c实现银行家算法
时间: 2023-06-29 13:13:54 浏览: 39
下面是一个简单的C语言实现银行家算法的例子,其中包含了银行家算法的主要步骤:
```c
#include <stdio.h>
#include <stdbool.h>
#define NUMBER_OF_PROCESSES 5
#define NUMBER_OF_RESOURCES 3
int available[NUMBER_OF_RESOURCES];
int maximum[NUMBER_OF_PROCESSES][NUMBER_OF_RESOURCES];
int allocation[NUMBER_OF_PROCESSES][NUMBER_OF_RESOURCES];
int need[NUMBER_OF_PROCESSES][NUMBER_OF_RESOURCES];
bool is_safe();
bool request_resources(int pid, int request[]);
void release_resources(int pid, int release[]);
int main() {
// 初始化available, maximum, allocation, need等数组
// ...
// 检查是否安全
if (is_safe()) {
printf("当前状态安全\n");
} else {
printf("当前状态不安全\n");
}
// 进行资源请求
int pid = 0;
int request[NUMBER_OF_RESOURCES] = {1, 0, 2};
if (request_resources(pid, request)) {
printf("资源分配成功\n");
} else {
printf("资源分配失败\n");
}
// 释放资源
int release[NUMBER_OF_RESOURCES] = {0, 0, 2};
release_resources(pid, release);
return 0;
}
bool is_safe() {
int work[NUMBER_OF_RESOURCES];
bool finish[NUMBER_OF_PROCESSES];
// 初始化work和finish数组
// ...
// 找到一个未完成的进程
bool found;
do {
found = false;
for (int i = 0; i < NUMBER_OF_PROCESSES; i++) {
if (!finish[i]) {
bool enough_resources = true;
for (int j = 0; j < NUMBER_OF_RESOURCES; j++) {
if (need[i][j] > work[j]) {
enough_resources = false;
break;
}
}
if (enough_resources) {
for (int j = 0; j < NUMBER_OF_RESOURCES; j++) {
work[j] += allocation[i][j];
}
finish[i] = true;
found = true;
}
}
}
} while (found);
// 检查是否所有进程都已完成
for (int i = 0; i < NUMBER_OF_PROCESSES; i++) {
if (!finish[i]) {
return false;
}
}
return true;
}
bool request_resources(int pid, int request[]) {
// 检查请求是否合法
for (int i = 0; i < NUMBER_OF_RESOURCES; i++) {
if (request[i] > need[pid][i] || request[i] > available[i]) {
return false;
}
}
// 尝试分配资源
for (int i = 0; i < NUMBER_OF_RESOURCES; i++) {
available[i] -= request[i];
allocation[pid][i] += request[i];
need[pid][i] -= request[i];
}
// 检查是否安全
if (is_safe()) {
return true;
} else {
// 回滚分配
for (int i = 0; i < NUMBER_OF_RESOURCES; i++) {
available[i] += request[i];
allocation[pid][i] -= request[i];
need[pid][i] += request[i];
}
return false;
}
}
void release_resources(int pid, int release[]) {
// 释放资源
for (int i = 0; i < NUMBER_OF_RESOURCES; i++) {
available[i] += release[i];
allocation[pid][i] -= release[i];
need[pid][i] += release[i];
}
}
```
这是一个简单的示例代码,实际上,银行家算法的实现还需要考虑更多的细节,例如进程的优先级、资源分配的策略等等。