// re2c $INPUT -o $OUTPUT #include <assert.h> #include <stdint.h> static uint32_t num(const char *s, const char *e) { uint32_t n = 0; for (; s < e; ++s) n = n * 10 + (*s - '0'); return n; } /*!maxnmatch:re2c*/ static const uint64_t ERROR = ~0lu; static uint64_t lex(const char *YYCURSOR) { const char *YYMARKER; const char *yypmatch[YYMAXNMATCH * 2]; uint32_t yynmatch; /*!stags:re2c format = 'const char *@@;\n'; */ /*!re2c re2c:yyfill:enable = 0; re2c:flags:posix-captures = 1; re2c:define:YYCTYPE = char; octet = [0-9] | [1-9][0-9] | [1][0-9][0-9] | [2][0-4][0-9] | [2][5][0-5]; dot = [.]; end = [\x00]; (octet) dot (octet) dot (octet) dot (octet) end { assert(yynmatch == 5); return num(yypmatch[8], yypmatch[9]) + (num(yypmatch[6], yypmatch[7]) << 8) + (num(yypmatch[4], yypmatch[5]) << 16) + (num(yypmatch[2], yypmatch[3]) << 24); } * { return ERROR; } */ } int main() { assert(lex("1.2.3.4") == 0x01020304); assert(lex("127.0.0.1") == 0x7f000001); assert(lex("255.255.255.255") == 0xffffffff); assert(lex("1.2.3.") == ERROR); assert(lex("1.2.3.256") == ERROR); return 0; }