re2dfa transforms regular expressions into deterministic finite state machines and outputs Go source code containing the matching function.

go get -u github.com/opennota/re2dfa

re2dfa ^a+$ main.matchAPlus string

All patterns are anchored at the beginning of data, whether or not the pattern starts with ^.

Regular expression:

^(?:
    <[A-Za-z][A-Za-z0-9\-]*(?:\s+[a-zA-Z_:][a-zA-Z0-9:._-]*(?:\s*=\s*(?:[^"'=<>`\x00-\x20]+|'[^']*'|"[^"]*"))?)*\s*\/?> |

    <\/[A-Za-z][A-Za-z0-9\-]*\s*> |

    <!----> |

    <!--(?:-?[^>-])(?:-?[^-])*--> |

    <[?].*?[?]> |

    <![A-Z]+\s+[^>]*> |

    <!\[CDATA\[[\s\S]*?\]\]>
)

Benchmark results (Go 1.10, Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz):

BenchmarkFSM1-4        500000         2778 ns/op          0 B/op        0 allocs/op
BenchmarkRegexp1-4     100000        12643 ns/op        112 B/op        7 allocs/op

re2dfa is released under the GNU General Public License version 3.0. As a special exception to the GPLv3, you may use the parts of re2dfa output copied from re2dfa source without restriction. Use of re2dfa makes no requirements about the license of generated code.