On 04/20/2017 06:01 AM, Michal Privoznik wrote:
> This flag is for virStreamRecvFlags API. Its purpose is to stop
> reading from the stream if a hole occurred as holes are to be
> threated separately.
Consider:
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@xxxxxxxxxx>
> ---
> include/libvirt/libvirt-stream.h | 4 ++++
> src/libvirt-stream.c | 30 +++++++++++++++++++++++++++++-
> 2 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/include/libvirt/libvirt-stream.h b/include/libvirt/libvirt-stream.h
> index 2ebda74..23fcc26 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 3ac9e0d..1162d33 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
> @@ -301,6 +301,29 @@ virStreamRecv(virStreamPtr stream,
> * nbytes, 0) is equivalent to calling virStreamRecv(stream,
> * data, nbytes) and vice versa.
> *
> + * 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 virStreamHoleSize() should be
Obvious API name impact from patch 11/12...
Consider perhaps VIR_STREAM_RECV_HANDLE_SPARSE - or something that
indicates sparse management.
> + * 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) {
> + * unsigned long long len;
> + * ret = virStreamHoleSize(st, &len);
...if ((ret = vir*()) < 0)
report error
? IDC exactly, just noting.
> + * ...seek len bytes in target...
> + * } else {
> + * return -1;
> + * }
> + * } else {
> + * ...write buf to target...
> + * }
> + * }
The entire code snippet needs an extra space indent; otherwise, it
doesn't look right on the generated web page.
I would think this is ACK-able w/ the minor adjustments - there could be
side effects from previous adjustments though.
John
> + *
> * Returns 0 when the end of the stream is reached, at
> * which time the caller should invoke virStreamFinish()
> * to get confirmation of stream completion.
> @@ -311,6 +334,9 @@ virStreamRecv(virStreamPtr stream,
> *
> * Returns -2 if there is no data pending to be read & the
> * stream is marked as non-blocking.
> + *
> + * Returns -3 if there is a hole in stream and caller requested
> + * to stop at a hole.
> */
> int
> virStreamRecvFlags(virStreamPtr stream,
> @@ -332,6 +358,8 @@ virStreamRecvFlags(virStreamPtr stream,
> ret = (stream->driver->streamRecvFlags)(stream, data, nbytes, flags);
> if (ret == -2)
> return -2;
> + if (ret == -3)
> + return -3;
> if (ret < 0)
> goto error;
> return ret;
>
--
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