[FFmpeg-devel] [PATCH]lavc/opus_rc: Case a const pointer to uint8_t *

[Carl Eugen Hoyos]

2018-12-17 22:02 GMT+01:00, Paul B Mahol <onemda at gmail.com>:
> On 12/17/18, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>> 2018-12-17 21:35 GMT+01:00, Rostislav Pehlivanov <atomnuker at gmail.com>:
>>> On Mon, 17 Dec 2018 at 01:47, Carl Eugen Hoyos <ceffmpeg at gmail.com>
>>> wrote:
>>>
>>>> Hi!
>>>>
>>>> The Opus struct RawBitsContext is used in both the decoder and the
>>>> encoder.
>>>> The fact that *position is const avoids warnings in the decoder where
>>>> it points into the bitstream. The encoder writes into the same
>>>> pointer, attached cast silences the warning on targets where AV_WB32()
>>>> does not internally cast the qualifier away.
>>>>
>>>> It is also possible to use a union if anybody prefers this:
>>>> diff --git a/libavcodec/opus_rc.h b/libavcodec/opus_rc.h
>>>> index 627f832..baad4ce 100644
>>>> --- a/libavcodec/opus_rc.h
>>>> +++ b/libavcodec/opus_rc.h
>>>> @@ -37,9 +37,19 @@ typedef struct RawBitsContext {
>>>>      uint32_t cacheval;
>>>>  } RawBitsContext;
>>>>
>>>> +typedef struct RawBitsEncContext {
>>>> +    uint8_t *position;
>>>> +    uint32_t bytes;
>>>> +    uint32_t cachelen;
>>>> +    uint32_t cacheval;
>>>> +} RawBitsEncContext;
>>>> +
>>>>  typedef struct OpusRangeCoder {
>>>>      GetBitContext gb;
>>>> -    RawBitsContext rb;
>>>> +    union {
>>>> +        RawBitsContext rb;
>>>> +        RawBitsEncContext rbe;
>>>> +    };
>>>>      uint32_t range;
>>>>      uint32_t value;
>>>>      uint32_t total_bits;
>>>>
>>>> and use rbe in ff_opus_rc_put_raw().
>>
>>> NAK, we don't do anyonymous unions.
>>
>> The suggested patch does not contain unions.
>
> It does, Are you author of this patch?

This is a poc to show that there is a possible (although
ugly) alternative to the - imo - unavoidable cast that I
attached as a git-formatted patch.

Carl Eugen