On 05.05.2016 16:49, Eric Blake wrote:
> On 04/28/2016 04:04 AM, Michal Privoznik wrote:
>> The former is a public API and registers a callback that
>> will be called whenever the other side of a stream calls
>> virStreamSkip. The latter is a wrapper that actually calls
>> the callback. It is not made public as it is intended to be
>> used purely internally.
>>
>> Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
>> ---
>
>> +/**
>> + * virStreamSkipFunc:
>> + * @stream: stream
>> + * @offset: size of hole in bytes
>
> Again, naming this 'length' makes more sense (you're not skipping TO a
> particular offset, but OVER a given length).
>
>> +++ b/src/libvirt-stream.c
>> @@ -286,6 +286,76 @@ virStreamRecv(virStreamPtr stream,
>>
>>
>> /**
>> + * virStreamRegisterSkip:
>> + * @stream: stream
>> + * @skipCb: callback function
>> + * @opaque: optional application provided data
>> + *
>> + * This function registers callback that will be called whenever
>
> s/callback/a callback/
>
>> + * the other side of the @stream is willing to skip a hole in the
>> + * stream.
>> + *
>> + * Returns 0 on success,
>> + * -1 otherwise.
>> + */
>> +int
>> +virStreamRegisterSkip(virStreamPtr stream,
>> + virStreamSkipFunc skipCb,
>> + void *opaque)
>> +{
>> + VIR_DEBUG("stream=%p, skipCb=%p opaque=%p", stream, skipCb, opaque);
>> +
>> + virResetLastError();
>> +
>> + virCheckStreamReturn(stream, -1);
>> + virCheckNonNullArgReturn(skipCb, -1);
>> +
>> + if (stream->skipCb) {
>> + virReportError(VIR_ERR_OPERATION_INVALID, "%s",
>> + _("A skip callback is already registered"));
>> + return -1;
>
> I guess that means we allow passing skipCb=NULL to deregister a
> callback; does it need to be specifically documented? Are there
> scenarios where you WANT to deregister before closing something else, to
> make sure that a stale callback is not called during a race scenario?
I haven't thought of that. I mean, the line just above this check
prohibits skipCB being NULL. But it seems like this will be thrown away
anyway.
>
>> +int
>> +virStreamSkipCallback(virStreamPtr stream,
>> + unsigned long long offset)
>> +{
>> + VIR_DEBUG("stream=%p, offset=%llu", stream, offset);
>> +
>> + virCheckStreamReturn(stream, -1);
>> +
>> + if (stream->skipCb) {
>> + int ret;
>> + ret = (stream->skipCb)(stream, offset, stream->skipCbOpaque);
>
> I might have omitted the () around stream->skipCb, but I don't know if
> we have a consistent style, and yours makes it obvious that we know we
> are dereferencing a function pointer.
>
>> +++ b/src/libvirt_public.syms
>> @@ -735,6 +735,7 @@ LIBVIRT_1.3.3 {
>> LIBVIRT_1.3.5 {
>> global:
>> virStreamSkip;
>> + virStreamRegisterSkip;
>
> Worth keeping sorted?
>
Sure.
Michal
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