grub scale nearest + improvement with memcpy

static grub_err_t
scale_nn (struct grub_video_bitmap *dst, struct grub_video_bitmap *src)
{
  grub_err_t err = verify_bitmaps(dst, src);
  if (err != GRUB_ERR_NONE)
    return err;

  grub_uint8_t *ddata = dst->data;
  grub_uint8_t *sdata = src->data;
  unsigned dw = dst->mode_info.width;
  unsigned dh = dst->mode_info.height;
  unsigned sw = src->mode_info.width;
  unsigned sh = src->mode_info.height;
  unsigned dstride = dst->mode_info.pitch;
  unsigned sstride = src->mode_info.pitch;
  unsigned bytes_per_pixel = dst->mode_info.bytes_per_pixel;
  unsigned x_ratio = ((sw << 16) / dw) + 1;
  unsigned y_ratio = ((sh << 16) / dh) + 1;
  unsigned src_line, dst_line, src_pos, dst_pos, ratio, i, j;

  /* grub scale nearest + improvement with memcpy & reduce multiplication */
  unsigned dw_bpp = dw*bytes_per_pixel;

  for (i=0;i<dh;i++) {
    src_line = ((i*y_ratio)>>16)*sstride;
    dst_line = i*dstride;
    ratio   = 0;
    for (j=0;j<dw_bpp;j+=bytes_per_pixel){
      src_pos = src_line+(ratio>>16)*bytes_per_pixel;
      dst_pos = dst_line+j;

      /* improve with memcpy */
      memcpy(ddata+dst_pos, sdata+src_pos, bytes_per_pixel);
      ratio+=x_ratio;
    }
  }
  return GRUB_ERR_NONE;
}