[libvirt] [PATCH v2 14/38] Introduce virStreamSparseRecvAll
John Ferlan
jferlan at redhat.com
Thu May 4 21:33:58 UTC 2017
On 04/20/2017 06:01 AM, Michal Privoznik wrote:
> This is just a wrapper over new functions that have been just
> introduced: virStreamRecvFlags(), virStreamHoleSize(). It's very
> similar to virStreamRecvAll() except it handles sparse streams
> well.
You could have some API name adjustments not only in the commit message
but also within code.
>
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
> include/libvirt/libvirt-stream.h | 28 ++++++++-
> src/libvirt-stream.c | 119 +++++++++++++++++++++++++++++++++++++++
> src/libvirt_public.syms | 1 +
> 3 files changed, 145 insertions(+), 3 deletions(-)
>
> diff --git a/include/libvirt/libvirt-stream.h b/include/libvirt/libvirt-stream.h
> index 23fcc26..e5f5126 100644
> --- a/include/libvirt/libvirt-stream.h
> +++ b/include/libvirt/libvirt-stream.h
> @@ -102,9 +102,9 @@ int virStreamSendAll(virStreamPtr st,
> * @nbytes: size of the data array
> * @opaque: optional application provided data
> *
> - * The virStreamSinkFunc callback is used together
> - * with the virStreamRecvAll function for libvirt to
> - * provide the data that has been received.
> + * The virStreamSinkFunc callback is used together with the
> + * virStreamRecvAll or virStreamSparseRecvAll functions for
> + * libvirt to provide the data that has been received.
> *
> * The callback will be invoked multiple times,
> * providing data in small chunks. The application
> @@ -127,6 +127,28 @@ int virStreamRecvAll(virStreamPtr st,
> virStreamSinkFunc handler,
> void *opaque);
>
> +/**
> + * virStreamSinkHoleFunc:
> + * @st: the stream object
> + * @length: stream hole size
> + * @opaque: optional application provided data
> + *
> + * This callback is used together with the virStreamSparseRecvAll
> + * function for libvirt to provide the size of a hole that
> + * occurred in the stream.
The callback may be invoked multiple times as holes are found during
processing a stream. The application should create the hole in the
stream target and then return. A return value of -1 at any time will
abort the receive operation.
> + *
> + * Returns 0 on success,
> + * -1 upon error
> + */
> +typedef int (*virStreamSinkHoleFunc)(virStreamPtr st,
> + unsigned long long length,
> + void *opaque);
> +
> +int virStreamSparseRecvAll(virStreamPtr stream,
> + virStreamSinkFunc handler,
> + virStreamSinkHoleFunc holeHandler,
> + void *opaque);
> +
> typedef enum {
> VIR_STREAM_EVENT_READABLE = (1 << 0),
> VIR_STREAM_EVENT_WRITABLE = (1 << 1),
> diff --git a/src/libvirt-stream.c b/src/libvirt-stream.c
> index 1162d33..81190cc 100644
> --- a/src/libvirt-stream.c
> +++ b/src/libvirt-stream.c
> @@ -660,6 +660,125 @@ virStreamRecvAll(virStreamPtr stream,
>
>
> /**
> + * virStreamSparseRecvAll:
> + * @stream: pointer to the stream object
> + * @handler: sink callback for writing data to application
> + * @holeHandler: stream hole callback for skipping holes
> + * @opaque: application defined data
> + *
> + * Receive the entire data stream, sending the data to the
> + * requested data sink. This is simply a convenient alternative
s/sink./sink @handler and calling the skip @holeHandler to generate
holes for sparse stream targets.
> + * to virStreamRecv, for apps that do blocking-I/O.
s/virStreamRecv/virStreamRecvAll/
> + *
> + * An example using this with a hypothetical file download
> + * API looks like:
> + *
> + * int mysink(virStreamPtr st, const char *buf, int nbytes, void *opaque) {
> + * int *fd = opaque;
> + *
> + * return write(*fd, buf, nbytes);
> + * }
> + *
> + * int myskip(virStreamPtr st, unsigned long long offset, void *opaque) {
> + * int *fd = opaque;
> + *
> + * return lseek(*fd, offset, SEEK_CUR) == (off_t) -1 ? -1 : 0;
> + * }
> + *
> + * virStreamPtr st = virStreamNew(conn, 0);
> + * int fd = open("demo.iso", O_WRONLY);
> + *
> + * virConnectDownloadSparseFile(conn, st);
> + * if (virStreamSparseRecvAll(st, mysink, myskip, &fd) < 0) {
> + * ...report an error ...
> + * goto done;
> + * }
> + * if (virStreamFinish(st) < 0)
> + * ...report an error...
> + * virStreamFree(st);
> + * close(fd);
> + *
> + * Note that @opaque data is shared between both @handler and
> + * @holeHandler callbacks.
> + *
> + * Returns 0 if all the data was successfully received. The caller
> + * should invoke virStreamFinish(st) to flush the stream upon
> + * success and then virStreamFree
s/Free/Free().
> + *
> + * Returns -1 upon any error, with virStreamAbort() already
> + * having been called, so the caller need only call
> + * virStreamFree()
s/, so/, so/
s/Free()/Free()./
(e.g. lose the extra space and add a period)
Could virStreamFree(). go on the previous line?
> + */
> +int
> +virStreamSparseRecvAll(virStreamPtr stream,
> + virStreamSinkFunc handler,
> + virStreamSinkHoleFunc holeHandler,
> + void *opaque)
> +{
> + char *bytes = NULL;
> + size_t want = VIR_NET_MESSAGE_LEGACY_PAYLOAD_MAX;
> + const unsigned int flags = VIR_STREAM_RECV_STOP_AT_HOLE;
> + int ret = -1;
> +
> + VIR_DEBUG("stream=%p handler=%p holeHandler=%p opaque=%p",
> + stream, handler, holeHandler, opaque);
> +
> + virResetLastError();
> +
> + virCheckStreamReturn(stream, -1);
> + virCheckNonNullArgGoto(handler, cleanup);
> + virCheckNonNullArgGoto(holeHandler, cleanup);
> +
> + if (stream->flags & VIR_STREAM_NONBLOCK) {
> + virReportError(VIR_ERR_OPERATION_INVALID, "%s",
> + _("data sinks cannot be used for non-blocking streams"));
> + goto cleanup;
> + }
> +
> + if (VIR_ALLOC_N(bytes, want) < 0)
> + goto cleanup;
> +
> + for (;;) {
> + int got, offset = 0;
> + unsigned long long holeLen;
> + got = virStreamRecvFlags(stream, bytes, want, flags);
> + if (got == -3) {
> + if (virStreamHoleSize(stream, &holeLen) < 0) {
> + virStreamAbort(stream);
> + goto cleanup;
> + }
> +
> + if (holeHandler(stream, holeLen, opaque) < 0) {
> + virStreamAbort(stream);
> + goto cleanup;
> + }
We could continue; here, right? Although, I suppose (0 < -3) would fail
anyway, but if someone changed that someday and didn't read this part...
An ACK ends up being a bit dependent upon previous patches... What's
here seems fine to me though.
John
> + } else if (got < 0) {
> + goto cleanup;
> + } else if (got == 0) {
> + break;
> + }
> + while (offset < got) {
> + int done;
> + done = (handler)(stream, bytes + offset, got - offset, opaque);
> + if (done < 0) {
> + virStreamAbort(stream);
> + goto cleanup;
> + }
> + offset += done;
> + }
> + }
> + ret = 0;
> +
> + cleanup:
> + VIR_FREE(bytes);
> +
> + if (ret != 0)
> + virDispatchError(stream->conn);
> +
> + return ret;
> +}
> +
> +/**
> * virStreamEventAddCallback:
> * @stream: pointer to the stream object
> * @events: set of events to monitor
> diff --git a/src/libvirt_public.syms b/src/libvirt_public.syms
> index 0e34eee..008dc59 100644
> --- a/src/libvirt_public.syms
> +++ b/src/libvirt_public.syms
> @@ -764,6 +764,7 @@ LIBVIRT_3.3.0 {
> virStreamHoleSize;
> virStreamRecvFlags;
> virStreamSkip;
> + virStreamSparseRecvAll;
> } LIBVIRT_3.1.0;
>
> # .... define new API here using predicted next version number ....
>
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