写一个随机地申请和归还各种规格的存储块的c语言伙伴系统代码
时间: 2024-02-22 16:56:50 浏览: 24
这是一个简单的伙伴系统的C语言代码示例:
```c
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#define MIN_BLOCK_SIZE 16
#define MAX_BLOCK_SIZE 2048
#define NUM_BLOCK_SIZES (int)(log2(MAX_BLOCK_SIZE/MIN_BLOCK_SIZE)+1)
unsigned char *heap;
struct block {
int size;
int free;
struct block *next;
struct block *prev;
};
typedef struct block block_t;
block_t *free_lists[NUM_BLOCK_SIZES];
int get_block_size(int size) {
int i = 0;
while (size > MIN_BLOCK_SIZE) {
size = size >> 1;
i++;
}
return i;
}
void *get_memory(int size) {
int block_size_index = get_block_size(size + sizeof(block_t));
if (block_size_index >= NUM_BLOCK_SIZES) {
printf("Requested block size too large\n");
return NULL;
}
block_t *block = free_lists[block_size_index];
while (block != NULL) {
if (block->free == 1) {
block->free = 0;
return (void *)(block + 1);
}
block = block->next;
}
// No free blocks, allocate a new one
block = (block_t *)sbrk((int)pow(2, block_size_index) * MIN_BLOCK_SIZE);
block->size = block_size_index;
block->free = 0;
block->next = free_lists[block_size_index];
block->prev = NULL;
if (free_lists[block_size_index] != NULL) {
free_lists[block_size_index]->prev = block;
}
free_lists[block_size_index] = block;
return (void *)(block + 1);
}
void free_memory(void *ptr) {
if (ptr == NULL) {
return;
}
block_t *block = (block_t *)ptr - 1;
if (block->free == 1) {
printf("Error: double free attempted\n");
return;
}
block->free = 1;
if (block->prev != NULL && block->prev->free == 1) {
block_t *prev = block->prev;
prev->next = block->next;
if (block->next != NULL) {
block->next->prev = prev;
}
prev->size++;
free_lists[block->size] = block->next;
block = prev;
}
if (block->next != NULL && block->next->free == 1) {
block_t *next = block->next;
block->next = next->next;
if (next->next != NULL) {
next->next->prev = block;
}
block->size++;
free_lists[next->size] = next->next;
}
}
int main() {
heap = sbrk(0);
void *mem1 = get_memory(16);
void *mem2 = get_memory(32);
void *mem3 = get_memory(64);
void *mem4 = get_memory(128);
void *mem5 = get_memory(256);
free_memory(mem1);
free_memory(mem2);
free_memory(mem3);
free_memory(mem4);
free_memory(mem5);
sbrk(-((int)heap - (int)sbrk(0)));
return 0;
}
```
该代码使用伙伴系统算法实现了动态内存分配和释放。伙伴系统算法将内存块分成大小相等的块,并且每个块有一个“伙伴”块,其大小为原始块大小的两倍。当一个块被请求时,算法会找到一个大小最适合的块,如果没有可用的块,则会分配一个新块。当一个块被释放时,算法会将它的伙伴块与它合并,直到不能再合并为止。