2002-07-09 16:24:59 +04:00
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2009-10-20 02:42:52 +04:00
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<!-- $Id: BAutolockUseCases.html 10 2002-07-09 12:24:59Z ejakowatz $ -->
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2002-07-09 16:24:59 +04:00
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<TITLE>BAutolock Use Cases and Implementation Details</TITLE>
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<H1>BAutolock Use Cases and Implementation Details:</H1>
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<P>This document describes the BAutolock interface and some basics of how it is implemented.
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The document has the following sections:</P>
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<OL>
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<LI><A HREF="#interface">BAutolock Interface</A></LI>
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<LI><A HREF="#usecases">BAutolock Use Cases</A></LI>
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<LI><A HREF="#implement">BAutolock Implementation</A></LI>
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</OL>
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<A NAME="interface"></A><H2>BAutolock Interface:</H2>
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<P>The BAutolock class is a simple class for handling synchronization between threads. The best
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source of information for the BAutolock interface can be found
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<A HREF="file:///boot/beos/documentation/Be%20Book/The%20Support%20Kit/Autolock.html">here in the Be Book</A>.
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</P>
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<A NAME="usecases"></A><H2>BAutolock Use Cases:</H2>
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<P>The following use cases cover the BAutolock functionality:</P>
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<OL>
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<LI><P><B>Construction 1:</B> A BAutolock can be created by passing a pointer to a BLocker object.
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An attempt will be made to Lock() this BLocker during the construction of the BAutolock object.
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</P></LI>
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<LI><P><B>Construction 2:</B> A BAutolock can be created by passing a reference to a BLocker object.
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An attempt will be made to Lock() this BLocker during the construction of the BAutolock object.
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</P></LI>
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<LI><P><B>Construction 3:</B> A BAutolock can be created by passing a pointer to a BLooper object.
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An attempt will be made to Lock() this BLooper during the construction of the BAutolock object.
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</P></LI>
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<LI><P><B>Is Locked:</B> When the BAutolock is constructed, a lock is attempted on the BLocker or
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BLooper passed in. The result of that lock attempt is returned by calling IsLocked() on the
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BAutolock. The result is a boolean. True is returned if the lock was successfully acquired.
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False is returned if the lock could not be acquired. See the docs for BLocker and BLooper to
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find out why the lock acquisition may fail.</P></LI>
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<LI><P><B>Destruction 1:</B> If the lock acquisition on the BLocker or BLooper was successful at
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construction time, when the BAutolock is destructed, the lock will be released by calling Unlock()
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on the BLocker or BLooper.</P></LI>
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<LI><P><B>Destruction 2:</B> If the lock acquisition on the BLocker or BLooper failed at
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construction time, when the BAutolock is destructed, nothing is done to the BLocker or the BLooper.
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An Unlock() is not attempted because the lock at construction time failed.</P></LI>
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</OL>
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<A NAME="implement"></A><H2>BAutolock Implementation:</H2>
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<P>The entire BAutolock implementation is inline. Because BAutolock is implemented inline, there
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is no code for BAutolock in libbe.so. The code is all in Be's Autolock.h header file and compiled
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at build time directly into any object being built.</P>
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<P>This has some interesting implications from a backwards compatibility perspective. Because
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there are no references from existing non-Be executables and libraries to libbe.so expecting
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to find the BAutolock class, the entire definition of BAutolock can be changed almost without risk
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of breaking compatibility. This gives anyone wishing to expand and build on the current BAutolock
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class a great deal of flexibility.</P>
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<P>However, it may be worthwhile when changing BAutolock in the future to try and stay source
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compatible. That way, existing source code will continue to compile without having to update
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it.</P>
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