[FFmpeg-devel] [PATCH 1/2] avutil/random_seed: add av_random()

[James Almer]

On 7/4/2023 5:14 PM, Anton Khirnov wrote:
> Quoting James Almer (2023-07-04 22:08:40)
>> On 7/4/2023 4:59 PM, Anton Khirnov wrote:
>>>>
>>>> Not if any of the functions above were called but failed to fill the buffer.
>>>>
>>>> I could add return AVERROR(ENOSYS) to the HAVE_UNISTD_H block, and
>>>> return AVERROR_INVALIDDATA outside.
>>>
>>> AVERROR_INVALIDDATA is defined as 'Invalid data found when processing
>>> input'.
>>> This function does not process any input, so IMO that code never makes
>>> sense for it.
>>>
>>> I'd say make it ENOSYS, AVERROR_UNKNOWN, or keep around one of
>>> individual method errors.
>>
>> For the cases read() is used for /dev/random/, i can return
>> AVERROR(errno), given the doxy states read() returns -1 on error and
>> sets errno to some value. Although if it succeeds and returns a value
>> smaller than len i would need to return AVERROR_UNKNOWN like you suggested.
> 
> I wonder if we should be trying /dev/random at all. I cannot think of
> any remotely sane configuration where /dev/urandom fails, but
> /dev/random works. So it only makes sense to use /dev/urandom.

I think the problem is that one may not generate the requested amount of 
bytes.