Regular expression matching equipment and method on basis of deterministic finite automaton

A technology of expression matching and finite state, which is applied in the fields of instruments, computing, and electrical digital data processing, etc., can solve problems such as difficult to support regular expressions, DFA space explosion, etc., and achieve the effect of reducing storage space and fast matching speed

Active Publication Date: 2012-06-27
DAWNING INFORMATION IND BEIJING +1
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Problems solved by technology

Various state machines are mainly used to achieve regular expression matching, but DFA ha

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  • Regular expression matching equipment and method on basis of deterministic finite automaton
  • Regular expression matching equipment and method on basis of deterministic finite automaton
  • Regular expression matching equipment and method on basis of deterministic finite automaton

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Embodiment Construction

[0028] The key steps are illustrated through an example of a regular expression and its DFA. Suppose the regular expression is: \$[0-9]+(\.[0-9][0-9])? .

[0029] The role of this expression is to identify the number of dollars (beginning with $, followed by multiple numbers, if there is a ".", it must be followed by two numbers, such as "$12" and "$12.34" can be successfully matched). figure 1 is a state transition diagram, figure 2 is the state transition table. The transfer table has 256 columns (the character set of this paper is example with the ASCII character table, so there are 256 next states, but the applicable character set of the present invention is not limited to the ASCII table), corresponding to 256 values ​​of a byte respectively; The ~... in the last column in the figure represents all letters except 0~9, ., $. The jump process is as follows. Suppose you are in state C, if you enter "$", you will enter state B; if you enter a value between 0 and 9, you ...

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Abstract

The invention provides regular expression matching equipment and a method on the basis of a deterministic finite automaton. The regular expression matching equipment comprises a packet dispatcher and a result collecting module. A regular expression matching system comprises a matching unit and a storage unit connected with the matching unit, the matching unit is respectively connected with the packet dispatcher and the result collecting module. In the method, each status transfer table is disintegrated into a character substitution table and a simplified status table, many statuses have identical character substitution tables and can be shared after disintegration, and furthermore, many statuses have identical character substitution tables, and can share the identical character substitution tables after minority skips are extracted. By the regular expression matching equipment and the method on the basis of the deterministic finite automaton, storage space for the DFA (deterministic finite automaton) is greatly reduced, and more regular expressions can be stored in a limited space.

Description

technical field [0001] The invention relates to the field of regular expressions belonging to network information processing, in particular to a regular expression matching device and method based on a definite finite state automaton. Background technique [0002] Regular expressions are widely used in the field of network information processing, such as protocol identification, intrusion detection, etc. Various state machines are mainly used to achieve regular expression matching, but DFA has the problem of space explosion, and it is difficult to support more regular expressions. There are several regular expression matching schemes using DFA at present. One is to appropriately rewrite regular expressions to improve storage efficiency; the second is to mine the characteristics of state transitions. For example, the next state of most states has only a few different values. Delayed transfer and other methods can be used to reduce the cost of matching speed. Save storage sp...

Claims

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Application Information

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IPC IPC(8): G06F17/30
Inventor 刘兴奎张英文李静李锋伟窦晓光
Owner DAWNING INFORMATION IND BEIJING
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