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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1"><title>The Protothreads Library 1.4: pt-sem.h Source File</title><link href="doxygen.css" rel="stylesheet" type="text/css"><link href="tabs.css" rel="stylesheet" type="text/css"></head><body><!-- Generated by Doxygen 1.4.6 --><div class="tabs"> <ul> <li><a href="main.html"><span>Main Page</span></a></li> <li><a href="modules.html"><span>Modules</span></a></li> <li><a href="annotated.html"><span>Data Structures</span></a></li> <li id="current"><a href="files.html"><span>Files</span></a></li> </ul></div><div class="tabs"> <ul> <li><a href="files.html"><span>File List</span></a></li> <li><a href="globals.html"><span>Globals</span></a></li> </ul></div><h1>pt-sem.h</h1><a href="a00012.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/*</span><a name="l00002"></a>00002 <span class="comment"> * Copyright (c) 2004, Swedish Institute of Computer Science.</span><a name="l00003"></a>00003 <span class="comment"> * All rights reserved. </span><a name="l00004"></a>00004 <span class="comment"> *</span><a name="l00005"></a>00005 <span class="comment"> * Redistribution and use in source and binary forms, with or without </span><a name="l00006"></a>00006 <span class="comment"> * modification, are permitted provided that the following conditions </span><a name="l00007"></a>00007 <span class="comment"> * are met: </span><a name="l00008"></a>00008 <span class="comment"> * 1. Redistributions of source code must retain the above copyright </span><a name="l00009"></a>00009 <span class="comment"> * notice, this list of conditions and the following disclaimer. </span><a name="l00010"></a>00010 <span class="comment"> * 2. Redistributions in binary form must reproduce the above copyright </span><a name="l00011"></a>00011 <span class="comment"> * notice, this list of conditions and the following disclaimer in the </span><a name="l00012"></a>00012 <span class="comment"> * documentation and/or other materials provided with the distribution. </span><a name="l00013"></a>00013 <span class="comment"> * 3. Neither the name of the Institute nor the names of its contributors </span><a name="l00014"></a>00014 <span class="comment"> * may be used to endorse or promote products derived from this software </span><a name="l00015"></a>00015 <span class="comment"> * without specific prior written permission. </span><a name="l00016"></a>00016 <span class="comment"> *</span><a name="l00017"></a>00017 <span class="comment"> * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND </span><a name="l00018"></a>00018 <span class="comment"> * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE </span><a name="l00019"></a>00019 <span class="comment"> * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE </span><a name="l00020"></a>00020 <span class="comment"> * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE </span><a name="l00021"></a>00021 <span class="comment"> * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL </span><a name="l00022"></a>00022 <span class="comment"> * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS </span><a name="l00023"></a>00023 <span class="comment"> * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) </span><a name="l00024"></a>00024 <span class="comment"> * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT </span><a name="l00025"></a>00025 <span class="comment"> * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY </span><a name="l00026"></a>00026 <span class="comment"> * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF </span><a name="l00027"></a>00027 <span class="comment"> * SUCH DAMAGE. </span><a name="l00028"></a>00028 <span class="comment"> *</span><a name="l00029"></a>00029 <span class="comment"> * This file is part of the protothreads library.</span><a name="l00030"></a>00030 <span class="comment"> * </span><a name="l00031"></a>00031 <span class="comment"> * Author: Adam Dunkels <adam@sics.se></span><a name="l00032"></a>00032 <span class="comment"> *</span><a name="l00033"></a>00033 <span class="comment"> * $Id: pt-sem.h,v 1.2 2005/02/24 10:36:59 adam Exp $</span><a name="l00034"></a>00034 <span class="comment"> */</span><a name="l00035"></a>00035 <span class="comment"></span><a name="l00036"></a>00036 <span class="comment">/**</span><a name="l00037"></a>00037 <span class="comment"> * \addtogroup pt</span><a name="l00038"></a>00038 <span class="comment"> * @{</span><a name="l00039"></a>00039 <span class="comment"> */</span><a name="l00040"></a>00040 <span class="comment"></span><a name="l00041"></a>00041 <span class="comment">/**</span><a name="l00042"></a>00042 <span class="comment"> * \defgroup ptsem Protothread semaphores</span><a name="l00043"></a>00043 <span class="comment"> * @{</span><a name="l00044"></a>00044 <span class="comment"> *</span><a name="l00045"></a>00045 <span class="comment"> * This module implements counting semaphores on top of</span><a name="l00046"></a>00046 <span class="comment"> * protothreads. Semaphores are a synchronization primitive that</span><a name="l00047"></a>00047 <span class="comment"> * provide two operations: "wait" and "signal". The "wait" operation</span><a name="l00048"></a>00048 <span class="comment"> * checks the semaphore counter and blocks the thread if the counter</span><a name="l00049"></a>00049 <span class="comment"> * is zero. The "signal" operation increases the semaphore counter but</span><a name="l00050"></a>00050 <span class="comment"> * does not block. If another thread has blocked waiting for the</span><a name="l00051"></a>00051 <span class="comment"> * semaphore that is signalled, the blocked thread will become</span><a name="l00052"></a>00052 <span class="comment"> * runnable again.</span><a name="l00053"></a>00053 <span class="comment"> *</span><a name="l00054"></a>00054 <span class="comment"> * Semaphores can be used to implement other, more structured,</span><a name="l00055"></a>00055 <span class="comment"> * synchronization primitives such as monitors and message</span><a name="l00056"></a>00056 <span class="comment"> * queues/bounded buffers (see below).</span><a name="l00057"></a>00057 <span class="comment"> *</span><a name="l00058"></a>00058 <span class="comment"> * The following example shows how the producer-consumer problem, also</span><a name="l00059"></a>00059 <span class="comment"> * known as the bounded buffer problem, can be solved using</span><a name="l00060"></a>00060 <span class="comment"> * protothreads and semaphores. Notes on the program follow after the</span><a name="l00061"></a>00061 <span class="comment"> * example.</span><a name="l00062"></a>00062 <span class="comment"> *</span><a name="l00063"></a>00063 <span class="comment"> \code</span><a name="l00064"></a>00064 <span class="comment">#include "pt-sem.h"</span><a name="l00065"></a>00065 <span class="comment"></span><a name="l00066"></a>00066 <span class="comment">#define NUM_ITEMS 32</span><a name="l00067"></a>00067 <span class="comment">#define BUFSIZE 8</span><a name="l00068"></a>00068 <span class="comment"></span><a name="l00069"></a>00069 <span class="comment">static struct pt_sem mutex, full, empty;</span><a name="l00070"></a>00070 <span class="comment"></span><a name="l00071"></a>00071 <span class="comment">PT_THREAD(producer(struct pt *pt))</span><a name="l00072"></a>00072 <span class="comment">{</span><a name="l00073"></a>00073 <span class="comment"> static int produced;</span><a name="l00074"></a>00074 <span class="comment"> </span><a name="l00075"></a>00075 <span class="comment"> PT_BEGIN(pt);</span><a name="l00076"></a>00076 <span class="comment"> </span><a name="l00077"></a>00077 <span class="comment"> for(produced = 0; produced < NUM_ITEMS; ++produced) {</span><a name="l00078"></a>00078 <span class="comment"> </span><a name="l00079"></a>00079 <span class="comment"> PT_SEM_WAIT(pt, &full);</span><a name="l00080"></a>00080 <span class="comment"> </span><a name="l00081"></a>00081 <span class="comment"> PT_SEM_WAIT(pt, &mutex);</span><a name="l00082"></a>00082 <span class="comment"> add_to_buffer(produce_item()); </span><a name="l00083"></a>00083 <span class="comment"> PT_SEM_SIGNAL(pt, &mutex);</span><a name="l00084"></a>00084 <span class="comment"> </span><a name="l00085"></a>00085 <span class="comment"> PT_SEM_SIGNAL(pt, &empty);</span><a name="l00086"></a>00086 <span class="comment"> }</span><a name="l00087"></a>00087 <span class="comment"></span><a name="l00088"></a>00088 <span class="comment"> PT_END(pt);</span><a name="l00089"></a>00089 <span class="comment">}</span><a name="l00090"></a>00090 <span class="comment"></span><a name="l00091"></a>00091 <span class="comment">PT_THREAD(consumer(struct pt *pt))</span><a name="l00092"></a>00092 <span class="comment">{</span><a name="l00093"></a>00093 <span class="comment"> static int consumed;</span><a name="l00094"></a>00094 <span class="comment"> </span><a name="l00095"></a>00095 <span class="comment"> PT_BEGIN(pt);</span><a name="l00096"></a>00096 <span class="comment"></span><a name="l00097"></a>00097 <span class="comment"> for(consumed = 0; consumed < NUM_ITEMS; ++consumed) {</span><a name="l00098"></a>00098 <span class="comment"> </span><a name="l00099"></a>00099 <span class="comment"> PT_SEM_WAIT(pt, &empty);</span><a name="l00100"></a>00100 <span class="comment"> </span><a name="l00101"></a>00101 <span class="comment"> PT_SEM_WAIT(pt, &mutex); </span><a name="l00102"></a>00102 <span class="comment"> consume_item(get_from_buffer()); </span><a name="l00103"></a>00103 <span class="comment"> PT_SEM_SIGNAL(pt, &mutex);</span><a name="l00104"></a>00104 <span class="comment"> </span><a name="l00105"></a>00105 <span class="comment"> PT_SEM_SIGNAL(pt, &full);</span><a name="l00106"></a>00106 <span class="comment"> }</span><a name="l00107"></a>00107 <span class="comment"></span><a name="l00108"></a>00108 <span class="comment"> PT_END(pt);</span>⌨️ 快捷键说明
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