source: trunk/libs/newlib/src/newlib/libc/string/wcpncpy.c

/*
FUNCTION
        <<wcpncpy>>---copy part of a wide-character string returning a pointer to its end

SYNOPSIS
        #include <wchar.h>
        wchar_t *wcpncpy(wchar_t *__restrict <[s1]>,
                         const wchar_t *__restrict <[s2]>, size_t <[n]>);

DESCRIPTION
        The <<wcpncpy>> function copies not more than n wide-character codes
        (wide-character codes that follow a null wide-character code are not
        copied) from the array pointed to by <[s2]> to the array pointed to
        by <[s1]>. If copying takes place between objects that overlap, the
        behaviour is undefined.

        If the array pointed to by <[s2]> is a wide-character string that is
        shorter than <[n]> wide-character codes, null wide-character codes are
        appended to the copy in the array pointed to by <[s1]>, until <[n]>
        wide-character codes in all are written. 

RETURNS
        The <<wcpncpy>> function returns <[s1]>; no return value is reserved to
        indicate an error. 

PORTABILITY
<<wcpncpy>> is ISO/IEC 9899/AMD1:1995 (ISO C).

No supporting OS subroutines are required.
*/

#include <_ansi.h>
#include <wchar.h>

wchar_t *
wcpncpy (wchar_t *__restrict dst,
        const wchar_t *__restrict src,
        size_t count)
{
  wchar_t *ret = NULL;

  while (count > 0)
    {
      --count;
      if ((*dst++ = *src++) == L'\0')
        {
          ret = dst - 1;
          break;
        }
    }
  while (count-- > 0)
    *dst++ = L'\0';

  return ret ? ret : dst;
}