Difference between revisions of "Uno/Spec/Thread Affinity Bridge"

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A [[../Purpose Bridge|Purpose Bridge]] protecting [[../Thread Affine|Thread Affine]] objects.
 
A [[../Purpose Bridge|Purpose Bridge]] protecting [[../Thread Affine|Thread Affine]] objects.
  
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=== Feature ===
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===Feature===
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The Thread Affine Bridge protects [[../Thread Affine|Thread Affine]] objects from being called by wrong threads. It does this by providing a dedicated thread, into which it delegates the calls prior to invoking a particular object. This dedicated thread is therefor the thread objects may create an affinity to.
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The Thread Affinity Bridge ensures that encapsulated objects are always called by the same thread, thus compensating any [[../Thread Affine|thread affinity]]. The Affinity Bridge also ensures, that calls into or through it do not show any [[Uno/Term/Thread Aware|thread awareness]].
  
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The Affinity Bridge behaves as follows,
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Only one thread at a time can enter a Affinity Environment, an Affinity Environment is entered, if any thread has one of the methods provided by the <code>Enterable</code> API on the stack.
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* entering a Thread Affine environment associates the current thread with it, in case the environment already has a thread associated, the enter blocks until no object is mapped anymore,
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* leaving a Thread Affine environment disassociates the current thread from the [[../Environment|Environment]], in case objects are still mapped, the leave blocks until no object is mapped anymore,
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* calling into the Thread Affine environment, leads to the invocation of the passed function by the associated thread,
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* calling out of the Thread Affine environment, leads to the invocation of the passed function by the in-calling thread, in case of no in-calling thread, the associated thread calls out directly.
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=== Rationale ===
 
=== Rationale ===

Revision as of 11:19, 29 June 2006

version: 13032
state: draft
type: specification

Thread Affinity Bridge

A Purpose Bridge protecting Thread Affine objects.

Feature

The Thread Affinity Bridge ensures that encapsulated objects are always called by the same thread, thus compensating any thread affinity. The Affinity Bridge also ensures, that calls into or through it do not show any thread awareness.

Only one thread at a time can enter a Affinity Environment, an Affinity Environment is entered, if any thread has one of the methods provided by the Enterable API on the stack.

Rationale

Some APIs have thread affinities in respect to particular handles they return. For example, on Win32 the window-destroy and -message functions require to be called by the same thread which actually created the window. This thread affinity is inherited when developing APIs on top of these thread affine APIs. In general, thread affine APIs are hard to program, especially in generic frameworks where it is not knowable before hand how long a thread lives and on whichs objects it calls.

API

A purpose bridge named "affine".

Dependencies

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