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<?xml version="1.0" encoding="UTF-8" ?>
<class name="Semaphore" inherits="Reference" version="3.6" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
<brief_description>
A synchronization semaphore.
</brief_description>
<description>
A synchronization semaphore which can be used to synchronize multiple [Thread]s. Initialized to zero on creation. Be careful to avoid deadlocks. For a binary version, see [Mutex].
[b]Warning:[/b]
To guarantee that the operating system is able to perform proper cleanup (no crashes, no deadlocks), these conditions must be met:
- By the time a [Semaphore]'s reference count reaches zero and therefore it is destroyed, no threads must be waiting on it.
- By the time a [Thread]'s reference count reaches zero and therefore it is destroyed, it must not be waiting on any semaphore.
</description>
<tutorials>
<link>$DOCS_URL/tutorials/performance/threads/using_multiple_threads.html</link>
</tutorials>
<methods>
<method name="post">
<return type="int" enum="Error" />
<description>
Lowers the [Semaphore], allowing one more thread in.
[b]Note:[/b] This method internals' can't possibly fail, but an error code is returned for backwards compatibility, which will always be [constant OK].
</description>
</method>
<method name="try_wait">
<return type="int" enum="Error" />
<description>
Like [method wait], but won't block, so if the value is zero, fails immediately and returns [constant ERR_BUSY]. If non-zero, it returns [constant OK] to report success.
</description>
</method>
<method name="wait">
<return type="int" enum="Error" />
<description>
Waits for the [Semaphore], if its value is zero, blocks until non-zero.
[b]Note:[/b] This method internals' can't possibly fail, but an error code is returned for backwards compatibility, which will always be [constant OK].
</description>
</method>
</methods>
<constants>
</constants>
</class>
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