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event: improve public API docs
Since libvirt 0.9.3, the entire virevent.c file has been a public API, so improve the documentation in this file. Also, fix a potential core dump - it could only be triggered by bogus use of the API and would only affect the caller (not libvirtd), but we might as well be nice. * src/libvirt.c (virConnectSetKeepAlive) (virConnectDomainEventRegister, virConnectDomainEventRegisterAny) (virConnectNetworkEventRegisterAny): Document event loop requirement. * src/util/virevent.c (virEventAddHandle, virEventRemoveHandle) (virEventAddTimeout, virEventRemoveTimeout): Likewise. (virEventUpdateHandle, virEventUpdateTimeout): Likewise, and avoid core dump if caller didn't register handler. (virEventRunDefaultImpl): Expand example, and set up code block in html docs. (virEventRegisterImpl, virEventRegisterDefaultImpl): Document more on the use of the event loop. Signed-off-by: Eric Blake <eblake@redhat.com>
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Eric Blake
parent
cfd62c1f61
commit
c8f95fff63
@ -2,7 +2,7 @@
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* libvirt.c: Main interfaces for the libvirt library to handle virtualization
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* domains from a process running in domain 0
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*
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* Copyright (C) 2005-2006, 2008-2013 Red Hat, Inc.
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* Copyright (C) 2005-2006, 2008-2014 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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@ -16121,11 +16121,13 @@ error:
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* @freecb: optional function to deallocate opaque when not used anymore
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*
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* Adds a callback to receive notifications of domain lifecycle events
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* occurring on a connection
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* occurring on a connection. This function requires that an event loop
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* has been previously registered with virEventRegisterImpl() or
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* virEventRegisterDefaultImpl().
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*
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* Use of this method is no longer recommended. Instead applications
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* should try virConnectDomainEventRegisterAny() which has a more flexible
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* API contract
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* API contract.
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*
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* The virDomainPtr object handle passed into the callback upon delivery
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* of an event is only valid for the duration of execution of the callback.
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@ -16134,7 +16136,7 @@ error:
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* The reference can be released once the object is no longer required
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* by calling virDomainFree.
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*
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* Returns 0 on success, -1 on failure
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* Returns 0 on success, -1 on failure.
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*/
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int
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virConnectDomainEventRegister(virConnectPtr conn,
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@ -19064,10 +19066,12 @@ error:
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* @freecb: optional function to deallocate opaque when not used anymore
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*
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* Adds a callback to receive notifications of arbitrary domain events
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* occurring on a domain.
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* occurring on a domain. This function requires that an event loop
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* has been previously registered with virEventRegisterImpl() or
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* virEventRegisterDefaultImpl().
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*
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* If @dom is NULL, then events will be monitored for any domain. If @dom
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* is non-NULL, then only the specific domain will be monitored
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* is non-NULL, then only the specific domain will be monitored.
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*
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* Most types of event have a callback providing a custom set of parameters
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* for the event. When registering an event, it is thus necessary to use
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@ -19085,7 +19089,7 @@ error:
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* for the callback. To unregister a callback, this callback ID should
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* be passed to the virConnectDomainEventDeregisterAny() method.
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*
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* Returns a callback identifier on success, -1 on failure
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* Returns a callback identifier on success, -1 on failure.
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*/
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int
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virConnectDomainEventRegisterAny(virConnectPtr conn,
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@ -19183,10 +19187,12 @@ error:
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* @freecb: optional function to deallocate opaque when not used anymore
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*
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* Adds a callback to receive notifications of arbitrary network events
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* occurring on a network.
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* occurring on a network. This function requires that an event loop
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* has been previously registered with virEventRegisterImpl() or
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* virEventRegisterDefaultImpl().
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*
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* If @net is NULL, then events will be monitored for any network. If @net
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* is non-NULL, then only the specific network will be monitored
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* is non-NULL, then only the specific network will be monitored.
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*
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* Most types of event have a callback providing a custom set of parameters
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* for the event. When registering an event, it is thus necessary to use
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@ -19204,7 +19210,7 @@ error:
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* for the callback. To unregister a callback, this callback ID should
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* be passed to the virConnectNetworkEventDeregisterAny() method.
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*
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* Returns a callback identifier on success, -1 on failure
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* Returns a callback identifier on success, -1 on failure.
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*/
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int
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virConnectNetworkEventRegisterAny(virConnectPtr conn,
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@ -21448,17 +21454,18 @@ error:
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* @interval: number of seconds of inactivity before a keepalive message is sent
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* @count: number of messages that can be sent in a row
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*
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* Start sending keepalive messages after interval second of inactivity and
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* Start sending keepalive messages after @interval seconds of inactivity and
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* consider the connection to be broken when no response is received after
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* count keepalive messages sent in a row. In other words, sending count + 1
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* keepalive message results in closing the connection. When interval is <= 0,
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* no keepalive messages will be sent. When count is 0, the connection will be
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* automatically closed after interval seconds of inactivity without sending
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* any keepalive messages.
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* @count keepalive messages sent in a row. In other words, sending count + 1
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* keepalive message results in closing the connection. When @interval is
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* <= 0, no keepalive messages will be sent. When @count is 0, the connection
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* will be automatically closed after @interval seconds of inactivity without
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* sending any keepalive messages.
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*
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* Note: client has to implement and run event loop to be able to use keepalive
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* messages. Failure to do so may result in connections being closed
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* unexpectedly.
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* Note: The client has to implement and run an event loop with
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* virEventRegisterImpl() or virEventRegisterDefaultImpl() to be able to
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* use keepalive messages. Failure to do so may result in connections
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* being closed unexpectedly.
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*
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* Note: This API function controls only keepalive messages sent by the client.
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* If the server is configured to use keepalive you still need to run the event
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@ -1,7 +1,7 @@
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/*
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* virevent.c: event loop for monitoring file handles
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*
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* Copyright (C) 2007, 2011, 2013 Red Hat, Inc.
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* Copyright (C) 2007, 2011-2014 Red Hat, Inc.
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* Copyright (C) 2007 Daniel P. Berrange
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*
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* This library is free software; you can redistribute it and/or
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@ -37,6 +37,16 @@ static virEventAddTimeoutFunc addTimeoutImpl = NULL;
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static virEventUpdateTimeoutFunc updateTimeoutImpl = NULL;
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static virEventRemoveTimeoutFunc removeTimeoutImpl = NULL;
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/*****************************************************
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*
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* Below this point are *PUBLIC* APIs for event
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* loop integration with applications using libvirt.
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* These API contracts cannot be changed.
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*
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*****************************************************/
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/**
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* virEventAddHandle:
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*
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@ -46,10 +56,12 @@ static virEventRemoveTimeoutFunc removeTimeoutImpl = NULL;
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* @opaque: user data to pass to callback
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* @ff: callback to free opaque when handle is removed
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*
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* Register a callback for monitoring file handle events.
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* Register a callback for monitoring file handle events. This function
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* requires that an event loop has previously been registered with
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* virEventRegisterImpl() or virEventRegisterDefaultImpl().
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*
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* Returns -1 if the file handle cannot be registered, otherwise a handle
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* watch number to be used for updating and unregistering for events
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* watch number to be used for updating and unregistering for events.
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*/
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int
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virEventAddHandle(int fd,
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@ -70,14 +82,17 @@ virEventAddHandle(int fd,
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* @watch: watch whose file handle to update
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* @events: bitset of events to watch from virEventHandleType constants
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*
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* Change event set for a monitored file handle.
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* Change event set for a monitored file handle. This function
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* requires that an event loop has previously been registered with
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* virEventRegisterImpl() or virEventRegisterDefaultImpl().
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*
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* Will not fail if fd exists
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* Will not fail if fd exists.
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*/
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void
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virEventUpdateHandle(int watch, int events)
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{
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updateHandleImpl(watch, events);
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if (updateHandleImpl)
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updateHandleImpl(watch, events);
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}
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/**
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@ -85,7 +100,9 @@ virEventUpdateHandle(int watch, int events)
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*
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* @watch: watch whose file handle to remove
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*
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* Unregister a callback from a file handle.
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* Unregister a callback from a file handle. This function
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* requires that an event loop has previously been registered with
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* virEventRegisterImpl() or virEventRegisterDefaultImpl().
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*
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* Returns -1 if the file handle was not registered, 0 upon success.
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*/
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@ -106,9 +123,11 @@ virEventRemoveHandle(int watch)
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* @opaque: user data to pass to callback
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* @ff: callback to free opaque when timeout is removed
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*
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* Register a callback for a timer event.
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* Register a callback for a timer event. This function
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* requires that an event loop has previously been registered with
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* virEventRegisterImpl() or virEventRegisterDefaultImpl().
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*
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* Setting timeout to -1 will disable the timer. Setting the timeout
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* Setting @timeout to -1 will disable the timer. Setting @timeout
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* to zero will cause it to fire on every event loop iteration.
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*
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* Returns -1 if the timer cannot be registered, a positive
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@ -132,17 +151,20 @@ virEventAddTimeout(int timeout,
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* @timer: timer id to change
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* @timeout: time between events in milliseconds
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*
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* Change frequency for a timer.
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* Change frequency for a timer. This function
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* requires that an event loop has previously been registered with
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* virEventRegisterImpl() or virEventRegisterDefaultImpl().
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*
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* Setting frequency to -1 will disable the timer. Setting the frequency
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* to zero will cause it to fire on every event loop iteration.
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*
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* Will not fail if timer exists
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* Will not fail if timer exists.
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*/
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void
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virEventUpdateTimeout(int timer, int timeout)
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{
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updateTimeoutImpl(timer, timeout);
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if (updateTimeoutImpl)
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updateTimeoutImpl(timer, timeout);
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}
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/**
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@ -150,7 +172,9 @@ virEventUpdateTimeout(int timer, int timeout)
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*
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* @timer: the timer id to remove
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*
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* Unregister a callback for a timer.
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* Unregister a callback for a timer. This function
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* requires that an event loop has previously been registered with
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* virEventRegisterImpl() or virEventRegisterDefaultImpl().
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*
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* Returns -1 if the timer was not registered, 0 upon success.
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*/
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@ -164,14 +188,6 @@ virEventRemoveTimeout(int timer)
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}
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/*****************************************************
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*
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* Below this point are 3 *PUBLIC* APIs for event
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* loop integration with applications using libvirt.
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* These API contracts cannot be changed.
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*
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*****************************************************/
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/**
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* virEventRegisterImpl:
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* @addHandle: the callback to add fd handles
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@ -186,9 +202,18 @@ virEventRemoveTimeout(int timer)
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* to integrate with the libglib2 event loop, or libevent
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* or the QT event loop.
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*
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* Use of the virEventAddHandle() and similar APIs require that the
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* corresponding handler is registered. Use of the
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* virConnectDomainEventRegisterAny() and similar APIs requires that
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* the three timeout handlers are registered. Likewise, the three
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* timeout handlers must be registered if the remote server has been
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* configured to send keepalive messages, or if the client intends
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* to call virConnectSetKeepAlive(), to avoid either side from
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* unexpectedly closing the connection due to inactivity.
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*
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* If an application does not need to integrate with an
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* existing event loop implementation, then the
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* virEventRegisterDefaultImpl method can be used to setup
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* virEventRegisterDefaultImpl() method can be used to setup
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* the generic libvirt implementation.
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*/
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void virEventRegisterImpl(virEventAddHandleFunc addHandle,
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@ -220,9 +245,12 @@ void virEventRegisterImpl(virEventAddHandleFunc addHandle,
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* not have a need to integrate with an external event
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* loop impl.
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*
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* Once registered, the application has to invoke virEventRunDefaultImpl in
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* Once registered, the application has to invoke virEventRunDefaultImpl() in
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* a loop to process events. Failure to do so may result in connections being
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* closed unexpectedly as a result of keepalive timeout.
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* closed unexpectedly as a result of keepalive timeout. The default
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* event loop fully supports handle and timeout events, but only
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* wakes up on events registered by libvirt API calls such as
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* virEventAddHandle() or virConnectDomainEventRegisterAny().
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*
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* Returns 0 on success, -1 on failure.
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*/
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@ -255,14 +283,18 @@ int virEventRegisterDefaultImpl(void)
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*
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* Run one iteration of the event loop. Applications
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* will generally want to have a thread which invokes
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* this method in an infinite loop
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* this method in an infinite loop. Furthermore, it is wise
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* to set up a pipe-to-self handler (via virEventAddHandle())
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* or a timeout (via virEventAddTimeout()) before calling this
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* function, as it will block forever if there are no
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* registered events.
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*
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* static bool quit = false;
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* static bool quit = false;
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*
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* while (!quit) {
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* if (virEventRunDefaultImpl() < 0)
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* while (!quit) {
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* if (virEventRunDefaultImpl() < 0)
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* ...print error...
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* }
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* }
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*
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* Returns 0 on success, -1 on failure.
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*/
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