100165404.htm
来自「C#高级编程(第三版),顶死你们。。 。up」· HTM 代码 · 共 145 行 · 第 1/2 页
HTM
145 行
<p class="2" style="FTEL: 8.15pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">为了说明这些内容，下面修改了命名空间和类名，给类添加了</span><span lang="EN-US">3</span><span style="FONT-FAMILY: 宋体">个方法。虚拟方法</span><span lang="EN-US">Hello2()</span><span style="FONT-FAMILY: 宋体">使用一个</span><span lang="EN-US">C</span><span style="FONT-FAMILY: 宋体">运行函数</span><span lang="EN-US">printf()</span><span style="FONT-FAMILY: 宋体">，以说明如何在托管类中使用本机代码。为了使这个方法可用，必须包括头文件</span><span lang="EN-US">stdio.h</span><span style="FONT-FAMILY: 宋体">。在</span><span lang="EN-US">Hello()</span><span style="FONT-FAMILY: 宋体">方法中，使用</span><span lang="EN-US">System </span><span style="FONT-FAMILY: 宋体">命名空间中的</span><span lang="EN-US">Console</span><span style="FONT-FAMILY: 宋体">托管类。</span><span lang="EN-US">C++</span><span style="FONT-FAMILY: 宋体">的</span><span lang="EN-US">using namespace</span><span style="FONT-FAMILY: 宋体">语句类似于</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">的</span><span lang="EN-US">using </span><span style="FONT-FAMILY: 宋体">语句，</span><span lang="EN-US">using namespace System</span><span style="FONT-FAMILY: 宋体">语句打开了</span><span lang="EN-US">System </span><span style="FONT-FAMILY: 宋体">命名空间，所以不需要编写</span><span lang="EN-US">System::Console::WriteLine()</span><span style="FONT-FAMILY: 宋体">。</span><span lang="EN-US">Hello()</span><span style="FONT-FAMILY: 宋体">方法也标记为</span><span lang="EN-US">virtual</span><span style="FONT-FAMILY: 宋体">，所以可以重写。在</span><span lang="EN-US">VB</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">类中重写</span><span lang="EN-US">Hello()</span><span style="FONT-FAMILY: 宋体">方法。与</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">类似，</span><span lang="EN-US">C++</span><span style="FONT-FAMILY: 宋体">成员函数在默认情况下不是虚拟的。添加到类中的第三个方法</span><span lang="EN-US">Add()</span><span style="FONT-FAMILY: 宋体">返回两个</span><span lang="EN-US">int</span><span style="FONT-FAMILY: 宋体">参数的和，这样，就可以比较生成的</span><span lang="EN-US">MSIL</span><span style="FONT-FAMILY: 宋体">和不同语言，看看它们是如何处理数字的。这</span><span lang="EN-US">3</span><span style="FONT-FAMILY: 宋体">个示例都使用相同的命名空间</span><span lang="EN-US">Wrox.ProCSharp. Assemblies.CrossLanguage</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt"><span lang="EN-US">// HelloMCPP.h</span></p>
<p class="a6" style="LINE-HEIGHT: 16pt"><span lang="EN-US">#pragma once</span></p>
<p class="2" style="MARGIN-TOP: 6pt; LINE-HEIGHT: 16pt"><span lang="EN-US">#include <stdio.h></span></p>
<p class="2" style="LINE-HEIGHT: 16pt"><span lang="EN-US">using namespace System;</span></p>
<p class="2" style="LINE-HEIGHT: 16pt"><span lang="EN-US">namespace Wrox</span></p>
<p class="2"><span lang="EN-US">{</span></p>
<p class="2"><span lang="EN-US"> namespace ProCSharp</span></p>
<p class="2"><span lang="EN-US"> {</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> namespace Assemblies</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> {</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> namespace CrossLanguage</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> {</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> public </span><span lang="EN-US" style="FONT-FAMILY: "Baskerville BE Regular"">__</span><span lang="EN-US">gc class HelloMCPP</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> {</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> public:</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> virtual void Hello()</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> {</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> Console::WriteLine(S"Hello, Managed C++");</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> }</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> virtual void Hello2()</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> {</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> printf("Hello, calling native code\n");</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> }</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> int Add(int val1, int val2)</span></p>
<p class="2" style="LINE-HEIGHT: 14.3pt"><span lang="EN-US"> {</span></p>
<p class="2"><span lang="EN-US"> return val1 + val2;</span></p>
<p class="2" style="LINE-HEIGHT: 14.5pt"><span lang="EN-US"> }</span></p>
<p class="2" style="LINE-HEIGHT: 14.5pt"><span lang="EN-US"> };</span></p>
<p class="2" style="LINE-HEIGHT: 14.5pt"><span lang="EN-US"> }</span></p>
<p class="2" style="LINE-HEIGHT: 14.5pt"><span lang="EN-US"> }</span></p>
<p class="2" style="LINE-HEIGHT: 14.5pt"><span lang="EN-US"> }</span></p>
<p class="2" style="LINE-HEIGHT: 14.5pt; FTEL: 8.15pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 17.6pt"><span style="FONT-FAMILY: 宋体">要比较程序和运行的代码之间的不同，我们使用发布配置，而不是调试配置。使用调试配置会看到未优化的</span><span lang="EN-US">IL</span><span style="FONT-FAMILY: 宋体">代码。看看使用</span><span lang="EN-US">ILDASM</span><span style="FONT-FAMILY: 宋体">生成的</span><span lang="EN-US">DLL(</span><span style="FONT-FAMILY: 宋体">如图</span><span lang="EN-US">13-14</span><span style="FONT-FAMILY: 宋体">所示</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">，除了类</span><span lang="EN-US">HelloMCPP</span><span style="FONT-FAMILY: 宋体">及其成员之外，还有一个静态方法</span><span lang="EN-US">printf()</span><span style="FONT-FAMILY: 宋体">。这个方法使用</span><span lang="EN-US">pinvoke</span><span style="FONT-FAMILY: 宋体">调用本机非托管函数。私有字段</span><span lang="EN-US">$ArrayType$0xf2eda509</span><span style="FONT-FAMILY: 宋体">保存字符串</span><span lang="EN-US">"Hello, calling native code\n"</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p align="center"><span lang="EN-US"><img height="205" src="13/image024.jpg" width="234" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 13-14 </span></p>
<p class="MsoNormal"><span lang="EN-US">Hello2()</span><span style="FONT-FAMILY: 宋体">方法提取字段</span><span lang="EN-US">$ArrayType$0xf2eda509</span><span style="FONT-FAMILY: 宋体">的地址，在堆栈中保存字符串。在</span><span lang="EN-US">IL_0005</span><span style="FONT-FAMILY: 宋体">行上，调用了静态方法</span><span lang="EN-US">printf()</span><span style="FONT-FAMILY: 宋体">，其中传送了一个字符串指针</span><span lang="EN-US">"Hello</span><span style="FONT-FAMILY: 宋体">，</span><span lang="EN-US">calling native code"</span><span style="FONT-FAMILY: 宋体">，如图</span><span lang="EN-US">13-15</span><span style="FONT-FAMILY: 宋体">所示。</span></p>
<p align="center"><span lang="EN-US"><img height="134" src="13/image025.jpg" width="373" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 13-15</span></p>
<p class="MsoNormal"><span lang="EN-US">printf()</span><span style="FONT-FAMILY: 宋体">本身通过平台调用机制来调用</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">如图</span><span lang="EN-US">13-16</span><span style="FONT-FAMILY: 宋体">所示</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">。利用平台调用机制，可以调用所有的本机函数，如</span><span lang="EN-US">C</span><span style="FONT-FAMILY: 宋体">运行库和</span><span lang="EN-US">Win32 API</span><span style="FONT-FAMILY: 宋体">调用。</span></p>
<p align="center"><span lang="EN-US"><img height="142" src="13/image026.jpg" width="432" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 13-16</span></p>
<p class="MsoNormal"><span lang="EN-US">Hello()</span><span style="FONT-FAMILY: 宋体">方法完全是由</span><span lang="EN-US">MSIL</span><span style="FONT-FAMILY: 宋体">代码组成，没有本机代码。因为字符串有前缀</span><span lang="EN-US">S</span><span style="FONT-FAMILY: 宋体">，所以托管的字符串就会写入程序集，并用</span><span lang="EN-US">ldstr</span><span style="FONT-FAMILY: 宋体">推入堆栈。在</span><span lang="EN-US">IL_0005</span><span style="FONT-FAMILY: 宋体">行上，调用了</span><span lang="EN-US">System.Console</span><span style="FONT-FAMILY: 宋体">类的</span><span lang="EN-US">WriteLine()</span><span style="FONT-FAMILY: 宋体">方法，使用堆栈中的字符串，如图</span><span lang="EN-US">13-17</span><span style="FONT-FAMILY: 宋体">所示。</span></p>
<p align="center"><span lang="EN-US"><img height="142" src="13/image027.jpg" width="433" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 13-17</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">要说明在</span><span lang="EN-US">Managed C++</span><span style="FONT-FAMILY: 宋体">中如何使用数字，下面看看</span><span lang="EN-US">Add()</span><span style="FONT-FAMILY: 宋体">方法的</span><span lang="EN-US">MSIL</span><span style="FONT-FAMILY: 宋体">代码。通过</span><span lang="EN-US">ldarg.1</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">ldarg.2</span><span style="FONT-FAMILY: 宋体">，把传送的参数入栈，</span><span lang="EN-US">Add</span><span style="FONT-FAMILY: 宋体">添加堆栈值，把结果入栈，在</span><span lang="EN-US">IL_0003</span><span style="FONT-FAMILY: 宋体">行上，返回了结果，如图</span><span lang="EN-US">13-18</span><span style="FONT-FAMILY: 宋体">所示。</span></p>
<p align="center"><span lang="EN-US"><img height="146" src="13/image028.jpg" width="431" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 13-18</span></p>
<p class="a3" style="MARGIN-TOP: 8.15pt; FTEL: 21.45pt"><span style="FONT-FAMILY: 黑体">注意：</span></p>
<p class="a1" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 10.7pt; MARGIN-RIGHT: 0cm; FTEL: 10.7pt"><span style="FONT-FAMILY: 楷体_GB2312">与使用</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 楷体_GB2312">和</span><span lang="EN-US">.NET Framework</span><span style="FONT-FAMILY: 楷体_GB2312">的其他语言相比，使用</span><span lang="EN-US">Managed C++</span><span style="FONT-FAMILY: 楷体_GB2312">有什么优点？</span><span lang="EN-US">Managed C++</span><span style="FONT-FAMILY: 楷体_GB2312">很容易把传统的</span><span lang="EN-US">C++</span><span style="FONT-FAMILY: 楷体_GB2312">代码用于</span><span lang="EN-US">.NET</span><span style="FONT-FAMILY: 楷体_GB2312">。</span><span lang="EN-US">MSIL</span><span style="FONT-FAMILY: 楷体_GB2312">代码和本机代码很容易混合在一起。</span></p></div>
<!-- page -->
<div class="page" style="text-align: center">
<a href="100165403.htm">上一页</a> <a href="index.html">首页</a> <a href="100165405.htm">下一页</a>
</div>
<div style="margin: 0px auto; width: 700px; border: solid 1px #0b5f98;">
<div style="float: left; width: 16px; background-color: #0b5f98; color: White; padding: 1px;">
图书导读
</div>
<div style="float: right; width: 670px; text-align: left; line-height: 16pt; padding-left: 2px">
<!--导读-->
<h1 id="divCurrentNode2" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165404.htm'><font color='red'>13.3.2 语言无关性(1)</font></a></h1>
<div id="divRealteNod2" style="padding-left: 2px">
<div style='float:left;width:49%'>·<a href='100165401.htm'>13.2.5 构建程序集</a></div><div style='float:right;width:49%'>·<a href='100165402.htm'>13.3 跨语言支持</a></div><div style='float:left;width:49%'>·<a href='100165403.htm'>13.3.1 CTS和CLS</a></div><div style='float:right;width:49%'>·<a href='100165405.htm'>13.3.2 语言无关性(2)</a></div><div style='float:left;width:49%'>·<a href='100165406.htm'>13.3.3 CLS要求</a></div><div style='float:right;width:49%'>·<a href='100165407.htm'>13.4 全局程序集缓存</a></div></div>
</div>
</div>
</div></div>
</body>
</html>
⌨️ 快捷键说明
复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?