实习1：进程同步--读者优先
实习要求
在Windows 2000 环境下，创建一个包含n 个线程的控制台进程。用这n 个线程来表示n
个读者或写者。每个线程按相应测试数据文件的要求，进行读写操作。请用信号量机制分别
实现读者优先和写者优先的读者-写者问题。
读者-写者问题的读写操作限制：
1）写-写互斥；
2）读-写互斥；
3）读-读允许；
读者优先的附加限制：如果一个读者申请进行读操作时已有另一读者正在进行读操作，
则该读者可直接开始读操作。
写者优先的附加限制：如果一个读者申请进行读操作时已有另一写者在等待访问共享资
源，则该读者必须等到没有写者处于等待状态后才能开始读操作。
运行结果显示要求：要求在每个线程创建、发出读写操作申请、开始读写操作和结束读
写操作时分别显示一行提示信息，以确信所有处理都遵守相应的读写操作限制。
测试数据文件格式
测试数据文件包括n 行测试数据，分别描述创建的n 个线程是读者还是写者，以及读写
操作的开始时间和持续时间。每行测试数据包括四个字段，各字段间用空格分隔。第一字段
为一个正整数，表示线程序号。第二字段表示相应线程角色，R 表示读者是，W 表示写者。
第三字段为一个正数，表示读写操作的开始时间。线程创建后，延时相应时间（单位为秒）
后发出对共享资源的读写申请。第四字段为一个正数，表示读写操作的持续时间。当线程读
写申请成功后，开始对共享资源的读写操作，该操作持续相应时间后结束，并释放共享资源。
下面是一个测试数据文件的例子：
1 R 3 5
2 W 4 5
3 R 5 2
4 R 6 5
源代码如下:
/************************************************************************/
/* 操作系统实践-- 读者写者问题
/* 读者优先算法实现
/* 时间: 2004-12.10
/* 作者: 唐良
/************************************************************************/
#include <windows.h>
#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <malloc.h>
#define MAX_PERSON 100
#define READER 0
#define WRITER 1
#define END -1
#define R READER
#define W WRITER
typedef struct _Person
{
HANDLE m_hThread;
int m_nType;
int m_nStartTime;
int m_nWorkTime;
int m_nID;
}Person;
Person g_Persons[MAX_PERSON];
int g_NumPerson = 0;
long g_CurrentTime= 0;
int g_PersonLists[] = {
1, R, 3, 5,
2, W, 4, 5,
3, R, 5, 2,
4, R, 6, 5,
END,
};
int g_NumOfReading = 0;
HANDLE g_hReadSemaphore;
HANDLE g_hWriteSemaphore;
void CreatePersonList(int *pPersonList);
bool CreateReader(int StartTime,int WorkTime,int ID);
bool CreateWriter(int StartTime,int WorkTime,int ID);
DWORD WINAPI ReaderProc(LPVOID lpParam);
DWORD WINAPI WriterProc(LPVOID lpParam);
int main()
{
g_hReadSemaphore = CreateSemaphore(NULL,1,100,NULL);
g_hWriteSemaphore = CreateSemaphore(NULL,1,100,NULL); // CreateSemaphore(NULL,FALSE,NULL);
CreatePersonList(g_PersonLists); // Create All the reader and writers
printf("Created all the reader and writer\n...\n");
g_CurrentTime = 0;
while(true)
{
g_CurrentTime++;
Sleep(300); // 300 ms
printf("CurrentTime = %d\n",g_CurrentTime);
}
return 0;
}
void CreatePersonList(int *pPersonLists)
{
int i=0;
int *pList = pPersonLists;
bool Ret;
while(pList[0] != END)
{
switch(pList[1])
{
case R:
Ret = CreateReader(pList[2],pList[3],pList[0]);
break;
case W:
Ret = CreateWriter(pList[2],pList[3],pList[0]);
break;
}
if(!Ret)
printf("Create Person %d is wrong\n",pList[0]);
pList += 4; // move to next person list
}
}
DWORD WINAPI ReaderProc(LPVOID lpParam)
{
Person *pPerson = (Person*)lpParam;
// wait for the start time
while(g_CurrentTime != pPerson->m_nStartTime)
{
}
printf("Reader %d is Requesting ...\n",pPerson->m_nID);
WaitForSingleObject(g_hReadSemaphore,INFINITE);
if(g_NumOfReading ==0)
{
WaitForSingleObject(g_hWriteSemaphore,INFINITE);
}
g_NumOfReading++;
ReleaseSemaphore(g_hReadSemaphore,1,NULL);
// modify the reader's real start time
pPerson->m_nStartTime = g_CurrentTime;
printf("Reader %d is Reading the Shared Buffer...\n",pPerson->m_nID);
while(g_CurrentTime <= pPerson->m_nStartTime + pPerson->m_nWorkTime)
{
// .. perform read operations
}
printf("Reader %d is Exit...\n",pPerson->m_nID);
WaitForSingleObject(g_hReadSemaphore,INFINITE);
g_NumOfReading--;
if(g_NumOfReading == 0)
{
ReleaseSemaphore(g_hWriteSemaphore,1,NULL);
}
ReleaseSemaphore(g_hReadSemaphore,1,NULL);
ExitThread(0);
return 0;
}
DWORD WINAPI WriterProc(LPVOID lpParam)
{
Person *pPerson = (Person*)lpParam;
// wait for the start time
while(g_CurrentTime != pPerson->m_nStartTime)
{
}
printf("Writer %d is Requesting ...\n",pPerson->m_nID);
WaitForSingleObject(g_hWriteSemaphore,INFINITE);
// modify the writer's real start time
pPerson->m_nStartTime = g_CurrentTime;
printf("Writer %d is Writting the Shared Buffer...\n",pPerson->m_nID);
while(g_CurrentTime <= pPerson->m_nStartTime + pPerson->m_nWorkTime)
{
// .. perform write operations
}
printf("Writer %d is Exit...\n",pPerson->m_nID);
ReleaseSemaphore(g_hWriteSemaphore,1,NULL);
ExitThread(0);
return 0;
}
bool CreateReader(int StartTime,int WorkTime,int ID)
{
DWORD dwThreadID;
if(g_NumPerson >= MAX_PERSON)
return false;
Person *pPerson = &g_Persons[g_NumPerson];
pPerson->m_nID = ID;
pPerson->m_nStartTime = StartTime;
pPerson->m_nWorkTime = WorkTime;
pPerson->m_nType = READER;
g_NumPerson++;
// Create an New Thread
pPerson->m_hThread = CreateThread(NULL,0,ReaderProc,(LPVOID)pPerson,0,&dwThreadID);
if(pPerson->m_hThread == NULL)
return false;
return true;
}
bool CreateWriter(int StartTime,int WorkTime,int ID)
{
DWORD dwThreadID;
if(g_NumPerson >= MAX_PERSON)
return false;
Person *pPerson = &g_Persons[g_NumPerson];
pPerson->m_nID = ID;
pPerson->m_nStartTime = StartTime;
pPerson->m_nWorkTime = WorkTime;
pPerson->m_nType = WRITER;
g_NumPerson++;
// Create an New Thread
pPerson->m_hThread = CreateThread(NULL,0,WriterProc,(LPVOID)pPerson,0,&dwThreadID);
if(pPerson->m_hThread == NULL)
return false;
return true;
}
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