newlib/libc/string/strnlen.c

   1 /*
   2 FUNCTION
   3         <<strnlen>>---character string length
   4
   5 INDEX
   6         strnlen
   7
   8 SYNOPSIS
   9         #include <string.h>
  10         size_t strnlen(const char *<[str]>, size_t <[n]>);
  11
  12 DESCRIPTION
  13         The <<strnlen>> function works out the length of the string
  14         starting at <<*<[str]>>> by counting chararacters until it
  15         reaches a NUL character or the maximum: <[n]> number of
  16         characters have been inspected.
  17
  18 RETURNS
  19         <<strnlen>> returns the character count or <[n]>.
  20
  21 PORTABILITY
  22 <<strnlen>> is a GNU extension.
  23
  24 <<strnlen>> requires no supporting OS subroutines.
  25
  26 */
  27
  28 #undef __STRICT_ANSI__
  29 #include <_ansi.h>
  30 #include <string.h>
  31
  32 size_t
  33 strnlen (const char *str,
  34         size_t n)
  35 {
  36   const char *start = str;
  37
  38   while (n-- > 0 && *str)
  39     str++;
  40
  41   return str - start;
  42 }