[PATCH v2 2/2] mfplat: Return HRESULT_FROM_WIN32(ERROR_HANDLE_EOF) when reading past the end of a file stream.

[Nikolay Sivov]

On 10/15/21 11:20 PM, Zebediah Figura wrote:
> On 10/8/21 3:25 AM, Nikolay Sivov wrote:
>>
>>
>> On 10/8/21 7:06 AM, Zebediah Figura wrote:
>>> Signed-off-by: Zebediah Figura <zfigura at codeweavers.com>
>>> ---
>>>   dlls/mfplat/main.c         | 15 ++++++++++++++-
>>>   dlls/mfplat/tests/mfplat.c |  2 +-
>>>   2 files changed, 15 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/dlls/mfplat/main.c b/dlls/mfplat/main.c
>>> index 7fd713261fc..fb55a8afb21 100644
>>> --- a/dlls/mfplat/main.c
>>> +++ b/dlls/mfplat/main.c
>>> @@ -3843,7 +3843,7 @@ static HRESULT WINAPI
>>> bytestream_file_IsEndOfStream(IMFByteStream *iface, BOOL *
>>>   static HRESULT WINAPI bytestream_file_Read(IMFByteStream *iface,
>>> BYTE *buffer, ULONG size, ULONG *read_len)
>>>   {
>>>       struct bytestream *stream = impl_from_IMFByteStream(iface);
>>> -    LARGE_INTEGER position;
>>> +    LARGE_INTEGER position, file_size;
>>>       HRESULT hr = S_OK;
>>>       BOOL ret;
>>>   @@ -3851,6 +3851,19 @@ static HRESULT WINAPI
>>> bytestream_file_Read(IMFByteStream *iface, BYTE *buffer, U
>>>         EnterCriticalSection(&stream->cs);
>>>   +    if (!GetFileSizeEx(stream->hfile, &file_size))
>>> +    {
>>> +        LeaveCriticalSection(&stream->cs);
>>> +        return HRESULT_FROM_WIN32(GetLastError());
>>> +    }
>>> +
>>> +    if (stream->position > file_size.QuadPart)
>>> +    {
>>> +        LeaveCriticalSection(&stream->cs);
>>> +        *read_len = 0;
>>> +        return HRESULT_FROM_WIN32(ERROR_HANDLE_EOF);
>>> +    }
>>> +
>>
>> I think this is too explicit. Can we rely on read length that ReadFile
>> returns? Doing (ret && size && !*read_len) -> EOF. Depending on how 0
>> reads work, when EOF is already reached.
>>
>
> Sorry for the late reply. Unfortunately that doesn't work. The tests
> from patch 1 show that the bytestream reader returns S_OK when reading
> at the end of the file, but ERROR_HANDLE_EOF when reading past it.
> ReadFile() however only returns ERROR_HANDLE_EOF when doing an
> overlapped read.
>
I was thinking not about the error that ReadFile would set, but a
combination of its return value and returned read_len.