Implement parse_nat, an error-checking variant of atoi.

util.c

@@ -27,6 +27,7 @@ THE SOFTWARE.
 #include <time.h>
 #include <stdio.h>
 #include <unistd.h>
+#include <limits.h>
 
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -131,6 +132,26 @@ timeval_min_sec(struct timeval *d, time_t secs)
     }
 }
 
+/* There's no good name for a positive int in C, call it nat. */
+int
+parse_nat(const char *string)
+{
+    long l;
+    char *end;
+
+    l = strtol(string, &end, 0);
+
+    while(*end == ' ' || *end == '\t')
+        end++;
+    if(*end != '\0')
+        return -1;
+
+    if(l < 0 || l > INT_MAX)
+        return -1;
+
+    return (int)l;
+}
+
 int
 parse_msec(const char *string)
 {

util.h

@@ -77,6 +77,7 @@ int timeval_compare(const struct timeval *s1, const struct timeval *s2)
     ATTRIBUTE ((pure));
 void timeval_min(struct timeval *d, const struct timeval *s);
 void timeval_min_sec(struct timeval *d, time_t secs);
+int parse_nat(const char *string) ATTRIBUTE ((pure));
 int parse_msec(const char *string) ATTRIBUTE ((pure));
 void do_debugf(int level, const char *format, ...)
     ATTRIBUTE ((format (printf, 2, 3))) COLD;