Re: [PATCH 05/10] EmulatorPkg/Win: Do not zero out file content

["Wu, Hao A" <hao.a.wu@intel.com>]

> -----Original Message-----
> From: Ni, Ruiyu
> Sent: Monday, August 27, 2018 3:53 PM
> To: edk2-devel@lists.01.org
> Cc: Wu, Hao A; Andrew Fish
> Subject: [PATCH 05/10] EmulatorPkg/Win: Do not zero out file content
> 
> The patch changes the behavior to not zero out file content
> when the file size is not multiple of block size.
> Instead, it just provides access to the contents that are
> multiple of block size and leaves the remaining content (less than
> block size) untouched.
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
> Cc: Hao Wu <hao.a.wu@intel.com>
> Cc: Andrew Fish <afish@apple.com>
> ---
>  EmulatorPkg/Win/Host/WinBlockIo.c | 28 +++++++++++++++++++++++++---
>  1 file changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/EmulatorPkg/Win/Host/WinBlockIo.c
> b/EmulatorPkg/Win/Host/WinBlockIo.c
> index 14491a6e90..7df7d42c7c 100644
> --- a/EmulatorPkg/Win/Host/WinBlockIo.c
> +++ b/EmulatorPkg/Win/Host/WinBlockIo.c
> @@ -90,6 +90,7 @@ WinNtBlockIoOpenDevice (
>  {
>    EFI_STATUS            Status;
>    UINT64                FileSize;
> +  UINT64                EndOfFile;
> 
>    //
>    // If the device is already opened, close it
> @@ -112,7 +113,7 @@ WinNtBlockIoOpenDevice (
>    );
> 
>    if (Private->NtHandle == INVALID_HANDLE_VALUE) {
> -    DEBUG ((EFI_D_INFO, "OpenBlock: Could not open %S, %x\n", Private-
> >FileName, GetLastError ()));
> +    DEBUG ((EFI_D_INFO, "PlOpenBlock: Could not open %S, %x\n", Private-
> >FileName, GetLastError ()));
>      Media->MediaPresent = FALSE;
>      Status = EFI_NO_MEDIA;
>      goto Done;
> @@ -124,14 +125,35 @@ WinNtBlockIoOpenDevice (
>    Status = SetFilePointer64 (Private, 0, &FileSize, FILE_END);
> 
>    if (EFI_ERROR (Status)) {
> -    DEBUG ((EFI_D_ERROR, "OpenBlock: Could not get filesize of %s\n", Private-
> >FileName));
> +    DEBUG ((EFI_D_ERROR, "PlOpenBlock: Could not get filesize of %s\n",
> Private->FileName));
>      Status = EFI_UNSUPPORTED;
>      goto Done;
>    }
> 
>    Media->LastBlock = DivU64x32 (FileSize, (UINT32)Private->BlockSize) - 1;
> 
> -  DEBUG ((EFI_D_INIT, "OpenBlock: opened %S\n", Private->FileName));
> +  EndOfFile = MultU64x32 (Media->LastBlock + 1, (UINT32)Private->BlockSize);
> +

Hi Ray,

The below logic seems actually zeroing out the file content if the file
size is not a multiple of block size. Could you help to double confirm
this one?

Best Regards,
Hao Wu

> +  if (FileSize != EndOfFile) {
> +    //
> +    // file is not the proper size, change it
> +    //
> +    DEBUG ((EFI_D_INIT, "PlOpenBlock: Initializing block device: %hs\n",
> Private->FileName));
> +
> +    //
> +    // first set it to 0
> +    //
> +    SetFilePointer64 (Private, 0, NULL, FILE_BEGIN);
> +    SetEndOfFile (Private->NtHandle);
> +
> +    //
> +    // then set it to the needed file size (OS will zero fill it)
> +    //
> +    SetFilePointer64 (Private, EndOfFile, NULL, FILE_BEGIN);
> +    SetEndOfFile (Private->NtHandle);
> +  }
> +
> +  DEBUG ((EFI_D_INIT, "PlOpenBlock: opened %S\n", Private->FileName));
>    Status = EFI_SUCCESS;
> 
>  Done:
> --
> 2.16.1.windows.1