AutomaticEvent (Type of variable)

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Process management functions

Threads, semaphores, signals and mutex

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AutomaticEvent

Presentation

Example

Declaration

See also

AutomaticEvent (Type of variable)

In french: SignalAutomatique

The AutomaticEvent type is used to manage an automatic event. An automatic event is used to simplify the synchronization between several threads.

After its opening, an "Automatic" event is automatically closed as soon as a single thread is unlocked.

Remark: We recommend that you use an AutomaticEvent or ManualEvent variable to create an event rather than naming it using a character string. Indeed, using a variable allows you to:

manage the variable scope,
avoid having 2 events with the same name in 2 different threads.

Example

// MAIN THREAD
//------------------
// Define the event
s is AutomaticEvent
// Start the thread
ThreadExecute("Thread", threadNormal, ProcThread, s)

// Code in parallel with the thread
...
// Wait for the event triggered by the thread
EventWait("s")

// SECONDARY THREAD
// ----------------------
PROCEDURE ProcThread(s)

// Code in the thread
...
// Unlock the main thread
EventOpen(s)

Declaration

Declaring an automatic event (simple syntax) Hide the details

MyVariable is AutomaticEvent

In this case, the automatic event is closed when it is created.

Declaring an automatic event (advanced syntax) Hide the details

MyVariable is AutomaticEvent(<Initial state>)

<Initial state>: Integer constant

Initial state of the event:
eventOpen The event is open when it is created.
eventClose The event is closed when it is created.

Remarks

Using the AutomaticEvent variables

The AutomaticEvent variables can be used to synchronize threads in functions:

standard syntax:


EventClose	Closes a synchronization event between several threads.
EventOpen	Opens a synchronization event between several threads.
EventWait	Locks the current thread while waiting for the specified event to be opened.

prefix syntax:


<AutomaticEvent variable>.Close	Closes a synchronization event between several threads.
<AutomaticEvent variable>.Open	Opens a synchronization event between several threads.
<AutomaticEvent variable>.Wait	Locks the current thread while waiting for the specified event to be opened.

When EventOpen (or <AutomaticEvent variable>.Open) is called:

if there is at least one pending thread, a single thread is freed.
if there is no pending thread, the event remains open until a thread calls EventWait (or <AutomaticEvent variable>.Wait).