sregex

/*
    Rob Pike's regex algorithm
    Copyright (C) 2015  Victor C. Martins "dxhj"

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
#if defined _sregex_included
    #endinput
#endif
#define _sregex_included

stock sregex_match(regexp[], text[])
{
    new i = 0;
    if (regexp[0] == '^')
        return _matchhere(regexp, 1, text, 0);
    do
        if (_matchhere(regexp, 0, text[i], i))
            return 1;
    while (text[i++]);
    return 0;
}

stock _matchhere(regexp[], iregex, text[], itext)
{
    if (!regexp[iregex]) return 1;
    if (regexp[iregex+1] == '*')
        return _matchstar(regexp[iregex], regexp, iregex+2, text, itext);
    if (regexp[iregex] == '$' && !regexp[iregex+1])
        return text[itext] == '\0';
    if (text[itext] && (regexp[iregex] == '.' || regexp[iregex] == text[itext]))
        return _matchhere(regexp, ++iregex, text, ++itext);
    return 0;
}

stock _matchstar(chr, regexp[], iregex, text[], itext)
{
    do {
        if (_matchhere(regexp, iregex, text, itext)) return 1;
    } while (text[itext] && (text[itext++] == chr || chr == '.'));
    return 0;
}