[boost-doc-zh] r291 committed - [No log message]

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Date: Mon Aug 24 20:07:05 2009
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http://code.google.com/p/boost-doc-zh/source/detail?r=291

Modified:
 /trunk/doc/html/boost_asio/tutorial/tuttimer3.html

=======================================

--- /trunk/doc/html/boost_asio/tutorial/tuttimer3.html Wed May 27 03:09:502009+++ /trunk/doc/html/boost_asio/tutorial/tuttimer3.html Mon Aug 24 20:07:052009

@@ -1,6 +1,6 @@
 <html>
 <head>
-<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
+<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 <title>Timer.3 - Binding arguments to a handler</title>
 <link rel="stylesheet" href="../../boostbook.css" type="text/css">
 <meta name="generator" content="DocBook XSL Stylesheets V1.74.3">
@@ -24,13 +24,10 @@
 </div>
 <div class="section" lang="en">
 <div class="titlepage"><div><div><h3 class="title">

-<a name="boost_asio.tutorial.tuttimer3"></a><a class="link"href="tuttimer3.html" title="Timer.3 - Binding arguments to a handler">Timer.3 - Binding arguments

-      to a handler</a>

+<a name="boost_asio.tutorial.tuttimer3"></a><a class="link"href="tuttimer3.html" title="Timer.3 - Binding arguments to a handler">Timer.3 - 回调函数绑定参数</a>

 </h3></div></div></div>
 <p>

- In this tutorial we will modify the program from tutorial Timer.2so that- the timer fires once a second. This will show how to passadditional parameters

-        to your handler function.

+ 在本示例程序中我们将修改Timer.2中的例子，使定时器每秒被激活一次。例子将示范如何给你的函数指针传递附加参数。

       </p>

<pre class="programlisting">#include<<spanclass="identifier">iostream>#include <spanclass="special"><boost<spanclass="special">/asio<spanclass="special">.hpp<spanclass="special">>

@@ -38,19 +35,15 @@

#include <spanclass="special"><boost<spanclass="special">/date_time<spanclass="special">/posix_time<spanclass="special">/posix_time<spanclass="special">.hpp<spanclass="special">>

 </pre>
 <p>

- To implement a repeating timer using asio you need to change thetimer's- expiry time in your callback function, and to then start a newasynchronous- wait. Obviously this means that the callback function will need tobe able- to access the timer object. To this end we add two new parametersto the- <code class="computeroutput"><spanclass="identifier">print</code> function:+ 使用Asio实现一个重复定时器，你必须在你的回调函数中去改变定时器的终止时间，然后开始一个新的异步等待。显然这意味着回调函数必须拥有改变定时器对象的权限。为此我们为+ <code class="computeroutput"><spanclass="identifier">print</code>函数增加两个新参数:

       </p>
 <div class="itemizedlist"><ul type="disc">
 <li>
-          A pointer to a timer object.
+          一个指向定时器对象的指针。
         </li>
 <li>

- A counter so that we can stop the program when the timer firesfor the

-          sixth time.
+          一个用于当定时器第6次被激活时我们可以中止程序的计数器。
         </li>
 </ul></div>

<pre class="programlisting">void <spanclass="identifier">print(<spanclass="keyword">const boost<spanclass="special">::system<spanclass="special">::error_code<spanclass="special">& /*e*/<spanclass="special">,

@@ -58,13 +51,9 @@
 <span class="special">{</span>
 </pre>
 <p>

- As mentioned above, this tutorial program uses a counter to stoprunning- when the timer fires for the sixth time. However you will observethat there- is no explicit call to ask the io_service to stop. Recall that intutorial- Timer.2 we learnt that the <a class="link"href="../reference/io_service/run.html"title="io_service::run">io_service::run()</a>- function completes when there is no more "work" to do. By notstarting- a new asynchronous wait on the timer when <codeclass="computeroutput">count</code>

-        reaches 5, the io_service will run out of work and stop running.

+ 如上所示，示例程序使用了一个计数器,当定时器被第6次激活时，用来中止程序。然而，你将看到这里并没有显式地要求io_service对象中止。回忆示例2中，当没有更多“工作”去做时，<a class="link"href="../reference/io_service/run.html"title="io_service::run">io_service::run()</a>+ 函数完成。在计数器<code class="computeroutput"><spanclass="identifier">达到</code>+ 5时，定时器并没有启动一个新的异步等待。该io_service执行完工作后停止运行。

       </p>

<pre class="programlisting"> if <spanclass="special">(*count <spanclass="special">< 5<spanclass="special">)

   <span class="special">{</span>
@@ -72,33 +61,22 @@

++(*<spanclass="identifier">count);

 </pre>
 <p>

- Next we move the expiry time for the timer along by one secondfrom the previous- expiry time. By calculating the new expiry time relative to theold, we can- ensure that the timer does not drift away from the whole-secondmark due

-        to any delays in processing the handler.

+ 接着，我们推迟定时器的终止时间。通过在原先的终止时间上增加延时，我们可以确保定时器不会在处理回调函数所需时间内到期。

       </p>

<pre class="programlisting"> t<spanclass="special">->expires_at<spanclass="special">(t<spanclass="special">->expires_at<spanclass="special">() + <spanclass="identifier">boost::<spanclass="identifier">posix_time::<spanclass="identifier">seconds(<spanclass="number">1));

 </pre>
 <p>

- Then we start a new asynchronous wait on the timer. As you cansee, the boost::bind()- function is used to associate the extra parameters with yourcallback handler.- The <a class="link"href="../reference/basic_deadline_timer/async_wait.html"title="basic_deadline_timer::async_wait">deadline_timer::async_wait()</a>- function expects a handler function (or function object) with thesignature- <code class="computeroutput"><spanclass="keyword">void(<spanclass="keyword">const boost<spanclass="special">::system<spanclass="special">::error_code<spanclass="special">&)</code>. Binding the additional parameters- converts your <code class="computeroutput"><spanclass="identifier">print</code> function

-        into a function object that matches the signature correctly.

+ 接着我们在定时器中启动一个新的异步等待。我们必须使用boost::bind()函数给你的回调函数绑定额外的参数，因为<a class="link"href="../reference/basic_deadline_timer/async_wait.html"title="basic_deadline_timer::async_wait">deadline_timer::async_wait()</a>

+        函数只期望得到一个拥用

+ <code class="computeroutput"><spanclass="keyword">void(<spanclass="keyword">const boost<spanclass="special">::system<spanclass="special">::error_code<spanclass="special">&)</code>+ 签名的函数指针（或函数对象）。为你的<codeclass="computeroutput">print</code>函数绑定附加的参数后，它就成为与签名精确匹配的函数对象。

       </p>
 <p>

- See the <a href="http://www.boost.org/libs/bind/bind.html";target="_top">Boost.Bind

-        documentation</a> for more information on how to use boost::bind().

+ 查看<a href="http://www.boost.org/libs/bind/bind.html";target="_top">Boost.Bind

+        文档</a>文档以获得更多如何使用boost::bind()的信息。
       </p>
 <p>

- In this example, the boost::asio::placeholders::error argument toboost::bind()- is a named placeholder for the error object passed to the handler.When initiating- the asynchronous operation, and if using boost::bind(), you mustspecify- only the arguments that match the handler's parameter list. Intutorial Timer.4- you will see that this placeholder may be elided if the parameteris not

-        needed by the callback handler.

+ 在本例中，boost::bind（）的boost::asio::placeholders::error参数是为了给回调函数传入一个error对象。当开始异步操作时，如果使用boost::bind()，你必须指定和回调函数的参数列表相匹配的一个参数。在示例4中，如果在回调函数中，这个参数不是必需的，这个占位符会被省略。

       </p>

<pre class="programlisting"> t<spanclass="special">->async_wait<spanclass="special">(boost<spanclass="special">::bind<spanclass="special">(print<spanclass="special">,boost<spanclass="special">::asio<spanclass="special">::placeholders<spanclass="special">::error<spanclass="special">, t<spanclass="special">, count<spanclass="special">));

@@ -110,17 +88,14 @@

boost<spanclass="special">::asio<spanclass="special">::io_service <spanclass="identifier">io;

 </pre>
 <p>

- A new <code class="computeroutput"><spanclass="identifier">count</code> variable is added- so that we can stop the program when the timer fires for the sixthtime.+ 为了在定时器第6次被激活时终止程序，我们添加一个新的<codeclass="computeroutput">count</code>变量。

       </p>

<pre class="programlisting"> int <spanclass="identifier">count = <spanclass="number">0;boost<spanclass="special">::asio<spanclass="special">::deadline_timert(<spanclass="identifier">io, <spanclass="identifier">boost::<spanclass="identifier">posix_time::<spanclass="identifier">seconds(<spanclass="number">1));

 </pre>
 <p>

- As in Step 4, when making the call to <a class="link"href="../reference/basic_deadline_timer/async_wait.html"title="basic_deadline_timer::async_wait">deadline_timer::async_wait()</a>- from <code class="computeroutput"><spanclass="identifier">main</code> we bind the additional- parameters needed for the <code class="computeroutput"><spanclass="identifier">print</code>

-        function.

+ 在第四步中，当在<code class="computeroutput"><spanclass="identifier">主函数</code>中的调用<a class="link"href="../reference/basic_deadline_timer/async_wait.html"title="basic_deadline_timer::async_wait">deadline_timer::async_wait()</a>+ 函数时，我们绑定<code class="computeroutput"><spanclass="identifier">print</code>函数所需要的附加参数。

       </p>

<pre class="programlisting"> t<spanclass="special">.async_wait<spanclass="special">(boost<spanclass="special">::bind<spanclass="special">(print<spanclass="special">,boost<spanclass="special">::asio<spanclass="special">::placeholders<spanclass="special">::error<spanclass="special">, &<spanclass="identifier">t, <spanclass="special">&count<spanclass="special">));

@@ -128,9 +103,9 @@

io.<spanclass="identifier">run();

 </pre>
 <p>

- Finally, just to prove that the <code class="computeroutput"><spanclass="identifier">count</code>- variable was being used in the <code class="computeroutput"><spanclass="identifier">print</code>

-        handler function, we will print out its new value.

+ 最后，为了证明<code class="computeroutput"><spanclass="identifier">count</code>+ 变量在<code class="computeroutput"><spanclass="identifier">print</code>

+        函数句柄中被使用，我们打印出它的值。
       </p>

<pre class="programlisting"> std<spanclass="special">::cout <spanclass="special"><< "Final countis " << <spanclass="identifier">count << <spanclass="string">"\n";


@@ -138,18 +113,16 @@
 <span class="special">}</span>
 </pre>
 <p>

- See the <a class="link" href="tuttimer3/src.html" title="Sourcelisting for Timer.3">full source listing</a>+ 查看<a class="link" href="tuttimer3/src.html" title="Sourcelisting for Timer.3">本例全部源代码</a>

       </p>
 <p>

- Return to the <a class="link" href="../tutorial.html"title="Tutorial">tutorial index</a>+ 返回<a class="link" href="../tutorial.html" title="Tutorial">指南</a>

       </p>
 <p>

- Previous: <a class="link" href="tuttimer2.html" title="Timer.2 -Using a timer asynchronously">Timer.2 - Using a

-        timer asynchronously</a>

+ 前一例: <a class="link" href="tuttimer2.html" title="Timer.2 -Using a timer asynchronously">Timer.2 - 使用异步定时器</a>

       </p>
 <p>

- Next: <a class="link" href="tuttimer4.html" title="Timer.4 - Usinga member function as a handler">Timer.4 - Using a member

-        function as a handler</a>

+ 后一例: <a class="link" href="tuttimer4.html" title="Timer.4 -Using a member function as a handler">Timer.4 - 成员函数作为回调函数</a>

       </p>
 </div>

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