| Package | flash.concurrent |
| Class | public final class Mutex |
| Inheritance | Mutex  Object |
| Language version: | ActionScript 3.0 |
| Runtime version: | AIR 3.5 |
shareable property is true). However, a Mutex can be
used to manage workers' access to any shareable resource, such as an AIR native
extension or a filesystem file. No matter what the resource, the purpose of
the mutex is to ensure that only one set of code accesses the resource at a time.
A mutex manages access using the concept of resource ownership. At any time a single mutex is "owned" by at most one worker. When ownership of a mutex switches from one worker to another the transision is atomic. This guarantees that it will never be possible for more than one worker to take ownership of the mutex. As long as code in a worker only operates on a shared resource when that worker owns the mutex, you can be certain that there will never be a conflict from multiple workers.
Use the tryLock() method to take ownership of the mutex if
it is available. Use the lock() method to pause the current
worker's execution until the mutex is available, then take ownership of the
mutex. Once the current worker has ownership of the mutex, it can safely
operate on the shared resource. When those operations are complete, call the
unlock() method to release the mutex. At that point the current
worker should no longer access the shared resource.
The Mutex class is one of the special object types that are shared
between workers rather than copied between them. When you pass a mutex from
one worker to another worker either by calling the Worker object's
setSharedProperty() method or by using a MessageChannel object,
both workers have a reference to the same Mutex object in the runtime's memory.
See also
| Property | Defined by | ||
|---|---|---|---|
 | constructor : Object
A reference to the class object or constructor function for a given object instance.
| Object | |
| isSupported : Boolean
[static][read-only]
Indicates whether the use of the Mutex class is supported for the current platform.
| Mutex | ||
| prototype : Object
[static]
A reference to the prototype object of a class or function object.
| Object | |
| Method | Defined by | ||
|---|---|---|---|
|
Mutex()
Creates a new Mutex instance.
| Mutex | ||
|
Indicates whether an object has a specified property defined.
| Object | |
|
Indicates whether an instance of the Object class is in the prototype chain of the object specified
as the parameter.
| Object | |
|
Pauses execution of the current worker until this mutex is available and
then takes ownership of the mutex.
| Mutex | ||
|
Indicates whether the specified property exists and is enumerable.
| Object | |
|
Sets the availability of a dynamic property for loop operations.
| Object | |
|
Returns the string representation of this object, formatted according to locale-specific conventions.
| Object | |
|
Returns the string representation of the specified object.
| Object | |
|
Acquires ownership of the mutex if it is available.
| Mutex | ||
|
Releases ownership of this mutex, allowing any worker to acquire it and
perform work on the associated resource.
| Mutex | ||
|
Returns the primitive value of the specified object.
| Object | |
| isSupported | property |
Hide Inherited Public Properties
Show Inherited Public PropertiesisSupported:Boolean [read-only]
| Language version: | ActionScript 3.0 |
| Runtime version: | AIR 3.5 |
Indicates whether the use of the Mutex class is supported for the current platform.
This property is true if the current platform supports mutexes; otherwise
false.
public static function get isSupported():Boolean
| Mutex | () | constructor |
public function Mutex()
| Language version: | ActionScript 3.0 |
| Runtime version: | AIR 3.5 |
Creates a new Mutex instance.
Error — if the mutex could not be initialized.
|
| lock | () | method |
public function lock():void
| Language version: | ActionScript 3.0 |
| Runtime version: | AIR 3.5 |
Pauses execution of the current worker until this mutex is available and
then takes ownership of the mutex. If another worker owns the
mutex when lock() is called, the calling worker's execution thread pauses at the
lock() call and the worker is added to the queue of ownership
requests. Once the calling worker acquires the mutex, the worker's
execution continues with the line of code following the
lock() call.
Once the current worker has ownership of the mutex, it can safely
operate on the shared resource. When those operations are complete, call
the unlock() method to release the mutex. At that point the
current worker should no longer access the shared resource.
Internally, a mutex keeps a count of the number of lock requests it
has received. The mutex must receive the same number of unlock requests
before it is completely released. If code in the worker that owns the
mutex locks it again (by calling the lock() method) the
internal lock count increases by one. You must call the
unlock() method as many times as the number of lock requests
to release ownership of the mutex.
When multiple workers are waiting for a mutex, the mutex gives priority to assigning ownership to the longest-waiting worker. However, scheduling of worker threads is managed by the host operating system so there is no guarantee of a particular code execution order across workers.
| tryLock | () | method |
public function tryLock():Boolean
| Language version: | ActionScript 3.0 |
| Runtime version: | AIR 3.5 |
Acquires ownership of the mutex if it is available. If another worker
already owns the mutex or another worker has called the lock()
method and is waiting to acquire the mutex, the mutex is not available.
In that case, calling this method returns false and code
execution continues immediately.
Once the current worker has ownership of the mutex, it can safely
operate on the shared resource. When those operations are complete, call
the unlock() method to release the mutex. At that point the
current worker should no longer access the shared resource.
When multiple workers are waiting for a mutex, the mutex gives priority to assigning ownership to the longest-waiting worker. However, scheduling of worker threads is managed by the host operating system so there is no guarantee of a particular code execution order across workers.
ReturnsBoolean —
true if the mutex was available (and is now owned
by the current worker), or false if the current worker did
not acquire ownership of the mutex.
|
| unlock | () | method |
public function unlock():void
| Language version: | ActionScript 3.0 |
| Runtime version: | AIR 3.5 |
Releases ownership of this mutex, allowing any worker to acquire it and perform work on the associated resource.
Internally, a mutex keeps a count of the number of lock requests it
has received. Code in a worker must call the unlock()
method as many times as the number of lock requests in order to release
ownership of the mutex.
Error — when the current worker
doesn't own the mutex.
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