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      1 /*	$NetBSD: atouint.c,v 1.9 2020/05/25 20:47:24 christos Exp $	*/
      2 
      3 #include <config.h>
      4 #include <sys/types.h>
      5 #include <ctype.h>
      6 
      7 #include "ntp_types.h"
      8 #include "ntp_stdlib.h"
      9 
     10 /*
     11  * atouint() - convert an ascii string representing a whole base 10
     12  *	       number to u_long *uval, returning TRUE if successful.
     13  *	       Does not modify *uval and returns FALSE if str is not
     14  *	       a positive base10 integer or is too large for a u_int32.
     15  *	       this function uses u_long but should use u_int32, and
     16  *	       probably be renamed.
     17  */
     18 int
     19 atouint(
     20 	const char *str,
     21 	u_long *uval
     22 	)
     23 {
     24 	u_long u;
     25 	const char *cp;
     26 
     27 	cp = str;
     28 	if ('\0' == *cp)
     29 		return 0;
     30 
     31 	u = 0;
     32 	while ('\0' != *cp) {
     33 		if (!isdigit((unsigned char)*cp))
     34 			return 0;
     35 		if (u > 429496729 || (u == 429496729 && *cp >= '6'))
     36 			return 0;		/* overflow */
     37 		/* hand-optimized u *= 10; */
     38 		u = (u << 3) + (u << 1);
     39 		u += *cp++ - '0';		/* not '\0' */
     40 	}
     41 
     42 	*uval = u;
     43 	return 1;
     44 }
     45