操作系统实验内存管理算法c语言源代码

操作系统中的内存管理算法有很多种，以下是其中的几种常见的算法的 C 语言源代码实现。

1. 首次适应算法（First Fit）

#include <stdio.h>

#define MAX_SIZE 100

int mem[MAX_SIZE];
int mem_size = MAX_SIZE;

void init_mem() {
    for (int i = 0; i < mem_size; i++) {
        mem[i] = -1;
    }
}

int first_fit(int size) {
    int start = -1;
    int cnt = 0;
    for (int i = 0; i < mem_size; i++) {
        if (mem[i] == -1) {
            if (start == -1) {
                start = i;
            }
            cnt++;
        } else {
            start = -1;
            cnt = 0;
        }
        if (cnt >= size) {
            return start;
        }
    }
    return -1;
}

void alloc_mem(int size, int pid) {
    int start = first_fit(size);
    if (start == -1) {
        printf("Memory allocation failed for process %d\n", pid);
    } else {
        for (int i = start; i < start + size; i++) {
            mem[i] = pid;
        }
        printf("Memory allocated for process %d starting from address %d\n", pid, start);
    }
}

void dealloc_mem(int pid) {
    for (int i = 0; i < mem_size; i++) {
        if (mem[i] == pid) {
            mem[i] = -1;
        }
    }
}

void print_mem() {
    for (int i = 0; i < mem_size; i++) {
        if (i % 10 == 0) {
            printf("\n");
        }
        if (mem[i] == -1) {
            printf(". ");
        } else {
            printf("%d ", mem[i]);
        }
    }
    printf("\n");
}

int main() {
    init_mem();
    alloc_mem(5, 1);
    print_mem();
    alloc_mem(3, 2);
    print_mem();
    dealloc_mem(1);
    print_mem();
    alloc_mem(4, 3);
    print_mem();
    return 0;
}

2. 循环首次适应算法（Next Fit）

#include <stdio.h>

#define MAX_SIZE 100

int mem[MAX_SIZE];
int mem_size = MAX_SIZE;
int last_alloc = 0;

void init_mem() {
    for (int i = 0; i < mem_size; i++) {
        mem[i] = -1;
    }
}

int next_fit(int size) {
    int start = -1;
    int cnt = 0;
    for (int i = last_alloc; i < mem_size; i++) {
        if (mem[i] == -1) {
            if (start == -1) {
                start = i;
            }
            cnt++;
        } else {
            start = -1;
            cnt = 0;
        }
        if (cnt >= size) {
            last_alloc = start + size;
            return start;
        }
    }
    for (int i = 0; i < last_alloc; i++) {
        if (mem[i] == -1) {
            if (start == -1) {
                start = i;
            }
            cnt++;
        } else {
            start = -1;
            cnt = 0;
        }
        if (cnt >= size) {
            last_alloc = start + size;
            return start;
        }
    }
    return -1;
}

void alloc_mem(int size, int pid) {
    int start = next_fit(size);
    if (start == -1) {
        printf("Memory allocation failed for process %d\n", pid);
    } else {
        for (int i = start; i < start + size; i++) {
            mem[i] = pid;
        }
        printf("Memory allocated for process %d starting from address %d\n", pid, start);
    }
}

void dealloc_mem(int pid) {
    for (int i = 0; i < mem_size; i++) {
        if (mem[i] == pid) {
            mem[i] = -1;
        }
    }
}

void print_mem() {
    for (int i = 0; i < mem_size; i++) {
        if (i % 10 == 0) {
            printf("\n");
        }
        if (mem[i] == -1) {
            printf(". ");
        } else {
            printf("%d ", mem[i]);
        }
    }
    printf("\n");
}

int main() {
    init_mem();
    alloc_mem(5, 1);
    print_mem();
    alloc_mem(3, 2);
    print_mem();
    dealloc_mem(1);
    print_mem();
    alloc_mem(4, 3);
    print_mem();
    return 0;
}

3. 最佳适应算法（Best Fit）

#include <stdio.h>

#define MAX_SIZE 100

int mem[MAX_SIZE];
int mem_size = MAX_SIZE;

void init_mem() {
    for (int i = 0; i < mem_size; i++) {
        mem[i] = -1;
    }
}

int best_fit(int size) {
    int start = -1;
    int cnt = 0;
    int min_size = mem_size + 1;
    for (int i = 0; i < mem_size; i++) {
        if (mem[i] == -1) {
            if (start == -1) {
                start = i;
            }
            cnt++;
        } else {
            if (cnt >= size && cnt < min_size) {
                min_size = cnt;
                start = i - cnt;
            }
            start = -1;
            cnt = 0;
        }
    }
    if (cnt >= size && cnt < min_size) {
        min_size = cnt;
        start = mem_size - cnt;
    }
    if (min_size == mem_size + 1) {
        return -1;
    }
    return start;
}

void alloc_mem(int size, int pid) {
    int start = best_fit(size);
    if (start == -1) {
        printf("Memory allocation failed for process %d\n", pid);
    } else {
        for (int i = start; i < start + size; i++) {
            mem[i] = pid;
        }
        printf("Memory allocated for process %d starting from address %d\n", pid, start);
    }
}

void dealloc_mem(int pid) {
    for (int i = 0; i < mem_size; i++) {
        if (mem[i] == pid) {
            mem[i] = -1;
        }
    }
}

void print_mem() {
    for (int i = 0; i < mem_size; i++) {
        if (i % 10 == 0) {
            printf("\n");
        }
        if (mem[i] == -1) {
            printf(". ");
        } else {
            printf("%d ", mem[i]);
        }
    }
    printf("\n");
}

int main() {
    init_mem();
    alloc_mem(5, 1);
    print_mem();
    alloc_mem(3, 2);
    print_mem();
    dealloc_mem(1);
    print_mem();
    alloc_mem(4, 3);
    print_mem();
    return 0;
}

以上是三种常见的内存管理算法的 C 语言源代码实现，希望能够对你有所帮助。