这就是com组件

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本文深入浅出地介绍了COM组件的思想及其重要性，并通过一个实际的例子详细展示了如何创建和使用COM组件，包括自注册的过程。

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【VS开发】这就是COM组件

2016-04-09 21:42 13人阅读评论(0) 收藏举报

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[实例]这就是COM组件

时间 2012-02-21 10:49:15 优快云博客

原文 http://blog.youkuaiyun.com/btwsmile/article/details/7278492

主题 COM技术

[实例]这就是COM组件

Author: ume Date:2012-02-21

自从微软推出.NET以来，COM技术就渐渐淡出人们的视野，然而这并不意味COM不再发挥作用，相反，COM非常重要。可以说.NET的实现离不开COM的支撑。COM是好东西，但是它太难了，不利于产品推广，于是微软只能在之上增加一层封装从而提高产品的易用性。对COM有所了解是很有必要的，希望这篇文章给你带来一点启发。

1. COM的思想

开篇就讲COM的思想肯定让人泄气，因为它极有可能抽象空洞、晦涩难懂。换个角度来说，我觉得COM的思想仍然是需要自己去体会的，这里给出的不过是一个思考的线索而已，你大可不求甚解。

软件的开发是永无止境的，只要软件还在存活期，它就应当不断被完善和更新。一款软件可能十分庞大，但真正可变的部分却是很有限的。我们当然希望在更新软件的时候，只更新变化的部分，而不要笨手笨脚把整个软件都换掉。只更新变化的部分？这就要求模块支持动态链接。所谓动态链接就是模块只在被使用的时候才被加载，程序调用模块中的某个函数是通过指针来完成的。动态链接允许模块分离出去，而不像静态链接那样须经过编译才能整合到程序中来。dll是实现动态链接的一种方法，它使更新软件的工作浓缩成了更新dll，用户无需重新安装软件，只需替换相应的dll文件就能实现软件的升级。

动态链接是针对普通用户而言的，现在换一个对象：模块的用户。模块的用户是应用程序开发人员，对于模块的提供商来说也算得上同行了，只不过术业有专攻，各自工作的重点不同而已。显然采用dll的形式，模块的提供商可以很方便的发布自己的产品。其中不可忽视的另一点即信息的封装(或称隐藏)，即将模块的实现细节隐蔽起来，用户无法知道模块的提供商采用何种语言、何种算法，简而言之就是用户看不到模块的源代码。dll是二进制级别上的代码复用，它实现了信息的封装。

综上所述，软件开发要求模块支持“动态链接”和“信息封装”，更直白地说就是要求模块和客户代码之间更低的耦合度。把模块制作成组件是必然的选择，而COM本质上是一种创建组件的方法和规范。

注：dll并不等同于组件，它只是组件的一种形式。由于dll的易用性，它的应用很广泛。

2. 实例说明

我们创建一个COM组件，它将实现接口ICouplet，用户可通过该接口调用what()方法输出一副对联。what()方法不值一提，不过你可以将它当作程序可变的部分。我们创建的COM组件也要实现接口IClassFactory，它是创建组件的简单组件。之所以这么设计是为了让组件与客户代码彻底脱耦，尽可能少的联系。

除了实现接口ICouplet和IClassFactory外， COM组件还要能实现自注册，因此它必须导出函数DllRegister/DllUnregister。另外两个导出函数DllCanUnloadNow和DllGetClassObject也非常重要，前者用来询问当前dll能否被卸载，它被CoFreeUnusedLibraries调用；后者用来创建类厂组件，它被CoCreateInstance调用。名称形如Coxxx的函数是COM库函数，它是实现COM组件的公共操作，由微软提供，类似于Win32 API。我们常见的客户代码中CoInitialize/CoUninitialize函数就起到初始化和卸载COM库的作用。要导出上述4个函数就必须编写一个.def文件，具体写法见代码清单。

最后要说明的是COM组件的自注册。我们知道注册表是Windows的公共系统数据库，其中记录了软件、硬件、用户配置等信息。而COM组件是用一个128比特的GUID标识的，为了使得COM组件的安装目录更灵活，我们可以在注册表中对它进行注册，注册的主要信息即COM组件的GUID标识与其存储路径的对应关系，在使用该组件时就到注册表中去查找。注册一个COM组件一般使用regsvr32.exe程序来完成，当然你也可以自己写一个类似于regsvr32.exe的小程序来完成COM组件的注册，regsvr32.exe本质上调用了组件的导出函数DllRegister/DllUnregister。

生成Couplet.dll文件后，首先在控制台注册它。具体方法：切换到Couplet.dll所在目录，输入指令regsvr32 Couplet.dll。然后运行客户程序Reader.exe，其结果如下所示：

<span class="operator"><span class="keyword" style="font-weight:bold">Create</span> Couplet object
Succeeded <span class="keyword" style="font-weight:bold">in</span> getting the pointer <span class="keyword" style="font-weight:bold">to</span> ICouplet

<span class="number" style="color:rgb(0,153,153)">1</span>st <span class="keyword" style="font-weight:bold">Scroll</span>: Study Hard, <span class="keyword" style="font-weight:bold">Work</span> Hard, Make Money More <span class="keyword" style="font-weight:bold">and</span> More
<span class="number" style="color:rgb(0,153,153)">2</span>nd <span class="keyword" style="font-weight:bold">Scroll</span>: Eat Well, Sleep Well, Have Fun <span class="keyword" style="font-weight:bold">Day</span> <span class="keyword" style="font-weight:bold">by</span> <span class="keyword" style="font-weight:bold">Day</span>
Top <span class="keyword" style="font-weight:bold">Scroll</span>: Gelievable

Couplet object deleted
请按任意键继续. . .</span>

然后修改Couplet::what()方法，让它输出中文，重新生成Couplet.dll。这一步不用重新注册Couplet.dll，因为Couplet.dll的路径没变，CLSID_Couplet也没变。运行客户程序Reader.exe，其结果如下所示：

CreateCouplet <span class="keyword" style="font-weight:bold">object</span>

Succeededin getting the pointer to ICouplet

 

上联：我爱的人名花有主

下联：爱我的人惨不忍睹

横批：命苦

 

Coupletobject deleted

请按任意键继续. . .

这个例子证明了COM组件的更新不会对客户端造成影响，使用COM组件可以实现模块与客户代码彻底脱耦。实验结束后，在控制台输入指令regsvr32 /u Couplet.dll，从注册表中将dll模块信息清除。

3. 代码清单

<span class="comment" style="color:rgb(153,153,136); font-style:italic">/* File List: (COM) IFace.h Register.h Register.cpp Couplet.cpp Couple.def
 *           (Client) IFace.h Reader.cpp
 * date: 2012-02-21
 * author: ume
 */</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic"><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span>//</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// IFace.h 接口的声明，组件ID、接口ID的定义</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//</span>
<span class="preprocessor" style="color:rgb(153,153,153); font-weight:bold">#include <ObjBase.h></span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// interface</span>
<span class="keyword" style="font-weight:bold">interface</span> ICouplet : IUnknown
{
    <span class="keyword" style="font-weight:bold">virtual</span> <span class="keyword" style="font-weight:bold">void</span> what() = <span class="number" style="color:rgb(0,153,153)">0</span>;
};
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// GUIDs</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// {03844548-B0B9-4B12-869D-061AAE2E4B7F}</span>
<span class="keyword" style="font-weight:bold">static</span> <span class="keyword" style="font-weight:bold">const</span> GUID IID_ICouplet = 
{ <span class="number" style="color:rgb(0,153,153)">0x3844548</span>, <span class="number" style="color:rgb(0,153,153)">0xb0b9</span>, <span class="number" style="color:rgb(0,153,153)">0x4b12</span>, { <span class="number" style="color:rgb(0,153,153)">0x86</span>, <span class="number" style="color:rgb(0,153,153)">0x9d</span>, <span class="number" style="color:rgb(0,153,153)">0x6</span>, <span class="number" style="color:rgb(0,153,153)">0x1a</span>, <span class="number" style="color:rgb(0,153,153)">0xae</span>, <span class="number" style="color:rgb(0,153,153)">0x2e</span>, <span class="number" style="color:rgb(0,153,153)">0x4b</span>, <span class="number" style="color:rgb(0,153,153)">0x7f</span> } };
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// {26615B48-1D2E-4A40-9C07-AD5B1B48368C}</span>
<span class="keyword" style="font-weight:bold">static</span> <span class="keyword" style="font-weight:bold">const</span> GUID CLSID_Couplet = 
{ <span class="number" style="color:rgb(0,153,153)">0x26615b48</span>, <span class="number" style="color:rgb(0,153,153)">0x1d2e</span>, <span class="number" style="color:rgb(0,153,153)">0x4a40</span>, { <span class="number" style="color:rgb(0,153,153)">0x9c</span>, <span class="number" style="color:rgb(0,153,153)">0x7</span>, <span class="number" style="color:rgb(0,153,153)">0xad</span>, <span class="number" style="color:rgb(0,153,153)">0x5b</span>, <span class="number" style="color:rgb(0,153,153)">0x1b</span>, <span class="number" style="color:rgb(0,153,153)">0x48</span>, <span class="number" style="color:rgb(0,153,153)">0x36</span>, <span class="number" style="color:rgb(0,153,153)">0x8c</span> } };
<span class="comment" style="color:rgb(153,153,136); font-style:italic"><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span>//</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// Register.h 注册函数的声明</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//</span>
HRESULT RegisterServer(HMODULE hModule,               
    <span class="keyword" style="font-weight:bold">const</span> CLSID& clsid,               
    <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szFriendlyName,           
    <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szVerIndProgID,           
    <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szProgID);
HRESULT UnRegisterServer(<span class="keyword" style="font-weight:bold">const</span> CLSID& clsid,        
    <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szVerIndProgID,         
    <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szProgID);
<span class="comment" style="color:rgb(153,153,136); font-style:italic"><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span>//</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// Register.cpp 注册函数的定义</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// 这些函数可重复使用，非本文重点</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//</span>
<span class="preprocessor" style="color:rgb(153,153,153); font-weight:bold">#include <objbase.h></span>
<span class="preprocessor" style="color:rgb(153,153,153); font-weight:bold">#include "Register.h"</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//set the given key and its value;</span>
BOOL setKeyAndValue(<span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* pszPath,
                    <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szSubkey,
                    <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szValue);
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//Convert a CLSID into a char string</span>
<span class="keyword" style="font-weight:bold">void</span> CLSIDtochar(<span class="keyword" style="font-weight:bold">const</span> CLSID& clsid,
                 <span class="keyword" style="font-weight:bold">char</span>* szCLSID,
                 <span class="keyword" style="font-weight:bold">int</span> length);
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//Delete szKeyChild and all of its descendents</span>
LONG recursiveDeleteKey(HKEY hKeyParent,<span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szKeyChild);
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//size of a CLSID as a string</span>
<span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">int</span> CLSID_STRING_SIZE = <span class="number" style="color:rgb(0,153,153)">39</span>;
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//Register the component in the registry</span>
HRESULT RegisterServer(HMODULE hModule,
                       <span class="keyword" style="font-weight:bold">const</span> CLSID& clsid,
                       <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szFriendlyName,
                       <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szVerIndProgID,
                       <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szProgID)
{
    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Get the Server location</span>
    <span class="keyword" style="font-weight:bold">char</span> szModule[<span class="number" style="color:rgb(0,153,153)">512</span>];
    DWORD dwResult = ::GetModuleFileName(hModule,szModule,<span class="keyword" style="font-weight:bold">sizeof</span>(szModule)/<span class="keyword" style="font-weight:bold">sizeof</span>(<span class="keyword" style="font-weight:bold">char</span>));
    assert(dwResult!=<span class="number" style="color:rgb(0,153,153)">0</span>);

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Convert the CLSID into a char</span>
    <span class="keyword" style="font-weight:bold">char</span> szCLSID[CLSID_STRING_SIZE];
    CLSIDtochar(clsid,szCLSID,<span class="keyword" style="font-weight:bold">sizeof</span>(szCLSID));

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Build the key CLSID\\{}</span>
    <span class="keyword" style="font-weight:bold">char</span> szKey[<span class="number" style="color:rgb(0,153,153)">64</span>];
    strcpy(szKey,<span class="string" style="color:rgb(221,17,68)">"CLSID\\"</span>);
    strcat(szKey,szCLSID);

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Add the CLSID to the registry</span>
    setKeyAndValue(szKey,NULL,szFriendlyName);

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Add the Server filename subkey under the CLSID key</span>
    setKeyAndValue(szKey,<span class="string" style="color:rgb(221,17,68)">"InprocServer32"</span>,szModule);

    setKeyAndValue(szKey,<span class="string" style="color:rgb(221,17,68)">"ProgID"</span>,szProgID);

    setKeyAndValue(szKey,<span class="string" style="color:rgb(221,17,68)">"VersionIndependentProgID"</span>,szVerIndProgID);

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Add the version-independent ProgID subkey under HKEY_CLASSES_ROOT</span>
    setKeyAndValue(szVerIndProgID,NULL,szFriendlyName);
    setKeyAndValue(szVerIndProgID,<span class="string" style="color:rgb(221,17,68)">"CLSID"</span>,szCLSID);
    setKeyAndValue(szVerIndProgID,<span class="string" style="color:rgb(221,17,68)">"CurVer"</span>,szProgID);

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Add the versioned ProgID subkey under HKEY_CLASSES_ROOT</span>
    setKeyAndValue(szProgID,NULL,szFriendlyName);
    setKeyAndValue(szProgID,<span class="string" style="color:rgb(221,17,68)">"CLSID"</span>,szCLSID);
    <span class="keyword" style="font-weight:bold">return</span> S_OK;
}

<span class="comment" style="color:rgb(153,153,136); font-style:italic">//</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//Remove the component from the register</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//</span>
HRESULT UnRegisterServer(<span class="keyword" style="font-weight:bold">const</span> CLSID& clsid,           <span class="comment" style="color:rgb(153,153,136); font-style:italic">// Class ID</span>
                         <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szVerIndProgID,   <span class="comment" style="color:rgb(153,153,136); font-style:italic">// Programmatic</span>
                         <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szProgID)           <span class="comment" style="color:rgb(153,153,136); font-style:italic">// IDs</span>
{
    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Convert the CLSID into a char.</span>
    <span class="keyword" style="font-weight:bold">char</span> szCLSID[CLSID_STRING_SIZE];
    CLSIDtochar(clsid,szCLSID,<span class="keyword" style="font-weight:bold">sizeof</span>(szCLSID));

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Build the key CLSID\\{}</span>
    <span class="keyword" style="font-weight:bold">char</span> szKey[<span class="number" style="color:rgb(0,153,153)">64</span>];
    strcpy(szKey,<span class="string" style="color:rgb(221,17,68)">"CLSID\\"</span>);
    strcat(szKey,szCLSID);

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Delete the CLSID key - CLSID\{}</span>
    LONG lResult = recursiveDeleteKey(HKEY_CLASSES_ROOT,szKey);
    assert((lResult == ERROR_SUCCESS) || (lResult == ERROR_FILE_NOT_FOUND));

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Delete the version-independent ProgID Key</span>
    lResult = recursiveDeleteKey(HKEY_CLASSES_ROOT,szVerIndProgID);
    assert((lResult == ERROR_SUCCESS) || (lResult == ERROR_FILE_NOT_FOUND));

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Delete the ProgID key.</span>
    lResult = recursiveDeleteKey(HKEY_CLASSES_ROOT,szProgID);
    assert((lResult == ERROR_SUCCESS) || (lResult == ERROR_FILE_NOT_FOUND));

    <span class="keyword" style="font-weight:bold">return</span> S_OK;
}
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//Convert a CLSID to a char string</span>
<span class="keyword" style="font-weight:bold">void</span> CLSIDtochar(<span class="keyword" style="font-weight:bold">const</span> CLSID& clsid,
                 <span class="keyword" style="font-weight:bold">char</span>* szCLSID,
                 <span class="keyword" style="font-weight:bold">int</span> length)
{
    assert(length>=CLSID_STRING_SIZE);

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Get CLSID</span>
    LPOLESTR wszCLSID = NULL;
    HRESULT hr = StringFromCLSID(clsid,&wszCLSID);
    assert(SUCCEEDED(hr));

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Convert from wide characters to non_wide</span>
    wcstombs(szCLSID,wszCLSID,length);
    
    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Free memory</span>
    CoTaskMemFree(wszCLSID);
}
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// Delete a Key and all of its descendents</span>
LONG recursiveDeleteKey(HKEY hKeyParent,<span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* lpszKeyChild)
{
    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Open the child.</span>
    HKEY hKeyChild;
    LONG lRes = RegOpenKeyEx(hKeyParent,lpszKeyChild,<span class="number" style="color:rgb(0,153,153)">0</span>,KEY_ALL_ACCESS,&hKeyChild);

    <span class="keyword" style="font-weight:bold">if</span>(lRes != ERROR_SUCCESS)
        <span class="keyword" style="font-weight:bold">return</span> lRes;

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Enumerate all of the decendents of this child</span>
    FILETIME time;
    <span class="keyword" style="font-weight:bold">char</span> szBuffer[<span class="number" style="color:rgb(0,153,153)">256</span>];
    DWORD dwSize = <span class="number" style="color:rgb(0,153,153)">256</span> ;
    
    <span class="keyword" style="font-weight:bold">while</span>(RegEnumKeyEx(hKeyChild,<span class="number" style="color:rgb(0,153,153)">0</span>,szBuffer,&dwSize,NULL,
        NULL,NULL,&time) == S_OK)
    {
        <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Delete the decendents of this child.</span>
        lRes = recursiveDeleteKey(hKeyChild,szBuffer);
        <span class="keyword" style="font-weight:bold">if</span>(lRes != ERROR_SUCCESS)
        {
            RegCloseKey(hKeyChild);
            <span class="keyword" style="font-weight:bold">return</span> lRes;
        }
        dwSize = <span class="number" style="color:rgb(0,153,153)">256</span>;
    }
    RegCloseKey(hKeyChild);
    <span class="keyword" style="font-weight:bold">return</span> RegDeleteKey(hKeyParent,lpszKeyChild);
}

BOOL setKeyAndValue(<span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szKey,
                    <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szSubkey,
                    <span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* szValue)
{
    HKEY hKey;
    <span class="keyword" style="font-weight:bold">char</span> szKeyBuf[<span class="number" style="color:rgb(0,153,153)">1024</span>];

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Copy keyname into buffer.</span>
    strcpy(szKeyBuf,szKey);

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">//Add subkey name to buffer.</span>
    <span class="keyword" style="font-weight:bold">if</span>(szSubkey!=NULL)
    {
        strcat(szKeyBuf,<span class="string" style="color:rgb(221,17,68)">"\\"</span>);
        strcat(szKeyBuf,szSubkey);
    }

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">// Create and open key and subkey.</span>
    <span class="keyword" style="font-weight:bold">long</span> lResult = RegCreateKeyEx(HKEY_CLASSES_ROOT ,
                                  szKeyBuf, 
                                  <span class="number" style="color:rgb(0,153,153)">0</span>, NULL, REG_OPTION_NON_VOLATILE,
                                  KEY_ALL_ACCESS, NULL, 
                                  &hKey, NULL) ;
    <span class="keyword" style="font-weight:bold">if</span> (lResult != ERROR_SUCCESS)

    {
        <span class="keyword" style="font-weight:bold">return</span> FALSE ;
    }

    <span class="comment" style="color:rgb(153,153,136); font-style:italic">// Set the Value.</span>
    <span class="keyword" style="font-weight:bold">if</span> (szValue != NULL)
    {
        RegSetValueEx(hKey, NULL, <span class="number" style="color:rgb(0,153,153)">0</span>, REG_SZ, 
                      (BYTE *)szValue, 
                      strlen(szValue)+<span class="number" style="color:rgb(0,153,153)">1</span>) ;
    }

    RegCloseKey(hKey) ;
    <span class="keyword" style="font-weight:bold">return</span> TRUE ;
}
<span class="comment" style="color:rgb(153,153,136); font-style:italic"><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span>//</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// Couplet.cpp 接口的实现</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// 本文的重点，尤其是Couplet和CFactory的实现</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//</span>
<span class="preprocessor" style="color:rgb(153,153,153); font-weight:bold">#include "IFace.h"</span>
<span class="preprocessor" style="color:rgb(153,153,153); font-weight:bold">#include "Register.h"</span>
<span class="preprocessor" style="color:rgb(153,153,153); font-weight:bold">#include <iostream></span>
<span class="keyword" style="font-weight:bold">using</span> <span class="keyword" style="font-weight:bold">namespace</span> std;
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// trace</span>
<span class="keyword" style="font-weight:bold">void</span> trace(<span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* msg) { cout<<msg<<endl; }
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// global variables</span>
HMODULE g_hModule;
<span class="keyword" style="font-weight:bold">static</span> <span class="keyword" style="font-weight:bold">long</span> g_cComponents = <span class="number" style="color:rgb(0,153,153)">0</span>;
<span class="keyword" style="font-weight:bold">static</span> <span class="keyword" style="font-weight:bold">long</span> g_cLocks = <span class="number" style="color:rgb(0,153,153)">0</span>;
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// Friendly name of component</span>
<span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span> g_szFriendlyName[] = <span class="string" style="color:rgb(221,17,68)">"A Couplet"</span>;
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// Version independent ProgID</span>
<span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span> g_szVerIndProgID[] = <span class="string" style="color:rgb(221,17,68)">"Couplet.Test"</span>;
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// ProgID</span>
<span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span> g_szProgID[] = <span class="string" style="color:rgb(221,17,68)">"Couplet.Test.1"</span>;
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// implementation</span>
<span class="keyword" style="font-weight:bold">class</span> Couplet : <span class="keyword" style="font-weight:bold">public</span> ICouplet
{
<span class="keyword" style="font-weight:bold">public</span>:
    <span class="keyword" style="font-weight:bold">virtual</span> LRESULT __stdcall QueryInterface(<span class="keyword" style="font-weight:bold">const</span> IID& iid, <span class="keyword" style="font-weight:bold">void</span>** ppv);
    <span class="keyword" style="font-weight:bold">virtual</span> ULONG __stdcall AddRef()
    {
        <span class="keyword" style="font-weight:bold">return</span> ::InterlockedIncrement(&m_cRef);
    }
    <span class="keyword" style="font-weight:bold">virtual</span> ULONG __stdcall Release()
    {
        <span class="keyword" style="font-weight:bold">if</span>(::InterlockedDecrement(&m_cRef) == <span class="number" style="color:rgb(0,153,153)">0</span>)
        {
            delete <span class="keyword" style="font-weight:bold">this</span>;
            <span class="keyword" style="font-weight:bold">return</span> <span class="number" style="color:rgb(0,153,153)">0</span>;
        }
        <span class="keyword" style="font-weight:bold">return</span> m_cRef;
    }
    <span class="keyword" style="font-weight:bold">virtual</span> <span class="keyword" style="font-weight:bold">void</span> what() 
    { 
        <span class="comment" style="color:rgb(153,153,136); font-style:italic">//cout<<"\n上联：我爱的人名花有主\n下联：爱我的人惨不忍睹\n横批：命苦\n\n"; </span>
        cout<<<span class="string" style="color:rgb(221,17,68)">"\n1st Scroll: Study Hard, Work Hard, Make Money More and More\n\
2nd Scroll: Eat Well, Sleep Well, Have Fun Day by Day\nTop Scroll: Gelievable\n\n"</span>; 
    }
    <span class="comment" style="color:rgb(153,153,136); font-style:italic">// constructor</span>
    Couplet() : m_cRef(<span class="number" style="color:rgb(0,153,153)">1</span>) 
    {
        ::InterlockedIncrement(&g_cComponents);
        trace(<span class="string" style="color:rgb(221,17,68)">"Create Couplet object"</span>); 
    }
    <span class="comment" style="color:rgb(153,153,136); font-style:italic">// destructor</span>
    ~Couplet()
    {
        ::InterlockedDecrement(&g_cComponents);
        trace(<span class="string" style="color:rgb(221,17,68)">"Couplet object deleted"</span>);
    }
<span class="keyword" style="font-weight:bold">private</span>:
    <span class="keyword" style="font-weight:bold">long</span> m_cRef;
};
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// definition of QueryInterface</span>
LRESULT __stdcall Couplet::QueryInterface(<span class="keyword" style="font-weight:bold">const</span> IID& iid, <span class="keyword" style="font-weight:bold">void</span>** ppv)
{
    <span class="keyword" style="font-weight:bold">if</span>((iid == IID_IUnknown) || (iid == IID_ICouplet))
    {
        *ppv = static_cast<ICouplet*>(<span class="keyword" style="font-weight:bold">this</span>);
    }
    <span class="keyword" style="font-weight:bold">else</span>
    {
        *ppv = NULL;
        <span class="keyword" style="font-weight:bold">return</span> E_NOINTERFACE;
    }
    static_cast<IUnknown*>(*ppv)->AddRef();
    <span class="keyword" style="font-weight:bold">return</span> S_OK;
}
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// class CFactory</span>
<span class="keyword" style="font-weight:bold">class</span> CFactory : <span class="keyword" style="font-weight:bold">public</span> IClassFactory
{
<span class="keyword" style="font-weight:bold">public</span>:
    <span class="keyword" style="font-weight:bold">virtual</span> LRESULT __stdcall QueryInterface(<span class="keyword" style="font-weight:bold">const</span> IID& iid, <span class="keyword" style="font-weight:bold">void</span>** ppv);
    <span class="keyword" style="font-weight:bold">virtual</span> ULONG __stdcall AddRef()
    {
        <span class="keyword" style="font-weight:bold">return</span> ::InterlockedIncrement(&m_cRef);
    }
    <span class="keyword" style="font-weight:bold">virtual</span> ULONG __stdcall Release()
    {
        <span class="keyword" style="font-weight:bold">if</span>(::InterlockedDecrement(&m_cRef) == <span class="number" style="color:rgb(0,153,153)">0</span>)
        {
            delete <span class="keyword" style="font-weight:bold">this</span>;
            <span class="keyword" style="font-weight:bold">return</span> <span class="number" style="color:rgb(0,153,153)">0</span>;
        }
        <span class="keyword" style="font-weight:bold">return</span> m_cRef;
    }
    <span class="keyword" style="font-weight:bold">virtual</span> LRESULT __stdcall CreateInstance(IUnknown* pCmpntOuter,
                                   <span class="keyword" style="font-weight:bold">const</span> IID& iid,
                                   <span class="keyword" style="font-weight:bold">void</span>** ppv);
    <span class="keyword" style="font-weight:bold">virtual</span> LRESULT __stdcall LockServer(BOOL bLock);
<span class="keyword" style="font-weight:bold">private</span>:
    <span class="keyword" style="font-weight:bold">long</span> m_cRef;
};
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// definition of QueryInterface</span>
LRESULT __stdcall CFactory::QueryInterface(<span class="keyword" style="font-weight:bold">const</span> IID& iid, <span class="keyword" style="font-weight:bold">void</span>** ppv)
{
    <span class="keyword" style="font-weight:bold">if</span>((iid == IID_IUnknown) || (iid == IID_IClassFactory))
    {
        *ppv = static_cast<IClassFactory*>(<span class="keyword" style="font-weight:bold">this</span>);
    }
    <span class="keyword" style="font-weight:bold">else</span>
    {
        *ppv = NULL;
        <span class="keyword" style="font-weight:bold">return</span> E_NOINTERFACE;
    }
    static_cast<IUnknown*>(*ppv)->AddRef();
    <span class="keyword" style="font-weight:bold">return</span> S_OK;
}
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// definition of CreateInstance</span>
LRESULT __stdcall CFactory::CreateInstance(IUnknown* pCmpntOuter,
                                 <span class="keyword" style="font-weight:bold">const</span> IID& iid,
                                 <span class="keyword" style="font-weight:bold">void</span>** ppv)
{
    <span class="keyword" style="font-weight:bold">if</span>(pCmpntOuter != NULL)
    {
        cout<<<span class="string" style="color:rgb(221,17,68)">"No Aggregate in this Class Factory"</span><<endl;
        <span class="keyword" style="font-weight:bold">return</span> CLASS_E_NOAGGREGATION;
    }
    Couplet* pCouplet = <span class="keyword" style="font-weight:bold">new</span> Couplet;
    <span class="keyword" style="font-weight:bold">if</span>(pCouplet == NULL)
        <span class="keyword" style="font-weight:bold">return</span> E_OUTOFMEMORY;
    HRESULT hr = pCouplet->QueryInterface(iid, ppv);
    pCouplet->Release();
    <span class="keyword" style="font-weight:bold">return</span> hr;
}
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// definition of LockServer</span>
LRESULT __stdcall CFactory::LockServer(BOOL bLock)
{
    <span class="keyword" style="font-weight:bold">if</span>(bLock)
    {
        ::InterlockedIncrement(&g_cLocks);
    }
    <span class="keyword" style="font-weight:bold">else</span>
    {
        ::InterlockedDecrement(&g_cLocks);
    }
    <span class="keyword" style="font-weight:bold">return</span> S_OK;
}
STDAPI DllCanUnloadNow()
{
    <span class="keyword" style="font-weight:bold">if</span>((g_cComponents == <span class="number" style="color:rgb(0,153,153)">0</span>) && (g_cLocks == <span class="number" style="color:rgb(0,153,153)">0</span>))
    {
        <span class="keyword" style="font-weight:bold">return</span> S_OK;
    }
    <span class="keyword" style="font-weight:bold">else</span>
    {
        <span class="keyword" style="font-weight:bold">return</span> S_FALSE;
    }
}
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// Get class factory</span>
STDAPI DllGetClassObject(<span class="keyword" style="font-weight:bold">const</span> CLSID& clsid,
                         <span class="keyword" style="font-weight:bold">const</span> IID& iid,
                         <span class="keyword" style="font-weight:bold">void</span>** ppv)
{
    <span class="comment" style="color:rgb(153,153,136); font-style:italic">// Can we create this component?</span>
    <span class="keyword" style="font-weight:bold">if</span>(clsid != CLSID_Couplet)
    {
        <span class="keyword" style="font-weight:bold">return</span> CLASS_E_CLASSNOTAVAILABLE;
    }
    <span class="comment" style="color:rgb(153,153,136); font-style:italic">// Create class factory</span>
    CFactory* pFactory = <span class="keyword" style="font-weight:bold">new</span> CFactory;
    <span class="keyword" style="font-weight:bold">if</span>(pFactory == NULL)
    {
        <span class="keyword" style="font-weight:bold">return</span> E_OUTOFMEMORY;
    }
    <span class="comment" style="color:rgb(153,153,136); font-style:italic">// Get requested interface</span>
    HRESULT hr = pFactory->QueryInterface(iid, ppv);
    pFactory->Release();
    <span class="keyword" style="font-weight:bold">return</span> hr;
}
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// register and unregister component</span>
STDAPI DllRegisterServer()
{
    <span class="keyword" style="font-weight:bold">return</span> RegisterServer(g_hModule,
                          CLSID_Couplet,
                          g_szFriendlyName,
                          g_szVerIndProgID,
                          g_szProgID);
}
STDAPI DllUnregisterServer()
{
    <span class="keyword" style="font-weight:bold">return</span> UnRegisterServer(CLSID_Couplet,
                            g_szVerIndProgID,
                            g_szProgID);
}
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// dll main</span>
BOOL APIENTRY DllMain(HANDLE hModule,
                     DWORD dwReason,
                     <span class="keyword" style="font-weight:bold">void</span>* lpReserved)
{
    <span class="keyword" style="font-weight:bold">if</span>(dwReason == DLL_PROCESS_ATTACH)
    {
        g_hModule = (HMODULE)hModule;
    }
    <span class="keyword" style="font-weight:bold">return</span> TRUE;
}
<span class="comment" style="color:rgb(153,153,136); font-style:italic"><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span>//</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// Couplet.def 模块定义文件</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//</span>
LIBRARY Couplet.dll
EXPORTS
    DllCanUnloadNow @<span class="number" style="color:rgb(0,153,153)">1</span> PRIVATE
    DllGetClassObject @<span class="number" style="color:rgb(0,153,153)">2</span> PRIVATE
    DllRegisterServer @<span class="number" style="color:rgb(0,153,153)">3</span> PRIVATE
    DllUnregisterServer @<span class="number" style="color:rgb(0,153,153)">4</span> PRIVATE
<span class="comment" style="color:rgb(153,153,136); font-style:italic"><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span><span class="xmlDocTag">///</span>//</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// Reader.cpp 通过ICouplet接口调用what()方法读取对联内容</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// 注意： 客户端的IFace.h与COM组件中的IFace.h完全一样</span>
<span class="comment" style="color:rgb(153,153,136); font-style:italic">//</span>
<span class="preprocessor" style="color:rgb(153,153,153); font-weight:bold">#include <iostream></span>
<span class="preprocessor" style="color:rgb(153,153,153); font-weight:bold">#include <ObjBase.h></span>
<span class="preprocessor" style="color:rgb(153,153,153); font-weight:bold">#include "IFace.h"</span>
<span class="keyword" style="font-weight:bold">using</span> <span class="keyword" style="font-weight:bold">namespace</span> std;
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// global function</span>
<span class="keyword" style="font-weight:bold">void</span> trace(<span class="keyword" style="font-weight:bold">const</span> <span class="keyword" style="font-weight:bold">char</span>* pMsg){ cout<<pMsg<<endl; }
<span class="comment" style="color:rgb(153,153,136); font-style:italic">// main function</span>
<span class="keyword" style="font-weight:bold">int</span> main()
{
    ::CoInitialize(NULL);
    ICouplet* pICouplet = NULL;
    HRESULT hr = ::CoCreateInstance(CLSID_Couplet, NULL, CLSCTX_INPROC_SERVER, IID_ICouplet, 
                                   (<span class="keyword" style="font-weight:bold">void</span>**)&pICouplet);
    <span class="keyword" style="font-weight:bold">if</span>(SUCCEEDED(hr))
    {
        trace(<span class="string" style="color:rgb(221,17,68)">"Succeeded in getting the pointer to ICouplet"</span>);
        pICouplet->what();
        pICouplet->Release();
    }
    <span class="keyword" style="font-weight:bold">else</span> 
    {
        trace(<span class="string" style="color:rgb(221,17,68)">"Failed to get the pointer to ICouplet"</span>);
    }
    ::CoUninitialize();
    system(<span class="string" style="color:rgb(221,17,68)">"pause"</span>);
    <span class="keyword" style="font-weight:bold">return</span> <span class="number" style="color:rgb(0,153,153)">0</span>;
}

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