newlib/libc/string/wcsncpy.c

   1 /*
   2 FUNCTION
   3         <<wcsncpy>>---copy part of a wide-character string
   4
   5 SYNOPSIS
   6         #include <wchar.h>
   7         wchar_t *wcsncpy(wchar_t *__restrict <[s1]>,
   8                         const wchar_t *__restrict <[s2]>, size_t <[n]>);
   9
  10 DESCRIPTION
  11         The <<wcsncpy>> 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.  Note that if <[s1]> contains more than <[n]>
  16         wide characters before its terminating null, the result is not
  17         null-terminated.
  18
  19         If the array pointed to by <[s2]> is a wide-character string that is
  20         shorter than <[n]> wide-character codes, null wide-character codes are
  21         appended to the copy in the array pointed to by <[s1]>, until <[n]>
  22         wide-character codes in all are written.
  23
  24 RETURNS
  25         The <<wcsncpy>> function returns <[s1]>; no return value is reserved to
  26         indicate an error.
  27
  28 PORTABILITY
  29 ISO/IEC 9899; POSIX.1.
  30
  31 No supporting OS subroutines are required.
  32 */
  33
  34 #include <_ansi.h>
  35 #include <wchar.h>
  36
  37 wchar_t *
  38 wcsncpy (wchar_t *__restrict s1,
  39         const wchar_t *__restrict s2,
  40         size_t n)
  41 {
  42   wchar_t *dscan=s1;
  43
  44   while(n > 0)
  45     {
  46       --n;
  47       if((*dscan++ = *s2++) == L'\0')  break;
  48     }
  49   while(n-- > 0)  *dscan++ = L'\0';
  50
  51   return s1;
  52 }