操作系统读者优先算法实现

//读者优先算法实现 #include <windows.h> #include <iostream.h> #include <fstream.h> #define MAX_PERSON 100 #define INPUT "D:\\wrinput.txt"//输入文件流的地址，可适当修改 typedef struct { HANDLE hThread; int ID; char Type; int StartTime; int WorkTime; }Person; Person Persons[MAX_PERSON]; int numPerson=0; int numExit=0; int currentTime=0; int readCount=0; HANDLE Mutex; HANDLE w; DWORD WINAPI ReaderProc(LPVOID lpParam) { Person *pPerson = (Person*)lpParam; while(currentTime != pPerson->StartTime) { } cout<<"CurrentTime = "<<currentTime<<" :Reader "<<pPerson->ID<<" is Requesting"<<endl; WaitForSingleObject(Mutex,INFINITE);//对应于P(Mutex)操作 readCount++; if(readCount == 1) WaitForSingleObject(w,INFINITE);//对应于P(w)操作 ReleaseSemaphore(Mutex,1,NULL);//相对应于V(Mutex)操作 pPerson->StartTime = currentTime; cout<<"CurrentTime = "<<currentTime<<" :Reader "<<pPerson->ID<<" is Reading"<<endl; while(currentTime < pPerson->StartTime + pPerson->WorkTime) { // 读 } cout<<"CurrentTime = "<<currentTime<<" :Reader "<<pPerson->ID<<" is Exit"<<endl; WaitForSingleObject(Mutex,INFINITE);//相对应于P(Mutex)操作 readCount--; if(readCount == 0) ReleaseSemaphore(w,1,NULL);//对应于V(w)操作 ReleaseSemaphore(Mutex,1,NULL);//相对应于V(Mutex)操作 numExit++; ExitThread(0);//结束线程 return 0; } DWORD WINAPI WriterProc(LPVOID lpParam) { Person *pPerson = (Person*)lpParam; while(currentTime != pPerson->StartTime) { } cout<<"CurrentTime = "<<currentTime<<" :Writer "<<pPerson->ID<<" is Requesting"<<endl; WaitForSingleObject(w,INFINITE);//相对应于P(w)操作 pPerson->StartTime = currentTime; cout<<"CurrentTime = "<<currentTime<<" :Writer "<<pPerson->ID<<" is Writing"<<endl; while(currentTime < pPerson->StartTime + pPerson->WorkTime) { // 写 } cout<<"CurrentTime = "<<currentTime<<" :Writer "<<pPerson->ID<<" is Exit"<<endl; ReleaseSemaphore(w,1,NULL);//相对应于V(w)操作 numExit++; ExitThread(0); return 0; } void CreateReadersAndWriters()//创建读者、写者线程 { int i; DWORD dwThreadID; Person *pPerson; ifstream fin(INPUT);//由文件输入 while( fin >> Persons[numPerson].ID >> Persons[numPerson].Type >> Persons[numPerson].StartTime >> Persons[numPerson].WorkTime ) { numPerson++; } if( numPerson > MAX_PERSON )//如果大于规定的人数，报错 { cout<<"超过规定人数!"<<endl; return ; } for(i=0; i<numPerson; i++) { switch(Persons[i].Type) { case 'R': pPerson = &Persons[i]; pPerson->hThread = CreateThread(NULL,0,ReaderProc,(LPVOID)pPerson,0,&dwThreadID); if(pPerson->hThread == NULL) cout<<"Reader "<<Persons[i].ID<<" 线程创建失败!"<<endl; break; case 'W': pPerson = &Persons[i]; pPerson->hThread = CreateThread(NULL,0,WriterProc,(LPVOID)pPerson,0,&dwThreadID); if(pPerson->hThread == NULL) cout<<"Writer "<<Persons[i].ID<<" 线程创建失败!"<<endl; break; } } } int main() { Mutex = CreateSemaphore(NULL,1,100,NULL);//创建Mutex信号量 w = CreateSemaphore(NULL,1,100,NULL);//创建w信号量 CreateReadersAndWriters();//创建读者、写者进程 if(numPerson > MAX_PERSON) return 0; //如果大于规定人数，跳出 else cout<<"读者、写者均已创建 !"<<endl; while(numExit != numPerson) { currentTime++; //改变当前时间 Sleep(500); } return 0; }