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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"><HTML><HEAD>    <TITLE>线程</TITLE>    <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=gb2312-80">    <META NAME="COPYRIGHT" CONTENT="魏永明">    <META NAME="AUTHOR" CONTENT="魏永明">    <STYLE>    <!--        H1 { color: #ffff00 }        H2 { color: #ffff00 }        H3 { color: #ff00ff }        H4 { color: #ffff00 }        TD P { color: #b880b8 }        LI { color: #ffffff }        P { color: #00ffff }        PRE { color: #ffffff; font-family: "fixed" }        A:link { color: #00b8ff }        A:visited { color: #ff3366 }    -->    </STYLE></HEAD><BODY TEXT="#ffff00" LINK="#00b8ff" VLINK="#ff3366" BACKGROUND="images/velvet.jpg"><A HREF="proctl.html"><IMG SRC="prev.gif" ALT="Previous"></A><A HREF="procrelate.html"><IMG SRC="next.gif" ALT="Next"></A><A HREF="index.html"><IMG SRC="toc.gif" ALT="Contents"></A><H1 ALIGN=CENTER>5.9&nbsp;&nbsp;线程<BR><BR></H1><UL>    <LI><P>基本概念</LI>    <LI><P>线程的创建和销毁</LI>    <LI><P>线程同步机制</LI>    <LI><P>实例分析: MiniGUI 中的消息传递</LI>    <LI><P>其他</LI></UL><H3>5.9.1&nbsp;&nbsp;基本概念</H3><UL>    <LI>线程是程序中代码的不同执行路线</LI>    <LI>Linux 中的核心线程实际是共享地址空间的两个进程</LI>    <LI>LinuxThread 实现了 Linux 上的 POSIX 兼容核心线程.</LI></UL><H3>5.9.2&nbsp;&nbsp;线程的创建和销毁</H3><UL>    <LI>pthread_create/pthread_exit</LI><PRE>===============================================================================        #include &lt;pthread.h&gt;        int  pthread_create (pthread_t  *  thread, pthread_attr_t *                            attr, void * (*start_routine)(void *), void * arg);        void pthread_exit (void *retval);===============================================================================</PRE>    <LI></LI></UL><H3>5.9.3&nbsp;&nbsp;线程同步机制</H3><UL>    <LI>pthread_join: 类似 wait</LI><PRE>===============================================================================        #include &lt;pthread.h&gt;       int pthread_join (pthread_t th, void **thread_return);===============================================================================</PRE>    <LI>互斥锁</LI>    <LI>信号量</LI>    <LI>条件变量</LI><PRE>===============================================================================条件变量:    * 可广播, 可设置超时.    * 需要有一个互斥量协作.===============================================================================</PRE></UL><H3>5.9.4&nbsp;&nbsp;实例分析: MiniGUI 中的消息传递</H3><UL>    <LI>两种消息传递方式: SendMessage, PostMessage</LI><PRE>===============================================================================MiniGUI 的消息结构:        typedef struct _MSG        {            HWND             hwnd;            int              message;            WPARAM           wParam;            LPARAM           lParam;            struct timeval   time;            POINT            pt;            void*            pAdd;        }MSG;        typedef MSG* PMSG;        typedef struct _QMSG        {            MSG                 Msg;            struct _QMSG*       next;            BOOL                fromheap;        }QMSG;        typedef QMSG* PQMSG;        typedef struct _SYNCMSG        {            MSG              Msg;            int              retval;            sem_t            sem_handle;            struct _SYNCMSG* pNext;        }SYNCMSG;        typedef SYNCMSG* PSYNCMSG;        typedef struct _MSGQUEUE        {            DWORD dwState;              // message queue states            pthread_mutex_t lock;       // lock            sem_t wait;                 // wait semaphores            PQMSG  pFirstNotifyMsg;     // head of the notify message queue            PQMSG  pLastNotifyMsg;      // tail of the notify message queue            PSYNCMSG pFirstSyncMsg;     // head of the sync message queue            PSYNCMSG pLastSyncMsg;      // tail of the sync message queue            MSG* msg;                   // post message buffer            int len;                    // buffer len            int readpos, writepos;      // positions for reading and writing            /*             * One thread can only support eight timers.             * And number of all timers in a MiniGUI applicatoin is 16.             */            HWND TimerOwner[8];         // Timer owner            int  TimerID[8];            // timer identifiers.            BYTE TimerMask;             // used timer slots mask        }MSGQUEUE;-------------------------------------------------------------------------------    * lock 用来实现消息队列的互斥访问    * wait 用来实现 GetMessage 等待消息, 有消息 (PostMessage, SendMessage) 时执行 UP 操作    * 不同进程间的同步消息 (SendMessage) 在 pFirstSyncMsg 上排队, 服务器线程处理之后, 利用      信号量 (sem_handle) 通知客户线程    * 如果利用条件量处理同步消息, 可实现 SendMessageTime 等接口.===============================================================================</PRE></UL><H3>5.9.5&nbsp;&nbsp;其他</H3><UL>    <LI>线程的取消点: 能够让其他线程请求自己终止执行</LI>    <LI>线程局部存储</LI>    <LI>一次执行函数</LI>    <LI>线程的信号处理</LI></UL><PRE>===============================================================================EXAMPLE:        /* 为每个线程建立局部存储 */        static pthread_key_t con_key;        /* Once-only initialisation of the key */        static pthread_once_t con_key_once = PTHREAD_ONCE_INIT;        /* Allocate the key */        static void con_key_alloc()        {            pthread_key_create (&con_key, NULL);        }        /* Set thread-specific date */        void set_coninfo (void* data)        {            pthread_once (&con_key_once, con_key_alloc);            pthread_setspecific (con_key, data);        }===============================================================================</PRE><P><BR><BR></P><P ALIGN=CENTER><IMG SRC="images/striped.gif" NAME="Ruler" ALIGN=BOTTOM WIDTH=532 HEIGHT=13 BORDER=0></P><P><BR><BR></P><A HREF="proctl.html"><IMG SRC="prev.gif" ALT="Previous"></A><A HREF="procrelate.html"><IMG SRC="next.gif" ALT="Next"></A><A HREF="index.html"><IMG SRC="toc.gif" ALT="Contents"></A></BODY></HTML>
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