[FFmpeg-devel] [PATCH 1/2] lavf: Add general API for IO buffer synchtonization.
andrey.semashev at gmail.com
Mon Dec 3 15:52:40 EET 2018
On 12/3/18 3:43 PM, Nicolas George wrote:
> Andrey Semashev (2018-12-03):
>> This commit adds a new set of functions to avio and url subsystems, which
>> allow users to invoke IO buffer synchronization with the underlying media.
>> The most obvious target for this extension if the filesystem streams. Invoking
>> IO synchronization allows user applications to ensure that all written content
>> has reached the filesystem on the media and can be observed by other processes.
>> The public API for this is avio_sync() function, which can be called on
>> AVIOContext. The internal, lower layer API is ffurl_sync(), which works
>> directly on the underlying URLContext. URLContext backends can add support for
>> this new API by setting the sync handler to the new url_sync member of
>> URLProtocol. When no handler is set then the sync operation is a no-op.
>> libavformat/avio.c | 7 +++++++
>> libavformat/avio.h | 16 ++++++++++++++++
>> libavformat/aviobuf.c | 17 +++++++++++++++++
>> libavformat/url.h | 12 ++++++++++++
>> 4 files changed, 52 insertions(+)
>> diff --git a/libavformat/avio.c b/libavformat/avio.c
>> index 663789ec02..19413ac586 100644
>> --- a/libavformat/avio.c
>> +++ b/libavformat/avio.c
>> @@ -623,6 +623,13 @@ int64_t ffurl_size(URLContext *h)
>> return size;
>> +int ffurl_sync(URLContext *h)
>> + if (h->prot->url_sync)
>> + return h->prot->url_sync(h);
>> + return 0;
> I think it should be an error, probably ENOSUP. Otherwise, the
> application will assume it was done.
I don't think this would be useful to users. I mean, the application can
already check whether the operations is supported or not by inspecting
url_sync. When the application doesn't care (which, I think, will be the
majority of cases), they will treat ENOTSUP the same way as a success,
so it only adds more burden to test for this error code.
I could use some separate "success" code for the "not supported" result,
if there is one. Is there?
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