/* strnlen.c - determine the length of a fixed-size string
 * Andrew Ho (andrew@zeuscat.com)
 * 
 * Implements strnlen(), which is defined on some BSD systems and Linux
 * but not on Solaris. This is just like strlen(), but you provide a
 * maximum number of bytes to count, which saves time if you know
 * what the maximum allowed size of the string is.
 *
 * Compile with -DMAX=n where n is a positive integer to change the way
 * the demonstration driver works.
 *
 * Build: gcc -Wall -o strnlen strnlen.c
 * Usage: strnlen string1 [string2 [string3 ...]]
 */

#include <stdio.h>
#include <string.h>

#ifndef MAX
#define MAX 5
#endif

/* just like strlen(3), but cap the number of bytes we count */
static size_t strnlen(const char *s, size_t max) {
    register const char *p;
    for(p = s; *p && max--; ++p);
    return(p - s);
}

int main(int argc, char **argv) {
    int i;
    for(i = 1; i < argc; i++)
        printf( "strnlen(\"%s\", %d) = %d\n",
            argv[i], MAX, strnlen(argv[i], MAX) );
    return 0;
}