2, in step 203, the value of C reflecting the 9-bit value input in step 201 is checked, and C
Is less than 256, the value of C is simply expressed in 8-bit length and output in step 210, and the process proceeds to step 201 to process the next 9 bits.

When it is determined in step 203 that the value of C is 256 or more, the value of (C-256) is first read in step 204 in order to restore the 8-bit string of numerical value 0 by 256 bytes or (C-256) bytes. Is set to CNT, and it is checked in step 205 whether the value of CNT is 0 or not.

If the value of CNT is 0, step 206
In, the CNT value is set to 256 in order to restore the 8-bit string of the numerical value 0 by 256 bytes. If the value of CNT is not 0, the value of CNT is left as it is.

The next step 207 is a check step for repeating the processes of steps 208 and 209 until the value of CNT becomes 0, and step 208 of subtracting 1 from the value of CNT and 1 byte for the value 0 of 8-bit length. By repeating the step of outputting 209 and the step 209 until the value of CNT becomes 0, the 8-bit string having the numerical value 0 is restored by a predetermined number of bytes.

[0043]

As described above, according to the present invention, attention is paid to the fact that most of the station data existing in the main memory of the electronic exchange frequently occurs when the value of each byte is 0. Since the data in the main memory is compressed by a simple method such as compressing only the patterns and stored in the backup file, there is an effect that the capacity required for the external storage device can be significantly reduced compared to the conventional method. ..

Also, the data compression method used is an extremely simple method of compressing only the pattern of 0, and therefore the restoration method is also simple. Therefore, in combination with the reduction of the file capacity, the system can be used for reading and writing the backup file. There is an effect that the applied load can be suppressed sufficiently small.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of an electronic exchange to which the present invention has been applied.

FIG. 2 is an explanatory diagram of a compression method showing in what bit string 8-bit data is compressed.

FIG. 3 is a flowchart showing a procedure of a compression method.

FIG. 4 is a flowchart showing a procedure of a restoration method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electronic exchange 2 ... Backup file 3 ... Main memory 4 ... Compression means 5 ... Restoration means 6 ... Input / output means

Claims (3)

[Claims] 1. Data to be compressed is sequentially divided into 1-byte units, continuous n-byte data having a value of 0 is converted into 9-bit length data having a value of 256 + n, and 1 having a numerical value i other than 0 is obtained. A data compression method that compresses data by converting byte data into 9-bit data having the value of i. 2. The data to be restored is sequentially divided every 9 bits, and 9-bit length data having a value n of 256 or more is converted into n-256 bytes of continuous data having a value of 0, and a value less than 256. A data restoration method for restoring data by converting 9-bit data having i to 8-bit data having a value of i. 3. The data restoration method according to claim 2, wherein the data in the main memory of the electronic exchange is compressed by the data compression method according to claim 1 and stored in a backup file on an external storage device. A backup method for an electronic exchange, which is restored by the method and loaded into the main memory of the electronic exchange.