OS银行家算法

#include <iostream>
using namespace std;
/*子函数声明*/
int Isprocessallover();                //判断系统中的进程是否全部运行完毕
void Systemstatus();                   //显示当前系统中的资源及进程情况
int Banker(int, int*);                //银行家算法
void Allow(int, int*);                //若进程申请不导致死锁，用此函数分配资源
void Forbidenseason(int);             //若发生死锁，则显示原因

/*全局变量*/
int Availiable[3] = { 3,3,2 };              //初始状态，系统可用资源量                         
int Max[5][3] = { {7,5,3},{3,2,2},{9,0,2},{2,2,2},{4,3,3} };
//各进程对各资源的最大需求量
int Allocation[5][3] = { {0,1,0},{2,0,0},{3,0,2},{2,1,1},{0,0,2} };
//初始状态，各进程占有资源量
int Need[5][3] = { {7,4,3},{1,2,2},{6,0,0},{0,1,1},{4,3,1} };
//初始状态时，各进程运行完毕，还需要的资源量 
int over[5] = { 0,0,0,0,0 };               //标记对应进程是否得到所有资源并运行完毕  

 
/*主函数*/
int main()
{
	int process = 0;                           //发出请求的进程
	int decide = 0;                            //银行家算法的返回值
	int Request[3] = { 0,0,0 };                  //申请的资源量数组
	int sourcenum = 0;                         //申请的各资源量
	/*判断系统中进程是否全部运行完毕*/
step1:    if (Isprocessallover() == 1)
{
	cout << "系统中全部进程运行完毕！";
	return;
}
/*显示系统当前状态*/
Systemstatus();
/*人机交互界面*/
step2: cout << "\n输入发出请求的进程（输入 “0”退出系统）: ";
cin >> process;
if (process == 0)
{
	cout << "放弃申请,退出系统！";
	return;
}
if (process < 1 || process>5 || over[process - 1] == 1)
{
	cout << "系统无此进程！\n";
	goto step2;
}
cout << "此进程申请各资源（A，B，C）数目：\n";
for (int h = 0; h < 3; h++)
{
	cout << char(65 + h) << "资源:";
	cin >> sourcenum;
	Request[h] = sourcenum;
}
/*用银行家算法判断是否能够进行分配*/
decide = Banker(process, Request);
if (decide == 0)
{
	/*将此进程申请资源分配给它*/
	Allow(process, Request);
	goto step1;
}
else
{
	/*不能分配，显示原因*/
	Forbidenseason(decide);
	goto step2;
}
}

/*子函数Isprocessallover( )的实现*/
int Isprocessallover()
{
	int processnum = 0;
	for (int i = 0; i < 5; i++)
	{
		/*判断每个进程是否运行完毕*/
		if (over[i] == 1)
			processnum++;
	}
	if (processnum == 5)
		/*系统中全部进程运行完毕*/
		return 1;
	else
		return 0;
}

/*子函数Systemstatus( )的实现*/
void Systemstatus()
{
	cout << "此刻系统中存在的进程：\n";
	for (int i = 0; i < 5; i++)
	{
		if (over[i] != 1)
			cout << "P" << i + 1 << "  ";
	}
	cout << endl;
	cout << "此刻系统可利用资源（单位：个）：\n";
	cout << "A  B  C\n";
	for (int a = 0; a < 3; a++)
	{
		cout << Availiable[a] << "  ";
	}
	cout << endl;
	cout << "此刻各进程已占有资源如下（单位：个）: \n"
		<< "    A  B  C\n";
	for (int b = 0; b < 5; b++)
	{
		if (over[b] == 1)
			continue;
		cout << "P" << b + 1 << "  ";
		for (int c = 0; c < 3; c++)
			cout << Allocation[b][c] << "  ";
		cout << endl;
	}
	cout << "各进程运行完毕还需各资源如下（单位：个）:\n"
		<< "    A  B  C\n";
	for (int f = 0; f < 5; f++)
	{
		if (over[f] == 1)
			continue;
		cout << "P" << f + 1 << "  ";
		for (int g = 0; g < 3; g++)
			cout << Need[f][g] << "  ";
		cout << endl;
	}
}

/*子函数Banker(int ,int &)的实现*/
int Banker(int p, int* R)
{
	int num = 0;                            //标记各资源是否能满足各进程需要
	int Finish[5] = { 0,0,0,0,0 };                //标记各进程是否安全运行完毕
	int work[5] = { 0,0,0,0,0 };                 //用于安全检查
	int AvailiableTest[3];                   //用于试分配  
	int AllocationTest[5][3];                //同上
	int NeedTest[5][3];                    //同上
	/*判断申请的资源是否大于系统可提供的资源总量*/
	for (int j = 0; j < 3; j++)
	{
		if (*(R + j) > Availiable[j])
			/*返回拒绝分配原因*/
			return 1;
	}
	/*判断该进程申请资源量是否大于初始时其申明的需求量*/
	for (int i = 0; i < 3; i++)
	{
		if (*(R + i) > Need[p - 1][i])
			/*返回拒绝原因*/
			return 2;
	}
	/*为检查分配的各数据结构赋初值*/
	for (int t = 0; t < 3; t++)
	{
		AvailiableTest[t] = Availiable[t];
	}
	for (int u = 0; u < 5; u++)
	{
		for (int v = 0; v < 3; v++)
		{
			AllocationTest[u][v] = Allocation[u][v];
		}
	}
	for (int w = 0; w < 5; w++)
	{
		for (int x = 0; x < 3; x++)
		{
			NeedTest[w][x] = Need[w][x];
		}
	}
	/*进行试分配*/
	for (int k = 0; k < 3; k++)                      		                                         //修改NeedTest[]
	{
		AvailiableTest[k] -= *(R + k);
		AllocationTest[p - 1][k] += *(R + k);
		NeedTest[p - 1][k] -= *(R + k);
	}
	/*检测进程申请得到满足后，系统是否处于安全状态*/
	for (int l = 0; l < 3; l++)
	{
		work[l] = AvailiableTest[l];
	}
	for (int m = 1; m <= 5; m++)
	{
		for (int n = 0; n < 5; n++)
		{
			num = 0;
			/*寻找用此刻系统中没有运行完的进程*/
			if (Finish[n] == 0 && over[n] != 1)
			{
				for (int p = 0; p < 3; p++)
				{
					if (NeedTest[n][p] <= work[p])
						num++;
				}
				if (num == 3)
				{
					for (int q = 0; q < 3; q++)
					{
						work[q] = work[q] + AllocationTest[n][q];
					}
					Finish[n] = 1;
				}
			}
		}
	}
	for (int r = 0; r < 5; r++)
	{
		if (Finish[r] == 0 && over[r] != 1)
			/*返回拒绝分配原因*/
			return 3;
	}
	return 0;
}

/*子函数Allow(int ,int &)的实现*/
void Allow(int p, int* R)
{
	cout << "可以满足申请！";
	static int overnum;
	/*对进程所需的资源进行分配*/
	for (int t = 0; t < 3; t++)
	{
		Availiable[t] = Availiable[t] - *(R + t);
		Allocation[p - 1][t] = Allocation[p - 1][t] + *(R + t);
		Need[p - 1][t] = Need[p - 1][t] - *(R + t);
	}
	/*分配后判断其是否运行完毕*/
	overnum = 0;
	for (int v = 0; v < 3; v++)
	{
		if (Need[p - 1][v] == 0)
			overnum++;
	}
	if (overnum == 3)
	{
		/*此进程运行完毕，释放其占有的全部资源*/
		for (int q = 0; q < 3; q++)
			Availiable[q] = Availiable[q] + Allocation[p - 1][q];
		/*标记该进程运行完毕*/
		over[p - 1] = 1;
		cout << "进程P" << p << "所需资源全部满足，此进程运行完毕！\n";
	}
}

/*子函数Forbidenseason(int )的实现*/
void Forbidenseason(int d)
{
	cout << "不能满足申请，此进程挂起，原因为：\n";
	switch (d)
	{
	case 1:cout << "申请的资源量大于系统可提供的资源量！"; break;
	case 2:cout << "申请的资源中有某种资源大于其声明的需求量！"; break;
	case 3:cout << "若满足申请，系统将进入不安全状态，可能导致死锁！";
	}
}