newlib/libc/string/wcpncpy.c

   1 /*
   2 FUNCTION
   3         <<wcpncpy>>---copy part of a wide-character string returning a pointer to its end
   4
   5 SYNOPSIS
   6         #include <wchar.h>
   7         wchar_t *wcpncpy(wchar_t *__restrict <[s1]>,
   8                          const wchar_t *__restrict <[s2]>, size_t <[n]>);
   9
  10 DESCRIPTION
  11         The <<wcpncpy>> function copies not more than n wide-character codes
  12         (wide-character codes that follow a null wide-character code are not
  13         copied) from the array pointed to by <[s2]> to the array pointed to
  14         by <[s1]>. If copying takes place between objects that overlap, the
  15         behaviour is undefined.
  16
  17         If the array pointed to by <[s2]> is a wide-character string that is
  18         shorter than <[n]> wide-character codes, null wide-character codes are
  19         appended to the copy in the array pointed to by <[s1]>, until <[n]>
  20         wide-character codes in all are written.
  21
  22 RETURNS
  23         The <<wcpncpy>> function returns <[s1]>; no return value is reserved to
  24         indicate an error.
  25
  26 PORTABILITY
  27 <<wcpncpy>> is ISO/IEC 9899/AMD1:1995 (ISO C).
  28
  29 No supporting OS subroutines are required.
  30 */
  31
  32 #include <_ansi.h>
  33 #include <wchar.h>
  34
  35 wchar_t *
  36 wcpncpy (wchar_t *__restrict dst,
  37         const wchar_t *__restrict src,
  38         size_t count)
  39 {
  40   wchar_t *ret = NULL;
  41
  42   while (count > 0)
  43     {
  44       --count;
  45       if ((*dst++ = *src++) == L'\0')
  46         {
  47           ret = dst - 1;
  48           break;
  49         }
  50     }
  51   while (count-- > 0)
  52     *dst++ = L'\0';
  53
  54   return ret ? ret : dst;
  55 }