author | Dominic Pinkman <Dominic.Pinkman@Nokia.com> |
Wed, 31 Mar 2010 11:11:55 +0100 | |
changeset 7 | 51a74ef9ed63 |
child 8 | ae94777fff8f |
permissions | -rw-r--r-- |
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Week 12 contribution of API Specs and fix SDK submission
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<?xml version="1.0" encoding="utf-8"?> |
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<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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<!-- This component and the accompanying materials are made available under the terms of the License |
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"Eclipse Public License v1.0" which accompanies this distribution, |
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and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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<!-- Initial Contributors: |
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Nokia Corporation - initial contribution. |
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Contributors: |
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--> |
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<!DOCTYPE concept |
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PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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<concept id="GUID-3829BD20-3DCB-5489-8FC4-07F954E391BF" xml:lang="en"><title>Local |
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and global handles</title><shortdesc>This document explains the distinction between local and global |
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handles.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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<p>This is the issue of Kernel side object visibility.</p> |
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<p>Handles are said to be local or global.</p> |
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<p>A handle is <i>local</i>, if the Kernel object which that handle represents |
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is only visible to the thread that created it; no other thread can open a |
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handle to the same Kernel object.</p> |
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<p>Typically, code constructs the appropriate <codeph>RHandleBase</codeph> derived |
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object, e.g. an <codeph>RMutex</codeph>, and calls its <codeph>Create()</codeph>, <codeph>CreateLocal()</codeph> or |
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equivalent function to create the corresponding Kernel object.</p> |
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<p>A handle is <i>global</i>, if the Kernel object which that handle represents |
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is visible to all threads across all processes; any thread in any process |
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can open a handle to that same Kernel object. Typically, such a Kernel object |
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is intended for sharing.</p> |
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<p>For a global handle. the corresponding Kernel object is assigned a name. |
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The name gives that Kernel object an identity and is the key property which |
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allows other threads to open a handle onto that same object. It is usual to |
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use a <codeph>TFindHandleBase</codeph> <i>derived</i> class to locate a global |
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Kernel object. The following diagram shows the general idea.</p> |
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<fig id="GUID-01C60CFA-8CA7-51CC-904E-158EC02959DE"> |
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<image href="GUID-5398C2DC-9AFA-5517-BCBF-5964970B9656_d0e234441_href.png" placement="inline"/> |
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</fig> |
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<p>See also:</p> |
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<ul> |
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<li id="GUID-56D39619-C90C-51DF-9475-3B75FB189258"><p><xref href="GUID-FC639517-F138-5E84-B57A-6347F5A47B88.dita">Names |
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and fullnames</xref> in reference counting objects.</p> </li> |
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</ul> |
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</conbody></concept> |