JPH05181641A - Data compressing/restoring device - Google Patents

Abstract

PURPOSE:To improve data compression and restoration processing speeds. CONSTITUTION:This device is constituted of a data compressing circuit and a data restoring circuit. The data compressing circuit is constituted of a dictionary retrieving means 1, a dictionary registering means 2, an encoding means 3, an initial dictionary access means 4, a regular dictionary access means 5, an initial dictionary D1 and a regular dictionary D2. Among them, the dictionary retrieving means 1, the dictionary registering means 2 and the encoding means 3 are subjected to parallel processing by a pipeline. Also, the data restoring circuit is constituted of a decoding means 11, a dictionary retrieving means 12, a first accumulating means 13, a second accumulating means 14, an output selecting means 15, a document registering means 16 and a dictionary access means 17. Amount them, the decoding means 11, the dictionary retrieving means 12 and the output selecting means 15 are subjected to parallel processing by a pipeline.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data compression / decompression device, and more particularly to a data compression / decompression device for compressing and decompressing data by universal encoding and decoding.

[0002] In recent years, due to remarkable technological development, the processing speed, storage capacity, etc. of computers have been dramatically improved. However, since computers have been handling data such as vector information and image information, the amount of data to be handled is increasing more than ever before. In order to cope with such a large increase in the amount of data, various data compression methods have been proposed that reduce the amount of data without damaging the content of the data.

These data compression methods are methods for compressing data by omitting redundant portions contained in data and encoding. The data compression method can reduce the amount of data and consequently the storage capacity. Further, in communication, by transmitting compressed data, information having the same content can be transmitted at high speed.

The definitions of "Character" and "Character String" are defined in JIS-C6230.
In addition to obeying the name used in information theory,
Data composed of one word unit is called "character", and data composed of arbitrary word unit is called "character string".

[0005]

2. Description of the Related Art Conventionally, a universal coding system has been proposed as an example of compressing the above data.
As a typical example of the universal coding system, LZ (Le
mpel-Ziv) There are an encoding method and an arithmetic encoding method. Also, L
Universal encoding and incremental decomposition type (Increm
(ental persing) algorithm has been proposed. Further, as an improved encoding method of these algorithms, there are an LZSS encoding method belonging to a universal type and an LZW (Lempel-Ziv-Welch) encoding method belonging to an incremental decomposition type.

The LZ coding method is described in, for example, “Lempel-Ziv data compression method” by Seiji Munakata, Information Processing, pp.2-6, V.
See ol.26, No.1, 1985 for details. Also, L
The ZSS encoding method is TC Bell, "Better OPM / L Text Co.
mpression ", IEEE Trans.on Commu., Vol.COM-34, No.1
2, Dec. 1986. Furthermore, LZW
The encoding method is TA Welch, "A Technique for High-Perf
ormance Data Compression ", Computer, Jun. 1984. The incremental decomposition type encoding method and the LZW encoding method are disclosed in Japanese Patent Laid-Open No. 59-231683 and US Pat.
o. 4,558,302.

Among these encoding methods, the LZW encoding method has been generally used because of its advantages of high-speed processing and simple algorithm. The LZW encoding method is a method that has a rewritable dictionary and performs encoding by the processing described below. First, a new input character string is divided into different partial character strings, and if this partial character string is not registered in the dictionary, all are registered in the dictionary with an identification number in the order of appearance. At the same time, of the currently input partial character strings, a partial character string that matches the longest partial character string is selected from the dictionary and encoded with the identification number attached to the selected partial character string.

The details of the data compression circuit and the data decompression circuit using the LZW encoding method will be described below. FIG. 15 is a diagram showing a conventional data compression circuit. In the figure, the conventional data compression circuit includes a dictionary search means 121,
The dictionary registration unit 122, the universal encoding unit 123, and the dictionary D12 are included.

The dictionary search means 121 searches the registered character strings registered in the dictionary D12 for a registered character string that matches the inputted input character string. Dictionary registration means 122
Adds an identification number to the input character string that could not be searched by the dictionary search means 121 and registers it in the dictionary 122. The universal encoding means 123 encodes the identification number added to the registered character string searched by the dictionary searching means 121 or the identification number newly added to the input character string by the dictionary registration means 122 to the output code.

Dictionary search means 121 and dictionary registration means 122
The encoding process of the universal encoding means 123 is performed sequentially. FIG. 16 shows an example of this encoding processing procedure.

FIG. 16 is a diagram showing a processing procedure by a conventional data compression circuit. In the figure, the processing character number column 125,
Dictionary search column 126, dictionary registration column 127, and encoding column 12
A table consisting of 8 is shown.

The processed character number column 125 shows the character rank from the beginning processed when the input character string is encoded.
The dictionary search column 126 shows the contents processed by the dictionary search means 121 of FIG. The dictionary registration column 127 shows the contents processed by the dictionary registration means 122. The encoding column 128 shows the contents processed by the universal encoding means 123. The numbers in the circles indicate the order of processing procedures. Hereinafter, the “number X in the circle” will be referred to as the “cycle X”.

First, in cycle 1 to cycle 3, a process in which the dictionary registration means 122 searches the dictionary D12 for the first one character of the input character string is shown. Specifically, the dictionary search result indicates that the input character string and the registered character string do not match in cycle 1 and cycle 2, but match in cycle 3.

Next, in cycle 4 to cycle 6, the dictionary registration means 1 for the second character of the input character string that has been input.
22 shows a process of searching the dictionary D12. In particular,
The input character string and the registered character string do not match in cycle 4 and cycle 5, and in cycle 6 it indicates that there is no character registered in the dictionary.

At this time, the dictionary registration means 122 adds an identification number to the input character string and registers it in the dictionary D12. This is the “registration” shown in cycle 7. In addition, for encoding, the universal encoding means 123 encodes the identification number given at the time of dictionary registration. This is the "encoding" shown in cycle 8. Hereinafter, the encoding process is similarly performed.

FIG. 17 is a diagram showing a conventional data restoration circuit. In the figure, the conventional data recovery circuit is
Universal decoding means 131, dictionary search means 132,
The stack storage unit 133, the dictionary registration unit 134, and the dictionary D13 are included.

The universal decoding means 131 decodes the inputted input code. The dictionary search means 121 searches the registered character code registered in the dictionary D13 for a character code that matches the decoded character code. The stack accumulating unit 133 accumulates the characters searched by the dictionary searching unit 121 in the stack, and outputs all the accumulated characters when the search is completed. The dictionary registration means 134
When the restored character string output by the stack accumulating unit 133 is not registered in the dictionary D13, a new code is added to the restored character string and registered in the dictionary D13.

These universal decoding means 131,
The decoding process of the dictionary search unit 132, the stack storage unit 133, and the dictionary registration unit 134 is performed sequentially. FIG. 18 shows an example of this decoding processing procedure.

FIG. 18 is a diagram showing a processing procedure by the conventional data restoration circuit. In the figure, the processing code number column 136,
Decryption column 137, search / accumulation column 138, character string output column 1
39 shows a table composed of 39 and a dictionary registration field 140.

The processing code number column 136 shows the number of codes processed when the input code is decoded. Decryption field 137
Shows the contents processed by the universal decoding means 131 of FIG. The search / accumulation column 138 is a dictionary search means 13
2 indicates a process of searching and the stack storage unit 133 stores the searched character. The character string output column 139 shows a process of outputting all the characters accumulated by the stack accumulating unit 133. The numbers in the circles indicate the order of processing procedures. Hereinafter, as in FIG. 16, the “number X in the circle” will be referred to as the “cycle X”.

First, in cycles 1 to 8, a process of decoding the input first input code string and outputting it as an output character string will be described. Specifically, each processing procedure is as follows. In cycle 1, universal decoding means 131 decodes the input code. In cycle 2 to cycle 4, the dictionary search means 132 recursively searches the character code decoded in cycle 1, and the stack storage means 133 stores the searched character in the stack. In cycle 5 to cycle 7, stack storage means 1
All characters accumulated by 33 are output. In cycle 8,
The dictionary registration unit 134 adds a new symbol to the output character string output by the stack storage unit 133, and the dictionary D13
Register with. Hereinafter, the decoding process is similarly performed.

[0022]

However, in the conventional data compression circuit, after the dictionary search, the dictionary registration and the encoding for a certain character string, the next character string is encoded.
The compression processing was performed by such batch serial processing. Similarly, in the data decompression circuit, the decompression process is performed by a batch serial process in which the decoding, dictionary search, stack accumulation, and dictionary registration for a certain code are performed before the next code is decoded. Was there.

Therefore, in such batch serial processing, there is a problem that it is difficult to speed up the encoding and decoding processing. The present invention has been made in view of the above circumstances, and an object thereof is to provide a data compression circuit that speeds up the compression processing of input data by parallel processing.

Another object of the present invention is to provide a data restoration circuit which speeds up the restoration processing of an input code by parallel processing. Still another object of the present invention is to provide a data compression / decompression device that speeds up the input data compression processing and the input code decompression processing by parallel processing.

[0025]

In the present invention, in order to achieve the above object, as shown in FIG. 1, the data compression circuit includes a first dictionary search means 1, a first dictionary registration means 2 and an encoding means. 3, an initial dictionary access unit 4, a normal dictionary access unit 5, an initial dictionary D1 and a normal dictionary D2. First
The dictionary search means 1 searches for the longest registered character string that matches the input character string input from the registered character strings registered in the initial dictionary D1 via the initial dictionary access means 4. If the initial dictionary D1 cannot be searched, the search ends. When the search is successful, the search is performed from the registered character string registered in the normal dictionary D2 via the normal dictionary access means 5. The first dictionary registration means 2 assigns an identification number to the character string obtained by adding one character to the longest registered character string searched by the first dictionary search means 1, and the normal dictionary D2 via the normal dictionary access means 5. Register with. The encoding means 3 is
The identification number attached to the longest registered character string is encoded as an output code.

The initial dictionary D1 and the normal dictionary D2 are
It is configured to perform data search and data registration by external hash. Further, the initial dictionary D1 is configured to perform data search and data registration for character strings up to the second character, and the normal dictionary D2 is configured to perform data search and data registration for character strings after the third character.

Then, the initial dictionary D1 and the normal dictionary D2
Is configured to perform data retrieval and data registration by using a complete hash. Then, the first dictionary search means 1,
The first dictionary registration means 2 and the encoding means 3 are connected by a pipeline and are processed in parallel.

Moreover, as shown in FIG. 3, the data restoration circuit includes a decoding means 11, a second dictionary searching means 12, a first accumulating means 13, a second accumulating means 14, an output selecting means 15, and a first accumulating means. 2 dictionary registration means 16 and dictionary access means 17
And a dictionary D3. The decoding means 11 decodes the inputted input code. Second dictionary search means 12
Searches the registered character strings registered in the dictionary D3 via the dictionary access means 17 for a character string that matches the character string restored by decoding. First storage means 13
The second storage means 14 stores the character string restored by this search. The output selection unit 15 selects a restored character string to be output from the accumulated character strings. The second dictionary registration means 16 adds a new symbol to a character string that is not registered in the dictionary D3 among the selected restored character strings and registers the character string.

Further, the decryption means 11, the second dictionary search means 12, the output selection means 15 and the second dictionary registration means 16 are provided.
Are connected by a pipeline and processed in parallel. And
As shown in FIG. 5, the data compression / decompression device includes a data compression circuit and a data decompression circuit. The data compression circuit comprises a first dictionary search means 1, a first dictionary registration means 2, an encoding means 3, an initial dictionary access means 4, a normal dictionary access means 5, an initial dictionary D1 and a normal dictionary D2. Further, the data restoration circuit includes a decoding unit 11, a second dictionary searching unit 12, a first storing unit 13, a second storing unit 14, an output selecting unit 15, a second dictionary registering unit 16,
It is composed of the dictionary access means 17 and the dictionary D3.

[0030]

In the data compression circuit, the first dictionary retrieval means 1 retrieves the input character string input from the initial dictionary D1 via the initial dictionary access means 4. If the initial dictionary D1 is not searched, the normal dictionary D2 is also searched via the normal dictionary access unit 5. Then, the first dictionary registration means 2 adds an identification number to the character string obtained by adding one character to the longest searched character string, and registers it in the normal dictionary D2 via the normal dictionary access means 5. The encoding means 3 encodes the identification number attached to the retrieved longest registered character string into an output code.

Further, the initial dictionary D1 and the normal dictionary D2 are
Perform data search and data registration by external hash.
Furthermore, the initial dictionary D1 is searched for and registered data for character strings up to the second character, and the ordinary dictionary D2 is searched and registered for character strings after the third character.

Then, the initial dictionary D1 and the normal dictionary D2
Performs data search and data registration using the complete hash. Then, the first dictionary search means 1, the first dictionary registration means 2 and the encoding means 3 are connected by a pipeline and processed in parallel.

Moreover, in the data restoration circuit, the decoding means 11 decodes the input code, and the second dictionary searching means 12 causes the dictionary D via the dictionary accessing means 17.
Among the three, the character string that matches the character string restored by decoding is searched, and the restored character string is output to the first storage unit 13 and the second storage unit 14. Output selection means 1
Reference numeral 5 selects the restored character string to be output, the second dictionary registration means 16 adds a new symbol to the unregistered restored character string, and registers it in the dictionary D3 via the dictionary access means 17.

Further, the decoding means 11, the second dictionary search means 12, the output selection means 15 and the second dictionary registration means 16 are provided.
Connect in a pipeline for parallel processing. In the data compression / decompression device, the first
Of the dictionary search means 1 through the initial dictionary access means 4
The input character string input is searched from the initial dictionary D1. If the initial dictionary D1 is not searched, the normal dictionary D2 is also searched via the normal dictionary access unit 5.
Then, the first dictionary registration means 2 adds an identification number to the character string obtained by adding one character to the longest searched character string, and registers it in the normal dictionary D2 via the normal dictionary access means 5.
The encoding means 3 encodes the identification number attached to the retrieved longest registered character string into an output code. In the data restoration circuit, the decoding means 11 decodes the input code, and the second dictionary searching means 12 matches the character string restored by decoding in the dictionary D3 via the dictionary access means 17. The retrieved character string is searched, and the restored character string is output to the first accumulating unit 13 and the second accumulating unit 14. The output selection unit 15 selects the restored character string to be output, the second dictionary registration unit 16 adds a new symbol to the unregistered restored character string, and registers it in the dictionary D3 via the dictionary access unit 17.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a data compression circuit of the present invention. In the figure, the data compression circuit comprises a first dictionary search means 1, a first dictionary registration means 2, an encoding means 3, an initial dictionary access means 4, a normal dictionary access means 5, an initial dictionary D1 and a normal dictionary D2. It

The first dictionary search means 1 is registered in the initial dictionary D1 via the initial dictionary access means 4 or registered in the normal dictionary D2 via the normal dictionary access means 5. Among the registered character strings, the longest registered character string that matches the input character string input from the information source is searched. The first dictionary registration means 2 attaches an identification number to the character string obtained by adding one character to the longest searched character string searched, and adds the identification number to the initial dictionary D1 via the initial dictionary access means 4.
Or in the normal dictionary D2 via the normal dictionary access means 5. The initial dictionary access unit 4 is a unit for accessing the initial dictionary D1 and is, for example, the first dictionary.
The logical addresses instructed by the dictionary search means 1 and the first dictionary registration means 2 are converted into physical addresses, and data is input / output to / from the initial dictionary D1. The normal dictionary access means 5 is a means for accessing the normal dictionary D2, for example, by converting a logical address instructed by the first dictionary search means 1 and the first dictionary registration means 2 into a physical address. , And inputs / outputs data to / from the normal dictionary D2. The encoding unit 3 uses, for example, an LZW encoding unit, and encodes the identification number attached to the longest searched registration character string as an output code.

The "character string obtained by adding one character to the longest registered character string" registered in the normal dictionary D2 is the following character string. For example, if the input character string is "abcd" and the longest registered character string already registered in the normal dictionary D2 is "ab", it matches the longest registered character string of the input character strings. It is a character string “abc” in which one character “c” next to “ab” is added.

The access from the initial dictionary access means 4 to the initial dictionary D1 and the access from the normal dictionary access means 5 to the normal dictionary D2 are performed by the complete hash method or the external hash method described later.

The first dictionary search means 1, the first dictionary registration means 2 and the encoding means 3 are all connected by a pipeline (not shown) and can be processed in parallel. it can. By this pipeline parallel processing, the encoding processing can be performed by a plurality of means, and the encoding processing can be performed at high speed.

An exception to this parallel processing is the first dictionary search means 1 and the first dictionary registration means 2.
Simultaneously requests access to the initial dictionary D1 or the normal dictionary D2. For example, this is a case where the first dictionary search means 1 and the first dictionary registration means 2 simultaneously request access to the initial dictionary D1. In this way, a state in which access requests are simultaneously made by two or more means is called “collision”. When a collision occurs, for example, the first dictionary registration means 2 accesses the initial dictionary D1 via the initial dictionary access means 4, and then the first dictionary search means 1 similarly accesses the initial dictionary D1. So you will access the dictionary sequentially. However, such a collision is an extremely rare phenomenon from the viewpoint of the entire encoding process. Therefore, the processing time is negligible from the viewpoint of the entire processing time, and there is no problem even if the dictionary and access processing are performed sequentially. An example of this encoding processing procedure is shown below in FIG.

FIG. 2 is a diagram showing a processing procedure by the data compression circuit of the present invention. The figure shows a table including a processing character number column 6, a dictionary search column 7, a dictionary registration column 8 and an encoding column 9. The processing character number column 6 shows the character rank from the beginning which is processed when the input character string is encoded. Dictionary search field 7
Indicates the contents processed by the first dictionary search means 1 in FIG. The dictionary registration column 8 shows the contents processed by the first dictionary registration means 2. The encoding column 9 shows the contents processed by the encoding means 3.

The numbers in the circles indicate the order of processing procedures. Hereinafter, the “number X in the circle” will be referred to as the “cycle X”. If there are numbers in the same circle, it means that the processes are performed in parallel at the same time. And the initial dictionary D1
Since the access to and is performed through the initial dictionary access means 4, and the access to the normal dictionary D2 is performed through the normal dictionary access means 5, the description of this process is omitted.

First, in cycle 1, the first dictionary searching means 1 searches the initial dictionary D1 for the second character following the first first character of the input character string input from the information source.
In cycle 2, the first dictionary searching means 1 searches the normal dictionary D2 for the third character of the input character string. Cycle 3
For the fourth character of the input character string, the first dictionary search means 1 searches the normal dictionary D2. At this time, cycle 3
Shows a case where the fourth character of the input character string is not registered in the normal dictionary D2. These cycle 1 to cycle 3
In the process of, each process is performed sequentially.

Next, in cycle 4 of the dictionary search column 7, the first dictionary search means 1 searches the initial dictionary D1 for the fifth character following the fourth character of the input character string. At the same time, in cycle 4 of the dictionary registration column 8, cycle 3 of the dictionary search column 7
Then, an identification number is given to the character string of the first character to the fourth character of the input character string which has not been registered in the normal dictionary D2, and the first dictionary registration means 2 registers it in the normal dictionary D2.

Then, in cycle 5 of the dictionary search field 7,
The first dictionary searching means 1 searches the normal dictionary D2 for the sixth character following the fifth character of the input character string. At the same time, in cycle 5 of encoding column 9, cycle 4 of dictionary registration column 8
The identification number attached to the registration character string performed in step 1 is encoded. Thereafter, similar processing is continued.

In this way, when the input character string is not registered as a result of searching the initial dictionary D1 or the normal dictionary D2 in the dictionary search field 7, the character string is registered and encoded in the dictionary registration field 8. The encoding in column 9 is performed in parallel with the dictionary search. Therefore, the encoding process can be performed at high speed.

FIG. 3 is a diagram showing an embodiment of the data restoration circuit of the present invention. In the figure, the data restoration circuit includes a decoding means 11, a second dictionary search means 12, a first storage means 13, a second storage means 14, an output selection means 15, a second dictionary registration means 16, and a dictionary access. Means 17 and dictionary D3
Composed of.

The decoding means 11 is, for example, an LZW decoding means, and decodes the input code input from the information source. The second dictionary search means 12 is the dictionary access means 1
Of the registered character strings registered in the dictionary D3 via 7, a character string that matches the character string restored by decoding is searched. First storage means 13 and second storage means 1
4 stores the character string restored by the search. The output selection unit 15 selects a restored character string to be output from the accumulated character strings. The second dictionary registration means 16 adds a new symbol to a character string that is not registered in the dictionary D3 among the selected restored character strings and registers the character string. The dictionary access unit 17 is a unit for accessing the dictionary D3, and for example, converts a logical address instructed by the second dictionary search unit 12 and the second dictionary registration unit 16 into a physical address, and then the dictionary. Inputs / outputs data to / from D3.

Incidentally, the dictionary D3 from the dictionary access means 17
The access to can also be performed by the complete hash method or the external hash method described later. The "collision" described in the data compression circuit of FIG. 1 also occurs in this data decompression circuit. For example, this is a case where the second dictionary search means 12 makes a search request and the second dictionary registration means 16 makes a registration request at the same time. In this case, for example, the second dictionary registration means 16
After the registration processing of, the search processing of the second dictionary search means 12 is sequentially performed. As in the case of the data compression circuit, collision is an extremely rare phenomenon from the viewpoint of the entire decoding process, so it is only a negligible processing time from the viewpoint of the overall processing time. There is no problem in processing.

Then, the decrypting means 11, the second dictionary searching means 12, the first accumulating means 13, the second accumulating means 14,
The output selecting means 15 and the second dictionary registering means 16 are connected by a pipeline (not shown), and can be processed in parallel. By this pipeline parallel processing, the encoding processing can be performed by a plurality of means, and the encoding processing can be performed at high speed. An example of this decoding processing procedure is shown below in FIG.

FIG. 4 is a diagram showing a processing procedure by the data restoration circuit of the present invention. The figure shows a table including a processing code number column 21, a decoding column 22, a search / accumulation column 23, a character string output column 24, and a dictionary registration column 25.

The processing code number column 21 shows the number of codes processed when the input code is decoded. The decryption column 22 shows the contents processed by the decryption means 11 in FIG. The search / accumulation column 23 shows a process of accumulating the characters searched by the second dictionary searching means 12 and searched by the stack accumulating means 13 and 14. The character string output column 24 shows a process in which the output selection unit 15 outputs all the characters stored in the stack storage units 13 and 14. The dictionary registration section 25 includes the second dictionary registration means 16
Indicates the contents processed by.

The numbers in the circles indicate the order of processing procedures. Hereinafter, as in FIG. 2, the “number X in the circle” will be referred to as the “cycle X”. If there are numbers in the same circle, it means that the processes are performed in parallel at the same time. The dictionary access means 17 is used to access the initial dictionary D3.
The description of this process will be omitted as it is performed through.

First, in cycle 1, the decoding means 11 decodes the first input code input from the information source. In cycle 2 of the decoding column 22, the decoding means 11 decodes the second input code. At the same time, in the cycle 2 of the search / accumulation column 23, the second dictionary search means 12
The coded character decoded by is searched from the dictionary D3. Also,
The retrieved restored character is stored in the stack by the stack storage unit 13. These cycles 2 are processed in parallel.

Next, in cycles 3 and 4, the code characters decoded by the second dictionary retrieval means 12 are retrieved from the dictionary D3 by recursive decoding, which will be described later, and the stack storage means 13 retrieves and restores them. Accumulate characters on the stack.

Then, in cycle 5 of the decryption column 22,
The decoding means 11 decodes the third input code. At the same time, in cycle 5 of the search / accumulation column 23, the coded characters decoded by the second dictionary search means 12 are searched from the dictionary D3, and the stack storage means 14 stores the searched restored characters in the stack. At the same time, the character string output field 24
In cycle 5, the first character of the character string accumulated in cycles 3 to 4 is output. These cycle 5
Processing is performed in parallel.

Then, the cycle 6 of the search / accumulation column 23
Searches the coded characters decoded by the second dictionary searching means 12 from the dictionary D3, and the stack storing means 14 stores the searched restored characters in the stack. At the same time, in cycle 6 of the character string output field 24, the second character of the character string accumulated in cycles 3 to 4 is output. These cycle 6
Also, the processing is performed in parallel. Thereafter, similar processing is continued.

In this way, in parallel with the decoding performed in the decoding column 22, the characters retrieved by one stack accumulating means are accumulated, and the character string accumulated by the other stack accumulating means is output as a restored character string. Processing can be performed. Therefore, the decoding process can be performed at high speed.

FIG. 5 is a diagram showing an embodiment of the data compression / decompression device of the present invention. In the figure, the data compression / decompression device comprises a data compression circuit and a data decompression circuit. The data compression circuit comprises a first dictionary search means 1, a first dictionary registration means 2, an encoding means 3, an initial dictionary access means 4, a normal dictionary access means 5, an initial dictionary D1 and a normal dictionary D2. Further, the data restoration circuit includes a decoding means 11 and a second dictionary search means 1
2, the first storage unit 13, the second storage unit 14, the output selection unit 15, the second dictionary registration unit 16, the dictionary access unit 17, and the dictionary D3.

The same elements as those in FIGS. 1 and 3 are designated by the same reference numerals, and the description thereof will be omitted. The operations of the data compression circuit and the data decompression circuit are the same as those in FIG. 1 and FIG.

With this device, the processing speed of the data compression processing and data decompression processing is improved. As in the processing procedure shown in FIGS. 2 and 4, since a plurality of means can perform processing in parallel, the processing speed of the entire apparatus can be further improved.

Next, regarding the dictionary search procedure and the dictionary registration procedure in each of the above embodiments, the hash method will be described first. The hash method is one of the methods of storing data and searching data using a table called a hash table, and uses the internal code ω of the search key to register the data and store the storage address. It is a way to decide. For this reason, a function for obtaining an address from the internal code ω of the search key is required, and this function is called a “hash function”. The address H (ω) obtained by the hash function H is called a “hash address”. In addition,
As in the case of registration, the search is performed by obtaining a hash address using a hash function and searching for data at the target address.

In the dictionary search and dictionary registration using such a hash method, no matter how the hash function H is selected, the hash addresses are H (ω) for the internal codes ω ₁ and ω _{2 of} different search keys. There may be cases where ₁ ) = H (ω ₂ ). Such a state is called “collision”, and an external hash method (also called “open hash method” or “chain method”) is used to avoid this collision.
Is used. Further, the perfect hash method is a method in which all possible values for the internal code ω of the search key are prepared in advance in the table so that no collision occurs. Hereinafter, the case of using the external hash method and the case of using the complete hash method will be described separately.

FIG. 6 is a diagram showing the data structure of the external hash method. In the external hash method, first, the hash function H
A table corresponding to the addresses obtained by the above, that is, an array called Bucket Header (BH) is prepared. In the figure, this bucket header BH is provided with b list headers (list headders) having hash addresses 0 to (b-1). Then, one of the list headers and one or more data elements having the same hash address, that is, the list L, are linked by a list structure. Here, one list includes a data storage area for storing data and a pointer storage area for storing a pointer to the next list.

For example, as shown in FIG. 6, the list header indicated by the hash address "0" is combined with the list L01 by setting a pointer to the list L01. This relationship is indicated by arrow A1. The list L01 and the list L02 are combined with each other by setting a pointer to the list L02. This relationship is indicated by arrow A2. If the lists L02 and the subsequent ones are not linked by the pointers, the terminal symbol “0” is set. Hereinafter, the list headers having hash addresses 1 to (b-1) are similarly linked to the list L by the list structure.

The data retrieval is performed in the following procedure. Note that, here, a case where the hash address obtained by the hash function H is “3” will be described as an example. From the list header of the bucket header BH corresponding to the obtained hash address “3”, the first list L3
Get a pointer to 1. And the first list L3
Match with the data in 1. If the data do not match, a pointer to the next list L32 is obtained and collated with the data in the next list L32. If the data do not match, it indicates that the desired data was not found.
If a pointer to the next list is set in the list L32, the target data is searched through similar search processing.

Data registration is performed according to the following procedure. Similar to the data search, the case where the hash address obtained by the hash function H is “3” will be described as an example. The pointer to the first list L31 is acquired from the list header of the bucket header BH corresponding to the obtained hash address “3”. Then, the list is traced until the pointer to the next list becomes "0". Since the list L32 is the last list in the example of FIG. 6, a new data list is generated here, and a pointer to the generated list is set in the pointer storage area in the list L32.

In the dictionary having such a data structure, data retrieval and registration processing is performed as follows.
FIG. 7 is a diagram showing an example of a dictionary search procedure and a dictionary registration procedure by the external hash method. In the figure, the dictionary is the first memory FM, next in order to speed up the search and registration process.
It is composed of three physical memories, a memory NM and an extention memory EM. Further, these three memories are divided into an initial dictionary and a normal dictionary according to the contents of data to be registered.

First, the data retrieval using this dictionary is processed in the following procedure. Here, a case where the character string to be searched is “K ₂₂ K ₃₂ K ₄₂ ” and the hash address obtained by the hash function H of this character string is “ω ₁ ” is described as an example.

First, the hash function H
Dress ω₁From the address of the first memory FM of the initial dictionary
Ω₁Pointer to the next list stored in_{twenty one}To
get. And a pointer ω to the next list_{twenty one}From
 address of extention memory EM ω_{twenty one}Stored in
Data K_{twenty one}To match. In this case, the character string K_{twenty two}K₃₂K ₄₂
First letter K_{twenty two}Does not match with, so next memory NM
Address of ω_{twenty one}To the next list from ω_{twenty two}Get
To do.

Next, from the pointer ω ₂₂ to the next list,
The pointer ω ₃₁ to the next list stored in the address ω ₂₂ of the first memory FM of the normal dictionary is acquired. Less than,
The same search as in the case of the initial dictionary is performed. Finally, the data K ₂₁ stored in the address ω ₄₁ of the extention memory EM was collated, but the matching character string could not be retrieved, and the process ended. This process is indicated by an arrow in FIG.

Data registration using this dictionary is performed by the following procedure. Note that, here, a case will be described as an example in which the character string “K ₂₂ K ₃₂ K ₄₂ ” that cannot be searched in the above is registered. The list is traced until the pointer to the next list becomes "0" by the same process as the above-mentioned data search. In this case, the address of the next memory NM becomes ω ₄₁ . Here, the character K ₄₂ is generated at another address of the extention memory EM. In FIG. 7, this address is ω ₄₂ , and “0” is set in the next memory NM at the same address. Also, to concatenate the lists, ne
At the address ω ₄₁ of the xt memory NM, ω ₄₂ which is a pointer to the newly generated list is registered. In this way, a new character string is registered.

It should be noted that the above-mentioned data search and data registration are performed for character strings up to the second character in the initial dictionary.
In the normal dictionary, the character string starting from the third character is used. This will optimally distribute the input string, so
It is possible to reduce the processing time when performing data search and data registration.

The initial dictionary is not limited to the character string up to the second character, and the normal dictionary is not limited to the character string after the third character.
For example, the initial dictionary may be a character string of up to the third character, and the normal dictionary may be a character string of the fourth character or later, depending on the nature of the input character string. By doing so, it is possible to construct an optimal dictionary corresponding to various properties of the input character string.

FIG. 8 is a diagram showing an example of a dictionary search procedure and a dictionary registration procedure by the perfect hash method. The perfect hash method is a key search method using a hash function that does not cause any collision. The dictionary constructed by this perfect hash method has, for example, a tree structure shown in FIG.
It has a structure having 256 "branches" for each "node".

In the figure, the dictionary is a complete hash memory P.
It is composed of a physical memory of only M, and is divided into an initial dictionary and a normal dictionary according to the contents of data to be registered.
Further, the address of the complete hash memory PM is composed of a hash address ω and a data address K in order to correspond one-to-one with the data of each character string.

For example, if the hash address ω is an address represented by 20 bits and the data address K is an address represented by 8 bits, the total of 2
The 8-bit address is used as the address of the complete hash memory PM. That is, each hash address ω
Indicates the start address of each block of 256 data addresses K. In FIG. 8, the complete hash memory P
The address of M is represented by “ω _nn · K _xx ”.

Data retrieval using this dictionary is performed by the following procedure. Here, a case where the character string to be searched is “K ₂ K ₃ K ₄ K ₅ ”, and the hash address obtained by the hash function H of this character string is “ω ₁ ” is described as an example.

First, the hash function H
Dress ω₁And the first character K in the string ₂From the data of
Term dictionary address ω₁・ K₂Flag F stored in
Get L. Flag FL indicates whether this address is valid or not.
The effect is indicated by "1" or "0". In this case, the flag FL
Since "1" is set to, the character K₂Is valid
It Therefore, the first character of the search string matches the dictionary.
Indicate what you have done.

Next, the second character K of the character string₃Is valid or not
To check the address ω₁・ K ₂Stored in
Pointer to next ω_{twenty one}To get. And the address ω_{twenty one}
And the second character K in the string₃Data of the initial dictionary
Dress ω_{twenty one}・ K₃To get the flag FL stored in
It Hereinafter, the search is performed by the same process. That
And finally the address ω₄₁・ K_FiveFlags stored in
Matches with FL, and ends without finding a matching character string.
ing. This process is indicated by an arrow in FIG.

Data registration using this dictionary is performed by the following procedure. Here, it is described as an example a case of registering the character string "K ₂ K ₃ K ₄ K _5" that could not be searched in the above. The list is traced until the pointer to the next list becomes "0" by the same process as the above-mentioned data search. In this case, the address of the complete hash memory PM is ω ₄₁ · K ₅ . Here, the flag FL is set to "1". In this way, a new character string is registered.

Next, the LZW encoding means and LZW decoding means shown in the above embodiment will be described. Figure 9
It is a figure which shows the specific example at the time of encoding an input character string by the encoding algorithm of a LZW code. This input character string is a character string consisting of a combination of only three characters a, b, and c. First, initialization is performed in advance by registering only one character a, b, and c in the dictionary in association with the codes 1, 2, and 3, respectively.

First, the input character string 71 is read character by character from left to right. The first letter a is read and this a is used as the prefix (string). Next, the second character b is read, and ab obtained by adding this b to the preceding letter a is collated with the registered character string in the dictionary. At this time, since there is no character string matching ab in the dictionary, the corresponding code 1 of the preceding letter a is output as the encoded output. The output code is shown in the output code column 72. At the same time, the character string ab is registered in the dictionary in association with the code 4. The contents registered in this dictionary are shown in the registration contents column 73. Here, let the second input character b be the initial letter again.

Next, the third character a of the input character string 71 is read, and ba, which is the initial character b plus this a, is collated with the registered character string in the dictionary. At this time, since the character string matching ba is not in the dictionary, the corresponding code 2 of the initial letter b is output as the encoded output, and the character string ba is registered in the dictionary in correspondence with the code 5. In addition, the third input character a is defined as the initial letter.

Further, the fourth character b is read and ab which is obtained by adding this b to the initial character a is collated with the registered character string in the dictionary. At this time, since the character string matching ab is registered in the dictionary, ab is the initial character string at this time.
Furthermore, the fifth input character c is read and the initial character string a
The abc obtained by adding the c to the b is collated with the registered character string in the dictionary. At this time, since there is no character string matching abc in the dictionary, the corresponding code 4 of the initial character string ab is output as an encoded output, and the character string abc is registered in the dictionary in correspondence with the code 6. Then, the fifth input character c is set as the initial letter again.

Thereafter, the encoding and the dictionary registration are continued by the same algorithm. With this algorithm, the input character strings a, b, a, b, c, ... Are encoded,
Codes 1, 2, 4, as shown in the output code column 72 of FIG.
3, ... Are output as encoded outputs. Then, the registered character string 91 and the corresponding code 92 as shown in FIG.
The correspondence relationship with is registered in the dictionary.

FIG. 10 is a flow chart showing the encoding processing procedure exemplified above. In the figure, the number following S indicates a step number. [S101] By initializing, all the one characters that may be input are registered in the dictionary in correspondence with the codes. The address n to be registered next in the dictionary
Is set to 256, for example. Here, n corresponds to the total number of registered character strings, when the codes are assigned 0, 1, 2, ... Corresponding to the character strings registered in the dictionary. Furthermore, the input character string is read, and the first character input is used as a prefix string ω.

[S102] The next input character K is read. [S103] In step S102, it is determined whether or not there is input character data. If the input character data exists, the process proceeds to step S105, and if not, the process proceeds to step S104.

[S104] The initial character string ω is collated with the dictionary, and the corresponding code code (ω) is read and output as a coded output. At this time, the code code (ω) is converted into a binary code having a bit number of [log ₂ n] and output. here,
The symbol [x] represents the smallest integer among the integers of the numerical value x or more. Hereinafter, the symbol [x] will be used in this sense. Since there is no character string to be processed in this step, this step is terminated after this step is executed.

[S105] Step S is added to the initial character string ω.
The character string ωK added with the character K read in 102 is collated with the dictionary to determine whether the character string ωK is registered in the dictionary. If registered, the process proceeds to step S106, and if not registered, the process proceeds to step S107.

[S106] The character string ωK is set again as the initial character string ω. Then, the process returns to step S102 again. In this way, by repeating steps S102 to S106, as a character string that matches the input character string,
The maximum length character string of the character strings registered in the dictionary is searched.

[S107] The initial character string ω is collated with the dictionary, and the corresponding code code (ω) is read out and output as a coded output. The number of bits of the code code (ω) at this time is [log ₂ n]. Further, the value of n is associated with the character string ωK and registered in the dictionary. That is, the address n of the dictionary
The character string ωK is stored in. Further, the character K read in step S102 is used as the initial character string ω, and the dictionary address n is incremented to prepare for execution of step S102 and subsequent steps for the next new input character string.

FIG. 12 is a diagram showing a specific example of the case where the encoded output shown in FIG. 9 is restored. Only the codes 1, 2, and 3 are registered in advance in the dictionary on the restoration side by initialization so as to be associated with the characters a, b, and c, respectively.

First, the input codes 81 are read from left to right one by one. The first code 1 is read and the character string a is restored by referring to the dictionary. The character string restored at this time is shown in the restored character string column 821. The first code is always registered in the dictionary by initialization. Then, the second code 2 is read, and the character string b is restored by referring to the dictionary. At this time, the last input code 1 and the first character b of the character string decoded this time
The reference numeral 4 is associated with “1b” that is a combination of and and registered in the dictionary. The registered contents at this time are displayed in the registered contents column 8
3 shows.

Next, the third code 4 of the input character string 81 is read, and the corresponding "1b" is read by referring to the dictionary. Further, the code 1 of "1b" is referenced to read the corresponding character a. Such a series of repeated read operations is called "recursive decoding". This is the recursive decoding field 8
2 shows. As a result, the character string ab is restored and output as a restored character string. The output character string is shown in the restored character string column 831. At the same time, a combination of the previous input code 2 and the first character a of the character string restored this time, "2
"5" is associated with "a" and registered in the dictionary.

Thereafter, character string restoration and dictionary registration are continued by the same algorithm. In this way, the input code 1,
Restoration is performed on 2, 4, 3, 5, ...
Character strings a, b, a as shown in the restored character string column 821
b, c, ba, ... Are output as a restored character string.
Then, the correspondence relationship between the registration code 93 and the corresponding character string 94 as shown in FIG. 11B is registered in the dictionary.

FIG. 13 is a flowchart showing the decoding processing procedure exemplified above. In the figure, the number following S indicates a step number. [S111] By initializing, the characters are registered in the dictionary in correspondence with the characters that may be input. Also, the address n to be registered next in the dictionary is
For example, it is set to 256. Here, n corresponds to the total number of registered character strings, when the codes are assigned 0, 1, 2, ... Corresponding to the character strings registered in the dictionary. Next, read the input code and set the first input code CODE (binary code) to 1
The input code ω is converted to a 0-ary number. In this case, ω was the input character string in the encoding of FIG. 10, but in this decoding ω
Note that is the input code. And this ω
OLD ω. At the same time, since the code to be input first is already registered in the dictionary, the character D corresponding to the input code ω
(Ω) is searched from the dictionary and output as a restored character. The output character is set in FINchar for exception processing in step S116 described later.

[S112] The next input code CODE is read. [S113] It is determined whether or not there is input code data in step S112. If it exists, the process proceeds to step S115, and if it does not exist, this processing procedure ends.

[S114] The read input code CODE is converted into the input code ω, and this input code ω is changed to INω.
Set to. [S115] The input code ω is compared with n. That is, it is determined whether or not the input code is registered in the dictionary (ω ≧ n). If ω is smaller than n, step S11
7 and proceeds to step S116 when ω is n or more. Note that ω becomes n or more when, for example, the input code column 81 in FIG. 12 is “8”.

[S116] OLD ω and FINchar set in step S111 or the previous step S119.
Replace the set (OLD ω, FINchar) with ωK. That is, the value set in OLD ω is set in ω, and the value set in FINchar is set in K. Then, K is pushed onto the stack (PUSH). Note that ω is in step S117
Is decrypted with.

[S117] Normally, since the input code ω is registered in the dictionary by the processing up to the previous time, the character string D (ω) corresponding to the input code ω is read from the dictionary. The read character string D (ω) is decomposed into ω _i K. ω _i is a code and K is a decoded character. Then, it is determined whether or not the character string D (ω) is one character that cannot be decomposed into ω _i K. D (ω)
Is decomposed into ω _i K, the process proceeds to step S118,
If D (ω) is one character, the process proceeds to step S119.

[S118] The letter K is temporarily pushed onto the stack, the code ω _{i is set} to a new ω, and the process returns to step S117. The execution of steps S117 and S118 is repeated until D (ω) reaches one character.

[S119] LIFO (Last In Fast Out) of each character pushed on the stack in step S118.
Pop (POP) in the format and output the restored character string. For example, if the input code column 81 in FIG. 12 is "5",
Pushed on the stack in the order of a and b, and the restored character string ba is output. At the same time, the first character of the character string restored this time is set to FINchar, and the previously set OLDω
A character string consisting of a combination with FINchar (OLDω, FINchar) is registered in the dictionary in correspondence with the value of n. That is, this character string is stored at address n of the dictionary. Further, n is incremented and IN set in step S114 is set.
ω is set to OLD ω to prepare for execution of the next step S112 and thereafter.

As described above, in the decoding process, the data before encoding is restored by repeating the steps S117 to S119 of FIG. That is, since the input code ω is registered in the dictionary by the processing up to the previous time,
The character string D (ω) corresponding to the input code ω is read from the dictionary. Further, the read character string D (ω) is decomposed into ω _i K, and this character K is temporarily saved in the stack. Then, using the code ω _i as a new input code ω, the character string D (ω) corresponding to the input code ω is read again from the dictionary. These procedures are recursively repeated until the new input code ω becomes one character. Then, the character saved in the stack is L
This is a method of popping and outputting in the IFO format.

FIG. 14 is a diagram showing an example of a tree structure of a dictionary used in the above processing procedure and the like. The tree structure of this dictionary is
It is the figure which shows the internal structure of the dictionary used at the time of encoding and decoding by the algorithm realized in the LZW encoding means and the LZW decoding means. In FIG. 14, the numbers in the circles indicate the identification numbers, and the places with the numbers in the circles are called “nodes”.

The dictionary 50 has a root 51 as a starting point. No characters are assigned to this route 51. Then, the first character is registered one level below the root 51, that is, in the first level 52. When registering the first character, different characters are registered.
It is done at the time of initialization. Although three characters “a”, “b”, and “c” are registered in the figure, actually 256 characters that can be represented by 8-bit data are registered.

The layers below the second layer 53 are characters registered by learning the character string input from the information source. A node having a layer one level below is called a "branch", and a node having a layer one level below is called a "leaf". Therefore, in the figure, the numbers 25, 26, 13, 14, 27, 28, 16,
The nodes of 6, ..., 22, 23, 24 are “leaf”, and the other nodes are “branches”.

Even if a certain node is currently a “leaf”, it may become a “branch” due to learning. For example,
When registering the character string “acd” in the dictionary 50, the character string “ac” is “a” (the number 1 in the circle) in the first layer 52 and “c” (the number 6 in the circle) in the second layer 53. ), The new “d” is registered in the third layer 54 below the “c” in the second layer 53. At this time, the node with the numeral 6 in the circle changes from “leaf” to “branch”.

In the above description of the embodiment, the code is output by the data compression circuit as the output code having the smallest integer bit number of log ₂ n or more.
Bit fraction compensation, Phasin, as disclosed in No. 23
You may output with g in Binary Codes or the output code which consists of multi-valued arithmetic codes.

Although the initial dictionary D1, the normal dictionary D2 and the dictionary D3 are constructed based on the external hash or the complete hash and the dictionary 50 is constructed based on the tree structure, the dictionaries may be constructed based on other construction methods. . For example, a dictionary may be constructed by a binary tree method, and data such as character strings registered in the dictionary may be searched by a binary search.

The above embodiments are applied to compression and decompression of character codes, vector information, image data and the like in workstations and the like, and the required storage capacity can be greatly reduced.

Further, it can be applied to data transmission / reception using a communication line, and the communication time can be shortened. For example, it can be applied to communication devices such as a modem and a facsimile.

[0113]

As described above, in the present invention, in the data compression circuit, the first dictionary searching means searches the initial dictionary or the normal dictionary for the longest registered character string that matches the input character string, and at the same time, The dictionary search unit 1 adds an identification number to the character string obtained by adding one character to the longest registered character string and registers it in the normal dictionary, and the encoding unit uses the identification number added to the longest registered character string as the output code. Since the encoding is performed, the encoding process can be performed quickly.

Further, in the data compression circuit, since the initial dictionary and the normal dictionary are configured to perform the data search and the data registration by the external hash, the data search and the data registration become faster, and the encoding process can be performed faster. it can.

Further, in the data compression circuit, data search and data registration are performed for character strings up to the second character in the initial dictionary, and data search and data registration are performed for character strings after the third character in the normal dictionary. Since it is configured as described above, it is possible to suppress the processing time related to data search and data registration.

In the data compression circuit, since the initial dictionary and the normal dictionary are configured to perform data retrieval and data registration by perfect hash, the data retrieval and data registration become faster, and the encoding process can be performed faster. it can.

Since the first dictionary searching means, the first dictionary registering means and the encoding means perform parallel processing by the pipeline, the encoding processing can be performed at high speed.
Moreover, in the data restoration circuit, the decoding means decodes the input code, and at the same time, the second dictionary searching means searches the dictionary for the character string restored by the decoding, and the first storing means and the second storing means. Accumulates the restored strings,
Since the restored character string output by the output selection unit is selected and the second dictionary registration unit adds a new code to the unregistered restored character string and registers it in the dictionary, the decoding process can be performed quickly.

Decoding means, second dictionary searching means,
Since the output selection means and the second dictionary registration means perform parallel processing by the pipeline, the decoding processing can be performed at high speed.

Then, in the data compression / decompression device,
In the data compression circuit, the first dictionary searching means searches the initial dictionary or the normal dictionary for the longest registered character string that matches the input character string, and at the same time, the first dictionary searching means adds one character to the longest registered character string. The character string is added with an identification number and registered in a normal dictionary, and the encoding means encodes the identification number given to the longest registered character string into an output code. Further, in the data restoration circuit, the decoding means decodes the input code, and at the same time, the second dictionary search means searches the dictionary for the character string restored by the decoding, and the first storage means and the second storage means The restored character string is accumulated, the restored character string output by the output selection means is selected, and the second dictionary registration means adds a new symbol to the unregistered restored character string and registers it in the dictionary. The encryption process and the decryption process can be performed quickly.

Therefore, the processing speed of each circuit and the entire device can be improved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of a data compression circuit according to the present invention.

FIG. 2 is a diagram showing a processing procedure by a data compression circuit of the present invention.

FIG. 3 is a diagram illustrating the principle of a data restoration circuit according to the present invention.

FIG. 4 is a diagram showing a processing procedure by the data restoration circuit of the present invention.

FIG. 5 is a diagram illustrating the principle of the data compression / decompression device of the present invention.

FIG. 6 is a diagram showing a data structure of an external hash method.

FIG. 7 is a diagram showing an example of a dictionary search procedure and a dictionary registration procedure by the external hash method.

FIG. 8 is a diagram showing an example of a dictionary search procedure and a dictionary registration procedure by the perfect hash method.

FIG. 9 is a diagram showing a specific example of encoding.

FIG. 10 is a diagram showing an encoding processing procedure.

FIG. 11 is a correspondence diagram of character strings and codes.

FIG. 12 is a diagram showing a specific example of decoding.

FIG. 13 is a diagram showing a decoding processing procedure.

FIG. 14 is a diagram showing an example of a tree structure of a dictionary.

FIG. 15 is a diagram showing a conventional data compression circuit.

FIG. 16 is a diagram showing a processing procedure by a conventional data compression circuit.

FIG. 17 is a diagram showing a conventional data restoration circuit.

FIG. 18 is a diagram showing a processing procedure by a conventional data restoration circuit.

[Explanation of symbols]

 1 dictionary search means 2 dictionary registration means 3 encoding means 4 initial dictionary 5 ordinary dictionary 11 decoding means 12 dictionary search means 13 first storage means 14 second storage means 15 output selection means 16 dictionary registration means 17 dictionary

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hirotaka Chiba 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited

Claims (8)

[Claims] 1. In a data compression circuit for compressing an input character string input from an information source by encoding, among registered character strings registered in an initial dictionary (D1) or a normal dictionary (D2), First dictionary search means (1) for searching the longest registered character string that matches the input character string that has been input
An initial dictionary access means (4) for accessing the initial dictionary (D1), a normal dictionary access means (5) for accessing the normal dictionary (D2), and one character in the longest registered character string. The first dictionary registration means (2) for adding an identification number to the character string added with and registering it in the normal dictionary (D2), and the identification number given to the longest registered character string as an output code. A data compression circuit comprising: an encoding means (3) for encoding. 2. The data compression circuit according to claim 1, wherein the initial dictionary (D1) and the normal dictionary (D2) are configured to perform data search and data registration by an external hash. 3. The data compression circuit according to claim 1, wherein the initial dictionary (D1) and the normal dictionary (D2) are configured to perform data search and data registration by perfect hash. 4. The initial dictionary (D1) performs data search and data registration for character strings up to the second character, and the normal dictionary (D2) performs data search and data registration for character strings after the third character. The data compression circuit according to claim 1, wherein the data compression circuit is configured to perform. 5. The first dictionary search means (1), the first dictionary registration means (2), and the encoding means (3),
The data compression circuit according to claim 1, wherein the data compression circuit is processed in parallel by a pipeline. 6. A decoding means (11) for decoding an input code input in a data recovery circuit for recovering by decoding an input code input from an information source.
A second dictionary search means (12) for searching a registered character string registered in the dictionary (D3) for a registered character string that matches the character string restored by the decryption; and the registered character string. In the first storage means (13), the second storage means (14) for storing the registered character string, the first storage means (13) or the second storage means (14) Output selection means (15) for selecting one of the stored registered character strings from the stored registered character strings and outputting it as a restored character string; and a registered character string registered in the dictionary (D3). home,
Second dictionary registration means (16) for searching for a registered character string that matches the restored character string, adding a new symbol to the unregistered restored character string, and registering it in the dictionary (D3); A data restoration circuit comprising: a dictionary access means (17) for accessing the dictionary (D3). 7. The decoding means (11), the second dictionary search means (12), the output selection means (15) and the second dictionary registration means (16) are processed in parallel by a pipeline. 7. The data restoration circuit according to claim 6, wherein: 8. A data compression / decompression device that compresses and decompresses an input character string or an input code input from an information source by encoding or decoding the initial dictionary (D1) or the normal dictionary (D2). A first dictionary search means (1) for searching the longest registered character string that matches the input character string input from the registered character strings registered in
Initial dictionary access means (4) for accessing with 1)
And a normal dictionary access means (5) for accessing the normal dictionary (D2), and a character string obtained by adding one character to the longest registered character string with an identification number, and the normal dictionary (D).
A data compression circuit comprising first dictionary registration means (2) for registration in 2) and encoding means (3) for encoding the identification number given to the longest registered character string into an output code; Decoding means (11) for decoding the inputted input code
And among the registered character strings registered in the dictionary (D3),
Second dictionary retrieval means (12) for retrieving a registered character string that matches the character string restored by the decryption, first accumulating means (13) for accumulating the registered character string, and the registered character string. Second accumulating means (14) for accumulating and storing the first accumulating means (13) or the second accumulating means (14)
Output selection means (15) for selecting one of the stored registered character strings from the stored registered character strings and outputting it as a restored character string; and the registered character string registered in the dictionary (D3). Second dictionary registration means (16) for searching for a registered character string that matches the restored character string among them, and adding a new symbol to the unregistered restored character string and registering it in the dictionary (D3) And a data decompression circuit comprising a dictionary access means (17) for accessing the dictionary (D3), and a data compression / decompression device.