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GStreamer 0.10 Core Reference Manual | ![]() |
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#include <gst/gst.h> GstTask; void (*GstTaskFunction) (void *data); enum GstTaskState; #define GST_TASK_BROADCAST (task) #define GST_TASK_GET_COND (task) #define GST_TASK_GET_LOCK (task) #define GST_TASK_SIGNAL (task) #define GST_TASK_STATE (task) #define GST_TASK_WAIT (task) void gst_task_cleanup_all (void); GstTask* gst_task_create (GstTaskFunction func, gpointer data); GstTaskState gst_task_get_state (GstTask *task); gboolean gst_task_join (GstTask *task); gboolean gst_task_pause (GstTask *task); void gst_task_set_lock (GstTask *task, GStaticRecMutex *mutex); gboolean gst_task_start (GstTask *task); gboolean gst_task_stop (GstTask *task);
GstTask is used by GstElement and GstPad to provide the data passing threads in a GstPipeline.
A GstPad will typically start a GstTask to push or pull data to/from the peer pads. Most source elements start a GstTask to push data. In some cases a demuxer element can start a GstTask to pull data from a peer element. This is typically done when the demuxer can perform random access on the upstream peer element for improved performance.
Although convenience functions exist on GstPad to start/pause/stop tasks, it might sometimes be needed to create a GstTask manually if it is not related to a GstPad.
Before the GstTask can be run, it needs a GStaticRecMutex that can be set with
gst_task_set_lock()
.
The task can be started, paused and stopped with gst_task_start()
, gst_task_pause()
and gst_task_stop()
respectively.
A GstTask will repeatedly call the GstTaskFunction with the user data
that was provided when creating the task with gst_task_create()
. Before calling
the function it will acquire the provided lock.
Stopping a task with gst_task_stop()
will not immediately make sure the task is
not running anymore. Use gst_task_join()
to make sure the task is completely
stopped and the thread is stopped.
After creating a GstTask, use gst_object_unref()
to free its resources. This can
only be done it the task is not running anymore.
Last reviewed on 2006-02-13 (0.10.4)
typedef struct { GstTaskState state; GCond *cond; GStaticRecMutex *lock; GstTaskFunction func; gpointer data; gboolean running; } GstTask;
The GstTask object.
GstTaskState state ; |
the state of the task |
GCond *cond ; |
used to pause/resume the task |
GStaticRecMutex *lock ; |
The lock taken when iterating the task function |
GstTaskFunction func ; |
the function executed by this task |
gpointer data ; |
data passed to the task function |
gboolean running ; |
a flag indicating that the task is running |
void (*GstTaskFunction) (void *data);
A function that will repeatedly be called in the thread created by a GstTask.
data : |
user data passed to the function |
typedef enum { GST_TASK_STARTED, GST_TASK_STOPPED, GST_TASK_PAUSED } GstTaskState;
The different states a task can be in
#define GST_TASK_BROADCAST(task) g_cond_breadcast(GST_TASK_GET_COND (task))
Send a broadcast signal to all waiting task conds
task : |
Task to broadcast |
#define GST_TASK_GET_COND(task) (GST_TASK_CAST(task)->cond)
Get access to the cond of the task.
task : |
Task to get the cond of |
#define GST_TASK_GET_LOCK(task) (GST_TASK_CAST(task)->lock)
Get access to the task lock.
task : |
Task to get the lock of |
#define GST_TASK_SIGNAL(task) g_cond_signal(GST_TASK_GET_COND (task))
Signal the task cond
task : |
Task to signal |
#define GST_TASK_STATE(task) (GST_TASK_CAST(task)->state)
Get access to the state of the task.
task : |
Task to get the state of |
#define GST_TASK_WAIT(task) g_cond_wait(GST_TASK_GET_COND (task), GST_OBJECT_GET_LOCK (task))
Wait for the task cond to be signalled
task : |
Task to wait for |
void gst_task_cleanup_all (void);
Wait for all tasks to be stopped. This is mainly used internally to ensure proper cleanup of internal data structures in test suites.
MT safe.
GstTask* gst_task_create (GstTaskFunction func, gpointer data);
Create a new Task that will repeatedly call the provided func
with data
as a parameter. Typically the task will run in
a new thread.
The function cannot be changed after the task has been created. You must create a new GstTask to change the function.
func : |
The GstTaskFunction to use |
data : |
User data to pass to func
|
Returns : | A new GstTask. MT safe. |
GstTaskState gst_task_get_state (GstTask *task);
Get the current state of the task.
task : |
The GstTask to query |
Returns : | The GstTaskState of the task MT safe. |
gboolean gst_task_join (GstTask *task);
Joins task
. After this call, it is safe to unref the task
and clean up the lock set with gst_task_set_lock()
.
The task will automatically be stopped with this call.
This function cannot be called from within a task function as this would cause a deadlock. The function will detect this and print a g_warning.
task : |
The GstTask to join |
Returns : | TRUE if the task could be joined.
MT safe.
|
gboolean gst_task_pause (GstTask *task);
Pauses task
. This method can also be called on a task in the
stopped state, in which case a thread will be started and will remain
in the paused state. This function does not wait for the task to complete
the paused state.
task : |
The GstTask to pause |
Returns : | TRUE if the task could be paused.
MT safe.
|
void gst_task_set_lock (GstTask *task, GStaticRecMutex *mutex);
Set the mutex used by the task. The mutex will be acquired before calling the GstTaskFunction.
This function has to be called before calling gst_task_pause()
or
gst_task_start()
.
MT safe.
task : |
The GstTask to use |
mutex : |
The GMutex to use |
gboolean gst_task_start (GstTask *task);
Starts task
. The task
must have a lock associated with it using
gst_task_set_lock()
or this function will return FALSE
.
task : |
The GstTask to start |
Returns : | TRUE if the task could be started.
MT safe.
|
gboolean gst_task_stop (GstTask *task);
Stops task
. This method merely schedules the task to stop and
will not wait for the task to have completely stopped. Use
gst_task_join()
to stop and wait for completion.
task : |
The GstTask to stop |
Returns : | TRUE if the task could be stopped.
MT safe.
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