toolchain/gcc/newlib/libc/string/strnlen.c

   1 /*
   2 FUNCTION
   3         <<strnlen>>---character string length
   4
   5 INDEX
   6         strnlen
   7
   8 ANSI_SYNOPSIS
   9         #include <string.h>
  10         size_t strnlen(const char *<[str]>, size_t <[n]>);
  11
  12 TRAD_SYNOPSIS
  13         #include <string.h>
  14         size_t strnlen(<[str]>, <[n]>)
  15         char *<[src]>;
  16         size_t <[n]>;
  17
  18 DESCRIPTION
  19         The <<strnlen>> function works out the length of the string
  20         starting at <<*<[str]>>> by counting chararacters until it
  21         reaches a NUL character or the maximum: <[n]> number of
  22         characters have been inspected.
  23
  24 RETURNS
  25         <<strnlen>> returns the character count or <[n]>.
  26
  27 PORTABILITY
  28 <<strnlen>> is a Gnu extension.
  29
  30 <<strnlen>> requires no supporting OS subroutines.
  31
  32 */
  33
  34 #undef __STRICT_ANSI__
  35 #include <_ansi.h>
  36 #include <string.h>
  37
  38 size_t
  39 _DEFUN (strnlen, (str, n),
  40         _CONST char *str _AND
  41         size_t n)
  42 {
  43   _CONST char *start = str;
  44
  45   while (*str && n-- > 0)
  46     str++;
  47
  48   return str - start;
  49 }