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RED - Regular Expression DFA

Red is a C++ regular expression engine based on deterministic finite automata (DFAs). DFAs are extremely fast pattern-matchers (linear in size of input). Red excels at matching from among large sets of regexes.

The world already has RE2. Why do we need Red?

  1. Red can report where each of many patterns matched. RE2::Set can only tell which of them did.

  2. Red compiled patterns are read-only, concurrent, and lock-free. RE2 locks the program every time it's used. This can make a 12-27x difference in performance.

  3. Red doesn't try to protect you from yourself. It will compile expressions for which RE2 complains "pattern too large - compile failed".

  4. Red can load/save DFAs as files.

  5. Red multi-pattern matching is 10x as fast as RE2::Set.

Red is a pure byte-oriented DFA.

RE2 has a lot of capture-and-extract functionality, but since DFA's don't support that, Red doesn't either.

Documentation