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libvirt Reference Manual |
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libvirt-stream - APIs for management of streams
Provides APIs for the management of streams
Author(s): Daniel Veillard <veillard@redhat.com> Copyright (C) 2006-2014 Red Hat, Inc. This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library. If not, see <http://www.gnu.org/licenses/>.
typedef enum virStreamEventType; typedef enum virStreamFlags; int virStreamAbort (virStreamPtr stream); int virStreamEventAddCallback (virStreamPtr stream,
int events,
virStreamEventCallback cb,
void * opaque,
virFreeCallback ff); typedef void virStreamEventCallback (virStreamPtr stream,
int events,
void * opaque); int virStreamEventRemoveCallback (virStreamPtr stream); int virStreamEventUpdateCallback (virStreamPtr stream,
int events); int virStreamFinish (virStreamPtr stream); int virStreamFree (virStreamPtr stream); virStreamPtr virStreamNew (virConnectPtr conn,
unsigned int flags); int virStreamRecv (virStreamPtr stream,
char * data,
size_t nbytes); int virStreamRecvAll (virStreamPtr stream,
virStreamSinkFunc handler,
void * opaque); int virStreamRef (virStreamPtr stream); int virStreamSend (virStreamPtr stream,
const char * data,
size_t nbytes); int virStreamSendAll (virStreamPtr stream,
virStreamSourceFunc handler,
void * opaque); typedef int virStreamSinkFunc (virStreamPtr st,
const char * data,
size_t nbytes,
void * opaque); typedef int virStreamSourceFunc (virStreamPtr st,
char * data,
size_t nbytes,
void * opaque);
enum virStreamEventType { VIR_STREAM_EVENT_READABLE = 1 VIR_STREAM_EVENT_WRITABLE = 2 VIR_STREAM_EVENT_ERROR = 4 VIR_STREAM_EVENT_HANGUP = 8 };
enum virStreamFlags { VIR_STREAM_NONBLOCK = 1 };
void virStreamEventCallback (virStreamPtr stream,
int events,
void * opaque)
Callback for receiving stream events. The callback will be invoked once for each event which is pending.
stream: | stream on which the event occurred |
events: | bitset of events from virEventHandleType constants |
opaque: | user data registered with handle |
int virStreamSinkFunc (virStreamPtr st,
const char * data,
size_t nbytes,
void * opaque)
The virStreamSinkFunc callback is used together with the virStreamRecvAll function for libvirt to provide the data that has been received. The callback will be invoked multiple times, providing data in small chunks. The application should consume up 'nbytes' from the 'data' array of data and then return the number actual number of bytes consumed. The callback will continue to be invoked until it indicates the end of the stream has been reached. A return value of -1 at any time will abort the receive operation
st: | the stream object |
data: | preallocated array to be filled with data |
nbytes: | size of the data array |
opaque: | optional application provided data |
Returns: | the number of bytes consumed or -1 upon error |
int virStreamSourceFunc (virStreamPtr st,
char * data,
size_t nbytes,
void * opaque)
The virStreamSourceFunc callback is used together with the virStreamSendAll function for libvirt to obtain the data that is to be sent. The callback will be invoked multiple times, fetching data in small chunks. The application should fill the 'data' array with up to 'nbytes' of data and then return the number actual number of bytes. The callback will continue to be invoked until it indicates the end of the source has been reached by returning 0. A return value of -1 at any time will abort the send operation
st: | the stream object |
data: | preallocated array to be filled with data |
nbytes: | size of the data array |
opaque: | optional application provided data |
Returns: | the number of bytes filled, 0 upon end of file, or -1 upon error |
int virStreamAbort (virStreamPtr stream)
Request that the in progress data transfer be cancelled abnormally before the end of the stream has been reached. For output streams this can be used to inform the driver that the stream is being terminated early. For input streams this can be used to inform the driver that it should stop sending data.
stream: | pointer to the stream object |
Returns: | 0 on success, -1 upon error |
int virStreamEventAddCallback (virStreamPtr stream,
int events,
virStreamEventCallback cb,
void * opaque,
virFreeCallback ff)
Register a callback to be notified when a stream becomes writable, or readable. This is most commonly used in conjunction with non-blocking data streams to integrate into an event loop
stream: | pointer to the stream object |
events: | set of events to monitor |
cb: | callback to invoke when an event occurs |
opaque: | application defined data |
ff: | callback to free @opaque data |
Returns: | 0 on success, -1 upon error |
int virStreamEventRemoveCallback (virStreamPtr stream)
Remove an event callback from the stream
stream: | pointer to the stream object |
Returns: | 0 on success, -1 on error |
int virStreamEventUpdateCallback (virStreamPtr stream,
int events)
Changes the set of events to monitor for a stream. This allows for event notification to be changed without having to unregister & register the callback completely. This method is guaranteed to succeed if a callback is already registered
stream: | pointer to the stream object |
events: | set of events to monitor |
Returns: | 0 on success, -1 if no callback is registered |
int virStreamFinish (virStreamPtr stream)
Indicate that there is no further data to be transmitted on the stream. For output streams this should be called once all data has been written. For input streams this should be called once virStreamRecv returns end-of-file. This method is a synchronization point for all asynchronous errors, so if this returns a success code the application can be sure that all data has been successfully processed.
stream: | pointer to the stream object |
Returns: | 0 on success, -1 upon error |
int virStreamFree (virStreamPtr stream)
Decrement the reference count on a stream, releasing the stream object if the reference count has hit zero. There must not be an active data transfer in progress when releasing the stream. If a stream needs to be disposed of prior to end of stream being reached, then the virStreamAbort function should be called first.
stream: | pointer to the stream object |
Returns: | 0 upon success, or -1 on error |
virStreamPtr virStreamNew (virConnectPtr conn,
unsigned int flags)
Creates a new stream object which can be used to perform streamed I/O with other public API function. When no longer needed, a stream object must be released with virStreamFree. If a data stream has been used, then the application must call virStreamFinish or virStreamAbort before free'ing to, in order to notify the driver of termination. If a non-blocking data stream is required passed VIR_STREAM_NONBLOCK for flags, otherwise pass 0.
conn: | pointer to the connection |
flags: | bitwise-OR of virStreamFlags |
Returns: | the new stream, or NULL upon error |
int virStreamRecv (virStreamPtr stream,
char * data,
size_t nbytes)
Reads a series of bytes from the stream. This method may block the calling application for an arbitrary amount of time. Errors are not guaranteed to be reported synchronously with the call, but may instead be delayed until a subsequent call. An example using this with a hypothetical file download API looks like virStreamPtr st = virStreamNew(conn, 0); int fd = open("demo.iso", O_WRONLY, 0600); virConnectDownloadFile(conn, "demo.iso", st); while (1) { char buf[1024]; int got = virStreamRecv(st, buf, 1024); if (got < 0) break; if (got == 0) { virStreamFinish(st); break; } int offset = 0; while (offset < got) { int sent = write(fd, buf + offset, got - offset); if (sent < 0) { virStreamAbort(st); goto done; } offset += sent; } } if (virStreamFinish(st) < 0) ... report an error .... done: virStreamFree(st); close(fd);
stream: | pointer to the stream object |
data: | buffer to read into from stream |
nbytes: | size of @data buffer |
Returns: | the number of bytes read, which may be less than requested. Returns 0 when the end of the stream is reached, at which time the caller should invoke virStreamFinish() to get confirmation of stream completion. Returns -1 upon error, at which time the stream will be marked as aborted, and the caller should now release the stream with virStreamFree. Returns -2 if there is no data pending to be read & the stream is marked as non-blocking. |
int virStreamRecvAll (virStreamPtr stream,
virStreamSinkFunc handler,
void * opaque)
Receive the entire data stream, sending the data to the requested data sink. This is simply a convenient alternative to virStreamRecv, for apps that do blocking-I/O. 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); } virStreamPtr st = virStreamNew(conn, 0); int fd = open("demo.iso", O_WRONLY); virConnectUploadFile(conn, st); if (virStreamRecvAll(st, mysink, &fd) < 0) { ...report an error ... goto done; } if (virStreamFinish(st) < 0) ...report an error... virStreamFree(st); close(fd);
stream: | pointer to the stream object |
handler: | sink callback for writing data to application |
opaque: | application defined data |
Returns: | 0 if all the data was successfully received. The caller should invoke virStreamFinish(st) to flush the stream upon success and then virStreamFree Returns -1 upon any error, with virStreamAbort() already having been called, so the caller need only call virStreamFree() |
int virStreamRef (virStreamPtr stream)
Increment the reference count on the stream. For each additional call to this method, there shall be a corresponding call to virStreamFree to release the reference count, once the caller no longer needs the reference to this object.
stream: | pointer to the stream |
Returns: | 0 in case of success, -1 in case of failure |
int virStreamSend (virStreamPtr stream,
const char * data,
size_t nbytes)
Write a series of bytes to the stream. This method may block the calling application for an arbitrary amount of time. Once an application has finished sending data it should call virStreamFinish to wait for successful confirmation from the driver, or detect any error. This method may not be used if a stream source has been registered. Errors are not guaranteed to be reported synchronously with the call, but may instead be delayed until a subsequent call. An example using this with a hypothetical file upload API looks like virStreamPtr st = virStreamNew(conn, 0); int fd = open("demo.iso", O_RDONLY); virConnectUploadFile(conn, "demo.iso", st); while (1) { char buf[1024]; int got = read(fd, buf, 1024); if (got < 0) { virStreamAbort(st); break; } if (got == 0) { virStreamFinish(st); break; } int offset = 0; while (offset < got) { int sent = virStreamSend(st, buf+offset, got-offset); if (sent < 0) { virStreamAbort(st); goto done; } offset += sent; } } if (virStreamFinish(st) < 0) ... report an error .... done: virStreamFree(st); close(fd);
stream: | pointer to the stream object |
data: | buffer to write to stream |
nbytes: | size of @data buffer |
Returns: | the number of bytes written, which may be less than requested. Returns -1 upon error, at which time the stream will be marked as aborted, and the caller should now release the stream with virStreamFree. Returns -2 if the outgoing transmit buffers are full & the stream is marked as non-blocking. |
int virStreamSendAll (virStreamPtr stream,
virStreamSourceFunc handler,
void * opaque)
Send the entire data stream, reading the data from the requested data source. This is simply a convenient alternative to virStreamSend, for apps that do blocking-I/O. An example using this with a hypothetical file upload API looks like int mysource(virStreamPtr st, char *buf, int nbytes, void *opaque) { int *fd = opaque; return read(*fd, buf, nbytes); } virStreamPtr st = virStreamNew(conn, 0); int fd = open("demo.iso", O_RDONLY); virConnectUploadFile(conn, st); if (virStreamSendAll(st, mysource, &fd) < 0) { ...report an error ... goto done; } if (virStreamFinish(st) < 0) ...report an error... virStreamFree(st); close(fd);
stream: | pointer to the stream object |
handler: | source callback for reading data from application |
opaque: | application defined data |
Returns: | 0 if all the data was successfully sent. The caller should invoke virStreamFinish(st) to flush the stream upon success and then virStreamFree Returns -1 upon any error, with virStreamAbort() already having been called, so the caller need only call virStreamFree() |