进程p.txt

进程通信与进程同步机制实践 有三个进程R、M、P

//进程P
#include <stdio.h>
#include <Windows.h>
#include<ctype.h>
//缓冲区和信号量
HANDLE g_hBuffer = NULL;
HANDLE g_hSemSynR = NULL, g_hSemSynM = NULL, g_hSemSynP = NULL;
char* g_pszBuffer = NULL;
//在缓冲区中的位置指针
unsigned char g_nR = 0, g_nM = 0, g_nP = 0;

//P,V操作
void P(HANDLE hSem)
{  WaitForSingleObject(hSem, INFINITE);
}

void V(HANDLE hSem)
{  ReleaseSemaphore(hSem, 1, NULL);
}

void main()
{  //创建共享内存,大小为320 + 3B=10条记录 + 3个指针
g_hBuffer= CreateFileMapping((HANDLE)0xFFFFFFFF, NULL,PAGE_READWRITE, 0, 323, "my_buffer");
	if(g_hBuffer == NULL)// 如果创建失败
	{  printf("创建或连接共享内存失败!\n");
		return;  
	}
else if(GetLastError() == ERROR_ALREADY_EXISTS)
	{//如果已经存在这个同名对象, 说明共享内存已经创建
g_pszBuffer=(char*)MapViewOfFile(g_hBuffer, FILE_MAP_WRITE | FILE_MAP_READ, 0,0,0);
unsigned char *pnPoint = (unsigned char*)g_pszBuffer;
		g_nR = pnPoint[0];
		g_nM = pnPoint[1];
		g_nP = pnPoint[2];
	}
	else 
	{ // 经过上面的检查, 说明这是第一次创建共享内存
g_pszBuffer=(char*)MapViewOfFile(g_hBuffer, FILE_MAP_WRITE | FILE_MAP_READ, 0,0,0);
	// 初始化内存
	memset(g_pszBuffer, 0, 323);
	g_nR = g_nM = g_nP = 0;
	}

	//创建信号量
g_hSemSynR=CreateSemaphore(NULL, 10, 10, "my_sem_R");
g_hSemSynM=CreateSemaphore(NULL, 0, 10, "my_sem_M");
g_hSemSynP=CreateSemaphore(NULL, 0, 10, "my_sem_P");

if(g_hSemSynR == NULL || g_hSemSynM == NULL || g_hSemSynP == NULL)	
	{// 如果创建失败 
		printf("创建或连接信号量失败!\n");
		return;  
	}

	//以上的代码对所有的程序都是一样的
//下面P自己的工作
	BOOL end = FALSE;
	while(!end)
	{
		char data[32];
		printf("***数据输出***\n");
printf("\tP(synP)\n");
P(g_hSemSynP); 
strncpy(data, g_pszBuffer + 3 + g_nP * 32, 31);
g_nP = g_pszBuffer[2];
g_pszBuffer[2] = g_nP = (g_nP + 1) % 10;
printf("\tV(synR)\n");
V(g_hSemSynR);
printf("输出数据:%s\n", data);
char endCH;
printf("Go on? ");
fflush(stdin);
scanf("%c", &endCH);
if(endCH != 'y' && endCH != 'Y' ) end = TRUE;
	}

	//P的工作到此结束
UnmapViewOfFile(g_pszBuffer); //断开和共享内存  的连接
CloseHandle(g_hBuffer); //关闭这个句柄
return;
}