学步园

#include <windows.h><br /> #include <stdio.h><br /> void main()<br /> {<br /> HANDLE hfile = CreateFile("test.txt",GENERIC_READ | GENERIC_WRITE,<br /> 0,NULL,CREATE_ALWAYS, FILE_FLAG_OVERLAPPED | FILE_ATTRIBUTE_NORMAL,NULL);<br /> if (hfile == INVALID_HANDLE_VALUE)<br /> {<br /> printf("invalid handle value./n");<br /> }<br /> OVERLAPPED oWrite = { 0 };<br /> oWrite.Offset = 0;<br /> oWrite.hEvent = CreateEvent(NULL,FALSE,FALSE,NULL);<br /> WriteFile(hfile, "Jeffery chen", 14, NULL, &oWrite);<br /> BYTE bBuffer[10];<br /> OVERLAPPED oRead = { 0 };<br /> oRead.Offset = 5; /**start from 6 char */<br /> oRead.hEvent = CreateEvent(NULL,FALSE,FALSE,NULL);<br /> ReadFile(hfile, bBuffer, 10, NULL, &oRead);</p> <p> HANDLE h[2];<br /> h[0] = oRead.hEvent;<br /> h[1] = oWrite.hEvent;<br /> while (true)<br /> {<br /> Sleep(3000);<br /> DWORD dw = WaitForMultipleObjects(2, h, FALSE, 1000);<br /> if(dw == WAIT_OBJECT_0)<br /> {<br /> printf("can be read./n");<br /> oRead.Offset += 1;<br /> // ReadFile(hfile,bBuffer,10,NULL,&oRead);<br /> // Handle to an event set to the signaled state when the transfer has been completed<br /> //当调用完ReadFile后，会自动设置到有信号状态。<br /> printf("%s/n",bBuffer);<br /> }<br /> else if (dw == (WAIT_OBJECT_0 + 1))<br /> {<br /> printf("can write io./n");<br /> // WriteFile(hfile,"shawn",6,NULL,&oWrite);<br /> // Handle to an event set to the signaled state when the transfer has been completed<br /> }<br /> else<br /> break;<br /> }<br /> getchar();<br /> } 

在创建event时，第二个参数表明是否为manual-reset event，此处设为false，表明系统自动管理。

当调用WaitForMultipleObject时使信号处于无信号状态。

当调用ReadFile或WriteFile时使信号处于有信号状态 。