PostThreadMessage http://www.cppblog.com/sandy/archive/2005/12/31/2320.html

PostThreadMessage的原型是这样的

BOOL PostThreadMessage( DWORD idThread,

UINT Msg,

WPARAM wParam,

LPARAM lParam

);

PostThreadMessage可以用于线程之间的异步通讯，因为它不用等待调用者返回，

这也许是线程通讯中最简单的一种方法了。

但是要注意以下问题

1 .PostThreadMessage有时会失败，报1444错误(Invalid thread identifier. )

其实这不一定是线程不存在的原因，也有可能是线程不存在消息队列(message queue)造成的。

事实上，并不是每个thread都有message queue,那如何让thread具有呢？

答案是，至少调用message相关的function一次，比如GetMessage,PeekMessage。

2.如果是post动态分配的memory给另外一个thread,要注意内存的正确释放。

3.PostThreadMessage不能够post WM_COPYDATE之类的同步消息，否则会报错

4.最好不要使用PostThreadMessage post message给一个窗口,使用PostMessage替代。

下面是我写的一个比较严整的例子，仅供参考。

#include <windows.h>

#include <cstdio>

#include <process.h>

#define MY_MSG WM_USER+100

const int MAX_INFO_SIZE = 20;

HANDLE hStartEvent; // thread start event

// thread function

unsigned __stdcall fun(void *param)

{

printf("thread fun start

\n");

MSG msg;

PeekMessage(&msg, NULL, WM_USER, WM_USER, PM_NOREMOVE);

if(!SetEvent(hStartEvent)) //set thread start event

{

printf("set start event failed,errno:%d\n",::GetLastError());

return 1;

}

while(true)

{

if(GetMessage(&msg,0,0,0)) //get msg from message queue

{

switch(msg.message)

{

case MY_MSG:

char * pInfo = (char *)msg.wParam;

printf("recv %s\n",pInfo);

delete[] pInfo;

break;

}

}

};

return 0;

}

int main()

{

HANDLE hThread;

unsigned nThreadID;

hStartEvent = ::CreateEvent(0,FALSE,FALSE,0); //create thread start event

if(hStartEvent == 0)

{

printf("create start event failed,errno:%d\n",::GetLastError());

return 1;

}

//start thread

hThread = (HANDLE)_beginthreadex( NULL, 0, &fun, NULL, 0, &nThreadID );

if(hThread == 0)

{

printf("start thread failed,errno:%d\n",::GetLastError());

CloseHandle(hStartEvent);

return 1;

}

//wait thread start event to avoid PostThreadMessage return errno:1444

::WaitForSingleObject(hStartEvent,INFINITE);

CloseHandle(hStartEvent);

int count = 0;

while(true)

{

char* pInfo = new char[MAX_INFO_SIZE]; //create dynamic msg

sprintf(pInfo,"msg_%d",++count);

if(!PostThreadMessage(nThreadID,MY_MSG,(WPARAM)pInfo,0))//post thread msg

{

printf("post message failed,errno:%d\n",::GetLastError());

delete[] pInfo;

}

::Sleep(1000);

}

CloseHandle(hThread);

return 0;

}

===========Happy New Year==============