a00015.html

这是一个用于创建多线程的程序

<span class="comment"> * Declaration of the protothread function implementing the code lock</span>
<span class="comment"> * logic. The protothread function is declared using the PT_THREAD()</span>
<span class="comment"> * macro. The function is declared with the "static" keyword since it</span>
<span class="comment"> * is local to this file. The name of the function is codelock_thread</span>
<span class="comment"> * and it takes one argument, pt, of the type struct pt.</span>
<span class="comment"> *</span>
<span class="comment"> */</span>
<span class="keyword">static</span>
<a class="code" href="a00014.html#g3d4c8bd4aada659eb34f5d2ffd3e7901">PT_THREAD</a>(codelock_thread(<span class="keyword">struct</span> pt *pt))
{
  <span class="comment">/* This is a local variable that holds the number of keys that have</span>
<span class="comment">   * been pressed. Note that it is declared with the "static" keyword</span>
<span class="comment">   * to make sure that the variable is *not* allocated on the stack.</span>
<span class="comment">   */</span>
  <span class="keyword">static</span> <span class="keywordtype">int</span> keys;

  <span class="comment">/*</span>
<span class="comment">   * Declare the beginning of the protothread.</span>
<span class="comment">   */</span>
  <a class="code" href="a00014.html#g2ffbb9e554e08a343ae2f9de4bedfdfc">PT_BEGIN</a>(pt);

  <span class="comment">/*</span>
<span class="comment">   * We'll let the protothread loop until the protothread is</span>
<span class="comment">   * expliticly exited with PT_EXIT().</span>
<span class="comment">   */</span>
  <span class="keywordflow">while</span>(1) {

    <span class="comment">/*</span>
<span class="comment">     * We'll be reading key presses until we get the right amount of</span>
<span class="comment">     * correct keys.</span>
<span class="comment">     */</span> 
    <span class="keywordflow">for</span>(keys = 0; keys &lt; <span class="keyword">sizeof</span>(code); ++keys) {

      <span class="comment">/*</span>
<span class="comment">       * If we haven't gotten any keypresses, we'll simply wait for one.</span>
<span class="comment">       */</span>
      <span class="keywordflow">if</span>(keys == 0) {

        <span class="comment">/*</span>
<span class="comment">         * The PT_WAIT_UNTIL() function will block until the condition</span>
<span class="comment">         * key_pressed() is true.</span>
<span class="comment">         */</span>
        <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, key_pressed());
      } <span class="keywordflow">else</span> {
        
        <span class="comment">/*</span>
<span class="comment">         * If the "key" variable was larger than zero, we have already</span>
<span class="comment">         * gotten at least one correct key press. If so, we'll not</span>
<span class="comment">         * only wait for the next key, but we'll also set a timer that</span>
<span class="comment">         * expires in one second. This gives the person pressing the</span>
<span class="comment">         * keys one second to press the next key in the code.</span>
<span class="comment">         */</span>
        timer_set(&amp;codelock_timer, 1000);

        <span class="comment">/*</span>
<span class="comment">         * The following statement shows how complex blocking</span>
<span class="comment">         * conditions can be easily expressed with protothreads and</span>
<span class="comment">         * the PT_WAIT_UNTIL() function.</span>
<span class="comment">         */</span>
        <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, key_pressed() || timer_expired(&amp;codelock_timer));

        <span class="comment">/*</span>
<span class="comment">         * If the timer expired, we should break out of the for() loop</span>
<span class="comment">         * and start reading keys from the beginning of the while(1)</span>
<span class="comment">         * loop instead.</span>
<span class="comment">         */</span>
        <span class="keywordflow">if</span>(timer_expired(&amp;codelock_timer)) {
          printf(<span class="stringliteral">"Code lock timer expired.\n"</span>);
          
          <span class="comment">/*</span>
<span class="comment">           * Break out from the for() loop and start from the</span>
<span class="comment">           * beginning of the while(1) loop.</span>
<span class="comment">           */</span>
          <span class="keywordflow">break</span>;
        }
      }

      <span class="comment">/*</span>
<span class="comment">       * Check if the pressed key was correct.</span>
<span class="comment">       */</span>
      <span class="keywordflow">if</span>(key != code[keys]) {
        printf(<span class="stringliteral">"Incorrect key '%c' found\n"</span>, key);
        <span class="comment">/*</span>
<span class="comment">         * Break out of the for() loop since the key was incorrect.</span>
<span class="comment">         */</span>
        <span class="keywordflow">break</span>;
      } <span class="keywordflow">else</span> {
        printf(<span class="stringliteral">"Correct key '%c' found\n"</span>, key);
      }
    }

    <span class="comment">/*</span>
<span class="comment">     * Check if we have gotten all keys.</span>
<span class="comment">     */</span>
    <span class="keywordflow">if</span>(keys == <span class="keyword">sizeof</span>(code)) {
      printf(<span class="stringliteral">"Correct code entered, waiting for 500 ms before unlocking.\n"</span>);

      <span class="comment">/*</span>
<span class="comment">       * Ok, we got the correct code. But to make sure that the code</span>
<span class="comment">       * was not just a fluke of luck by an intruder, but the correct</span>
<span class="comment">       * code entered by a person that knows the correct code, we'll</span>
<span class="comment">       * wait for half a second before opening the lock. If another</span>
<span class="comment">       * key is pressed during this time, we'll assume that it was a</span>
<span class="comment">       * fluke of luck that the correct code was entered the first</span>
<span class="comment">       * time.</span>
<span class="comment">       */</span>
      timer_set(&amp;codelock_timer, 500);      
      <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, key_pressed() || timer_expired(&amp;codelock_timer));

      <span class="comment">/*</span>
<span class="comment">       * If we continued from the PT_WAIT_UNTIL() statement without</span>
<span class="comment">       * the timer expired, we don't open the lock.</span>
<span class="comment">       */</span>
      <span class="keywordflow">if</span>(!timer_expired(&amp;codelock_timer)) {
        printf(<span class="stringliteral">"Key pressed during final wait, code lock locked again.\n"</span>);
      } <span class="keywordflow">else</span> {

        <span class="comment">/*</span>
<span class="comment">         * If the timer expired, we'll open the lock and exit from the</span>
<span class="comment">         * protothread.</span>
<span class="comment">         */</span>
        printf(<span class="stringliteral">"Code lock unlocked.\n"</span>);
        <a class="code" href="a00014.html#g905451249dca72ce0385bf2a9ff178ee">PT_EXIT</a>(pt);
      }
    }
  }

  <span class="comment">/*</span>
<span class="comment">   * Finally, we'll mark the end of the protothread.</span>
<span class="comment">   */</span>
  <a class="code" href="a00014.html#g7b04a0035bef29d905496c23bae066d2">PT_END</a>(pt);
}
<span class="comment">/*---------------------------------------------------------------------------*/</span>
<span class="comment">/*</span>
<span class="comment"> * This is the second protothread in this example. It implements a</span>
<span class="comment"> * simulated user pressing the keys. This illustrates how a linear</span>
<span class="comment"> * sequence of timed instructions can be implemented with</span>
<span class="comment"> * protothreads.</span>
<span class="comment"> */</span>
<span class="keyword">static</span>
<a class="code" href="a00014.html#g3d4c8bd4aada659eb34f5d2ffd3e7901">PT_THREAD</a>(input_thread(<span class="keyword">struct</span> pt *pt))
{
  <a class="code" href="a00014.html#g2ffbb9e554e08a343ae2f9de4bedfdfc">PT_BEGIN</a>(pt);

  printf(<span class="stringliteral">"Waiting 1 second before entering first key.\n"</span>);
  
  timer_set(&amp;input_timer, 1000);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));

  press_key(<span class="charliteral">'1'</span>);
  
  timer_set(&amp;input_timer, 100);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'2'</span>);

  timer_set(&amp;input_timer, 100);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'3'</span>);

  timer_set(&amp;input_timer, 2000);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'1'</span>);

  timer_set(&amp;input_timer, 200);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'4'</span>);

  timer_set(&amp;input_timer, 200);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'2'</span>);
  
  timer_set(&amp;input_timer, 2000);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'3'</span>);

  timer_set(&amp;input_timer, 200);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'1'</span>);

  timer_set(&amp;input_timer, 200);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'4'</span>);

  timer_set(&amp;input_timer, 200);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'2'</span>);
  
  timer_set(&amp;input_timer, 100);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'3'</span>);

  timer_set(&amp;input_timer, 100);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'4'</span>);

  timer_set(&amp;input_timer, 1500);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'1'</span>);

  timer_set(&amp;input_timer, 300);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'4'</span>);

  timer_set(&amp;input_timer, 400);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'2'</span>);

  timer_set(&amp;input_timer, 500);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  press_key(<span class="charliteral">'3'</span>);

  timer_set(&amp;input_timer, 2000);
  <a class="code" href="a00014.html#g99e43010ec61327164466aa2d902de45">PT_WAIT_UNTIL</a>(pt, timer_expired(&amp;input_timer));
  
  <a class="code" href="a00014.html#g7b04a0035bef29d905496c23bae066d2">PT_END</a>(pt);
}
<span class="comment">/*---------------------------------------------------------------------------*/</span>
<span class="comment">/*</span>
<span class="comment"> * This is the main function. It initializes the two protothread</span>
<span class="comment"> * control structures and schedules the two protothreads. The main</span>
<span class="comment"> * function returns when the protothread the runs the code lock exits.</span>
<span class="comment"> */</span>
<span class="keywordtype">int</span>