unrealircd

This code is structured roughly as follows:

regcomp.c:
  - Regexp parser.  Parses a POSIX regexp (with TRE extensions) into
    an abstract syntax tree (AST).
  - TNFA constructor.
    * routine that adds appropriate minimized or maximized tags to an
      AST to keep track of submatches
    * conversion of tagged ASTs to tagged nondeterministic state
      machines (TNFAs)
  - Implements the regfree() function.

tre-match-parallel.c:
  - Parallel TNFA matcher.
    * The matcher basically takes a string and a TNFA and finds the
      leftmost longest match and submatches in one pass over the input
      string (typically only the beginning of the input string is
      scanned until a leftmost match and longest match is found).
    * The matcher cannot handle back references, but the worst case
      time consumption is always directly proportional to the length
      of the input string.

tre-match-backtrack.c:
  - A traditional backtracking matcher.
    * Like the parallel matcher, takes a string and a TNFA and finds
      the leftmost longest match and submatches.  Portions of the
      input string may (and usually are) scanned multiple times.
    * Can handle back references.  The worst case time consumption,
      however, is O(k^l) where k is some constant and l is the length
      of the input string.

tre-match-approx.c:
  - Approximate TNFA matcher.
    * Finds the leftmost and longest match and submatches in one pass
      over the input string.  The match may contain errors.  Each
      missing, substituted, or extra character in the match increases
      the cost of the match.  A maximum cost for the returned match
      can be given.  The cost of the found match is returned.
    * Cannot handle back references.  Like the parallel exact matcher,
      the worst case time consumption is directly proportional to the
      length of the input string.

regexec.c:
  - Stubs for the regexec() family of functions.
    * If the TNFA contains back referencing nodes, the backtracking
      matcher is used.  Otherwise the parallel matcher is used.

regerror.c:
  - Implements the regerror() function.