JP2745710B2 - String search method and apparatus therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a string search method used in an information search system or the like, that is, an input data symbol string (hereinafter, referred to as an input data symbol string).
The present invention relates to a method and a device for determining whether or not a specified symbol string (referred to as “pattern”, “keyword”, etc.) exists in “text”. The string search device is indispensable for searching for text information.

[Conventional technology]

With the introduction of office automation (OA), the database of document information is rapidly progressing, and the scale of the database is also increasing. In such a situation,
There is a strong demand for speeding up document information processing. Above all,
String search processing for searching for a specified specific symbol string called a pattern or a keyword from a symbol string called a text is frequently used and has an extremely large processing load.

To address this, several methods have been proposed for processing the string search processing using dedicated hardware. Representative examples thereof include a cell array method and a table look at type finite automaton method.
In the former cell array method, as shown in FIG.
This is a method in which strings are connected in series in an array, and a string search is realized by transmitting a state signal 70 between cells. In each cell 10, the state signal of the preceding cell and the result of comparison between one pattern character and one text character in the cell are:
A new symbol string is generated and transmitted to a subsequent cell. The method of generating and transmitting the state signal 70 is based on the principle of a finite state automaton that causes a state transition in units of one character.

FIG. 34 shows a state transition diagram of the finite automaton used in the conventional method when the pattern is “HORSE”. Here, 100 represents the state number of the finite state automaton, and 200 represents the direction of the state transition with respect to the input character of the text. In this example, the character from the text is 1
When each character is continuously input as "H""O""R""S""E", the state number 100 is sequentially from S _0, S _1, S _2,
The state changes to S ₃ , S ₄ , and S _5, and a pattern is detected when the state number 100 becomes S ₅ . FIG. 33 shows the relationship between the state number and the corresponding search state.

On the other hand, the latter table-glance type finite automaton method is
This is a method in which a pattern is detected while inputting text one character at a time and referring to the state transition table each time and repeating the state transition of the finite state automaton. In particular, when searching for a plurality of patterns, conventionally, a search for a plurality of patterns is realized by referring to the same table by creating a state transition table in consideration of the search for the plurality of patterns. .

FIG. 35 shows a state transition diagram of the finite state automaton in the conventional method when the patterns are “CAT” and “DOG”.
Here, 100 indicates a state transition diagram of the finite state automaton, and 2
00 indicates the direction of the state transition for the input character of the text. In FIG. 35, when the character “C” is input in the state 0, the state becomes 1 and when the character “D” is input, the state becomes 4
, And when other characters are input, the state remains 0. When the character "A" is input in the state 1, the state becomes 2; when the character "D" is input, the state becomes 4; and when the character "C" is input, the state becomes 1.
In this state, when another character is input, the state returns to 0. FIG. 37 shows the relationship between the state number and the corresponding search state.

In order to realize the state transition as described above, the table-glance type finite state automaton method uses a state transition table as shown in FIG. This is a table for obtaining the next state from the input character and the current state. Here, the input characters refer to the table as integer character codes. In this example, if characters "C", "A", and "T" are successively input from the text one by one, the states are 1, 2,.
.. Sequentially, and when the state number becomes 3,
The detection of the pattern "CAT" is recognized. Similarly, "D"
When “O” and “G” are input, the state sequentially transitions to 4, 5,..., And when the state number becomes 6, the pattern “DO
The detection of "G" is recognized.

For the above technologies, for example, IEE
ETransactions on Computers, Sea 28 (1979), 384-394 (IEEE Transations on
Computers, vol. C-28, No. 6, pp. 384-394, 1979) and Computer, Vol. 13, No. 1, pp. 26-40 (Computer, vol. 1).
3, No. 1, pp. 26-40, 1980).

[Problems to be solved by the invention]

The above prior art is based on (1) a finite automaton that causes a state transition in units of one character, so that the search speed of the string search is, in principle, one character per unit time.
If the speed of fetching characters from the storage device storing the text is one character per unit time, this is no problem. However, at present, 16-bit / 32-bit machines have emerged, and 2-byte fetch / 4-byte fetch per time have become possible. The above-mentioned prior art cannot cope with this, and the search speed is limited to one character per unit time even if the fetch speed of text characters is increased in this way. (2) Simultaneous search for multiple patterns Therefore, the state transition becomes extremely complicated as shown in FIG. 35, and there is a problem that a large amount of overhead is required to create a state transition table. This is because the table must be created in consideration of the transition between a plurality of patterns. In particular, when the number of patterns is large, or when a partial character string of a certain pattern exists as a partial character string in another pattern, it becomes extremely complicated. This table creation time overhead is not negligible in performing a string search except when searching for a particularly long text.

The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-described problems in the related art, improve the detection speed, and provide a table-glance finite-size search for a plurality of patterns. It is an object of the present invention to provide a string search method and an apparatus therefor that can reduce the time required to create a state transition table in the automaton method.

[Means for solving the problem]

The above object of the present invention is to determine whether a specified second character string exists in a first character string composed of characters (symbols) represented by a code having a certain code length. In the string search method, data of a plurality of characters is input from the first character string, and the input data of the plurality of characters and a current search state are input using a finite automaton which causes a state transition in a plurality of characters. , The next search state is determined, and it is determined whether or not the new search state has entered the search state indicating that the second character string to be searched has been detected, and the second character string has been detected. When the state is entered, a detection process is performed, the input address of the first character string is updated by a plurality of characters first, and an operation of inputting data in units of the next plurality of characters from the first character string is performed. To repeat Characteristic string search method and whether or not a specified second character string exists in a first character string composed of characters (symbols) represented by a code having a certain code length In the string search device, the first character string is sequentially input in units of a plurality of characters, and a finite automaton that causes a state transition in units of a plurality of characters is used. Means for determining a next search state from the search state and comparing the new search state with a search state (pattern detection state) indicating that the second character string to be searched has been detected. This is achieved by a string search device.

[Action]

First, in the string search method according to the present invention, data of a plurality of characters is input from the first character string,
By using a finite automaton that causes a state transition in units of a plurality of characters, transition of a search state in a string search can be realized in units of a plurality of characters. From this, it is determined whether the new search state has entered the search state indicating that the second character string (pattern) to be searched has been detected, and if the second character string has been detected, Can perform a detection process. By these,
Since the string search can be executed with the character input of the text in units of a plurality of characters, the search speed can be improved.
The string search device according to the present invention can realize a string search device suitable for efficiently executing the above string search method.

Further, in the string search device according to the present invention,
By providing a plurality of table-glance type finite automaton mechanisms for a single pattern and introducing means for executing them in parallel, the search for a plurality of patterns can be expanded to the search for individual single patterns. Thus, when creating the state transition table, it is not necessary to consider the transition between patterns, and the state transition table for each pattern can be created independently, so that the table creation overhead can be reduced. It is.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the code length of a character is 1
Assume bytes.

First, as a first embodiment of the present invention, a case where a text is input in units of two characters will be described. FIG. 1 is a configuration example of a string search system according to the present embodiment. In the figure, 1 is a storage device for storing a text to be searched, 2 is a string search device for performing a string search on the text 1, 3 is a text data transfer path, and 4 is a signal line for outputting a search result. I have. In the present embodiment, text data is sequentially input from the storage device 1 to the string search device 2 via the text data transfer path 3 in units of a plurality of characters using the input unit 1001. Further, a pattern is detected by using a finite state automaton 1007 that causes a state transition in units of two characters. Hereinafter, as an example of a search pattern,
Think "HORSE".

In this case, the state of the finite state automaton is defined as shown in FIG. FIG. 3 shows a state transition diagram of the finite state automaton 1007 that causes a state transition every two characters. Here, 1200 represents the state number of the finite state automaton, and 1300 represents the text input character (2
It indicates the direction of state transition with respect to each character. This is "XH", where two characters from the text are consecutive
Is input to the "OR", "SE", state number sequentially from S _0,
S ₁₁ , S ₁₂ , S _13, and two characters from the text
When "HO", "RS", and "EX" are entered consecutively,
State number sequentially from S _0, which indicates that changes the _{S 21, S 22, S 23} . Here, X represents any one character. The state number S ₁₃ and S ₂₃ is a state in which pattern is detected. By using such a finite automaton, it is possible to execute a string search while inputting text in units of two characters.

FIGS. 4 and 5 show examples of the configuration of the string search device 2 that realizes this. FIG. 4 is an overall configuration diagram of the string search device 2 in the first embodiment, and FIG. 5 is a configuration diagram of a cell 110 used therein. In FIG. 4, reference numeral 120 denotes a pattern register for storing one character of the pattern, and 110 denotes a cell. The cell 110 includes 2-byte character data 130 of the text transferred from the storage device 3, 2-byte character data of the pattern input through the pattern data transfer path 140, and the state signal transferred from the preceding cell. This is a circuit that generates a pattern detection signal 150 and a state signal 170 of the present cell by inputting the signal 170 as an input. In the case of the two-character unit input finite automaton in the present embodiment, as shown in FIG. 4, a configuration is adopted in which cells connected in series are arranged in two stages. This corresponds to the state transition diagram of the finite state automaton shown in FIG. On the other hand, a detection signal generation circuit 160 generates a detection signal 4 from the pattern detection signal 150 transferred from each cell. This can be realized by, for example, a logic for ORing all the pattern detection signals 150.

Next, the configuration of the cell 110 shown in FIG. 5 will be described. In each cell 110, two bytes of text input characters are input through a text input line. 111 determines the match / mismatch of these two bytes of data with a mask,
This is a coincidence determination circuit that generates a coincidence signal 116. Also, 114
Denotes a mask latch, and indicates that when the content of the mask latch 114a is a binary code “1” (hereinafter simply referred to as “1”), the match determination circuit 111 masks the first byte. Similarly, when the content of the mask latch 114b is "1", it indicates that the match determination circuit 111 masks the second byte. 114a is called a first mask latch, and 114b is called a second mask latch.

The coincidence determination circuit 111 can be realized by, for example, a circuit as shown in FIG. In the circuit shown in FIG. 6, two bytes of data input from the text input line 130 and the pattern input line 140 are simultaneously compared by the 16 EXOR circuits. Line 118a, 1
The coincidence signal 116 is output in consideration of the value of 18b. Note that a content addressable memory may be used as the match determination circuit 111.

On the other hand, reference numeral 115 denotes an indicator latch. In particular, 115a is a head indicator latch indicating the head of the pattern, and 115b is a tail indicator latch indicating the end of the pattern.
A state latch 113 indicates the state of the finite state automaton. The control circuit 112 is a circuit that generates an input signal 117 to the status latch 113 of the present cell and a pattern detection signal 150 from the information of the indicator latch 115 and the status signal 170 and the coincidence signal 116 of the preceding cell. This can be realized, for example, by a circuit as shown in FIG. The input signal 117 is
This is an input to the state latch 113 of this cell.

Next, the operation of this embodiment when the pattern is “HORSE” will be described.

First, the patterns "H", "O", "R",
Pattern buffer of Fig. 4 shifting "S" and "E" by one character
Set to 120-1 to 120-5. Further, "1" is set in the mask latch 114 for an arbitrary character "X" among the input characters in the state transition diagram of FIG. That is, as shown in FIG. 8, "1" is set in the first mask latch 114a-11 and the second mask latch 114b-23. Further, in order to teach the first character and the last character of the pattern, the first indicator latch 115a-11 and 115a-21, the last indicator latch 1
Set “1” to 15b-13 and 115b-23.

Thereafter, a string search for text is started. In other words, the text is stored in the storage device 1 every 2 hours.
Characters are simultaneously input to all cells 110 of the string search device 2 through the text data transfer path 3. In each cell 110, first, the match determination circuit 111 compares a 2-byte text input character with a 2-byte pattern character transferred from the pattern buffer 120 to each cell. For example, a match determination circuit
At 111-12, the input character and the second character of the pattern are compared with the third character "OR". Similarly, the match determination circuit
At 111-13, 111-21, and 111-22, the input characters are compared with the patterns "SE", "HO", and "RS", respectively.

However, in the match determination circuit 111-11, the first mask latch 11
Since 4a-11 is "1", the first byte is masked and compared. Therefore, it is logically compared with "XH". Similarly, in the match determination circuit 111-23, since the second mask latch 114b-23 is "1", it is logically "EX"
Will be compared to Here, X is as described above.
Refers to any single character.

Next, as shown in FIG. 7, the control circuit 112 performs an AND operation between the OR signal of the state signal 170 of the preceding cell and the output line 119a of the head indicator latch 115a and the coincidence signal 116, and obtains a new state signal 117. Generate This new status signal 117
This is input to the state latch 113 of this cell. In addition, a result obtained by performing an AND operation between the main state signal 117 and the output line 119b of the end indicator 115b is referred to as a pattern detection signal 150. When this becomes “1”, it means detection of the pattern.

In the above configuration, the content of the status latch 113-ij is "1"
It is a state signal of the finite automaton in Figure 3 represents the fact that a S _ij is.

Hereinafter, as an example of the text, a 16-character text "CAT,
HORSE, MONKEY ". In this example, the text input line 130 for the time and the pattern input line 140 of each cell 110-ij
-ij, the match signal 116-ij, and the change in the value of the state latch 113-ij,
As shown in FIG. In this example, time 3, time 4, time 5,
The state latches 113-21, 113-22, and 113-23 respectively become "1". Also, the tail indicator latch 115b of cell 110-23
-23 is "1", so the pattern detection signal 150-23
Becomes "1", indicating that the pattern has been detected. In the case of this example, the string search can be completed at eight times.

Hereinafter, as a second embodiment, a method of inputting text in units of four characters will be described. In this case, a finite automaton that causes a state transition every four characters is used. As an example of the search pattern, the same as the first embodiment,
Think "HORSE".

The state of the finite state automaton in this case is defined as shown in FIG. The state transition diagram of the finite state automaton that causes state transition in units of four characters proposed here is
It looks like Figure 11. In FIG. 11, reference numeral 2200 denotes a state number of the finite state automaton, and reference numeral 2300 denotes a direction of state transition with respect to a text input character (in units of four characters). In the FIG. 11, in succession from the text characters of four characters "XXXH" is input as "ORSE", state number sequentially from S _0, remained as S _11, S _12, also characters from the text There 4 by characters consecutively "XXHO" is input as "RSEX" indicates that state number has remained sequentially S _21, S ₂₂ from S _0. Similarly, when a character is entered as "XHOR", "SEXX", state number sequentially from S _0, it remained as S _31, S _32,
"XHOR" is input as "SEXX", state number sequentially from S _0, which indicates that changes the S _41, S _42. X represents any one character, and state numbers S ₁₂ , S ₂₂ , S ₃₂ and S ₄₂ are all states in which a pattern has been detected.
By using such a finite automaton, it is possible to execute a string search while inputting text in units of four characters.

An example of the configuration of the string search device 2 that realizes this is shown in FIG.
Figure 12 shows. Here, as shown in the figure, a configuration in which cells 210 connected in series are arranged in four stages. Where 220
Is a pattern register that stores one character of the pattern, 260
Is a detection signal generation circuit. An example of the configuration of the cell 210 is shown in FIG. Here, reference numeral 211 denotes a match determination circuit for determining the match / mismatch of 4-byte data with a mask, 213 denotes a state latch indicating the state of the finite automaton, 214 denotes a mask latch, and 214a denotes a match determination circuit. At 211, a first mask latch indicating that the first byte is to be masked. Similarly, 210b, 214c, and 214d indicate that the match determination circuit 211 is to mask the second, third, and fourth bytes. It is a mask latch shown in FIG.

Reference numeral 215 denotes an indicator latch. In particular, 215a denotes a head indicator latch indicating the head of the pattern, and 215b denotes a tail indicator latch indicating the end of the pattern.
The control circuit 212 is a circuit that generates the state signal 270 of the present cell and the pattern detection information 250 as in the case of the first embodiment.

 Next, the operation will be described.

First, the search pattern “HORSE” is entered one character at a time
These are set in the pattern buffers 220-1 to 220-5 shown in FIG. A mask latch corresponding to an arbitrary character “X” among the input characters in the state transition diagram of FIG.
Set “1” in 214. That is, the mask latch 214
a-11,214b-11,214c-11,214a-21,214b-21,214a-31,214d-
22,214c-32,214d-32,214b-42,214c-42,214d-42, "1"
Is set. In addition, the first indicator latch 210a-11,21
"1" is set to 5a-21, 215a-31 and 215a-41 and the tail indicator latches 215b-12, 215b-22, 215b-32 and 215b-42.

Next, a text is input from the storage device 1 to each cell 210 through the text data transfer path 3 by four characters. In the coincidence determination circuit 211 in each cell 210, a 4-byte input character is compared with a 4-character pattern character. That is,
The match determination circuit 211-11 compares the input four characters with "XXXH". Similarly, the match determination circuits 211-12, 211-21, 211-2
For 2,211-31,211-32,211-41,211-42, input 4 characters and patterns "ORSE", "XXHO", "RSEX", "XH"
OR ”,“ SEXX ”,“ HORS ”, and“ EXXX ”are compared.

The control circuit 212 generates a state signal 217 of the present cell from the match signal 216 output from the match determination circuit 211, the state signal 270 of the preceding cell 210, and the output line 219a of the head indicator latch 215a. Is the input of the state latch 213.
It states latches 213-ij is "1", the state number of the automaton in Figure 12 represents the fact that a S _ij. The result of ANDing the status signal 217 of the present cell with the output line 219b of the tail indicator 215b is defined as a putter use detection signal 250. As described above, the fact that it becomes “1” means the detection of a pattern.

As an example of a text, a text "CAT, HORSE, MONKEY" of 16 characters is considered as in the first embodiment. The text input line 230 and each cell 210-ij for the time in this example
Pattern input line 240-ij, match signal 216-ij, status latch 21
The change in the value of 3-ij is shown in FIG. In this case,
At time 2 and time 3, the state latches 213-41 and 213-42 respectively become "1". Since the content of the tail indicator latch 215b-43 of the cell 210-43 is "1", the pattern detection signal 250-43 becomes "1", indicating that the pattern has been detected. In the case of this example, the string search ends at four times.

Next, as a third embodiment, a case of searching for a pattern that includes a don't care character (wild character) in the pattern will be described.

As an example, the finite automaton of two-character unit input used in the first embodiment is used. Consider "H! RSE" as an example of a search pattern. Here, "!" Represents a don't care character (wild character), that is, one arbitrary character. The state of the finite automaton in this case is
It is defined as shown in FIG. FIG. 16 shows a state transition diagram of a finite state automaton in which two characters are input in this case. State number S _13, S ₂₃ shows a state where the pattern is detected.

The string search device 2 expressing this may have the same configuration as that shown in the first embodiment. The data previously set in each register or latch may be the same except that “1” is set in the mask registers 114a-12 and 114b-21 corresponding to the don't care character. Setting “1” in the mask registers 114a-12 and 114b-21 means that
In the first embodiment, "! R" or "H" is used instead of inputting "OR" or "HO" as a pattern to cells 110-12 and 110-21.
! ". The operation in this case is the same as in FIG.

Next, a brief description will be given of a pattern search including the variable length don't care character “?”. Here, the variable-length don't care character “?” Represents an arbitrary character string of 0 or more characters. FIGS. 17 and 18 show examples of the definition of the state of the finite state automaton and the state transition in this case. In this example, a finite automaton that causes a state transition every two characters is used. The device for realizing this need only slightly change the internal logic of the cell 110 and the connection between the cells in the device shown in FIG. 4 so as to correspond to the state transition in FIG.

Simultaneous retrieval of a plurality of patterns can be easily realized by simply setting a plurality of patterns in a pattern buffer serially and setting a corresponding value in an indicator latch.

In the present embodiment, an apparatus based on the cell array method according to the above-mentioned document (former) has been described as an example, but the present invention can be easily applied to an apparatus based on another cell array method.

Next, as a fourth embodiment, an example in which a table glance type finite automaton method is used will be described. In the embodiment described below, a finite automaton that causes a state transition in units of two characters will be used.

FIG. 19 is a configuration example of a string search device according to the present embodiment. In the figure, reference numeral 510 denotes an input character register for 2 bytes for storing input characters of text input from a storage device through a text data transfer path; 511, a status register for storing information on the state of a finite state automaton;
Is a random access memory (RAM) that stores a state transition table for a search pattern; 515 is an address line for the RAM 512; 513 is a next state register that stores information on the state of the next finite automaton; 3 shows a pattern detection determination circuit that determines whether or not a state has been reached.

Considering "HORSE" as an example of a search pattern, its state transition diagram is as shown in FIG. The corresponding state transition table is as shown in FIG. The state transition table is a table in which the next state can be identified from the current state and the input characters. This state transition table is set in the RAM 512 in advance. After setting the initial state 0 in the state register 511, the search is started.

FIG. 22 shows the operation of this embodiment. Consider "CAT, HORSE, MONKEY" as an example of a text. The text is input two times at a time from the storage device through the text transfer path. At time 1, since the contents of the state register 511 and the input character register 510 are "0" and "CA", respectively, the state transition table stored in the RAM 512 is accessed using the contents as addresses. Then, the next state “0” is fetched and input to the next state register 513. Then, it is input to the status register 511 again. On the other hand, in the pattern detection circuit 514, the next state is “3”.
The detection of the pattern is monitored depending on whether or not it becomes "6".

Hereinafter, this operation is repeated, and as shown in FIG. 22,
At time 5, “6” is input to the next state register 513, and the pattern “HORSE” is detected. In this embodiment, the string search can be completed at eight times.

Next, a fifth embodiment will be described. FIG. 23 shows an example of the configuration of a string search device using the table glance type finite automaton method of the present invention. In this example, it is assumed that two patterns “CAT” and “DOG” are searched.
In the figure, reference numerals 11 and 21 denote state registers for storing information on the state of the finite state automaton for each of the above-described patterns, and reference numeral 10 denotes an input character register for storing input characters of text input from a storage device through a text data transfer path. , 12 and 22 are RAMs for storing a state transition table for each pattern, 15 and 25 are respective address lines for the RAMs 12 and 22, and 13 and 23 are states for the next finite automaton for each pattern. A next state register, 14 and 24 are pattern detection and determination circuits for determining whether the next state has detected a pattern, and 30 is a detection information generation circuit for generating pattern detection information.

Using this apparatus, the state transitions of the two patterns can be created separately. Therefore, the time for creating the state transition table can be reduced. Two patterns "CAT" and "D"
The state transition of the finite automaton for "OG" is shown in FIGS. 24 and 25. This is because, for “CAT”, when characters “C”, “A”, and “T” are input consecutively from the text, the state numbers change from 0 to 1, 2, and 3 sequentially. Indicates that a pattern is detected, and "DOG"
When the characters are successively input as "D", "O", and "G", the state number changes sequentially from 0 to 4, 5, and 6, and the pattern is detected. It is shown.
FIGS. 26 and 27 show the state transition tables corresponding thereto. The state transition tables are stored in the RAMs 12 and 22 in FIG. 23, respectively.

Next, the operation of this embodiment will be described with reference to FIG. No.
FIG. 28 shows changes in the contents of the status register, the input character register, and the next status register. As an example of text, consider the 13-character text "CAT, HORSE, DOG". First, before starting the search, the initial state 0 is set in the status registers 11 and 12. Then, the text data is input from the storage device to the apparatus through the text data transfer path, one character at a time.

At time 1, the contents of the state register 11 and the input character register 10 are "0" and "A", respectively.
Go to 6. Then, the next state “1” is fetched and input to the next state register 13. Then, it is input to the status register 11 again. On the other hand, the pattern detection determination circuit 14 monitors the detection of the pattern based on whether the next state has become “3”. Similar behavior,
The state register 21, the address line 22, the next state register 23, and the pattern detection / judgment circuit 24 perform the operation in parallel, and “0” is input to the state register 21. Thereafter, this operation is repeated, and as shown in FIG. 28, "3" is input to the next state register 13 at time 3, a pattern "CAT" is detected, and "3" is stored in the next state register 23 at time 13. Is input, and the pattern “DOG” is detected.

Next, a sixth embodiment will be described. FIG. 29 shows an example of the configuration of a string search device for executing the sixth embodiment. Here, the mechanism for performing the string search is the same as in the fifth embodiment. The difference from the fifth embodiment is that, in the present embodiment, the state transition table creation device
19 and 29 are provided for each RAM. Thus, a state transition table can be created in parallel for each pattern, so that the table creation time can be reduced.

Next, a seventh embodiment will be described below. In the fifth embodiment, a method has been described in which a state transition table is created for each pattern and a search is performed using the state transition table. According to this method, it is necessary to prepare RAMs that can be independently accessed by the number of search patterns. Therefore, in the present embodiment, an efficient search method in the case where the number of search patterns is larger than the number of independently accessible RAMs will be described. As an example, four search patterns are replaced with two RAMs,
That is, a search method using two state transition tables will be described.

Here, the four search patterns are referred to as pattern 1 to pattern 4. In the present embodiment, for example, a state transition table for simultaneously retrieving pattern 1 and pattern 2 (see FIG. 36) and a state transition table for simultaneously retrieving pattern 3 and pattern 4 are created. Then, a search is performed using the two state transition tables. Thereby, four patterns can be searched using two independently accessible RAMs.

Next, an eighth embodiment will be described. This can be realized by the configuration example described in the fifth embodiment (see FIG. 23). However, in this embodiment, the input character register 13 and the RAM 12 for storing the state transition table are provided in the input character register 510 for a plurality of characters described in the fourth embodiment (see FIG. 19) and in the unit of a plurality of characters. The RAM 512 that stores the state transition table of the finite automaton that causes the state transition,
Shall be used. This can simultaneously reduce the time required to create the state transition table and speed up the string search process by processing input text characters in units of a plurality of characters.

Next, as a ninth embodiment, a string search device including input means 1001 for inputting text data in units of a plurality of characters and a comparator 2003 in units of a plurality of characters as shown in FIG. 30 will be described. In this embodiment, a pattern character string to be compared with a text character string is stored in advance in a storage device 2001, and an arbitrary character in the pattern character string is stored in a key pattern register 2005 and a pattern data register 2004 in a plurality of characters. Store minutes. Using the input means 1001, the data of the text data register 2004 is compared with the data of the comparator 20.
03, and the search control means 2002 determines the result.

Here, the text is “BULL / HORSE” and the pattern is “H
The operation in the case of "ORSE" will be described. The text is input in units of four characters using the input unit 1001. The value of the key pattern register 2005 is “HHH” in which the first character “H” in the pattern character string is arranged in four characters.
H ”. FIG. 31 shows the inputs of the text data register 1004 and the pattern data register 2002 and the comparison results. First, at time 1, the text "BUL
L ”and the key pattern“ HHHH ”. Since all characters do not match, the result is shifted by four characters and the next text is input.

At time 2, the text “• HOR” and the key pattern “HHH
H ”. Here, since "H" of the second character matches, at time 3, the text is shifted by two characters, and the data of the second character and thereafter is input as the pattern. In other words, the input text here is “ORSE” and the input pattern is “ORSE”, which completely matches, and the pattern “HORSE” is detected. In this embodiment, the string search can be completed at three times.

Each of the embodiments described above is shown as an example of the present invention, and it is needless to say that the present invention should not be limited to these.

〔The invention's effect〕

As described above in detail, according to the present invention, data of a plurality of characters is input from a first character string, and a finite state automaton that causes a state transition to a plurality of characters is used, whereby a string is formed of a plurality of characters. Since a search state transition in a search can be realized, a string search method capable of improving the detection speed and shortening the time required to create a state transition table in a table-glance type finite automaton method for searching a plurality of patterns and a method for the same. This has a remarkable effect that the device can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a string search system and a string search device according to a first embodiment of the present invention.
9 is an explanatory view of the first embodiment, FIGS. 10 to 14 are explanatory views of the second embodiment, FIGS. 15 to 18 are explanatory views of the third embodiment, FIG. FIG. 22 to FIG. 22 are explanatory diagrams of the fourth embodiment, FIG. 23 to FIG. 28 are explanatory diagrams of the fifth embodiment, FIG. 29 is a configuration diagram of the string search device in the sixth embodiment, FIG. Figure to No.
FIG. 31 is a configuration diagram of a string search device in a ninth embodiment, FIG. 32 is a configuration diagram of a conventional string search device,
FIG. 33 to FIG. 37 are explanatory diagrams of the prior art. 1: Storage device, 2: String search device, 3: Text data transfer path, 4: Detection signal line, 10: Input character register, 11, 2
1: Status register, 12, 22: RAM, 13, 23: Next status register, 1
4, 24: pattern detection determination circuit, 19, 29: state table creation device, 30: detection information generation circuit, 110: cell, 111: match determination circuit, 112: control circuit, 113: state latch, 114: mask latch, 115: indicator latch, 120: pattern buffer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Kitajima 1099 Ozenji Temple, Aso-ku, Kawasaki City, Kanagawa Prefecture Within Hitachi, Ltd. Systems Development Laboratory Co., Ltd. (72) Inventor Hidetoshi Ito 3-1-1 Sachicho, Hitachi-shi, Ibaraki No. Hitachi Nuclear Engineering Co., Ltd. (56) References JP-A-60-211539 (JP, A) JP-A-63-73422 (JP, A) JP-A-61-52739 (JP, A) JP-A-63 -228220 (JP, A) JP-A-60-105039 (JP, A) JP-A-53-54937 (JP, A) Setsuo Arikawa, et al., "About SIGMA, a text data management system", Information Processing Society of Japan Technical Report Vol. . 87, No. 65 PP. 1-8, September 21, 1987

Claims (8)

(57) [Claims] A string for determining whether a specified second character string exists in a first character string composed of characters (symbols) represented by a code having a code length of a certain length In the search method, data of a plurality of characters is input from the first character string, and a finite state automaton that causes a state transition of the plurality of characters is used to determine the next from the input data of the plurality of characters and the current search state. Is determined, and it is determined whether the new search state has entered the search state indicating that the second character string to be searched has been detected, and the state changes to the state in which the second character string is detected. In this case, a detection process is performed, the input address of the first character string is updated by a plurality of characters in advance, and an operation of inputting data of the next plurality of characters from the first character string is repeated. Features String search method. 2. When the second character string to be searched is given, the next search state when input data of a plurality of characters is input for each search state corresponding to the character string. Create a state transition table that understands, input data in the first character string in units of a plurality of characters at the time of retrieval, and input the current search state and input data in units of a plurality of characters in the first character string as arguments. 2. The string search method according to claim 1, wherein a string search is executed by accessing the state transition table and acquiring a next state. 3. A string for determining whether a specified second character string exists in a first character string composed of characters (symbols) represented by a code having a code length of a certain length. In the search device, means for sequentially inputting the first character string in units of a plurality of characters, and a finite automaton that causes a state transition in units of a plurality of characters, are used to determine the input data in units of a plurality of characters and the current search state. String search means for determining a next search state and comparing the new search state with a search state (pattern detection state) indicating that the second character string to be searched has been detected. apparatus. 4. A comparison means for judging whether or not the input first character string and the second character string match each other in units of a plurality of characters, and a state expressing a search state from a preceding cell. Means for generating a new state signal from the signal and the coincidence signal from the determination means and transmitting the signal to a subsequent cell; and determining whether or not the second character string has entered the detection state from the new state signal. 4. The string search device according to claim 3, wherein cells comprising means are connected in series, and a plurality of cells are arranged in multiple stages. 5. The system according to claim 1, wherein all of the substrings of the second character string and the input character string of the first character string are simultaneously compared by using the cells connected in multiple stages. 5. The string search device according to 4. 6. A comparison means for accessing a storage means for storing said state transition table from a pair information of input data of a plurality of characters and a current search state, and acquiring a next search state. 4. The string search device according to claim 3, wherein: 7. The string search device according to claim 6, further comprising: storage means for storing a plurality of said state transition tables; and means for accessing said state transition tables in parallel. 8. Using the plurality of state transition tables,
8. The string search device according to claim 7, further comprising means for creating the state transition table independently for each character string when searching for a plurality of character strings.