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<!DOCTYPE html>
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<title>道可叨 | 程序如何找自己 </title>
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<h1 i18n>道可叨</h1>
<h2>Free Will</h2>
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<h1><a href="https://zhuoqiang.github.io/how-program-find-self.html">程序如何找自己</a></h1>
</header> <div>
<section>
<p>自我定位很重要，不但是对人，对程序来说也一样。如果能知道自己的路径位置，程序就可以通过相对定位找到身边的资源文件，这对于制作无需安装的绿色软件和各类插件很关键。下面列出几种程序的自我定位方法。</p>
<div class="contents local topic" id="id2">
<ul class="simple">
<li><a class="reference internal" href="#windows-api" id="id3">Windows API</a></li>
<li><a class="reference internal" href="#unix" id="id4">Unix 平台</a></li>
<li><a class="reference internal" href="#python" id="id5">Python</a></li>
<li><a class="reference internal" href="#mac-ios" id="id6">Mac & iOS</a></li>
<li><a class="reference internal" href="#mozilla-gecko" id="id7">Mozilla Gecko</a></li>
</ul>
</div>
<div class="section" id="windows-api">
<h2><a class="toc-backref" href="#id3">Windows API</a></h2>
<p>可利用 Win32 API <tt class="docutils literal">GetModuleHandleEx</tt> 来取得内存地址所在的程序路径。如果传入可执行文件自身的某个函数地址，那就能获得自己的路径。该方法如下，默认是取自身的路径:</p>
<div class="highlight"><pre><span></span><span class="n">std</span><span class="o">::</span><span class="n">wstring</span> <span class="n">get_module_path</span><span class="p">(</span><span class="kt">void</span><span class="o">*</span> <span class="n">address</span><span class="o">=</span><span class="nb">NULL</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="o">!</span> <span class="n">address</span><span class="p">)</span> <span class="p">{</span>
<span class="n">address</span> <span class="o">=</span> <span class="p">(</span><span class="kt">void</span><span class="o">*</span><span class="p">)(</span><span class="o">&</span><span class="n">get_module_path</span><span class="p">);</span>
<span class="p">}</span>
<span class="n">HMODULE</span> <span class="n">handle</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<span class="n">BOOL</span> <span class="k">const</span> <span class="n">ret</span> <span class="o">=</span> <span class="o">::</span><span class="n">GetModuleHandleExW</span><span class="p">(</span>
<span class="n">GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS</span><span class="p">,</span>
<span class="c1">//|GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,</span>
<span class="k">static_cast</span><span class="o"><</span><span class="kt">wchar_t</span><span class="o">*></span><span class="p">(</span><span class="n">address</span><span class="p">),</span>
<span class="o">&</span><span class="n">handle</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">ret</span> <span class="o">!=</span> <span class="mi">0</span> <span class="o">&&</span> <span class="n">handle</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">)</span> <span class="p">{</span>
<span class="kt">wchar_t</span> <span class="n">path_buffer</span><span class="p">[</span><span class="n">MAX_PATH</span><span class="p">]</span> <span class="o">=</span> <span class="p">{</span><span class="sa">L</span><span class="sc">'\0'</span><span class="p">};</span>
<span class="n">DWORD</span> <span class="k">const</span> <span class="n">ret</span> <span class="o">=</span> <span class="o">::</span><span class="n">GetModuleFileNameW</span><span class="p">(</span><span class="n">handle</span><span class="p">,</span> <span class="n">path_buffer</span><span class="p">,</span> <span class="n">MAX_PATH</span><span class="p">);</span>
<span class="c1">// We have to free it</span>
<span class="o">::</span><span class="n">FreeLibrary</span><span class="p">(</span><span class="n">handle</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="mi">0</span> <span class="o">!=</span> <span class="n">ret</span><span class="p">)</span> <span class="p">{</span>
<span class="k">return</span> <span class="n">path_buffer</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="k">return</span> <span class="sa">L</span><span class="s">""</span><span class="p">;</span> <span class="c1">// not found</span>
<span class="p">}</span>
</pre></div>
<p>这个方法也能在 DLL 中使用，让动态库也能获取自身的位置，方便插件的编写。</p>
</div>
<div class="section" id="unix">
<h2><a class="toc-backref" href="#id4">Unix 平台</a></h2>
<p>与 Win32 类似，在 POSIX 中 <tt class="docutils literal">dladdr</tt> 函数也可以获取某个地址所在可执行文件的路径:</p>
<div class="highlight"><pre><span></span><span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">get_module_path</span><span class="p">(</span><span class="kt">void</span><span class="o">*</span> <span class="n">address</span><span class="o">=</span><span class="nb">NULL</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="o">!</span> <span class="n">address</span><span class="p">)</span> <span class="p">{</span>
<span class="n">address</span> <span class="o">=</span> <span class="p">(</span><span class="kt">void</span><span class="o">*</span><span class="p">)(</span><span class="o">&</span><span class="n">get_module_path</span><span class="p">);</span>
<span class="p">}</span>
<span class="o">::</span><span class="n">Dl_info</span> <span class="n">dl_info</span><span class="p">;</span>
<span class="n">dl_info</span><span class="p">.</span><span class="n">dli_fname</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<span class="kt">int</span> <span class="k">const</span> <span class="n">ret</span> <span class="o">=</span> <span class="o">::</span><span class="n">dladdr</span><span class="p">(</span><span class="n">address</span><span class="p">,</span> <span class="o">&</span><span class="n">dl_info</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="mi">0</span> <span class="o">!=</span> <span class="n">ret</span> <span class="o">&&</span> <span class="n">dl_info</span><span class="p">.</span><span class="n">dli_fname</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">)</span> <span class="p">{</span>
<span class="k">return</span> <span class="n">dl_info</span><span class="p">.</span><span class="n">dli_fname</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">return</span> <span class="s">""</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
<p>该方法同样能让 so 动态库找到自身的位置，方便插件的编写。</p>
</div>
<div class="section" id="python">
<h2><a class="toc-backref" href="#id5">Python</a></h2>
<p>Python 内置变量 <tt class="docutils literal">__file__</tt> 的值就是脚本文件位置，很方便。不过一旦脚本被 py2exe 这类程序打包后，`` __file__`` 就不准确了。这时就需要用 <tt class="docutils literal">sys.argv[0]</tt> 甚至 <tt class="docutils literal">sys.executable</tt> 变量来取得打包后的程序文件的位置</p>
<div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">imp</span>
<span class="kn">import</span> <span class="nn">os</span>
<span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">import</span> <span class="nn">os.path</span>
<span class="k">def</span> <span class="nf">is_frozen</span><span class="p">():</span>
<span class="k">return</span> <span class="p">(</span><span class="nb">hasattr</span><span class="p">(</span><span class="n">sys</span><span class="p">,</span> <span class="s2">"frozen"</span><span class="p">)</span> <span class="ow">or</span> <span class="c1"># new py2exe</span>
<span class="nb">hasattr</span><span class="p">(</span><span class="n">sys</span><span class="p">,</span> <span class="s2">"importers"</span><span class="p">)</span> <span class="c1"># old py2exe</span>
<span class="ow">or</span> <span class="n">imp</span><span class="o">.</span><span class="n">is_frozen</span><span class="p">(</span><span class="s2">"__main__"</span><span class="p">))</span> <span class="c1"># tools/freeze</span>
<span class="k">def</span> <span class="nf">get_self_path</span><span class="p">():</span>
<span class="k">if</span> <span class="n">is_frozen</span><span class="p">():</span>
<span class="k">return</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">abspath</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">executable</span><span class="p">)</span>
<span class="k">return</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">abspath</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">[</span><span class="mi">0</span><span class="p">])</span>
</pre></div>
</div>
<div class="section" id="mac-ios">
<h2><a class="toc-backref" href="#id6">Mac & iOS</a></h2>
<p>Mac 和 iOS 平台上标准的 App 结构都是把可执行文件和资源文件打包在程序束 (bundle) 中，苹果还提供专门的 API 来取得 bundle 的路径，从这点上来说，苹果上的软件都是绿色的。不过如果需要，你还是可以取得自身的路径，</p>
<div class="highlight"><pre><span></span><span class="kt">char</span> <span class="n">path</span><span class="p">[</span><span class="mi">1024</span><span class="p">];</span>
<span class="kt">uint32_t</span> <span class="n">size</span> <span class="o">=</span> <span class="k">sizeof</span><span class="p">(</span><span class="n">path</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">_NSGetExecutablePath</span><span class="p">(</span><span class="n">path</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">)</span> <span class="o">==</span> <span class="mi">0</span><span class="p">)</span> <span class="p">{</span>
<span class="n">printf</span><span class="p">(</span><span class="s">"executable path is %s</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span> <span class="n">path</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">else</span> <span class="p">{</span>
<span class="n">printf</span><span class="p">(</span><span class="s">"buffer too small; need size %u</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span> <span class="n">size</span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
<p>这种方法不管是对传统的 Unix 可执行文件或是 Apple 自己标准的 App 都适用。</p>
</div>
<div class="section" id="mozilla-gecko">
<h2><a class="toc-backref" href="#id7">Mozilla Gecko</a></h2>
<p>Firefox 的扩展都基于 Gecko 架构提供的插件机制。要得到扩展自身的路径应该很方便才是，但实际上并非如此:</p>
<div class="highlight"><pre><span></span><span class="nx">Components</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="kr">import</span><span class="p">(</span><span class="s2">"resource://gre/modules/AddonManager.jsm"</span><span class="p">);</span>
<span class="nx">AddonManager</span><span class="p">.</span><span class="nx">getAddonByID</span><span class="p">(</span><span class="s2">"your@addon.name"</span><span class="p">,</span> <span class="kd">function</span><span class="p">(</span><span class="nx">addon</span><span class="p">)</span>
<span class="p">{</span>
<span class="kd">var</span> <span class="nx">uri</span> <span class="o">=</span> <span class="nx">addon</span><span class="p">.</span><span class="nx">getResourceURI</span><span class="p">(</span><span class="s2">"relative/path/to/file"</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="nx">uri</span> <span class="k">instanceof</span> <span class="nx">Components</span><span class="p">.</span><span class="nx">interfaces</span><span class="p">.</span><span class="nx">nsIFileURL</span><span class="p">)</span>
<span class="p">{</span>
<span class="c1">// get the absolute path to the file inside Your@Addon.name</span>
<span class="kd">var</span> <span class="nx">absolute_file_path</span> <span class="o">=</span> <span class="nx">uri</span><span class="p">.</span><span class="nx">file</span><span class="p">.</span><span class="nx">path</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">});</span>
</pre></div>
<p>这里，需要按扩展的名字去 <tt class="docutils literal">AddonManager</tt> 中找出扩展对象，再通过扩展对象取得扩展包内相对位置的文件路径，使用起来不太方便。</p>
<p>其实，Gecko 中有更直接的方法。你可以在 <tt class="docutils literal">manifest</tt> 文件里把需要引用的文件都声明成 <tt class="docutils literal">resource</tt>，所有的 <tt class="docutils literal">resource</tt> 都可以在扩展里通过 URI 名字直接获得路径</p>
<div class="highlight"><pre><span></span><span class="na">resource YOUR-ADDON-LIB path/to/libaddon.so ABI</span><span class="o">=</span><span class="s">Linux_x86-gcc3</span>
<span class="na">resource YOUR-ADDON-LIB path/to/addon.dll ABI</span><span class="o">=</span><span class="s">WINNT_x86-msvc</span>
</pre></div>
<div class="highlight"><pre><span></span><span class="kr">const</span> <span class="nx">ioService</span> <span class="o">=</span> <span class="nx">Cc</span><span class="p">[</span><span class="s2">"@mozilla.org/network/io-service;1"</span><span class="p">].</span><span class="nx">getService</span><span class="p">(</span><span class="nx">Ci</span><span class="p">.</span><span class="nx">nsIIOService</span><span class="p">);</span>
<span class="kd">var</span> <span class="nx">uri</span> <span class="o">=</span> <span class="nx">ioService</span><span class="p">.</span><span class="nx">newURI</span><span class="p">(</span><span class="s1">'resource://YOUR-ADDON-LIB'</span><span class="p">,</span> <span class="kc">null</span><span class="p">,</span> <span class="kc">null</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="nx">uri</span> <span class="k">instanceof</span> <span class="nx">Components</span><span class="p">.</span><span class="nx">interfaces</span><span class="p">.</span><span class="nx">nsIFileURL</span><span class="p">)</span> <span class="p">{</span>
<span class="kd">var</span> <span class="nx">lib</span> <span class="o">=</span> <span class="nx">ctypes</span><span class="p">.</span><span class="nx">open</span><span class="p">(</span><span class="nx">uri</span><span class="p">.</span><span class="nx">file</span><span class="p">.</span><span class="nx">path</span><span class="p">);</span>
<span class="c1">/// ...</span>
<span class="p">}</span>
</pre></div>
<p>在不同平台上，同一名字还能对应不同的资源文件，方便跨平台扩展的开发。在上面例子中，Win32 平台 <tt class="docutils literal"><span class="pre">js-ctypes</span></tt> 会使用 <tt class="docutils literal">addon.dll</tt> 而 Linux 上则会使用 <tt class="docutils literal">libaddon.so</tt>，这一切都由 gecko 帮着选择定位。我在 <a class="reference external" href="https://addons.mozilla.org/zh-cn/firefox/addon/chmfox/">chmfox</a> 里正是使用了这个手法。</p>
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