C++多线程记录1

Posted 2020-07-22 casic207

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本文主要记录C++中多线程程序的开发中调用windows API的CreateThread的使用方法。

创建线程

在Windows平台，Windows API提供了对多线程的支持。前面进程和线程的概念中我们提到，一个程序至少有一个线程，这个线程称为主线程(main thread)，如果我们不显示地创建线程，那我们产的程序就是只有主线程的间线程程序。
下面，我们看看Windows中线程相关的操作和方法：

CreateThread与CloseHandle

CreateThread用于创建一个线程，其函数原型如下：

HANDLE WINAPI CreateThread(
    LPSECURITY_ATTRIBUTES   lpThreadAttributes, //线程安全相关的属性，常置为NULL
    SIZE_T                  dwStackSize,        //新线程的初始化栈在大小，可设置为0
    LPTHREAD_START_ROUTINE  lpStartAddress,     //被线程执行的回调函数，也称为线程函数
    LPVOID                  lpParameter,        //传入线程函数的参数，不需传递参数时为NULL
    DWORD                   dwCreationFlags,    //控制线程创建的标志
    LPDWORD                 lpThreadId          //传出参数，用于获得线程ID，如果为NULL则不返回线程ID
);

**说明：**lpThreadAttributes：指向SECURITY_ATTRIBUTES结构的指针，决定返回的句柄是否可被子进程继承，如果为NULL则表示返回的句柄不能被子进程继承。

dwStackSize ：线程栈的初始化大小，字节单位。系统分配这个值对

lpStartAddress：指向一个函数指针，该函数将被线程调用执行。因此该函数也被称为线程函数(ThreadProc)，是线程执行的起始地址，线程函数是一个回调函数，由操作系统在线程中调用。线程函数的原型如下：

DWORD WINAPI ThreadProc(LPVOID lpParameter);    //lpParameter是传入的参数，是一个空指针

lpParameter：传入线程函数(ThreadProc)的参数，不需传递参数时为NULL

dwCreationFlags：控制线程创建的标志，有三个类型，0：线程创建后立即执行线程；CREATE_SUSPENDED：线程创建后进入就绪状态，直到线程被唤醒时才调用；STACK_SIZE_PARAM_IS_A_RESERVATION：dwStackSize 参数指定线程初始化栈的大小，如果STACK_SIZE_PARAM_IS_A_RESERVATION标志未指定，dwStackSize将会设为系统预留的值。

返回值：如果线程创建成功，则返回这个新线程的句柄，否则返回NULL。如果线程创建失败，可通过GetLastError函数获得错误信息。

BOOL WINAPI CloseHandle(HANDLE hObject);        //关闭一个被打开的对象句柄

可用这个函数关闭创建的线程句柄，如果函数执行成功则返回true(非0),如果失败则返回false(0)，如果执行失败可调用GetLastError.函数获得错误信息。

【Demo1】：创建一个最简单的线程

<code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include "stdafx.h"</span>
<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include <windows.h></span>
<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include <iostream></span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">using</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">namespace</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">std</span>;

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//线程函数</span>
DWORD WINAPI ThreadProc(LPVOID lpParameter)
{
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>; ++ i)
    {
        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">cout</span> << <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"子线程:i = "</span> << i << endl;
        Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>);
    }
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0L</span>;
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> main()
{
    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//创建一个线程</span>
    HANDLE thread = CreateThread(NULL, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, ThreadProc, NULL, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, NULL);
    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//关闭线程</span>
    CloseHandle(thread);

    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//主线程的执行路径</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>; ++ i)
    {
        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">cout</span> << <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"主线程:i = "</span> << i << endl;
        Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>);
    }

    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li></ul>

结果如下：
主线程:i = 0
子线程:i = 0
主线程:i = 1
子线程:i = 1
子线程:i = 2
主线程:i = 2
子线程:i = 3
主线程:i = 3
子线程:i = 4
主线程:i = 4

【Demo2】：在线程函数中传入参数

<code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include "stdafx.h"</span>
<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include <windows.h></span>
<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include <iostream></span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">using</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">namespace</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">std</span>;

<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#define NAME_LINE   40</span>

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//定义线程函数传入参数的结构体</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">typedef</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">struct</span> __THREAD_DATA
{
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> nMaxNum;
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> strThreadName[NAME_LINE];

    __THREAD_DATA() : nMaxNum(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>)
    {
        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">memset</span>(strThreadName, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, NAME_LINE * <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sizeof</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span>));
    }
}THREAD_DATA;



<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//线程函数</span>
DWORD WINAPI ThreadProc(LPVOID lpParameter)
{
    THREAD_DATA* pThreadData = (THREAD_DATA*)lpParameter;

    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < pThreadData->nMaxNum; ++ i)
    {
        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">cout</span> << pThreadData->strThreadName << <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" --- "</span> << i << endl;
        Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>);
    }
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0L</span>;
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> main()
{
    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//初始化线程数据</span>
    THREAD_DATA threadData1, threadData2;
    threadData1.nMaxNum = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>;
    <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">strcpy</span>(threadData1.strThreadName, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"线程1"</span>);
    threadData2.nMaxNum = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>;
    <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">strcpy</span>(threadData2.strThreadName, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"线程2"</span>);

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//创建第一个子线程</span>
    HANDLE hThread1 = CreateThread(NULL, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, ThreadProc, &threadData1, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, NULL);
    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//创建第二个子线程</span>
    HANDLE hThread2 = CreateThread(NULL, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, ThreadProc, &threadData2, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, NULL);
    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//关闭线程</span>
    CloseHandle(hThread1);
    CloseHandle(hThread2);

    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//主线程的执行路径</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>; ++ i)
    {
        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">cout</span> << <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"主线程 === "</span> << i << endl;
        Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>);
    }

    system(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"pause"</span>);
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li></ul>

结果：

主线程 === 线程1 — 0
0
线程2 — 0
线程1 — 1
主线程 === 1
线程2 — 1
主线程 === 2
线程1 — 2
线程2 — 2
主线程 === 3
线程2 — 3
线程1 — 3
主线程 === 4
线程2 — 4
线程1 — 4
线程2 — 5
请按任意键继续… 线程2 — 6
线程2 — 7
线程2 — 8
线程2 — 9

CreateMutex、WaitForSingleObject、ReleaseMutex

从【Demo2】中可以看出，虽然创建的子线程都正常执行起来了，但输出的结果并不是我们预期的效果。我们预期的效果是每输出一条语句后自动换行，但结果却并非都是这样。这是因为在线程执行时没有做同步处理，比如第一行的输出，主线程输出“主线程 ===”后时间片已用完，这时轮到子线程1输出，在子线程输出“线程1 —”后时间片也用完了，这时又轮到主线程执行输出“0”，之后又轮到子线程1输出“0”。于是就出现了“主线程 === 线程1 — 0 0”的结果。

主线程：cout << “主线程 === ” << i << endl;
子线程：cout << pThreadData->strThreadName << ” — ” << i << endl;

为避免出现这种情况，我们对线程做一些简单的同步处理，这里我们用互斥量(Mutex)，关于互斥量(Mutex)的概念，请看《编程思想之多线程与多进程(2)——线程优先级与线程安全》一文；更多C++线程同步的处理，请看下一节。

在使用互斥量进行线程同步时会用到以下几个函数：

HANDLE WINAPI CreateMutex(
    LPSECURITY_ATTRIBUTES lpMutexAttributes,        //线程安全相关的属性，常置为NULL
    BOOL                  bInitialOwner,            //创建Mutex时的当前线程是否拥有Mutex的所有权
    LPCTSTR               lpName                    //Mutex的名称
);

**说明：**lpMutexAttributes也是表示安全的结构，与CreateThread中的lpThreadAttributes功能相同，表示决定返回的句柄是否可被子进程继承，如果为NULL则表示返回的句柄不能被子进程继承。bInitialOwner表示创建Mutex时的当前线程是否拥有Mutex的所有权，若为TRUE则指定为当前的创建线程为Mutex对象的所有者，其它线程访问需要先ReleaseMutex。lpName为Mutex的名称。

DWORD WINAPI WaitForSingleObject(
    HANDLE hHandle,                             //要获取的锁的句柄
    DWORD  dwMilliseconds                           //超时间隔
);

**说明：**WaitForSingleObject的作用是等待一个指定的对象(如Mutex对象)，直到该对象处于非占用的状态(如Mutex对象被释放)或超出设定的时间间隔。除此之外，还有一个与它类似的函数WaitForMultipleObjects，它的作用是等待一个或所有指定的对象，直到所有的对象处于非占用的状态，或超出设定的时间间隔。
hHandle：要等待的指定对象的句柄。dwMilliseconds：超时的间隔，以毫秒为单位；如果dwMilliseconds为非0，则等待直到dwMilliseconds时间间隔用完或对象变为非占用的状态，如果dwMilliseconds 为INFINITE则表示无限等待，直到等待的对象处于非占用的状态。

BOOL WINAPI ReleaseMutex(HANDLE hMutex);

说明：释放所拥有的互斥量锁对象，hMutex为释放的互斥量的句柄。

【Demo3】：线程同步

<code class="hljs objectivec has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include "stdafx.h"</span>
<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include <windows.h></span>
<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include <iostream></span>

<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#define NAME_LINE   40</span>

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//定义线程函数传入参数的结构体</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">typedef</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">struct</span> __THREAD_DATA
{
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> nMaxNum;
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> strThreadName[NAME_LINE];

    __THREAD_DATA() : nMaxNum(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>)
    {
        memset(strThreadName, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, NAME_LINE * <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sizeof</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span>));
    }
}THREAD_DATA;

HANDLE g_hMutex = <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">NULL</span>;     <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//互斥量</span>

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//线程函数</span>
DWORD WINAPI ThreadProc(LPVOID lpParameter)
{
    THREAD_DATA* pThreadData = (THREAD_DATA*)lpParameter;

    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < pThreadData->nMaxNum; ++ i)
    {
        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//请求获得一个互斥量锁</span>
        WaitForSingleObject(g_hMutex, INFINITE);
        cout << pThreadData->strThreadName << <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" --- "</span> << i << endl;
        Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>);
        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//释放互斥量锁</span>
        ReleaseMutex(g_hMutex);
    }
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>L;
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> main()
{
    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//创建一个互斥量</span>
    g_hMutex = CreateMutex(<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">NULL</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">FALSE</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">NULL</span>);

    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//初始化线程数据</span>
    THREAD_DATA threadData1, threadData2;
    threadData1<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.nMaxNum</span> = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>;
    strcpy(threadData1<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.strThreadName</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"线程1"</span>);
    threadData2<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.nMaxNum</span> = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>;
    strcpy(threadData2<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.strThreadName</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"线程2"</span>);


    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//创建第一个子线程</span>
    HANDLE hThread1 = CreateThread(<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">NULL</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, ThreadProc, &threadData1, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">NULL</span>);
    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//创建第二个子线程</span>
    HANDLE hThread2 = CreateThread(<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">NULL</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, ThreadProc, &threadData2, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">NULL</span>);
    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//关闭线程</span>
    CloseHandle(hThread1);
    CloseHandle(hThread2);

    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//主线程的执行路径</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>; ++ i)
    {
        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//请求获得一个互斥量锁</span>
        WaitForSingleObject(g_hMutex, INFINITE);
        cout << <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"主线程 === "</span> << i << endl;
        Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>);
        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//释放互斥量锁</span>
        ReleaseMutex(g_hMutex);
    }

    system(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"pause"</span>);
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; 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