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271 lines
10 KiB
HTML
271 lines
10 KiB
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="content-type"
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content="text/html; charset=ISO-8859-1">
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<title>Convert Gecko from unmanged to managed code in .Net</title>
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</head>
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<body>
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<h1 style="margin-left: 40px; text-align: center;">Wrapping Gecko APIs
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using Microsoft Visual Studio .NET Managed Extensions for C++<big><big><big><br
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style="color: rgb(255, 0, 0);">
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</big></big></big> </h1>
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<div style="text-align: center;"> <big><big><big><span
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style="color: rgb(255, 0, 0);">**DRAFT**</span></big></big></big><br>
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</div>
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<br>
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<h2>Intended Audience:</h2>
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This paper is intended for a C++ programmer who would like to know how
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to wrap Gecko engine from unmanaged C++ to managed C++ . Author
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assumes the reader is familiar with Gecko and MS Visual Studio.NET with
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Managed Extensions for C++. <br>
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<br>
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<h2>Background:</h2>
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<ol>
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<li> Why do we go all this trouble? </li>
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<li>When we have Gecko as ActiveX control, then why don't we use the
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Runtime-Callable Wrapper (RCW) and COM-Callable Wrapper (CCW)? </li>
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</ol>
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<br>
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<h2 class="dtH1">How do we do this?</h2>
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There are few ways to convert the existing unmanaged code to managed
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code:
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<ol type="1">
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<li>You can use the built-in .NET runtime interop facilities (such as
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PInvoke or COM Interop)<br>
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</li>
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<li>You can wrap the unmanaged code using the managed extensions to
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C++.</li>
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<li>You can rewrite the entire code in a .NET language.</li>
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</ol>
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<h2 class="dtH1">What do we need?</h2>
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We need <br>
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<ol>
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<li>.NET Framework (1.1) <br>
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</li>
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<li>Microsoft Visual Studio .NET (preferably 2003)</li>
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<li>mozilla development environment
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(http://www.mozilla.org/build/win32.html)<br>
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</li>
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</ol>
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<h2>Terminology:</h2>
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Following terms are used throughout out this document and it is
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important to understand what each term means. <br>
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<ul>
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<li><span style="font-weight: bold;">Assembly</span><br>
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</li>
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</ul>
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<div style="margin-left: 80px;">Assembly is a building block of the
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.Net Framework. It is the fundamental unit of deployment, version
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control, reuse, activation, scoping, and security permissions. It
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provides the Common Language Runtime (CLR) with the information it needs
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to be aware of type implementations. It is a collection of types
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and resources that are built to work together and form a logical unit of
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functionality. <br>
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</div>
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<ul style="font-weight: bold;">
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<li>Global Assembly Cache</li>
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</ul>
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<div style="margin-left: 80px;">Global Assembly Cache is a machine wide
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code cache that is installed whereever the CLR is installed. In
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most cases, if you intend to share an assembly with multiple
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applications, you should deploy it into the global assembly cache.<br>
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</div>
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<ul>
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<li><span style="font-weight: bold;">Managed code vs Unmanaged code</span><br>
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</li>
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</ul>
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<div style="margin-left: 80px;"><span style="font-style: italic;">Manged
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code</span> requires the execution environment of the CLR.
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Compilers emit managed code as MSIL, the intermidate language. The
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reason for the name is that code is managed by the CLR and objects are
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allocated from heaps managed by the CLR.<br>
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</div>
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<div style="margin-left: 80px;"><span style="font-style: italic;">Unmanaged
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code</span> does not use nor require the execution environment of the
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Common Language Runtime (CLR). Unmanaged code is outside the
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reach of the CLR's security system, garbage collector and other
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services.</div>
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<ul>
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<li style="font-weight: bold;">CLR</li>
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<li style="font-weight: bold;">Runtime-Callable Wrapper (RCW)</li>
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<li style="font-weight: bold;">COM-Callable Wrapper (CCW)</li>
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<li style="font-weight: bold;">Boxing</li>
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</ul>
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<div style="margin-left: 80px;">Boxing is a technique to convert a
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value type to a __gc object by using the __box<br>
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<div style="margin-left: 40px;">Int32 i = 42;<br>
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__box Int32* b = __box(i);<br>
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</div>
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</div>
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<ul>
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<li style="font-weight: bold;">UnBoxing</li>
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</ul>
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<div style="margin-left: 80px;">UnBoxing (dereferencing) is a technique
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to convert a boxed object to value type by casting.<br>
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<div style="margin-left: 40px;">Color red;<br>
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Object* obj = Enum::Parse(__typeof(Color), S"red");<br>
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red = *static_cast<__box Color*>(obj);<br>
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</div>
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</div>
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<br>
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<ul>
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<li style="font-weight: bold;">Managed Objects</li>
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</ul>
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<div style="margin-left: 80px;">Managed Object is an instance of a
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class which is created in the heap and managed by the garbage collector
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by using the <span style="font-style: italic;">__gc</span>
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modifier. <br>
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<div style="margin-left: 40px;"><span style="font-style: italic;">__gc</span>
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class Point<br>
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{<br>
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</div>
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<div style="margin-left: 80px;">public:<br>
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</div>
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<div style="margin-left: 120px;"> int x;<br>
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int y;<br>
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</div>
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<div style="margin-left: 40px;"> };<br>
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</div>
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</div>
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<ul style="font-weight: bold;">
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<li>Value Types</li>
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</ul>
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<div style="margin-left: 80px;">Value Types ar typically small, short
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lived objects and they are usually created on the stack. In managed C++,
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the value types are defined by using <span style="font-style: italic;">__value</span>
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modifier. <br>
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<div style="margin-left: 40px;"><span style="font-style: italic;">__value</span>
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class Point<br>
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{<br>
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</div>
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<div style="margin-left: 80px;">public:<br>
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</div>
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<div style="margin-left: 120px;"> int x;<br>
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int y;<br>
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</div>
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<div style="margin-left: 40px;"> };<br>
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</div>
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</div>
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<br>
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<h2>Necessary Steps:</h2>
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<ul>
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</ul>
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<br>
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<h2>Gecko APIs</h2>
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We will be exposing list of Gecko APIs<br>
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<ul>
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<li>nsresult NS_InitEmbedding(nsILocalFile *aMozBinDirectory,
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nsIDirectoryServiceProvider *aAppFileLocProvider);<br>
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</li>
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<li>nsresult NS_TermEmbedding();</li>
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<li>...<br>
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</li>
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</ul>
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<br>
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<h2>Coding Techniques:</h2>
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<ul>
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<li>
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<h3>Using managed object in unmanaged code</h3>
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</li>
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</ul>
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<div style="margin-left: 40px;">Managed pointers are managed by the
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garbage collector so that when copies are made, the gc knows that
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references are created. When a pointer is passed to native code,
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the gc cannot track its usage and so cannot determine any change in
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object reference. Furthermore, if a garbage collection
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occures, the object can be moved in memory, so the gc changes all
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managed pointers so that they point to the new location. Because
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the gc doesn't have access to the pointers passed to native code
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(unmanaged code), potentially a pointer used in native code could
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suddenly become invalid. Use a pinned pointer which tells gc not
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to move the memory.<br>
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<div style="margin-left: 80px;">
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<table cellpadding="2" cellspacing="2" border="1"
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style="text-align: left; width: 100%;">
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<tbody>
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<tr>
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<td style="vertical-align: top;">//Using pinning<br>
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#progma unmanaged<br>
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void print(int *p)<br>
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{<br>
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printf("%ld\n", *p);<br>
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}<br>
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<br>
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#progma managed<br>
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_gc struct Test {<br>
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int i;<br>
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};<br>
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<br>
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void main()<br>
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{<br>
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Test * t = new Test;<br>
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int __pin* p = &t->i;<br>
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print(p);<br>
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}<br>
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</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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<div style="margin-left: 40px;"><br>
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</div>
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<ul>
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<li>
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<h3>Using unmanaged object in managed code</h3>
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</li>
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</ul>
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<div style="margin-left: 120px;">
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<table cellpadding="2" cellspacing="2" border="1"
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style="text-align: left; width: 100%;">
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<tbody>
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<tr>
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<td style="vertical-align: top;"><span class="clsCap">//Using
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GCHandle</span> <br>
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<pre>#using <mscorlib.dll><br><br>using namespace System;<br>using namespace System::Runtime::InteropServices;<br><br>#pragma managed<br>class AppDomainWrapper<br>{<br>private:<br> int m_handle;<br>public:<br> AppDomainWrapper() {<br> AppDomain* d = AppDomain::Current;<br> m_handle = (GCHandle::op_Explicit(GCHandle::Alloc(d))).ToInt32();<br> }<br> ~AppDomainWrapper() {<br> (GCHandle::op_Explicit(m_handle)).Free();<br> }<br> // more functions here...<br> void PrintBaseDir() {<br> AppDomain* domain = __try_cast<AppDomain*>(<br> (GCHandle::op_Explicit(m_handle)).Target);<br> Console::WriteLine ( S"AppDomain Base Directory: {0}",<br> domain->BaseDirectory );<br> }<br>};<br><br>#pragma unmanaged<br>int main() {<br> AppDomainWrapper w; <br> w.PrintBaseDir();<br> return 0; <br>}</pre>
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</td>
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<td style="vertical-align: top;"><span class="clsCap">//Using
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gcroot</span> <br>
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<pre>#using <mscorlib.dll><br>#include <gcroot.h><br><br>using namespace System;<br>using namespace System::Runtime::InteropServices;<br><br>#pragma managed<br>class AppDomainWrapper<br>{<br>private:<br> gcroot<AppDomain*> m_domain;<br>public:<br> AppDomainWrapper() {<br> m_domain = AppDomain::CurrentDomain;<br> }<br> ~AppDomainWrapper() {<br> }<br> // more functions here...<br> void PrintBaseDir() {<br> Console::WriteLine ( S"AppDomain Base Directory: {0}",<br> m_domain->BaseDirectory );<br> }<br>};<br><br>#pragma unmanaged<br>int main() {<br> AppDomainWrapper w; <br> w.PrintBaseDir();<br> return 0; <br><br><br><br>}</pre>
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</td>
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</tr>
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</tbody>
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</table>
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<span class="clsFigure"></span><span class="clsCap"></span> </div>
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<h2>Useful Tools:</h2>
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<ul>
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<li>Viewing Assembly Contents</li>
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<ul>
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<li>MSIL Disassembler (ildasm.exe)<br>
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</li>
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</ul>
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</ul>
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<ul>
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<li>TLBIMP.exe</li>
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<li>TLBEXP.exe</li>
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<li>REGASM.exe</li>
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<li>AXIMP.exe</li>
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<li>REGSVCS.exe</li>
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</ul>
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<br>
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<h2 class="dtH1">References<br>
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</h2>
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<ul>
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<li>Visual Studio .NET
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(http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vsintro7/html/vsstartpage.asp)<br>
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</li>
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<li>Managed Extensions for C++ programming (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vcmex/html/vcconmcoverview.asp)</li>
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<li>Managed Extensions for C++ specifications
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(http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vcmxspec/html/vcManagedExtensionsSpec_Start.asp)<br>
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</li>
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</ul>
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<h2><br>
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</h2>
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<h2>History:</h2>
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Draft 0.1 : April 9 2003 Roy Yokoyama<br>
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<br>
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<br>
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</body>
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</html>
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