C++多线程（一）

一 简单实例

比较简单的代码，创建10个线程，其中使第4个线程在一创建就挂起，等到其他的线程执行的差不多的时候再使第4个线程恢复执行。


#include
<stdio.h>


#include
<stdlib.h>


#include
<windows.h>




#define THREAD_NUM 10




DWORD WINAPI PrintThreads (LPVOID);




int main ()






{


    HANDLE hThread[THREAD_NUM];


    DWORD dwThreadID[THREAD_NUM];




   
for (int i=0; i<THREAD_NUM;
++i)




   


{


       
int isStartImmediate
= 0;


       
if(3
== i)


            isStartImmediate
= CREATE_SUSPENDED;


        hThread[i]=CreateThread(NULL,               
// security attributes that should be applied to the new thread,


                                                                                
// this is for NT. Use NULL to get the default security attributes. Use NULL for win95


                               
0,                                           
// default size of 1MB can be passed by passing zero.


                                PrintThreads,                    
// function name:address of the function where the new thread starts.


                                (LPVOID)i,                        
// parameter(void pointer): pointer to the 32 bit parameter that will be passed into the thread


                                isStartImmediate,            
// flags to control the creation of the thread. Passing zero starts the thread immediately.


                                                                          
// Passing CREATE_SUSPENDED suspends the thread until the ResumeThread( ) function is called.


                               
&dwThreadID[i]           
// pointer to a 32-bit variable that receives the thread identifier.


                                );


       
if (hThread[i])




       


{


            printf ("Thread launched successfully/n");               


        }        


    }


    printf("Start sleep 100, and let other thread excute/n");


    Sleep (100);   




    printf("Start sleep 100, and thread 3 excute/n");


    ResumeThread(hThread[3]);


   


    Sleep(100);




   
for(int i
= 0; i<THREAD_NUM;
++i)




   


{


       
if (hThread[i])




       


{           


            CloseHandle(hThread[i]);   
// You need to use this to release kernel objects when you are done using them.


                                       
// If a process exits without closing the thread handle,


                                       
// the operating system drops the reference counts for those objects.


                                       
// But if a process frequently creates threads without closing the handles,


                                       
// there could be hundreds of thread kernel objects lying around and these resource leaks can have a big hit on performance.


        }


    }


   
return (0);


}




//function PrintThreads


DWORD WINAPI PrintThreads (LPVOID num)






{


   
for (int i=0; i<10;
i++)


        printf ("Thread Number is %d%d%d/n",
num,num,num);


   
return
0;


}

二 其他基本API的说明

CreateThread() 调用成功返回句柄和一个id。

CloseHandle()  关闭一个打开的对象句柄，该对象句柄可以是线程句柄，也可以是进程、信号量等其他内核对象的句柄.

SuspendThread(HANDLE) 允许开发人员将HANDLE指定的线程挂起，如果要挂起的线程占有共享资源，则可能导致死锁。

ResumeThread(HANDLE)  恢复指定的线程。

TerminateThread() 立即终止线程的工作，不做任何清理工作。

ExitThread() 线程函数返回时回调用次函数，所以一般我们不去显示的调用。

ExitThread是推荐使用的结束一个线程的方法，当调用该函数时，当前线程的栈被释放，然后线程终止，相对于TerminateThread函数来说，这样做能够更好地完成附加在该线程上的DLL的清除工作. 但是ExitThread()会导致线程在清处构造器/自动变量之前就终止，所以我们最好不要显示的调用ExitThread()。