atouint.c revision 290001 
1#include <config.h>
2#include <sys/types.h>
3#include <ctype.h>
4
5#include "ntp_types.h"
6#include "ntp_stdlib.h"
7
8/*
9 * atouint() - convert an ascii string representing a whole base 10
10 *	       number to u_long *uval, returning TRUE if successful.
11 *	       Does not modify *uval and returns FALSE if str is not
12 *	       a positive base10 integer or is too large for a u_int32.
13 *	       this function uses u_long but should use u_int32, and
14 *	       probably be renamed.
15 */
16int
17atouint(
18	const char *str,
19	u_long *uval
20	)
21{
22	u_long u;
23	const char *cp;
24
25	cp = str;
26	if ('\0' == *cp)
27		return 0;
28
29	u = 0;
30	while ('\0' != *cp) {
31		if (!isdigit((unsigned char)*cp))
32			return 0;
33		if (u > 429496729 || (u == 429496729 && *cp >= '6'))
34			return 0;		/* overflow */
35		/* hand-optimized u *= 10; */
36		u = (u << 3) + (u << 1);
37		u += *cp++ - '0';		/* not '\0' */
38	}
39
40	*uval = u;
41	return 1;
42}
43