func: int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
  
                  const void *buf1, int count1)
  
  {
  
      BlockDriver *drv = bs->drv;
  
  
  
      if (!drv)
  
          return -ENOMEDIUM;
  
      if (!drv->bdrv_pwrite)
  
          return bdrv_pwrite_em(bs, offset, buf1, count1);
  
      if (bdrv_wr_badreq_bytes(bs, offset, count1))
  
          return -EDOM;
  
      return drv->bdrv_pwrite(bs, offset, buf1, count1);
  
  }
  