strnlen - determine length of a string up to a maximum length

Syntax	#include <string.h> size_t strnlen(const char *s, size_t maxlen);
Description	The strnlen() function calculates the minimum of the two following values: Number of bytes of the array to which s points, exclusively to the terminating NULL byte Value of the maxlen parameter.
Errors	No errors are defined.
Return val.	Length of the string s or value of the maxlen parameter when successful. The terminating null byte is not counted.