Re: [libvirt] [PATCH v3 07/31] Introduce VIR_STREAM_RECV_STOP_AT_HOLE flag

On 05/16/2017 10:03 AM, Michal Privoznik wrote: > Add a new flag to virStreamRecvFlags in order to handle being able to > stop reading from the stream so that the consumer can generate a "hole" > in stream target. Generation of a hole replaces the need to receive and > handle a sequence of zero bytes for sparse stream targets. > > Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; > --- > include/libvirt/libvirt-stream.h | 4 ++++ > src/libvirt-stream.c | 34 +++++++++++++++++++++++++++++++++- > 2 files changed, 37 insertions(+), 1 deletion(-) > > diff --git a/include/libvirt/libvirt-stream.h b/include/libvirt/libvirt-stream.h > index feaa8ad64..c4baaf7a3 100644 > --- a/include/libvirt/libvirt-stream.h > +++ b/include/libvirt/libvirt-stream.h > @@ -45,6 +45,10 @@ int virStreamRecv(virStreamPtr st, > char *data, > size_t nbytes); > > +typedef enum { > + VIR_STREAM_RECV_STOP_AT_HOLE = (1 << 0), > +} virStreamRecvFlagsValues; > + > int virStreamRecvFlags(virStreamPtr st, > char *data, > size_t nbytes, > diff --git a/src/libvirt-stream.c b/src/libvirt-stream.c > index dc0dc9ea3..bedb6159a 100644 > --- a/src/libvirt-stream.c > +++ b/src/libvirt-stream.c > @@ -290,7 +290,7 @@ virStreamRecv(virStreamPtr stream, > * @stream: pointer to the stream object > * @data: buffer to read into from stream > * @nbytes: size of @data buffer > - * @flags: extra flags; not used yet, so callers should always pass 0 > + * @flags: bitwise-OR of virStreamRecvFlagsValues > * > * Reads a series of bytes from the stream. This method may > * block the calling application for an arbitrary amount > @@ -300,6 +300,33 @@ virStreamRecv(virStreamPtr stream, > * @flags. Calling this function with no @flags set (equal to > * zero) is equivalent to calling virStreamRecv(stream, data, nbytes). > * > + * If flag VIR_STREAM_RECV_STOP_AT_HOLE is set, this function > + * will stop reading from stream if it has reached a hole. In > + * that case, -3 is returned and virStreamRecvHole() should be > + * called to get the hole size. An example using this flag might > + * look like this: > + * > + * while (1) { > + * char buf[4096]; > + * > + * int ret = virStreamRecvFlags(st, buf, len, VIR_STREAM_STOP_AT_HOLE); > + * if (ret < 0) { > + * if (ret == -3) { > + * long long len; > + * ret = virStreamRecvHole(st, &len, 0); > + * if (ret < 0) { > + * ...error.. > + * } else { > + * ...seek len bytes in target... Do/should we care to point out that @len is a "long long" and seeking is done in chunks of "off_t"?