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<meta name="description" content=" 一次性操作 - sync.Once # sync.Once用来完成一次性操作，比如配置加载，单例对象初始化等。
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源码分析 # sync.Once定义如下：
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type Once struct { done uint32 // 用来标志操作是否操作 m Mutex // 锁，用来第一操作时候，加锁处理 } 接下来看剩下的全部代码：
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func (o *Once) Do(f func()) { if atomic.LoadUint32(&o.done) == 0 {// 原子性加载o.done，若值为1，说明已完成操作，若为0，说明未完成操作 o.doSlow(f) } } func (o *Once) doSlow(f func()) { o.m.Lock() // 加锁 defer o.m.Unlock() if o.done == 0 { // 再次进行o.done是否等于0判断，因为存在并发调用doSlow的情况 defer atomic.StoreUint32(&o.done, 1) // 将o.done值设置为1，用来标志操作完成 f() // 执行操作 } } ">
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<meta property="og:description" content=" 一次性操作 - sync.Once # sync.Once用来完成一次性操作，比如配置加载，单例对象初始化等。
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源码分析 # sync.Once定义如下：
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type Once struct { done uint32 // 用来标志操作是否操作 m Mutex // 锁，用来第一操作时候，加锁处理 } 接下来看剩下的全部代码：
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func (o *Once) Do(f func()) { if atomic.LoadUint32(&o.done) == 0 {// 原子性加载o.done，若值为1，说明已完成操作，若为0，说明未完成操作 o.doSlow(f) } } func (o *Once) doSlow(f func()) { o.m.Lock() // 加锁 defer o.m.Unlock() if o.done == 0 { // 再次进行o.done是否等于0判断，因为存在并发调用doSlow的情况 defer atomic.StoreUint32(&o.done, 1) // 将o.done值设置为1，用来标志操作完成 f() // 执行操作 } } " />
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<strong>一次性操作 - sync.Once</strong>
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<article class="markdown"><h1 id="一次性操作---synconce">
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一次性操作 - sync.Once
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<a class="anchor" href="#%e4%b8%80%e6%ac%a1%e6%80%a7%e6%93%8d%e4%bd%9c---synconce">#</a>
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</h1>
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<p>sync.Once用来完成一次性操作，比如配置加载，单例对象初始化等。</p>
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<h2 id="源码分析">
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源码分析
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<a class="anchor" href="#%e6%ba%90%e7%a0%81%e5%88%86%e6%9e%90">#</a>
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</h2>
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<p>sync.Once定义如下：</p>
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<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-go" data-lang="go"><span style="display:flex;"><span><span style="color:#66d9ef">type</span> <span style="color:#a6e22e">Once</span> <span style="color:#66d9ef">struct</span> {
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</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">done</span> <span style="color:#66d9ef">uint32</span> <span style="color:#75715e">// 用来标志操作是否操作
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</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span> <span style="color:#a6e22e">m</span> <span style="color:#a6e22e">Mutex</span> <span style="color:#75715e">// 锁，用来第一操作时候，加锁处理
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</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span>}
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</span></span></code></pre></div><p>接下来看剩下的全部代码：</p>
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<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-go" data-lang="go"><span style="display:flex;"><span><span style="color:#66d9ef">func</span> (<span style="color:#a6e22e">o</span> <span style="color:#f92672">*</span><span style="color:#a6e22e">Once</span>) <span style="color:#a6e22e">Do</span>(<span style="color:#a6e22e">f</span> <span style="color:#66d9ef">func</span>()) {
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</span></span><span style="display:flex;"><span> <span style="color:#66d9ef">if</span> <span style="color:#a6e22e">atomic</span>.<span style="color:#a6e22e">LoadUint32</span>(<span style="color:#f92672">&</span><span style="color:#a6e22e">o</span>.<span style="color:#a6e22e">done</span>) <span style="color:#f92672">==</span> <span style="color:#ae81ff">0</span> {<span style="color:#75715e">// 原子性加载o.done，若值为1，说明已完成操作，若为0，说明未完成操作
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</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span> <span style="color:#a6e22e">o</span>.<span style="color:#a6e22e">doSlow</span>(<span style="color:#a6e22e">f</span>)
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</span></span><span style="display:flex;"><span> }
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</span></span><span style="display:flex;"><span>}
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</span></span><span style="display:flex;"><span>
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</span></span><span style="display:flex;"><span><span style="color:#66d9ef">func</span> (<span style="color:#a6e22e">o</span> <span style="color:#f92672">*</span><span style="color:#a6e22e">Once</span>) <span style="color:#a6e22e">doSlow</span>(<span style="color:#a6e22e">f</span> <span style="color:#66d9ef">func</span>()) {
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</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">o</span>.<span style="color:#a6e22e">m</span>.<span style="color:#a6e22e">Lock</span>() <span style="color:#75715e">// 加锁
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</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span> <span style="color:#66d9ef">defer</span> <span style="color:#a6e22e">o</span>.<span style="color:#a6e22e">m</span>.<span style="color:#a6e22e">Unlock</span>()
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</span></span><span style="display:flex;"><span> <span style="color:#66d9ef">if</span> <span style="color:#a6e22e">o</span>.<span style="color:#a6e22e">done</span> <span style="color:#f92672">==</span> <span style="color:#ae81ff">0</span> { <span style="color:#75715e">// 再次进行o.done是否等于0判断，因为存在并发调用doSlow的情况
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</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span> <span style="color:#66d9ef">defer</span> <span style="color:#a6e22e">atomic</span>.<span style="color:#a6e22e">StoreUint32</span>(<span style="color:#f92672">&</span><span style="color:#a6e22e">o</span>.<span style="color:#a6e22e">done</span>, <span style="color:#ae81ff">1</span>) <span style="color:#75715e">// 将o.done值设置为1，用来标志操作完成
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</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span> <span style="color:#a6e22e">f</span>() <span style="color:#75715e">// 执行操作
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</span></span></span><span style="display:flex;"><span><span style="color:#75715e"></span> }
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</span></span><span style="display:flex;"><span>}
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</span></span></code></pre></div></article>
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