📄 a00018.html
字号:
<!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 1.0: pt-sem.h Source File</title><link href="doxygen.css" rel="stylesheet" type="text/css"></head><body><!-- Generated by Doxygen 1.3.6 --><div class="qindex"><a class="qindex" href="main.html">Main Page</a> | <a class="qindex" href="modules.html">Modules</a> | <a class="qindex" href="files.html">File List</a> | <a class="qindex" href="globals.html">Globals</a></div><h1>pt-sem.h</h1><a href="a00010.html">Go to the documentation of this file.</a><div class="fragment"><pre>00001 <span class="comment">/*</span>00002 <span class="comment"> * Copyright (c) 2004, Swedish Institute of Computer Science.</span>00003 <span class="comment"> * All rights reserved. </span>00004 <span class="comment"> *</span>00005 <span class="comment"> * Redistribution and use in source and binary forms, with or without </span>00006 <span class="comment"> * modification, are permitted provided that the following conditions </span>00007 <span class="comment"> * are met: </span>00008 <span class="comment"> * 1. Redistributions of source code must retain the above copyright </span>00009 <span class="comment"> * notice, this list of conditions and the following disclaimer. </span>00010 <span class="comment"> * 2. Redistributions in binary form must reproduce the above copyright </span>00011 <span class="comment"> * notice, this list of conditions and the following disclaimer in the </span>00012 <span class="comment"> * documentation and/or other materials provided with the distribution. </span>00013 <span class="comment"> * 3. Neither the name of the Institute nor the names of its contributors </span>00014 <span class="comment"> * may be used to endorse or promote products derived from this software </span>00015 <span class="comment"> * without specific prior written permission. </span>00016 <span class="comment"> *</span>00017 <span class="comment"> * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND </span>00018 <span class="comment"> * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE </span>00019 <span class="comment"> * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE </span>00020 <span class="comment"> * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE </span>00021 <span class="comment"> * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL </span>00022 <span class="comment"> * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS </span>00023 <span class="comment"> * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) </span>00024 <span class="comment"> * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT </span>00025 <span class="comment"> * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY </span>00026 <span class="comment"> * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF </span>00027 <span class="comment"> * SUCH DAMAGE. </span>00028 <span class="comment"> *</span>00029 <span class="comment"> * This file is part of the protothreads library.</span>00030 <span class="comment"> * </span>00031 <span class="comment"> * Author: Adam Dunkels <adam@sics.se></span>00032 <span class="comment"> *</span>00033 <span class="comment"> * $Id: pt-sem.h,v 1.2 2005/02/24 10:36:59 adam Exp $</span>00034 <span class="comment"> */</span>00035 <span class="comment"></span>00036 <span class="comment">/**</span>00037 <span class="comment"> * \addtogroup pt</span>00038 <span class="comment"> * @{</span>00039 <span class="comment"> */</span>00040 <span class="comment"></span>00041 <span class="comment">/**</span>00042 <span class="comment"> * \defgroup ptsem Protothread semaphores</span>00043 <span class="comment"> * @{</span>00044 <span class="comment"> *</span>00045 <span class="comment"> * This module implements counting semaphores on top of</span>00046 <span class="comment"> * protothreads. Semaphores are a synchronization primitive that</span>00047 <span class="comment"> * provide two operations: "wait" and "signal". The "wait" operation</span>00048 <span class="comment"> * checks the semaphore counter and blocks the thread if the counter</span>00049 <span class="comment"> * is zero. The "signal" operation increases the semaphore counter but</span>00050 <span class="comment"> * does not block. If another thread has blocked waiting for the</span>00051 <span class="comment"> * semaphore that is signalled, the blocked thread will become</span>00052 <span class="comment"> * runnable again.</span>00053 <span class="comment"> *</span>00054 <span class="comment"> * Semaphores can be used to implement other, more structured,</span>00055 <span class="comment"> * synchronization primitives such as monitors and message</span>00056 <span class="comment"> * queues/bounded buffers (see below).</span>00057 <span class="comment"> *</span>00058 <span class="comment"> * The following example shows how the producer-consumer problem, also</span>00059 <span class="comment"> * known as the bounded buffer problem, can be solved using</span>00060 <span class="comment"> * protothreads and semaphores. Notes on the program follow after the</span>00061 <span class="comment"> * example.</span>00062 <span class="comment"> *</span>00063 <span class="comment"> \code</span>00064 <span class="comment">#include "pt-sem.h"</span>00065 <span class="comment"></span>00066 <span class="comment">#define NUM_ITEMS 32</span>00067 <span class="comment">#define BUFSIZE 8</span>00068 <span class="comment"></span>00069 <span class="comment">static struct pt_sem mutex, full, empty;</span>00070 <span class="comment"></span>00071 <span class="comment">PT_THREAD(producer(struct pt *pt))</span>00072 <span class="comment">{</span>00073 <span class="comment"> static int produced;</span>00074 <span class="comment"> </span>00075 <span class="comment"> PT_BEGIN(pt);</span>00076 <span class="comment"> </span>00077 <span class="comment"> for(produced = 0; produced < NUM_ITEMS; ++produced) {</span>00078 <span class="comment"> </span>00079 <span class="comment"> PT_SEM_WAIT(pt, &full);</span>00080 <span class="comment"> </span>00081 <span class="comment"> PT_SEM_WAIT(pt, &mutex);</span>00082 <span class="comment"> add_to_buffer(produce_item()); </span>00083 <span class="comment"> PT_SEM_SIGNAL(pt, &mutex);</span>00084 <span class="comment"> </span>00085 <span class="comment"> PT_SEM_SIGNAL(pt, &empty);</span>00086 <span class="comment"> }</span>00087 <span class="comment"></span>00088 <span class="comment"> PT_END(pt);</span>00089 <span class="comment">}</span>00090 <span class="comment"></span>00091 <span class="comment">PT_THREAD(consumer(struct pt *pt))</span>00092 <span class="comment">{</span>00093 <span class="comment"> static int consumed;</span>00094 <span class="comment"> </span>00095 <span class="comment"> PT_BEGIN(pt);</span>00096 <span class="comment"></span>00097 <span class="comment"> for(consumed = 0; consumed < NUM_ITEMS; ++consumed) {</span>00098 <span class="comment"> </span>00099 <span class="comment"> PT_SEM_WAIT(pt, &empty);</span>00100 <span class="comment"> </span>00101 <span class="comment"> PT_SEM_WAIT(pt, &mutex); </span>00102 <span class="comment"> consume_item(get_from_buffer()); </span>00103 <span class="comment"> PT_SEM_SIGNAL(pt, &mutex);</span>00104 <span class="comment"> </span>00105 <span class="comment"> PT_SEM_SIGNAL(pt, &full);</span>00106 <span class="comment"> }</span>00107 <span class="comment"></span>00108 <span class="comment"> PT_END(pt);</span>00109 <span class="comment">}</span>00110 <span class="comment"></span>00111 <span class="comment">PT_THREAD(driver_thread(struct pt *pt))</span>00112 <span class="comment">{</span>00113 <span class="comment"> static struct pt pt_producer, pt_consumer;</span>00114 <span class="comment"></span>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -