JPH05244015A - Data compression system - Google Patents

Abstract

PURPOSE:To utilize a communication medium efficiently in data transfer between a data generating system and a data processing system. CONSTITUTION:A data generating system 1 is provided with a dictionary retrieval compression code generating means 12 to obtain a compression code and a Huffman code generating means 13 applies Huffman code compression to compress the data. A data processing system 3 decodes the compressed data obtained through a communication medium 2 through inverse operation and the resulting decoded data is processed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data compression method, and more particularly to a data compression method for realizing efficient use of a communication medium in the transfer of general-purpose data between a data generation system and a data processing system. ..

[0002]

2. Description of the Related Art In the conventional dictionary search compression method for data,
The displacement of the reference position of the data string and the reference length are used as the compression code as they are.

[0003]

In the above-mentioned conventional dictionary search compression method, the number of bits required for expressing the maximum reference position displacement and the maximum reference length is used regardless of the values of the reference position displacement and the reference length, respectively. Is expressed. For this reason, if the reference position displacement or reference length is small, the number of bits required to represent it should be small, but the compression code must have the number of bits required to represent the maximum reference position displacement or reference length. There is a problem that it is generated.

[0004]

The data compression method of the present invention compresses data output from a data generation system,
In a data compression method in which data is transferred to a data processing system via a communication medium and the data processing system restores data from the communication medium, in the data generation system, data generation means for generating data and already input As a dictionary, a dictionary search compression code generation means for generating as a compression code a displacement and a length of a position in the dictionary of a data sequence that is equal to an input data sequence existing in the dictionary, and this dictionary search compression code generation means. Huffman code generating means for dynamically converting the displacement and length generated as compressed codes by Huffman code to generate a further compressed Huffman code sequence, and compression for outputting the data generated by the Huffman code generating means to a communication medium. In the data processing system, the code is output from the data generation system. Compressed code input means for inputting compressed data via a communication medium, and Huffman code decompression means for restoring the position and length in the dictionary in dictionary search compression from the Huffman code of the compressed data input by this compressed code input means, A dictionary search compression code decompression means for decompressing a data string from a dictionary based on the position and length decompressed by the Huffman code decompression means, and a data processing means for processing the data decompressed by the dictionary search compression code decompression means. It is constituted by having.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention.
The embodiment of FIG. 1 comprises a data generation system 1, a communication medium 2, and a data processing system 3. The data generation system 1 includes a data generation means 11, a dictionary search compression code generation means 12, a Huffman code generation means 13, and compression. The data processing system 3 includes a code output unit 14, a compressed code input unit 31, a Huffman code decompression unit 32,
It has a dictionary search compression code expansion means 33 and a data processing means 34.

In the above configuration, in the data generation system 1, the data generation means 11 generates data in units of octets. The dictionary search compression code generation means 12 encodes the octet data output from the data generation means 11 using a dictionary of several kilo octets inside and outputs the code to the Huffman code generation means 13.
The code is composed of the displacement from the position to be written next in the dictionary to the position of the octet data string to be referenced, and the length of the reference octet data string. When there is no octet data string to refer to, the reference length is set to 0 and the input octet data is output to the Huffman code generation means 13 as it is. After outputting the code, the compressed input octet data string is written in the dictionary, and the write position is shifted by that amount. When the writing position reaches the end of the dictionary, it is moved to the beginning so that the dictionary is used in a ring. The Huffman code generation unit 13 divides the reference position displacement and the reference length output from the dictionary search compression code generation unit 12 into several types,
A Huffman code is generated according to a generally used Huffman tree based on the respective appearance frequencies, and output to the compressed code output means 14. At this time, before outputting the Huffman code to the compressed code output means 14, it is necessary to output Huffman code information indicating which Huffman code is assigned to which type for the above classification. The compressed code output means 14 outputs the code of the bit string output from the Huffman code generation means 13 to the communication medium 2 in byte units. The communication medium 2 may be an ordinary storage medium.

Next, in the data processing system 3, the compressed code input means 31 inputs data in byte units from the communication medium 2 and outputs the data in bit units to the Huffman code decompression means 32. The Huffman code expansion means 32 is
A fixed number of Huffman codes are expanded on the basis of the Huffman code information added by the Huffman code generation unit 13, and the restored reference position displacement and reference length of the dictionary search compression are output to the dictionary search compression code expansion unit 33 as needed. The dictionary search compression code decompression means 33 decompresses the code consisting of these two pieces of information, and restores the data based on the internal dictionary. The restored data is output to the dictionary and data processing means 34.

FIG. 2 is a diagram showing a specific example of the processing of the data generation system 1. Hereinafter, the processing of the data generation system 1 will be described with reference to FIG. The size of the dictionary contained in the dictionary search compression code generation means 12 is 4096 octets, and the reference length and the reference position displacement in the Huffman code generation means 13 are classified into Table 1 and Table 2, respectively. In addition, a data string less than 3 octets is not subject to compression.

[0010]

[Table 1]

[0011]

[Table 2]

First, it is assumed that the data generating means 11 has generated 20-octet data as shown in FIG. The dictionary search compression code generation means 12 inputs this data one after another, but up to the first 6 octet data is 3 in the dictionary.
Since there is no octet data string to be referenced having a size of octet or more, the reference length 0 and the octet data are output to the Huffman code generation means 13, respectively. At this time, input octet data is stored in the first 6 octets of the dictionary, and the position to be written next is the 7th octet from the first. The 3 octet string input next has the same content as the 3 octets from the beginning of the dictionary, so the reference length 3 and the reference position displacement 6 (= 7-1) are output. When similar dictionary searches are continued, the contents shown in the dictionary search compression code of FIG. 2 are output to the Huffman code generation means 13 as a whole. In the conventional compression method, the compression is completed by the processing up to this point. If the reference length is 4 bits and the reference position displacement is 12 bits, a total of 120 bits are output in this example. The Huffman code generation means 13 classifies these outputs according to the contents of Tables 1 and 2, checks the frequency, and generates a Huffman tree to generate the Huffman code in the upper stage of the final compression code in FIG. To generate. Then, the reference length and the reference position displacement obtained as the input data are replaced with the Huffman code and output to the communication medium 2. The total size of compressed code is 8
It is 9 bits.

[0013]

As described above, the present invention has the effect that the Huffman code compression is applied to the dictionary search compression code to enable more efficient data transmission.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a specific example of processing of the data generation system of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 data generation system 2 communication medium 3 data processing system 11 data generation means 12 dictionary search compression code generation means 13 Huffman code generation means 14 compression code output means 31 compression code input means 32 Huffman code expansion means 33 dictionary search compression code expansion means 34 Data processing means

Claims (1)

[Claims] 1. A data compression method in which data output from a data generation system is compressed, transferred to a data processing system via a communication medium, and the data processing system restores data from the communication medium. In the system, data generating means for generating data,
A dictionary search compression code generation unit that generates a data string that has already been input as a dictionary, and a position of the data string that is equal to the input data string existing in the dictionary as a compression code of the displacement and length, and the dictionary search compression code. Huffman code generation means for dynamically converting the displacement and the length generated as a compressed code by the code generation means into a Huffman code sequence and further compressing the Huffman code sequence, and the data generated by this Huffman code generation means as a communication medium. In the data processing system, the compressed code output means for outputting the compressed code output means for inputting the compressed data output from the data generation system via the communication medium, and the compressed data input by the compressed code input means. Huffman code decompression that restores the position and length in the dictionary in dictionary search compression from the Huffman code Stage, a dictionary search compression code expansion means for recovering a data string from the dictionary based on the position and length restored by this Huffman code expansion means, and data for processing the data restored by this dictionary search compression code expansion means A data compression method comprising: a processing unit.