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Pattern matching using deterministic finite automata and organization of such automata

  • US 7,672,941 B2
  • Filed: 02/22/2005
  • Issued: 03/02/2010
  • Est. Priority Date: 01/21/2005
  • Status: Expired due to Fees
First Claim
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1. A method of operating a deterministic finite state machine as implemented in an integrated circuit to detect any one of a plurality of signatures each corresponding to a succession of characters and each defined by a sequence of states in the state machine, the method comprising;

  • organizing the states of the machine such that for each state after the first in any sequence there are not more than two allowed exit transitions of which one is to a default state;

    examining a stream of input characters received from a communications network to determine in response to each input character a transition from a current state of the machine to a next state; and

    when the machine responds to an input character to perform a transition to the default state, re-examining that input character to determine the next state of the state machine wherein input characters are held in a memory from which they are automatically read by an incrementing reader and the method further comprises comparing the current state of the machine with the default state and on detection of a match inhibiting for one incrementing cycle the incrementing of the reader.

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