Re: [PATCH 6/7] wcsmbs: optimize wcsncpy

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

If no one opposes it, I will commit this shortly.

On 06/02/2019 12:58, Adhemerval Zanella wrote:
> This patch rewrites wcsncpy using wcsnlen, wmemset, and wmemcpy.  This is
> similar to the optimization done on strncpy by f6482cf29d and 6423d4754c.
> 
> Checked on x86_64-linux-gnu.
> 
> 	* wcsmbs/wcsncpy.c (__wcsncpy): Rewrite using wcsnlen, wmemset, and
> 	wmemcpy.
> ---
>  wcsmbs/wcsncpy.c | 60 ++++--------------------------------------------
>  1 file changed, 4 insertions(+), 56 deletions(-)
> 
> diff --git a/wcsmbs/wcsncpy.c b/wcsmbs/wcsncpy.c
> index 2fd523c815..d5d7f4ad86 100644
> --- a/wcsmbs/wcsncpy.c
> +++ b/wcsmbs/wcsncpy.c
> @@ -26,62 +26,10 @@
>  wchar_t *
>  __wcsncpy (wchar_t *dest, const wchar_t *src, size_t n)
>  {
> -  wint_t c;
> -  wchar_t *const s = dest;
> -
> -  --dest;
> -
> -  if (n >= 4)
> -    {
> -      size_t n4 = n >> 2;
> -
> -      for (;;)
> -	{
> -	  c = *src++;
> -	  *++dest = c;
> -	  if (c == L'\0')
> -	    break;
> -	  c = *src++;
> -	  *++dest = c;
> -	  if (c == L'\0')
> -	    break;
> -	  c = *src++;
> -	  *++dest = c;
> -	  if (c == L'\0')
> -	    break;
> -	  c = *src++;
> -	  *++dest = c;
> -	  if (c == L'\0')
> -	    break;
> -	  if (--n4 == 0)
> -	    goto last_chars;
> -	}
> -      n = n - (dest - s) - 1;
> -      if (n == 0)
> -	return s;
> -      goto zero_fill;
> -    }
> -
> - last_chars:
> -  n &= 3;
> -  if (n == 0)
> -    return s;
> -
> -  do
> -    {
> -      c = *src++;
> -      *++dest = c;
> -      if (--n == 0)
> -	return s;
> -    }
> -  while (c != L'\0');
> -
> - zero_fill:
> -  do
> -    *++dest = L'\0';
> -  while (--n > 0);
> -
> -  return s;
> +  size_t size = __wcsnlen (src, n);
> +  if (size != n)
> +    __wmemset (dest + size, L'\0', n - size);
> +  return __wmemcpy (dest, src, size);
>  }
>  #ifndef WCSNCPY
>  weak_alias (__wcsncpy, wcsncpy)
>