/** @license 2022 Neil Edelman, distributed under the terms of the
 [MIT License](https://opensource.org/licenses/MIT).

 Lexer for journal entries.

 @std C89/90 */

#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <limits.h>
#include <errno.h>

static int parse_uint(const char *s, const char *e, unsigned *u) {
    uint32_t n = 0;
    for ( ; s < e; ++s) {
		unsigned digit = (unsigned)(*s - '0');
		assert(digit < 10);
		if(n > (UINT_MAX - digit) / 10) return errno = ERANGE, 0; /* check */
		n = n * 10 + digit;
	}
	*u = n;
    return 1;
}

static int lex_line(const char *YYCURSOR, unsigned *const u) {
	const char *YYMARKER, *o1, *o2, *o3, *o4;
	/*!stags:re2c format = 'const char *@@;\n'; */

	/*!re2c
	re2c:yyfill:enable = 0;
	re2c:flags:tags = 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];




	@o1 octet dot @o2 octet dot @o3 octet dot @o4 octet end {
		unsigned u1, u2, u3, u4;
		if(!parse_uint(o1, o2 - 1, &u1)
			|| !parse_uint(o2, o3 - 1, &u2)
			|| !parse_uint(o3, o4 - 1, &u3)
			|| !parse_uint(o4, YYCURSOR - 1, &u4)) return 0;
		*u = u4 + (u3 << 8) + (u2 << 16) + (u1 << 24);
		return 1;
	}
	* { return 0; }
	*/
}


int main(int argc, char **argv) {
	unsigned u;
	int success;
	success = lex_line("1.2.3.4", &u);
	assert(success);
	printf("%x\n", u);
	return EXIT_SUCCESS;
}