1、编写C程序,模拟实现首次/最佳/最坏适应算法的内存块分配与回收,要求每次分割与回收后显示出空闲分区和已分配分区的情况。 2、假设初始状态下,可用内存空间为640KB,并有下列请求序列: 序号 操作 1 作业1申请130KB 2 作业2申请60KB 3 作业3申请100KB 4 作业2释放60KB 5 作业3释放100KB 6 作业1释放130KB 请分别采用首次/最佳/最坏适应算法,对内存进行分配与回收,要求每次分配和回收后显示空闲内存分区链的情况。
时间: 2024-03-12 13:44:21 浏览: 65
用首次适应算法模拟内存的分配和回收
好的,我会尽力回答你的问题。但是需要注意,我是一个语言模型 AI,无法直接运行代码。我会用文字模拟实现首次/最佳/最坏适应算法的内存块分配与回收,并根据给出的请求序列进行模拟。
首先,我们需要了解一下内存分配算法:
- 首次适应算法(First Fit):从空闲分区链的头开始,找到第一个能满足要求的空闲分区进行分配。
- 最佳适应算法(Best Fit):从空闲分区链中找到最小的能满足要求的空闲分区进行分配。
- 最坏适应算法(Worst Fit):从空闲分区链中找到最大的空闲分区进行分配。
下面,我们分别用这三种算法进行模拟。
首先,我们定义一个结构体表示内存块:
```c
typedef struct MemoryBlock {
int size; // 内存块大小
int start; // 内存块起始地址
int end; // 内存块结束地址
int pid; // 进程 ID,为 0 表示空闲块
struct MemoryBlock* next; // 指向下一个内存块
} MemoryBlock;
```
然后,我们定义一个全局变量表示空闲分区链:
```c
MemoryBlock* freeList; // 空闲分区链表头指针
```
接下来,我们实现内存分配和回收的函数。
首次适应算法(First Fit):
```c
MemoryBlock* allocateFirstFit(int size, int pid) {
MemoryBlock* p = freeList;
MemoryBlock* prev = NULL;
while (p != NULL) {
if (p->size >= size) { // 找到满足要求的空闲分区
MemoryBlock* newBlock = (MemoryBlock*) malloc(sizeof(MemoryBlock));
newBlock->size = size;
newBlock->start = p->start;
newBlock->end = p->start + size - 1;
newBlock->pid = pid;
newBlock->next = NULL;
if (prev == NULL) { // 分配的空闲分区在链表头
freeList = p->next;
} else { // 分配的空闲分区在链表中间
prev->next = p->next;
}
if (p->size > size) { // 剩余空闲分区
MemoryBlock* remainBlock = (MemoryBlock*) malloc(sizeof(MemoryBlock));
remainBlock->size = p->size - size;
remainBlock->start = newBlock->end + 1;
remainBlock->end = p->end;
remainBlock->pid = 0;
remainBlock->next = freeList;
freeList = remainBlock;
}
return newBlock;
}
prev = p;
p = p->next;
}
return NULL; // 没有满足要求的空闲分区
}
void freeFirstFit(MemoryBlock* block) {
MemoryBlock* p = freeList;
MemoryBlock* prev = NULL;
while (p != NULL) {
if (p->start > block->end) { // 在该空闲分区前面
break;
}
prev = p;
p = p->next;
}
if (prev == NULL) { // 需要插入到链表头
block->next = freeList;
freeList = block;
} else { // 插入到链表中间
block->next = prev->next;
prev->next = block;
}
}
```
最佳适应算法(Best Fit):
```c
MemoryBlock* allocateBestFit(int size, int pid) {
MemoryBlock* p = freeList;
MemoryBlock* prev = NULL;
MemoryBlock* bestBlock = NULL;
while (p != NULL) {
if (p->size >= size) { // 找到满足要求的空闲分区
if (bestBlock == NULL || p->size < bestBlock->size) {
bestBlock = p;
prev = prev;
}
}
prev = p;
p = p->next;
}
if (bestBlock != NULL) {
MemoryBlock* newBlock = (MemoryBlock*) malloc(sizeof(MemoryBlock));
newBlock->size = size;
newBlock->start = bestBlock->start;
newBlock->end = bestBlock->start + size - 1;
newBlock->pid = pid;
newBlock->next = NULL;
if (prev == NULL) { // 分配的空闲分区在链表头
freeList = bestBlock->next;
} else { // 分配的空闲分区在链表中间
prev->next = bestBlock->next;
}
if (bestBlock->size > size) { // 剩余空闲分区
MemoryBlock* remainBlock = (MemoryBlock*) malloc(sizeof(MemoryBlock));
remainBlock->size = bestBlock->size - size;
remainBlock->start = newBlock->end + 1;
remainBlock->end = bestBlock->end;
remainBlock->pid = 0;
remainBlock->next = freeList;
freeList = remainBlock;
}
return newBlock;
}
return NULL; // 没有满足要求的空闲分区
}
void freeBestFit(MemoryBlock* block) {
MemoryBlock* p = freeList;
MemoryBlock* prev = NULL;
while (p != NULL) {
if (p->start > block->end) { // 在该空闲分区前面
break;
}
prev = p;
p = p->next;
}
if (prev == NULL) { // 需要插入到链表头
block->next = freeList;
freeList = block;
} else { // 插入到链表中间
block->next = prev->next;
prev->next = block;
}
// 如果前后空闲分区相连,合并它们
if (block->next != NULL && block->next->start == block->end + 1) {
block->size += block->next->size;
block->end = block->next->end;
block->next = block->next->next;
}
if (prev != NULL && prev->end == block->start - 1) {
prev->size += block->size;
prev->end = block->end;
prev->next = block->next;
}
}
```
最坏适应算法(Worst Fit):
```c
MemoryBlock* allocateWorstFit(int size, int pid) {
MemoryBlock* p = freeList;
MemoryBlock* prev = NULL;
MemoryBlock* worstBlock = NULL;
while (p != NULL) {
if (p->size >= size) { // 找到满足要求的空闲分区
if (worstBlock == NULL || p->size > worstBlock->size) {
worstBlock = p;
prev = prev;
}
}
prev = p;
p = p->next;
}
if (worstBlock != NULL) {
MemoryBlock* newBlock = (MemoryBlock*) malloc(sizeof(MemoryBlock));
newBlock->size = size;
newBlock->start = worstBlock->start;
newBlock->end = worstBlock->start + size - 1;
newBlock->pid = pid;
newBlock->next = NULL;
if (prev == NULL) { // 分配的空闲分区在链表头
freeList = worstBlock->next;
} else { // 分配的空闲分区在链表中间
prev->next = worstBlock->next;
}
if (worstBlock->size > size) { // 剩余空闲分区
MemoryBlock* remainBlock = (MemoryBlock*) malloc(sizeof(MemoryBlock));
remainBlock->size = worstBlock->size - size;
remainBlock->start = newBlock->end + 1;
remainBlock->end = worstBlock->end;
remainBlock->pid = 0;
remainBlock->next = freeList;
freeList = remainBlock;
}
return newBlock;
}
return NULL; // 没有满足要求的空闲分区
}
void freeWorstFit(MemoryBlock* block) {
MemoryBlock* p = freeList;
MemoryBlock* prev = NULL;
while (p != NULL) {
if (p->start > block->end) { // 在该空闲分区前面
break;
}
prev = p;
p = p->next;
}
if (prev == NULL) { // 需要插入到链表头
block->next = freeList;
freeList = block;
} else { // 插入到链表中间
block->next = prev->next;
prev->next = block;
}
// 如果前后空闲分区相连,合并它们
if (block->next != NULL && block->next->start == block->end + 1) {
block->size += block->next->size;
block->end = block->next->end;
block->next = block->next->next;
}
if (prev != NULL && prev->end == block->start - 1) {
prev->size += block->size;
prev->end = block->end;
prev->next = block->next;
}
}
```
接下来,我们用给出的请求序列进行模拟。
首先,我们初始化空闲分区链,可用内存空间为640KB:
```c
void init() {
MemoryBlock* block = (MemoryBlock*) malloc(sizeof(MemoryBlock));
block->size = 640;
block->start = 0;
block->end = 639;
block->pid = 0;
block->next = NULL;
freeList = block;
}
```
然后,我们按照顺序进行分配和回收操作:
```c
int main() {
init(); // 初始化空闲分区链
// 请求序列:作业1申请130KB,作业2申请60KB,作业3申请100KB
MemoryBlock* block1 = allocateFirstFit(130, 1);
MemoryBlock* block2 = allocateBestFit(60, 2);
MemoryBlock* block3 = allocateWorstFit(100, 3);
printMemory(); // 显示空闲分区链和已分配分区
// 请求序列:作业2释放60KB,作业3释放100KB,作业1释放130KB
freeFirstFit(block2);
freeBestFit(block3);
freeWorstFit(block1);
printMemory(); // 显示空闲分区链和已分配分区
return 0;
}
```
最后,我们实现显示空闲分区链和已分配分区的函数:
```c
void printMemory() {
printf("空闲分区链:\n");
MemoryBlock* p = freeList;
while (p != NULL) {
printf("[%d, %d] -> ", p->start, p->end);
p = p->next;
}
printf("NULL\n已分配分区:\n");
p = freeList;
while (p != NULL) {
if (p->pid != 0) {
printf("[%d, %d]: %d\n", p->start, p->end, p->pid);
}
p = p->next;
}
printf("\n");
}
```
这样,我们就完成了模拟实现首次/最佳/最坏适应算法的内存块分配与回收。
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