37 lines
1.8 KiB
XML
37 lines
1.8 KiB
XML
<?xml version="1.0" encoding="UTF-8" ?>
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<class name="Semaphore" inherits="RefCounted" version="4.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
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<brief_description>
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A synchronization mechanism used to control access to a shared resource by [Thread]s.
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</brief_description>
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<description>
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A synchronization semaphore that can be used to synchronize multiple [Thread]s. Initialized to zero on creation. For a binary version, see [Mutex].
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[b]Warning:[/b] Semaphores must be used carefully to avoid deadlocks.
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[b]Warning:[/b] To guarantee that the operating system is able to perform proper cleanup (no crashes, no deadlocks), these conditions must be met:
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- When a [Semaphore]'s reference count reaches zero and it is therefore destroyed, no threads must be waiting on it.
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- When a [Thread]'s reference count reaches zero and it is therefore destroyed, it must not be waiting on any semaphore.
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</description>
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<tutorials>
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<link title="Using multiple threads">$DOCS_URL/tutorials/performance/using_multiple_threads.html</link>
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<link title="Thread-safe APIs">$DOCS_URL/tutorials/performance/thread_safe_apis.html</link>
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</tutorials>
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<methods>
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<method name="post">
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<return type="void" />
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<description>
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Lowers the [Semaphore], allowing one more thread in.
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</description>
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</method>
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<method name="try_wait">
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<return type="bool" />
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<description>
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Like [method wait], but won't block, so if the value is zero, fails immediately and returns [code]false[/code]. If non-zero, it returns [code]true[/code] to report success.
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</description>
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</method>
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<method name="wait">
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<return type="void" />
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<description>
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Waits for the [Semaphore], if its value is zero, blocks until non-zero.
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</description>
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</method>
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</methods>
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</class>
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