计算机操作系统可变分区代码,操作系统实验一可变分区存储管理(含代码)

以下是一个简单的可变分区存储管理的代码示例，使用C语言编写：

#include<stdio.h>
#include<stdlib.h>

// 定义进程控制块结构体
typedef struct PCB {
    int pid; // 进程ID
    int size; // 占用内存大小
    int start; // 起始地址
} PCB;

// 定义空闲分区结构体
typedef struct FreeBlock {
    int size; // 分区大小
    int start; // 起始地址
    struct FreeBlock *next; // 指向下一个空闲分区
} FreeBlock;

FreeBlock *freeList; // 空闲分区链表
PCB *processTable[10]; // 进程控制块数组
int pidCount = 0; // 进程ID计数器

// 初始化空闲分区链表
void initFreeList(int size, int start) {
    freeList = (FreeBlock*)malloc(sizeof(FreeBlock));
    freeList->size = size;
    freeList->start = start;
    freeList->next = NULL;
}

// 查找合适的空闲分区
FreeBlock* findFreeBlock(int size) {
    FreeBlock *prev = NULL;
    FreeBlock *current = freeList;
    while (current != NULL) {
        if (current->size >= size) {
            return current;
        }
        prev = current;
        current = current->next;
    }
    return NULL;
}

// 分配空闲分区
void allocateMemory(int pid, int size) {
    FreeBlock *block = findFreeBlock(size);
    if (block == NULL) {
        printf("No free block available for allocation.\n");
        return;
    }
    PCB *process = (PCB*)malloc(sizeof(PCB));
    process->pid = pid;
    process->size = size;
    process->start = block->start;

    // 更新空闲分区链表
    if (block->size == size) {
        if (block == freeList) {
            freeList = block->next;
        } else {
            FreeBlock *prev = freeList;
            while (prev->next != block) {
                prev = prev->next;
            }
            prev->next = block->next;
        }
        free(block);
    } else {
        block->start += size;
        block->size -= size;
    }

    // 更新进程控制块数组
    processTable[pid] = process;
    printf("Process %d allocated %d bytes of memory from address %d.\n", pid, size, process->start);
}

// 释放已分配的空间
void freeMemory(int pid) {
    PCB *process = processTable[pid];
    FreeBlock *block = (FreeBlock*)malloc(sizeof(FreeBlock));
    block->size = process->size;
    block->start = process->start;

    // 查找插入位置
    FreeBlock *prev = NULL;
    FreeBlock *current = freeList;
    while (current != NULL && current->start < block->start) {
        prev = current;
        current = current->next;
    }

    // 插入空闲分区
    if (prev == NULL) {
        block->next = freeList;
        freeList = block;
    } else {
        prev->next = block;
        block->next = current;
    }

    // 更新进程控制块数组
    processTable[pid] = NULL;
    printf("Process %d freed %d bytes of memory from address %d.\n", pid, process->size, process->start);
    free(process);
}

int main() {
    // 初始化空闲分区链表
    initFreeList(512, 0);

    // 分配内存
    allocateMemory(pidCount++, 100);
    allocateMemory(pidCount++, 200);
    allocateMemory(pidCount++, 50);

    // 释放内存
    freeMemory(1);
    freeMemory(0);
    allocateMemory(pidCount++, 150);
    allocateMemory(pidCount++, 100);

    return 0;
}

该代码实现了以下功能：

1. 初始化一个大小为512，起始地址为0的空闲分区链表。
2. 定义了进程控制块结构体和空闲分区结构体。
3. 实现了查找合适的空闲分区的函数。
4. 实现了分配空闲分区的函数，该函数会更新空闲分区链表和进程控制块数组。
5. 实现了释放已分配的空间的函数，该函数会插入一个空闲分区到空闲分区链表，并更新进程控制块数组。
6. 在主函数中测试了分配和释放内存的功能。