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/**
* MessageQueueSource:
*
* This is a #GSource which wraps a #GAsyncQueue and is dispatched whenever a
* message can be pulled off the queue. Messages can be enqueued from any
* thread.
*
* The callbacks dispatched by a #MessageQueueSource have type
* #MessageQueueSourceFunc.
*
* #MessageQueueSource supports adding a #GCancellable child source which will
* additionally dispatch if a provided #GCancellable is cancelled.
*/
typedef struct {
GSource parent;
GAsyncQueue *queue; /* owned */
GDestroyNotify destroy_message;
} MessageQueueSource;
/**
* MessageQueueSourceFunc:
* @message: (transfer full) (nullable): message pulled off the queue
* @user_data: user data provided to g_source_set_callback()
*
* Callback function type for #MessageQueueSource.
*/
typedef gboolean (*MessageQueueSourceFunc) (gpointer message,
gpointer user_data);
static gboolean
message_queue_source_prepare (GSource *source,
gint *timeout_)
{
MessageQueueSource *message_queue_source = (MessageQueueSource *) source;
return (g_async_queue_length (message_queue_source->queue) > 0);
}
static gboolean
message_queue_source_dispatch (GSource *source,
GSourceFunc callback,
gpointer user_data)
{
MessageQueueSource *message_queue_source = (MessageQueueSource *) source;
gpointer message;
MessageQueueSourceFunc func = (MessageQueueSourceFunc) callback;
/* Pop a message off the queue. */
message = g_async_queue_try_pop (message_queue_source->queue);
/* If there was no message, bail. */
if (message == NULL)
{
/* Keep the source around to handle the next message. */
return TRUE;
}
/* @func may be %NULL if no callback was specified.
* If so, drop the message. */
if (func == NULL)
{
if (message_queue_source->destroy_message != NULL)
{
message_queue_source->destroy_message (message);
}
/* Keep the source around to consume the next message. */
return TRUE;
}
return func (message, user_data);
}
static void
message_queue_source_finalize (GSource *source)
{
MessageQueueSource *message_queue_source = (MessageQueueSource *) source;
g_async_queue_unref (message_queue_source->queue);
}
static gboolean
message_queue_source_closure_callback (gpointer message,
gpointer user_data)
{
GClosure *closure = user_data;
GValue param_value = G_VALUE_INIT;
GValue result_value = G_VALUE_INIT;
gboolean retval;
/* The invoked function is responsible for freeing @message. */
g_value_init (&result_value, G_TYPE_BOOLEAN);
g_value_init (¶m_value, G_TYPE_POINTER);
g_value_set_pointer (¶m_value, message);
g_closure_invoke (closure, &result_value, 1, ¶m_value, NULL);
retval = g_value_get_boolean (&result_value);
g_value_unset (¶m_value);
g_value_unset (&result_value);
return retval;
}
static GSourceFuncs message_queue_source_funcs =
{
message_queue_source_prepare,
NULL, /* check */
message_queue_source_dispatch,
message_queue_source_finalize,
(GSourceFunc) message_queue_source_closure_callback,
NULL,
};
/**
* message_queue_source_new:
* @queue: the queue to check
* @destroy_message: (nullable): function to free a message, or %NULL
* @cancellable: (nullable): a #GCancellable, or %NULL
*
* Create a new #MessageQueueSource, a type of #GSource which dispatches for
* each message queued to it.
*
* If a callback function of type #MessageQueueSourceFunc is connected to the
* returned #GSource using g_source_set_callback(), it will be invoked for each
* message, with the message passed as its first argument. It is responsible for
* freeing the message. If no callback is set, messages are automatically freed
* as they are queued.
*
* Returns: (transfer full): a new #MessageQueueSource
*/
GSource *
message_queue_source_new (GAsyncQueue *queue,
GDestroyNotify destroy_message,
GCancellable *cancellable)
{
GSource *source; /* alias of @message_queue_source */
MessageQueueSource *message_queue_source; /* alias of @source */
g_return_val_if_fail (queue != NULL, NULL);
g_return_val_if_fail (cancellable == NULL ||
G_IS_CANCELLABLE (cancellable), NULL);
source = g_source_new (&message_queue_source_funcs,
sizeof (MessageQueueSource));
message_queue_source = (MessageQueueSource *) source;
/* The caller can overwrite this name with something more useful later. */
g_source_set_name (source, "MessageQueueSource");
message_queue_source->queue = g_async_queue_ref (queue);
message_queue_source->destroy_message = destroy_message;
/* Add a cancellable source. */
if (cancellable != NULL)
{
GSource *cancellable_source;
cancellable_source = g_cancellable_source_new (cancellable);
g_source_set_dummy_callback (cancellable_source);
g_source_add_child_source (source, cancellable_source);
g_source_unref (cancellable_source);
}
return source;
}
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