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Regular Expressions to Finite-state Automaton (RE2FA)

codecov

Overview

The RE2FA is a small library that can generate Deterministic Finite-state Automata (DFA) from a set of Regular Expression. It could be used for researches of the Exponential Blowup problem.

Doxygen documentation is hosted at GitHub Pages.

Prerequisites

To build this library and corresponding tools you need the following software.

  • Autotools including Automake and Libtool.
  • (optional) libz library for DFA file compression.
  • (for OSX) argp library.

Building

To build this library and corresponding application you have to execute the following commands from the top directory of the project.

Create configure script:

$ autoreconf -i

Generate makefiles:

$ ./configure

Build:

$ make

Running application re2fa

Some simple usage examples provided.

Generate minimal dfa from provided regular expression and print number of states.

$ re2fa --input-type=regexp -v -m '/a.{4}c/is'

Generate minimal dfa from provided file with regular expressions (regular expressions are written line by line) and save result to the file.

$ re2fa --input-type=regexp-file -v -m regexp.file -o result.dfa

Merge multiple DFA into one.

$ re2fa --input-type=dfa-file -v -m re1.dfa re2.dfa re3.dfa -o result.dfa

Supported regular expressions

Currently library supports PCRE-like regular expressions with some limitations.

  • Regular expression starts and ends with slash '/'.

  • After the final slash 'm', 's' and 'i' modifiers can be appended.

  • Square brackets '[' and ']' can be used only for character class definition.

  • Syntax '(?...)' is not supported.

  • Simple metacharacters such as '\', '^', '$', '.', '[', ']', '|', '(', ')', '?', '*', '+', '{' and '}' are fully supported.