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hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><meta itemprop="name" content="从入门到放弃"></span><header class="post-header"><h2 class="post-title" itemprop="name headline">【从入门到放弃-Java】并发编程-NIO-Channel</h2><div class="post-meta"><span class="post-time"><span class="post-meta-item-icon"><i class="fa fa-calendar-o"></i></span> <span class="post-meta-item-text">发表于</span> <time title="创建于" itemprop="dateCreated datePublished" datetime="2019-06-25T13:39:01+08:00">2019-06-25</time></span> <span class="post-comments-count"><span class="post-meta-divider">|</span><span class="post-meta-item-icon"><i class="fa fa-comment-o"></i></span><a href="/3c79e6b3.html#comments" itemprop="discussionUrl"><span class="post-comments-count valine-comment-count" data-xid="/3c79e6b3.html" itemprop="commentCount"></span></a></span> <span class="post-meta-divider">|</span><span class="page-pv"><i class="fa fa-file-o"></i> 浏览<span class="busuanzi-value" id="busuanzi_value_page_pv"></span></span><div class="post-wordcount"><span class="post-meta-item-icon"><i class="fa fa-file-word-o"></i></span> <span class="post-meta-item-text">字数统计:</span> <span title="字数统计">4.6k</span> <span class="post-meta-divider">|</span><span class="post-meta-item-icon"><i class="fa fa-clock-o"></i></span> <span class="post-meta-item-text">阅读时长 ≈</span> <span title="阅读时长">23</span></div></div></header><div class="post-body" itemprop="articleBody"><h2 id="前言"><a href="#前言" class="headerlink" title="前言"></a>前言</h2><p>上篇<a href="https://nc2era.com/e57ab61.html">【从入门到放弃-Java】并发编程-NIO使用</a>简单介绍了nio的基础使用，本篇将深入源码分析nio中channel的实现。</p><h2 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h2><p>channel即通道，可以用来读、写数据，它是全双工的可以同时用来读写操作。这也是它与stream流的最大区别。</p><p>channel需要与buffer配合使用，channel通道的一端是buffer，一端是数据源实体，如文件、socket等。在nio中，通过channel的不同实现来处理 不同实体与数据buffer中的数据传输。</p><p>channel接口：<br></p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> java.nio.channels;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.io.IOException;</span><br><span class="line"><span class="keyword">import</span> java.io.Closeable;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * A nexus for I/O operations.</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <p> A channel represents an open connection to an entity such as a hardware</span></span><br><span class="line"><span class="comment"> * device, a file, a network socket, or a program component that is capable of</span></span><br><span class="line"><span class="comment"> * performing one or more distinct I/O operations, for example reading or</span></span><br><span class="line"><span class="comment"> * writing.</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <p> A channel is either open or closed. A channel is open upon creation,</span></span><br><span class="line"><span class="comment"> * and once closed it remains closed. Once a channel is closed, any attempt to</span></span><br><span class="line"><span class="comment"> * invoke an I/O operation upon it will cause a {<span class="doctag">@link</span> ClosedChannelException}</span></span><br><span class="line"><span class="comment"> * to be thrown. Whether or not a channel is open may be tested by invoking</span></span><br><span class="line"><span class="comment"> * its {<span class="doctag">@link</span> #isOpen isOpen} method.</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <p> Channels are, in general, intended to be safe for multithreaded access</span></span><br><span class="line"><span class="comment"> * as described in the specifications of the interfaces and classes that extend</span></span><br><span class="line"><span class="comment"> * and implement this interface.</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@author</span> Mark Reinhold</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@author</span> JSR-51 Expert Group</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@since</span> 1.4</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Channel</span> <span class="keyword">extends</span> <span class="title">Closeable</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Tells whether or not this channel is open.</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@return</span> <tt>true</tt> if, and only if, this channel is open</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">isOpen</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Closes this channel.</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <p> After a channel is closed, any further attempt to invoke I/O</span></span><br><span class="line"><span class="comment"> * operations upon it will cause a {<span class="doctag">@link</span> ClosedChannelException} to be</span></span><br><span class="line"><span class="comment"> * thrown.</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <p> If this channel is already closed then invoking this method has no</span></span><br><span class="line"><span class="comment"> * effect.</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <p> This method may be invoked at any time. If some other thread has</span></span><br><span class="line"><span class="comment"> * already invoked it, however, then another invocation will block until</span></span><br><span class="line"><span class="comment"> * the first invocation is complete, after which it will return without</span></span><br><span class="line"><span class="comment"> * effect. </p></span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@throws</span> IOException If an I/O error occurs</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">close</span><span class="params">()</span> <span class="keyword">throws</span> IOException</span>;</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure><p></p><p>常见的channel实现有：</p><ul><li>FileChannel：文件读写数据通道</li><li>SocketChannel：TCP读写网络数据通道</li><li>ServerSocketChannel：服务端网络数据读写通道，可以监听TCP连接。对每一个新进来的连接都会创建一个SocketChannel。</li><li>DatagramChannel：UDP读写网络数据通道</li></ul><h2 id="FileChannel"><a href="#FileChannel" class="headerlink" title="FileChannel"></a>FileChannel</h2><img src="/3c79e6b3/1.jpg"> <img src="/3c79e6b3/2.jpg"><p>FileChannel是一个抽象类，它继承了AbstractInterruptibleChannel类，并实现了 SeekableByteChannel, GatheringByteChannel, ScatteringByteChannel接口。<br>具体的实现类主要是sun.nio.ch.FileChannelImpl。下面详细分析下FileChannelImpl中每个方法的具体实现。</p><h3 id="open"><a href="#open" class="headerlink" title="open"></a>open</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">private</span> <span class="title">FileChannelImpl</span><span class="params">(FileDescriptor var1, String var2, <span class="keyword">boolean</span> var3, <span class="keyword">boolean</span> var4, <span class="keyword">boolean</span> var5, Object var6)</span> </span>{</span><br><span class="line"> <span class="comment">//主要记载操作系统维护的文件描述符</span></span><br><span class="line"> <span class="keyword">this</span>.fd = var1;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//是否可读</span></span><br><span class="line"> <span class="keyword">this</span>.readable = var3;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//是否可写</span></span><br><span class="line"> <span class="keyword">this</span>.writable = var4;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//是否以追加的方式打开</span></span><br><span class="line"> <span class="keyword">this</span>.append = var5;</span><br><span class="line"> </span><br><span class="line"> <span class="keyword">this</span>.parent = var6;</span><br><span class="line"> <span class="keyword">this</span>.path = var2;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//底层使用native的read和write来处理文件的</span></span><br><span class="line"> <span class="keyword">this</span>.nd = <span class="keyword">new</span> FileDispatcherImpl(var5);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//FileInputStream::getChannel 调用 FileChannelImpl.open(fd, path, true, false, this) 获取只读channel</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> FileChannel <span class="title">open</span><span class="params">(FileDescriptor var0, String var1, <span class="keyword">boolean</span> var2, <span class="keyword">boolean</span> var3, Object var4)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> FileChannelImpl(var0, var1, var2, var3, <span class="keyword">false</span>, var4);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//FileOutputStream::getChannel 调用 FileChannelImpl.open(fd, path, false, true, append, this) 获取只写channel</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> FileChannel <span class="title">open</span><span class="params">(FileDescriptor var0, String var1, <span class="keyword">boolean</span> var2, <span class="keyword">boolean</span> var3, <span class="keyword">boolean</span> var4, Object var5)</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> FileChannelImpl(var0, var1, var2, var3, var4, var5);</span><br><span class="line">}</span><br><span class="line"><span class="function"><span class="keyword">private</span> <span class="title">FileChannelImpl</span><span class="params">(FileDescriptor fd, String path, <span class="keyword">boolean</span> readable,</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">boolean</span> writable, <span class="keyword">boolean</span> direct, Object parent)</span></span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> <span class="keyword">this</span>.fd = fd;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//是否可读</span></span><br><span class="line"> <span class="keyword">this</span>.readable = readable;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//是否可写</span></span><br><span class="line"> <span class="keyword">this</span>.writable = writable;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//对于从流创建的channel，在结束时要做不同的清理动作，（openJDK中才有，sun的jdk中没有）</span></span><br><span class="line"> <span class="keyword">this</span>.parent = parent;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//源文件的path</span></span><br><span class="line"> <span class="keyword">this</span>.path = path;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//是否使用DirectIO</span></span><br><span class="line"> <span class="keyword">this</span>.direct = direct;</span><br><span class="line"> </span><br><span class="line"> <span class="keyword">this</span>.nd = <span class="keyword">new</span> FileDispatcherImpl();</span><br><span class="line"> <span class="keyword">if</span> (direct) {</span><br><span class="line"> <span class="keyword">assert</span> path != <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">this</span>.alignment = nd.setDirectIO(fd, path);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">this</span>.alignment = -<span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">//当parent不存在时，则注册一个cleaner，否则交由parent做清理动作。</span></span><br><span class="line"> <span class="comment">// Register a cleaning action if and only if there is no parent</span></span><br><span class="line"> <span class="comment">// as the parent will take care of closing the file descriptor.</span></span><br><span class="line"> <span class="comment">// FileChannel is used by the LambdaMetaFactory so a lambda cannot</span></span><br><span class="line"> <span class="comment">// be used here hence we use a nested class instead.</span></span><br><span class="line"> <span class="keyword">this</span>.closer = parent != <span class="keyword">null</span> ? <span class="keyword">null</span> :</span><br><span class="line"> CleanerFactory.cleaner().register(<span class="keyword">this</span>, <span class="keyword">new</span> Closer(fd));</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">// Used by FileInputStream.getChannel(), FileOutputStream.getChannel</span></span><br><span class="line"><span class="comment">// and RandomAccessFile.getChannel()</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> FileChannel <span class="title">open</span><span class="params">(FileDescriptor fd, String path,</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">boolean</span> readable, <span class="keyword">boolean</span> writable,</span></span></span><br><span class="line"><span class="function"><span class="params"> <span class="keyword">boolean</span> direct, Object parent)</span></span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> FileChannelImpl(fd, path, readable, writable, direct, parent);</span><br><span class="line">}</span><br></pre></td></tr></table></figure><ul><li>open方法主要是返回一个新new的FileChannelImpl对象，初始化时设置fileDescriptor、readable、writable、append、parent、path等属性，看变量名很容易理解，在此不赘述变量含义。</li></ul><h3 id="read"><a href="#read" class="headerlink" title="read"></a>read</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//实现自SeekableByteChannel接口的方法，将文件中的内容读取到给定的byteBuffer中</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">read</span><span class="params">(ByteBuffer dst)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> <span class="comment">//保证读写时，channel处于开启状态</span></span><br><span class="line"> ensureOpen();</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//判断是否可读</span></span><br><span class="line"> <span class="keyword">if</span> (!readable)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> NonReadableChannelException();</span><br><span class="line"> <span class="keyword">synchronized</span> (positionLock) {</span><br><span class="line"> <span class="keyword">if</span> (direct)</span><br><span class="line"> Util.checkChannelPositionAligned(position(), alignment);</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">int</span> ti = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//开始阻塞，并注册为Interruptible，可以被中断</span></span><br><span class="line"> beginBlocking();</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//将当前线程添加到NativeThreadSet中，并返回索引，方便后续操作。</span></span><br><span class="line"> <span class="comment">//NativeThreadSet是一个线程安全的本地线程集合，方便管理，用来发送信号</span></span><br><span class="line"> ti = threads.add();</span><br><span class="line"> <span class="keyword">if</span> (!isOpen())</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> <span class="comment">//当未被系统中断（即读取完毕）或channel未被关闭，则一直读，将内容写入到byteBuffer（dst）中</span></span><br><span class="line"> n = IOUtil.read(fd, dst, -<span class="number">1</span>, direct, alignment, nd);</span><br><span class="line"> } <span class="keyword">while</span> ((n == IOStatus.INTERRUPTED) && isOpen());</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(n);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="comment">//把当前线程从set中移出</span></span><br><span class="line"> threads.remove(ti);</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//结束，释放锁</span></span><br><span class="line"> endBlocking(n > <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">assert</span> IOStatus.check(n);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//实现自ScatteringByteChannel接口的方法，将文件中的内容依次读取到给定的byteBuffer数组中。</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">long</span> <span class="title">read</span><span class="params">(ByteBuffer[] dsts, <span class="keyword">int</span> offset, <span class="keyword">int</span> length)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> IOException</span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> <span class="keyword">if</span> ((offset < <span class="number">0</span>) || (length < <span class="number">0</span>) || (offset > dsts.length - length))</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> IndexOutOfBoundsException();</span><br><span class="line"> <span class="comment">//保证读写时，channel处于开启状态</span></span><br><span class="line"> ensureOpen();</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//判断是否可读</span></span><br><span class="line"> <span class="keyword">if</span> (!readable)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> NonReadableChannelException();</span><br><span class="line"> <span class="keyword">synchronized</span> (positionLock) {</span><br><span class="line"> <span class="keyword">if</span> (direct)</span><br><span class="line"> Util.checkChannelPositionAligned(position(), alignment);</span><br><span class="line"> <span class="keyword">long</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">int</span> ti = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//开始阻塞，并注册为Interruptible，可以被中断</span></span><br><span class="line"> beginBlocking();</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//将当前线程添加到NativeThreadSet中，并返回索引，方便后续操作。</span></span><br><span class="line"> <span class="comment">//NativeThreadSet是一个线程安全的本地线程集合，方便管理，用来发送信号</span></span><br><span class="line"> ti = threads.add();</span><br><span class="line"> <span class="keyword">if</span> (!isOpen())</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> <span class="comment">//当未被系统中断（即读取完毕）或channel未被关闭，则一直读，将内容写入到byteBuffer（dst）中</span></span><br><span class="line"> n = IOUtil.read(fd, dsts, offset, length,</span><br><span class="line"> direct, alignment, nd);</span><br><span class="line"> } <span class="keyword">while</span> ((n == IOStatus.INTERRUPTED) && isOpen());</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(n);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="comment">//把当前线程从set中移出</span></span><br><span class="line"> threads.remove(ti);</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//结束，释放锁</span></span><br><span class="line"> endBlocking(n > <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">assert</span> IOStatus.check(n);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="write"><a href="#write" class="headerlink" title="write"></a>write</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//实现自SeekableByteChannel接口的方法，将byteBuffer中的内容写入到文件中</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">write</span><span class="params">(ByteBuffer src)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> <span class="comment">//保证写时，channel处于开启状态</span></span><br><span class="line"> ensureOpen();</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//判断是否可写</span></span><br><span class="line"> <span class="keyword">if</span> (!writable)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> NonWritableChannelException();</span><br><span class="line"> <span class="keyword">synchronized</span> (positionLock) {</span><br><span class="line"> <span class="keyword">if</span> (direct)</span><br><span class="line"> Util.checkChannelPositionAligned(position(), alignment);</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">int</span> ti = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//开始阻塞，并注册为Interruptible，可以被中断</span></span><br><span class="line"> beginBlocking();</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//将当前线程添加到NativeThreadSet中，并返回索引，方便后续操作。</span></span><br><span class="line"> <span class="comment">//NativeThreadSet是一个线程安全的本地线程集合，方便管理，用来发送信号</span></span><br><span class="line"> ti = threads.add();</span><br><span class="line"> <span class="keyword">if</span> (!isOpen())</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> <span class="comment">//当未被系统中断（即写入完毕）或channel未被关闭，则一直写，将内容写入到文件中</span></span><br><span class="line"> n = IOUtil.write(fd, src, -<span class="number">1</span>, direct, alignment, nd);</span><br><span class="line"> } <span class="keyword">while</span> ((n == IOStatus.INTERRUPTED) && isOpen());</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(n);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="comment">//把当前线程从set中移出</span></span><br><span class="line"> threads.remove(ti);</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//结束，释放锁</span></span><br><span class="line"> <span class="keyword">assert</span> IOStatus.check(n);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//实现自GatheringByteChannel接口的方法，将byteBuffer数组中的内容依次写入到文件中</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">long</span> <span class="title">write</span><span class="params">(ByteBuffer[] srcs, <span class="keyword">int</span> offset, <span class="keyword">int</span> length)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> IOException</span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> <span class="keyword">if</span> ((offset < <span class="number">0</span>) || (length < <span class="number">0</span>) || (offset > srcs.length - length))</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> IndexOutOfBoundsException();</span><br><span class="line"> <span class="comment">//保证写时，channel处于开启状态</span></span><br><span class="line"> ensureOpen();</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//判断是否可写</span></span><br><span class="line"> <span class="keyword">if</span> (!writable)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> NonWritableChannelException();</span><br><span class="line"> <span class="keyword">synchronized</span> (positionLock) {</span><br><span class="line"> <span class="keyword">if</span> (direct)</span><br><span class="line"> Util.checkChannelPositionAligned(position(), alignment);</span><br><span class="line"> <span class="keyword">long</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">int</span> ti = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//开始阻塞，并注册为Interruptible，可以被中断</span></span><br><span class="line"> beginBlocking();</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//将当前线程添加到NativeThreadSet中，并返回索引，方便后续操作。</span></span><br><span class="line"> <span class="comment">//NativeThreadSet是一个线程安全的本地线程集合，方便管理，用来发送信号</span></span><br><span class="line"> ti = threads.add();</span><br><span class="line"> <span class="keyword">if</span> (!isOpen())</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> <span class="comment">//当未被系统中断（即写入完毕）或channel未被关闭，则一直写，将内容写入到文件中</span></span><br><span class="line"> n = IOUtil.write(fd, srcs, offset, length,</span><br><span class="line"> direct, alignment, nd);</span><br><span class="line"> } <span class="keyword">while</span> ((n == IOStatus.INTERRUPTED) && isOpen());</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(n);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="comment">//把当前线程从set中移出</span></span><br><span class="line"> threads.remove(ti);</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//结束，释放锁</span></span><br><span class="line"> <span class="keyword">assert</span> IOStatus.check(n);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="position"><a href="#position" class="headerlink" title="position"></a>position</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//实现自SeekableByteChannel接口的方法，获取当前channel的position</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">long</span> <span class="title">position</span><span class="params">()</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> ensureOpen();</span><br><span class="line"> <span class="keyword">synchronized</span> (positionLock) {</span><br><span class="line"> <span class="keyword">long</span> p = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">int</span> ti = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> beginBlocking();</span><br><span class="line"> ti = threads.add();</span><br><span class="line"> <span class="keyword">if</span> (!isOpen())</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">boolean</span> append = fdAccess.getAppend(fd);</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> <span class="comment">//append模式下，position在channel的末尾</span></span><br><span class="line"> <span class="comment">// in append-mode then position is advanced to end before writing</span></span><br><span class="line"> p = (append) ? nd.size(fd) : nd.seek(fd, -<span class="number">1</span>);</span><br><span class="line"> } <span class="keyword">while</span> ((p == IOStatus.INTERRUPTED) && isOpen());</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(p);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> threads.remove(ti);</span><br><span class="line"> endBlocking(p > -<span class="number">1</span>);</span><br><span class="line"> <span class="keyword">assert</span> IOStatus.check(p);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//实现自SeekableByteChannel接口的方法，设置当前channel的position为newPosition</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> FileChannel <span class="title">position</span><span class="params">(<span class="keyword">long</span> newPosition)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> ensureOpen();</span><br><span class="line"> <span class="keyword">if</span> (newPosition < <span class="number">0</span>)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> IllegalArgumentException();</span><br><span class="line"> <span class="keyword">synchronized</span> (positionLock) {</span><br><span class="line"> <span class="keyword">long</span> p = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">int</span> ti = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> beginBlocking();</span><br><span class="line"> ti = threads.add();</span><br><span class="line"> <span class="keyword">if</span> (!isOpen())</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> <span class="comment">//设置当前position为newPosition</span></span><br><span class="line"> p = nd.seek(fd, newPosition);</span><br><span class="line"> } <span class="keyword">while</span> ((p == IOStatus.INTERRUPTED) && isOpen());</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">this</span>;</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> threads.remove(ti);</span><br><span class="line"> endBlocking(p > -<span class="number">1</span>);</span><br><span class="line"> <span class="keyword">assert</span> IOStatus.check(p);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="size"><a href="#size" class="headerlink" title="size"></a>size</h3><p>实现自SeekableByteChannel接口的方法，返回当前实体（文件）的大小</p><h3 id="truncate"><a href="#truncate" class="headerlink" title="truncate"></a>truncate</h3><p>实现自SeekableByteChannel接口的方法，用来截取文件至newSize大小</p><h3 id="force"><a href="#force" class="headerlink" title="force"></a>force</h3><p>实现自SeekableByteChannel接口的方法，用来将channel中尚未写入磁盘的数据强制落盘</p><h3 id="transferTo"><a href="#transferTo" class="headerlink" title="transferTo"></a>transferTo</h3><p>将fileChannel中的数据传递至另一个channel</p><h3 id="transferFrom"><a href="#transferFrom" class="headerlink" title="transferFrom"></a>transferFrom</h3><p>从其它channel读取数据至fileChannel</p><h2 id="SocketChannel"><a href="#SocketChannel" class="headerlink" title="SocketChannel"></a>SocketChannel</h2><img src="/3c79e6b3/3.jpg"> <img src="/3c79e6b3/4.jpg"><h3 id="open-1"><a href="#open-1" class="headerlink" title="open"></a>open</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Opens a socket channel.</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <p> The new channel is created by invoking the {<span class="doctag">@link</span></span></span><br><span class="line"><span class="comment"> * java.nio.channels.spi.SelectorProvider#openSocketChannel</span></span><br><span class="line"><span class="comment"> * openSocketChannel} method of the system-wide default {<span class="doctag">@link</span></span></span><br><span class="line"><span class="comment"> * java.nio.channels.spi.SelectorProvider} object. </p></span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@return</span> A new socket channel</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@throws</span> IOException</span></span><br><span class="line"><span class="comment"> * If an I/O error occurs</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> SocketChannel <span class="title">open</span><span class="params">()</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> <span class="keyword">return</span> SelectorProvider.provider().openSocketChannel();</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>open方法是调用SelectorProvider中实现了java.nio.channels.spi.SelectorProvider#openSocketChannel的方法，底层实际是new SocketChannelImpl，调用native方法创建socket</p><h3 id="connect"><a href="#connect" class="headerlink" title="connect"></a>connect</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">connect</span><span class="params">(SocketAddress sa)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> <span class="comment">//校验Address是否合法</span></span><br><span class="line"> InetSocketAddress isa = Net.checkAddress(sa);</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//获取系统安全管理器</span></span><br><span class="line"> SecurityManager sm = System.getSecurityManager();</span><br><span class="line"> <span class="keyword">if</span> (sm != <span class="keyword">null</span>)</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//校验IP和端口是否被允许连接</span></span><br><span class="line"> sm.checkConnect(isa.getAddress().getHostAddress(), isa.getPort());</span><br><span class="line"></span><br><span class="line"> InetAddress ia = isa.getAddress();</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//如果是本机地址，则获取本机的host</span></span><br><span class="line"> <span class="keyword">if</span> (ia.isAnyLocalAddress())</span><br><span class="line"> ia = InetAddress.getLocalHost();</span><br><span class="line"></span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//加读锁</span></span><br><span class="line"> readLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//加写锁</span></span><br><span class="line"> writeLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//是否阻塞</span></span><br><span class="line"> <span class="keyword">boolean</span> blocking = isBlocking();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//开启connect前的校验并设置为ST_CONNECTIONPENDING，如果blocking是true 即阻塞模式，则记录当前线程的ID，以便接收信号处理。</span></span><br><span class="line"> beginConnect(blocking, isa);</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> <span class="comment">//调用native connect方法</span></span><br><span class="line"> n = Net.connect(fd, ia, isa.getPort());</span><br><span class="line"> } <span class="keyword">while</span> (n == IOStatus.INTERRUPTED && isOpen());</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="comment">//结束连接</span></span><br><span class="line"> endConnect(blocking, (n > <span class="number">0</span>));</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">assert</span> IOStatus.check(n);</span><br><span class="line"> <span class="keyword">return</span> n > <span class="number">0</span>;</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="comment">//释放写锁</span></span><br><span class="line"> writeLock.unlock();</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="comment">//释放读锁</span></span><br><span class="line"> readLock.unlock();</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">catch</span> (IOException ioe) {</span><br><span class="line"> <span class="comment">// connect failed, close the channel</span></span><br><span class="line"> close();</span><br><span class="line"> <span class="keyword">throw</span> SocketExceptions.of(ioe, isa);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="configureBlocking"><a href="#configureBlocking" class="headerlink" title="configureBlocking"></a>configureBlocking</h3><p>实现自SelectableChannel的接口方法，调用native方法设置socket的阻塞状态</p><h3 id="register"><a href="#register" class="headerlink" title="register"></a>register</h3><p>在AbstractSelectableChannel中定义，注册要监听的事件。<br></p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">final</span> SelectionKey <span class="title">register</span><span class="params">(Selector sel, <span class="keyword">int</span> ops, Object att)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> ClosedChannelException</span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> <span class="keyword">if</span> ((ops & ~validOps()) != <span class="number">0</span>)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> IllegalArgumentException();</span><br><span class="line"> <span class="keyword">if</span> (!isOpen())</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> ClosedChannelException();</span><br><span class="line"> <span class="keyword">synchronized</span> (regLock) {</span><br><span class="line"> <span class="keyword">if</span> (isBlocking())</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> IllegalBlockingModeException();</span><br><span class="line"> <span class="keyword">synchronized</span> (keyLock) {</span><br><span class="line"> <span class="comment">// re-check if channel has been closed</span></span><br><span class="line"> <span class="keyword">if</span> (!isOpen())</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> ClosedChannelException();</span><br><span class="line"> SelectionKey k = findKey(sel);</span><br><span class="line"> <span class="keyword">if</span> (k != <span class="keyword">null</span>) {</span><br><span class="line"> k.attach(att);</span><br><span class="line"> k.interestOps(ops);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">// 向Selector中注册事件</span></span><br><span class="line"> <span class="comment">// New registration</span></span><br><span class="line"> k = ((AbstractSelector)sel).register(<span class="keyword">this</span>, ops, att);</span><br><span class="line"> addKey(k);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> k;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p></p><h3 id="read-1"><a href="#read-1" class="headerlink" title="read"></a>read</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//实现自ReadableByteChannel接口的方法，从socket中读取数据至ByteBuffer</span></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">read</span><span class="params">(ByteBuffer buf)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> Objects.requireNonNull(buf);</span><br><span class="line"></span><br><span class="line"> readLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">boolean</span> blocking = isBlocking();</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//检查channel是否开启并已经是connected的状态。如果blocking是true 即阻塞模式，则记录当前线程的ID，以便接收信号处理。</span></span><br><span class="line"> beginRead(blocking);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// check if input is shutdown</span></span><br><span class="line"> <span class="keyword">if</span> (isInputClosed)</span><br><span class="line"> <span class="keyword">return</span> IOStatus.EOF;</span><br><span class="line"></span><br><span class="line"> <span class="comment">//如果是阻塞模式，则一直读取直到数据读取完毕；非阻塞模式则直接调用native方法不需要等待。</span></span><br><span class="line"> <span class="keyword">if</span> (blocking) {</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> n = IOUtil.read(fd, buf, -<span class="number">1</span>, nd);</span><br><span class="line"> } <span class="keyword">while</span> (n == IOStatus.INTERRUPTED && isOpen());</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> n = IOUtil.read(fd, buf, -<span class="number">1</span>, nd);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> endRead(blocking, n > <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">if</span> (n <= <span class="number">0</span> && isInputClosed)</span><br><span class="line"> <span class="keyword">return</span> IOStatus.EOF;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(n);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> readLock.unlock();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//实现自ScatteringByteChannel接口的方法，从socket中依次读取数据至ByteBuffer数组</span></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">long</span> <span class="title">read</span><span class="params">(ByteBuffer[] dsts, <span class="keyword">int</span> offset, <span class="keyword">int</span> length)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> IOException</span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> Objects.checkFromIndexSize(offset, length, dsts.length);</span><br><span class="line"></span><br><span class="line"> readLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">boolean</span> blocking = isBlocking();</span><br><span class="line"> <span class="keyword">long</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> beginRead(blocking);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// check if input is shutdown</span></span><br><span class="line"> <span class="keyword">if</span> (isInputClosed)</span><br><span class="line"> <span class="keyword">return</span> IOStatus.EOF;</span><br><span class="line"></span><br><span class="line"> <span class="comment">//如果是阻塞模式，则一直读取直到数据读取完毕；非阻塞模式则直接调用native方法不需要等待。</span></span><br><span class="line"> <span class="keyword">if</span> (blocking) {</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> n = IOUtil.read(fd, dsts, offset, length, nd);</span><br><span class="line"> } <span class="keyword">while</span> (n == IOStatus.INTERRUPTED && isOpen());</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> n = IOUtil.read(fd, dsts, offset, length, nd);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> endRead(blocking, n > <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">if</span> (n <= <span class="number">0</span> && isInputClosed)</span><br><span class="line"> <span class="keyword">return</span> IOStatus.EOF;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(n);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> readLock.unlock();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="write-1"><a href="#write-1" class="headerlink" title="write"></a>write</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//实现自ReadableByteChannel接口的方法，将ByteBuffer中的数据写入socket</span></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">write</span><span class="params">(ByteBuffer buf)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> Objects.requireNonNull(buf);</span><br><span class="line"></span><br><span class="line"> writeLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">boolean</span> blocking = isBlocking();</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> beginWrite(blocking);</span><br><span class="line"> <span class="comment">//如果是阻塞模式，则一直读取直到数据读取完毕；非阻塞模式则直接调用native方法不需要等待。</span></span><br><span class="line"> <span class="keyword">if</span> (blocking) {</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> n = IOUtil.write(fd, buf, -<span class="number">1</span>, nd);</span><br><span class="line"> } <span class="keyword">while</span> (n == IOStatus.INTERRUPTED && isOpen());</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> n = IOUtil.write(fd, buf, -<span class="number">1</span>, nd);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> endWrite(blocking, n > <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">if</span> (n <= <span class="number">0</span> && isOutputClosed)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> AsynchronousCloseException();</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(n);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> writeLock.unlock();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">long</span> <span class="title">write</span><span class="params">(ByteBuffer[] srcs, <span class="keyword">int</span> offset, <span class="keyword">int</span> length)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> IOException</span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> Objects.checkFromIndexSize(offset, length, srcs.length);</span><br><span class="line"></span><br><span class="line"> writeLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">boolean</span> blocking = isBlocking();</span><br><span class="line"> <span class="keyword">long</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> beginWrite(blocking);</span><br><span class="line"> <span class="comment">//如果是阻塞模式，则一直等待直到数据写入完毕；非阻塞模式则直接调用native方法不需要等待。</span></span><br><span class="line"> <span class="keyword">if</span> (blocking) {</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> n = IOUtil.write(fd, srcs, offset, length, nd);</span><br><span class="line"> } <span class="keyword">while</span> (n == IOStatus.INTERRUPTED && isOpen());</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> n = IOUtil.write(fd, srcs, offset, length, nd);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> endWrite(blocking, n > <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">if</span> (n <= <span class="number">0</span> && isOutputClosed)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> AsynchronousCloseException();</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(n);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> writeLock.unlock();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="comment">//实现自ReadableByteChannel接口的方法，将ByteBuffer数组中的数据依次写入socket</span></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Writes a byte of out of band data.</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">sendOutOfBandData</span><span class="params">(<span class="keyword">byte</span> b)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> writeLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">boolean</span> blocking = isBlocking();</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> beginWrite(blocking);</span><br><span class="line"> <span class="comment">//如果是阻塞模式，则一直等待直到数据写入完毕；非阻塞模式则直接调用native方法不需要等待。</span></span><br><span class="line"> <span class="keyword">if</span> (blocking) {</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> n = sendOutOfBandData(fd, b);</span><br><span class="line"> } <span class="keyword">while</span> (n == IOStatus.INTERRUPTED && isOpen());</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> n = sendOutOfBandData(fd, b);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> endWrite(blocking, n > <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">if</span> (n <= <span class="number">0</span> && isOutputClosed)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> AsynchronousCloseException();</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(n);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> writeLock.unlock();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h2 id="ServerSocketChannel"><a href="#ServerSocketChannel" class="headerlink" title="ServerSocketChannel"></a>ServerSocketChannel</h2><img src="/3c79e6b3/5.jpg"> <img src="/3c79e6b3/6.jpg"><h3 id="socket"><a href="#socket" class="headerlink" title="socket"></a>socket</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> ServerSocket <span class="title">socket</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">synchronized</span> (stateLock) {</span><br><span class="line"> <span class="keyword">if</span> (socket == <span class="keyword">null</span>)</span><br><span class="line"> socket = ServerSocketAdaptor.create(<span class="keyword">this</span>);</span><br><span class="line"> <span class="keyword">return</span> socket;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="bind"><a href="#bind" class="headerlink" title="bind"></a>bind</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> ServerSocketChannel <span class="title">bind</span><span class="params">(SocketAddress local, <span class="keyword">int</span> backlog)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> <span class="keyword">synchronized</span> (stateLock) {</span><br><span class="line"> ensureOpen();</span><br><span class="line"> <span class="keyword">if</span> (localAddress != <span class="keyword">null</span>)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> AlreadyBoundException();</span><br><span class="line"> InetSocketAddress isa = (local == <span class="keyword">null</span>)</span><br><span class="line"> ? <span class="keyword">new</span> InetSocketAddress(<span class="number">0</span>)</span><br><span class="line"> : Net.checkAddress(local);</span><br><span class="line"> SecurityManager sm = System.getSecurityManager();</span><br><span class="line"> <span class="keyword">if</span> (sm != <span class="keyword">null</span>)</span><br><span class="line"> sm.checkListen(isa.getPort());</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//绑定前做一些前置处理，如将tcp socket文件描述符转换成SDP</span></span><br><span class="line"> NetHooks.beforeTcpBind(fd, isa.getAddress(), isa.getPort());</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//绑定IP和地址</span></span><br><span class="line"> Net.bind(fd, isa.getAddress(), isa.getPort());</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//开始监听，设置socket上最多可以挂起backlog个连接，若backlog小于1 则默认设置50个</span></span><br><span class="line"> Net.listen(fd, backlog < <span class="number">1</span> ? <span class="number">50</span> : backlog);</span><br><span class="line"> </span><br><span class="line"> localAddress = Net.localAddress(fd);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">this</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="accept"><a href="#accept" class="headerlink" title="accept"></a>accept</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> SocketChannel <span class="title">accept</span><span class="params">()</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> acceptLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> FileDescriptor newfd = <span class="keyword">new</span> FileDescriptor();</span><br><span class="line"> InetSocketAddress[] isaa = <span class="keyword">new</span> InetSocketAddress[<span class="number">1</span>];</span><br><span class="line"></span><br><span class="line"> <span class="keyword">boolean</span> blocking = isBlocking();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> begin(blocking);</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> <span class="comment">//阻塞等待接收客户端链接</span></span><br><span class="line"> n = accept(<span class="keyword">this</span>.fd, newfd, isaa);</span><br><span class="line"> } <span class="keyword">while</span> (n == IOStatus.INTERRUPTED && isOpen());</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> end(blocking, n > <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">assert</span> IOStatus.check(n);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">if</span> (n < <span class="number">1</span>)</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line"></span><br><span class="line"> <span class="comment">//新接收的socket初始设置为阻塞模式（因此非阻塞模式的每次需要显示设置）</span></span><br><span class="line"> <span class="comment">// newly accepted socket is initially in blocking mode</span></span><br><span class="line"> IOUtil.configureBlocking(newfd, <span class="keyword">true</span>);</span><br><span class="line"></span><br><span class="line"> InetSocketAddress isa = isaa[<span class="number">0</span>];</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//用新接收的socket创建SocketChannel</span></span><br><span class="line"> SocketChannel sc = <span class="keyword">new</span> SocketChannelImpl(provider(), newfd, isa);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// check permitted to accept connections from the remote address</span></span><br><span class="line"> SecurityManager sm = System.getSecurityManager();</span><br><span class="line"> <span class="keyword">if</span> (sm != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> sm.checkAccept(isa.getAddress().getHostAddress(), isa.getPort());</span><br><span class="line"> } <span class="keyword">catch</span> (SecurityException x) {</span><br><span class="line"> sc.close();</span><br><span class="line"> <span class="keyword">throw</span> x;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> sc;</span><br><span class="line"></span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> acceptLock.unlock();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>ServerSocketChannel并没有read和write方法，只是继承了AbstractSelectableChannel，以便在selector中使用</p><h2 id="DatagramChannel"><a href="#DatagramChannel" class="headerlink" title="DatagramChannel"></a>DatagramChannel</h2><img src="/3c79e6b3/7.jpg"> <img src="/3c79e6b3/8.jpg"><h3 id="open-2"><a href="#open-2" class="headerlink" title="open"></a>open</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="title">DatagramChannelImpl</span><span class="params">(SelectorProvider sp)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> IOException</span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> <span class="keyword">super</span>(sp);</span><br><span class="line"> ResourceManager.beforeUdpCreate();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//如果不支持IPv6则使用IPv4</span></span><br><span class="line"> <span class="keyword">this</span>.family = Net.isIPv6Available()</span><br><span class="line"> ? StandardProtocolFamily.INET6</span><br><span class="line"> : StandardProtocolFamily.INET;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//设置非流式的socket（tcp是流模式协议，udp是数据报模式协议）</span></span><br><span class="line"> <span class="keyword">this</span>.fd = Net.socket(family, <span class="keyword">false</span>);</span><br><span class="line"> <span class="keyword">this</span>.fdVal = IOUtil.fdVal(fd);</span><br><span class="line"> } <span class="keyword">catch</span> (IOException ioe) {</span><br><span class="line"> ResourceManager.afterUdpClose();</span><br><span class="line"> <span class="keyword">throw</span> ioe;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="receive"><a href="#receive" class="headerlink" title="receive"></a>receive</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> SocketAddress <span class="title">receive</span><span class="params">(ByteBuffer dst)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> <span class="keyword">if</span> (dst.isReadOnly())</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> IllegalArgumentException(<span class="string">"Read-only buffer"</span>);</span><br><span class="line"></span><br><span class="line"> readLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">boolean</span> blocking = isBlocking();</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> ByteBuffer bb = <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> SocketAddress remote = beginRead(blocking, <span class="keyword">false</span>);</span><br><span class="line"> <span class="keyword">boolean</span> connected = (remote != <span class="keyword">null</span>);</span><br><span class="line"> SecurityManager sm = System.getSecurityManager();</span><br><span class="line"> <span class="keyword">if</span> (connected || (sm == <span class="keyword">null</span>)) {</span><br><span class="line"> <span class="comment">// connected or no security manager</span></span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> n = receive(fd, dst, connected);</span><br><span class="line"> } <span class="keyword">while</span> ((n == IOStatus.INTERRUPTED) && isOpen());</span><br><span class="line"> <span class="keyword">if</span> (n == IOStatus.UNAVAILABLE)</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">// Cannot receive into user's buffer when running with a</span></span><br><span class="line"> <span class="comment">// security manager and not connected</span></span><br><span class="line"> bb = Util.getTemporaryDirectBuffer(dst.remaining());</span><br><span class="line"> <span class="keyword">for</span> (;;) {</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> n = receive(fd, bb, connected);</span><br><span class="line"> } <span class="keyword">while</span> ((n == IOStatus.INTERRUPTED) && isOpen());</span><br><span class="line"> <span class="keyword">if</span> (n == IOStatus.UNAVAILABLE)</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line"> InetSocketAddress isa = (InetSocketAddress)sender;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> sm.checkAccept(isa.getAddress().getHostAddress(),</span><br><span class="line"> isa.getPort());</span><br><span class="line"> } <span class="keyword">catch</span> (SecurityException se) {</span><br><span class="line"> <span class="comment">// Ignore packet</span></span><br><span class="line"> bb.clear();</span><br><span class="line"> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">continue</span>;</span><br><span class="line"> }</span><br><span class="line"> bb.flip();</span><br><span class="line"> dst.put(bb);</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> <span class="comment">//sender:发送方地址， Set by receive0 (## ugh)</span></span><br><span class="line"> <span class="keyword">assert</span> sender != <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">return</span> sender;</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="keyword">if</span> (bb != <span class="keyword">null</span>)</span><br><span class="line"> Util.releaseTemporaryDirectBuffer(bb);</span><br><span class="line"> endRead(blocking, n > <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">assert</span> IOStatus.check(n);</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> readLock.unlock();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="send"><a href="#send" class="headerlink" title="send"></a>send</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">send</span><span class="params">(ByteBuffer src, SocketAddress target)</span></span></span><br><span class="line"><span class="function"> <span class="keyword">throws</span> IOException</span></span><br><span class="line"><span class="function"></span>{</span><br><span class="line"> Objects.requireNonNull(src);</span><br><span class="line"> InetSocketAddress isa = Net.checkAddress(target, family);</span><br><span class="line"></span><br><span class="line"> writeLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">boolean</span> blocking = isBlocking();</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="comment">//当connect后，remote会设置为连接的地址</span></span><br><span class="line"> SocketAddress remote = beginWrite(blocking, <span class="keyword">false</span>);</span><br><span class="line"> <span class="keyword">if</span> (remote != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">// connected</span></span><br><span class="line"> <span class="keyword">if</span> (!target.equals(remote)) {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> AlreadyConnectedException();</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> n = IOUtil.write(fd, src, -<span class="number">1</span>, nd);</span><br><span class="line"> } <span class="keyword">while</span> ((n == IOStatus.INTERRUPTED) && isOpen());</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="comment">// not connected</span></span><br><span class="line"> SecurityManager sm = System.getSecurityManager();</span><br><span class="line"> <span class="keyword">if</span> (sm != <span class="keyword">null</span>) {</span><br><span class="line"> InetAddress ia = isa.getAddress();</span><br><span class="line"> <span class="keyword">if</span> (ia.isMulticastAddress()) {</span><br><span class="line"> sm.checkMulticast(ia);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> sm.checkConnect(ia.getHostAddress(), isa.getPort());</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">do</span> {</span><br><span class="line"> n = send(fd, src, isa);</span><br><span class="line"> } <span class="keyword">while</span> ((n == IOStatus.INTERRUPTED) && isOpen());</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> endWrite(blocking, n > <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">assert</span> IOStatus.check(n);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> IOStatus.normalize(n);</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> writeLock.unlock();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="connect-1"><a href="#connect-1" class="headerlink" title="connect"></a>connect</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="function"><span class="keyword">public</span> DatagramChannel <span class="title">connect</span><span class="params">(SocketAddress sa)</span> <span class="keyword">throws</span> IOException </span>{</span><br><span class="line"> InetSocketAddress isa = Net.checkAddress(sa, family);</span><br><span class="line"> SecurityManager sm = System.getSecurityManager();</span><br><span class="line"> <span class="keyword">if</span> (sm != <span class="keyword">null</span>) {</span><br><span class="line"> InetAddress ia = isa.getAddress();</span><br><span class="line"> <span class="keyword">if</span> (ia.isMulticastAddress()) {</span><br><span class="line"> sm.checkMulticast(ia);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> sm.checkConnect(ia.getHostAddress(), isa.getPort());</span><br><span class="line"> sm.checkAccept(ia.getHostAddress(), isa.getPort());</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> readLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> writeLock.lock();</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> <span class="keyword">synchronized</span> (stateLock) {</span><br><span class="line"> ensureOpen();</span><br><span class="line"> <span class="keyword">if</span> (state == ST_CONNECTED)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> AlreadyConnectedException();</span><br><span class="line"></span><br><span class="line"> <span class="keyword">int</span> n = Net.connect(family,</span><br><span class="line"> fd,</span><br><span class="line"> isa.getAddress(),</span><br><span class="line"> isa.getPort());</span><br><span class="line"> <span class="keyword">if</span> (n <= <span class="number">0</span>)</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> Error(); <span class="comment">// Can't happen</span></span><br><span class="line"></span><br><span class="line"> <span class="comment">// connected</span></span><br><span class="line"> remoteAddress = isa;</span><br><span class="line"> state = ST_CONNECTED;</span><br><span class="line"></span><br><span class="line"> <span class="comment">// refresh local address</span></span><br><span class="line"> localAddress = Net.localAddress(fd);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// flush any packets already received.</span></span><br><span class="line"> <span class="keyword">boolean</span> blocking = isBlocking();</span><br><span class="line"> <span class="keyword">if</span> (blocking) {</span><br><span class="line"> IOUtil.configureBlocking(fd, <span class="keyword">false</span>);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">try</span> {</span><br><span class="line"> ByteBuffer buf = ByteBuffer.allocate(<span class="number">100</span>);</span><br><span class="line"> <span class="keyword">while</span> (receive(buf) != <span class="keyword">null</span>) {</span><br><span class="line"> buf.clear();</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> <span class="keyword">if</span> (blocking) {</span><br><span class="line"> IOUtil.configureBlocking(fd, <span class="keyword">true</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> writeLock.unlock();</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">finally</span> {</span><br><span class="line"> readLock.unlock();</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">this</span>;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>udp是数据报模式的协议，是没有connect的。这里的connect实际上是在底层忽略了与其他地址的数据传输。<br>在connect后，就可以像socketChannel似得使用read和write了</p><h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><p>本文学习了各种channel的实现，主要是对底层native方法的一些封装，针对不同属性的实体（文件、socket），使用对应的channel与byteBuffer传输数据。再通过byteBuffer与byte数据进行转换。<br>channel的实现中，封装了大量的native方法，重要的底层实现全在native中，后续可以深入学习下。</p><p>本文中出现的byteBuffer和selector将在接下来的文章中，单独分析。</p></div><footer class="post-footer"><div class="post-tags"> <a href="/tags/Java/" rel="tag"># Java</a> <a href="/tags/并发编程/" rel="tag"># 并发编程</a> <a href="/tags/NIO/" rel="tag"># NIO</a> <a href="/tags/socket/" rel="tag"># socket</a> <a href="/tags/channel/" rel="tag"># channel</a></div><div class="post-nav"><div class="post-nav-next post-nav-item"><a href="/e57ab61.html" rel="next" title="【从入门到放弃-Java】并发编程-NIO使用"><i class="fa fa-chevron-left"></i> 【从入门到放弃-Java】并发编程-NIO使用</a></div><span class="post-nav-divider"></span><div 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class="nav-text">read</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#write"><span class="nav-number">3.3.</span> <span class="nav-text">write</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#position"><span class="nav-number">3.4.</span> <span class="nav-text">position</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#size"><span class="nav-number">3.5.</span> <span class="nav-text">size</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#truncate"><span class="nav-number">3.6.</span> <span class="nav-text">truncate</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#force"><span class="nav-number">3.7.</span> <span class="nav-text">force</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#transferTo"><span class="nav-number">3.8.</span> <span class="nav-text">transferTo</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#transferFrom"><span class="nav-number">3.9.</span> <span class="nav-text">transferFrom</span></a></li></ol></li><li class="nav-item nav-level-2"><a class="nav-link" href="#SocketChannel"><span class="nav-number">4.</span> <span class="nav-text">SocketChannel</span></a><ol class="nav-child"><li class="nav-item nav-level-3"><a class="nav-link" href="#open-1"><span class="nav-number">4.1.</span> <span class="nav-text">open</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#connect"><span class="nav-number">4.2.</span> <span class="nav-text">connect</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#configureBlocking"><span class="nav-number">4.3.</span> <span class="nav-text">configureBlocking</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#register"><span class="nav-number">4.4.</span> <span class="nav-text">register</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#read-1"><span class="nav-number">4.5.</span> <span class="nav-text">read</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#write-1"><span class="nav-number">4.6.</span> <span class="nav-text">write</span></a></li></ol></li><li class="nav-item nav-level-2"><a class="nav-link" href="#ServerSocketChannel"><span class="nav-number">5.</span> <span class="nav-text">ServerSocketChannel</span></a><ol class="nav-child"><li class="nav-item nav-level-3"><a class="nav-link" href="#socket"><span class="nav-number">5.1.</span> <span class="nav-text">socket</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#bind"><span class="nav-number">5.2.</span> <span class="nav-text">bind</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#accept"><span class="nav-number">5.3.</span> <span class="nav-text">accept</span></a></li></ol></li><li class="nav-item nav-level-2"><a class="nav-link" href="#DatagramChannel"><span class="nav-number">6.</span> <span 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var start = position - 20;
var end = position + 80;
if(start < 0){
start = 0;
}
if (end < position + word.length) {
end = position + word.length;
}
if(end > content.length){
end = content.length;
}
slicesOfContent.push(mergeIntoSlice(content, start, end, indexOfContent));
}
// sort slices in content by search text's count and hits' count
slicesOfContent.sort(function (sliceLeft, sliceRight) {
if (sliceLeft.searchTextCount !== sliceRight.searchTextCount) {
return sliceRight.searchTextCount - sliceLeft.searchTextCount;
} else if (sliceLeft.hits.length !== sliceRight.hits.length) {
return sliceRight.hits.length - sliceLeft.hits.length;
} else {
return sliceLeft.start - sliceRight.start;
}
});
// select top N slices in content
var upperBound = parseInt('1');
if (upperBound >= 0) {
slicesOfContent = slicesOfContent.slice(0, upperBound);
}
// highlight title and content
function highlightKeyword(text, slice) {
var result = '';
var prevEnd = slice.start;
slice.hits.forEach(function (hit) {
result += text.substring(prevEnd, hit.position);
var end = hit.position + hit.length;
result += '<b class="search-keyword">' + text.substring(hit.position, end) + '</b>';
prevEnd = end;
});
result += text.substring(prevEnd, slice.end);
return result;
}
var resultItem = '';
if (slicesOfTitle.length != 0) {
resultItem += "<li><a href='" + articleUrl + "' class='search-result-title'>" + highlightKeyword(title, slicesOfTitle[0]) + "</a>";
} else {
resultItem += "<li><a href='" + articleUrl + "' class='search-result-title'>" + title + "</a>";
}
slicesOfContent.forEach(function (slice) {
resultItem += "<a href='" + articleUrl + "'>" +
"<p class=\"search-result\">" + highlightKeyword(content, slice) +
"...</p>" + "</a>";
});
resultItem += "</li>";
resultItems.push({
item: resultItem,
searchTextCount: searchTextCount,
hitCount: hitCount,
id: resultItems.length
});
}
})
};
if (keywords.length === 1 && keywords[0] === "") {
resultContent.innerHTML = '<div id="no-result"><i class="fa fa-search fa-5x" /></div>'
} else if (resultItems.length === 0) {
resultContent.innerHTML = '<div id="no-result"><i class="fa fa-frown-o fa-5x" /></div>'
} else {
resultItems.sort(function (resultLeft, resultRight) {
if (resultLeft.searchTextCount !== resultRight.searchTextCount) {
return resultRight.searchTextCount - resultLeft.searchTextCount;
} else if (resultLeft.hitCount !== resultRight.hitCount) {
return resultRight.hitCount - resultLeft.hitCount;
} else {
return resultRight.id - resultLeft.id;
}
});
var searchResultList = '<ul class=\"search-result-list\">';
resultItems.forEach(function (result) {
searchResultList += result.item;
})
searchResultList += "</ul>";
resultContent.innerHTML = searchResultList;
}
}
if ('auto' === 'auto') {
input.addEventListener('input', inputEventFunction);
} else {
$('.search-icon').click(inputEventFunction);
input.addEventListener('keypress', function (event) {
if (event.keyCode === 13) {
inputEventFunction();
}
});
}
// remove loading animation
$(".local-search-pop-overlay").remove();
$('body').css('overflow', '');
proceedsearch();
}
});
}
// handle and trigger popup window;
$('.popup-trigger').click(function(e) {
e.stopPropagation();
if (isfetched === false) {
searchFunc(path, 'local-search-input', 'local-search-result');
} else {
proceedsearch();
};
});
$('.popup-btn-close').click(onPopupClose);
$('.popup').click(function(e){
e.stopPropagation();
});
$(document).on('keyup', function (event) {
var shouldDismissSearchPopup = event.which === 27 &&
$('.search-popup').is(':visible');
if (shouldDismissSearchPopup) {
onPopupClose();
}
});
</script><script>!function(){var t=document.createElement("script"),e=window.location.protocol.split(":")[0];t.src="https"===e?"https://zz.bdstatic.com/linksubmit/push.js":"http://push.zhanzhang.baidu.com/push.js";var s=document.getElementsByTagName("script")[0];s.parentNode.insertBefore(t,s)}()</script></body></html>