计算机操作系统内存分配源码.doc

#include #includeusing namespace std;#define MEM_SIZE 200static char memMEM_SIZE;#define MINBLK 16struct block struct block * next;size_t length;char data0;static struct block * free_list = NULL;/free_list为空void malloc_init(void)free_list = (struct block *)mem;free_list-next = NULL;/next指向空free_list-length = MEM_SIZE - sizeof(struct block);/data段的长度/字节对齐void * malloc(size_t size)size = (size + 7) & 7;struct block * prev = (struct block *) &free_list;/block首段struct block * cur = free_list;/cur 指向空闲的块while (cur != NULL) if (cur-length = size) /判断cur指向的块是否满足所要求的大小break;prev = cur;cur = cur-next;if (cur = NULL)return NULL;/cur-length(data段的长度)-size后的大小可不可以放下blockif (cur-length - size) = MINBLK) struct block * temp = (struct block *)(cur-data + size);/temp指向新block的头temp-next = cur-next;/新block指向下一个空白temp-length = cur-length - size - sizeof(struct block);prev-next = temp;cur-length = size;else prev-next = cur-next;return cur-data;void free(void * ptr)if (ptr = NULL)return;struct block * temp = (struct block *)(char *)ptr - sizeof(struct block);char * tempn = (char *)ptr + temp-length; / 和temp物理上相邻的下一个block的地址struct block * prev = (struct block *) &free_list;struct block * cur = free_list;char * curn; / 和cur物理上相邻的下一个block的地址/ 考虑多种情况，完成free函数/ . .if (free_list temp)/空块地址大于要释放的块的地址，直接将释放的块放入空白块头部（第一种情况）if (char*)temp + sizeof(block)+temp-length) = (char*)free_list) temp-length += sizeof(block)+free_list-length;free_list = temp;else temp-next = free_list;free_list = temp;ptr = NULL;return;/若不一定插入头部，寻找插入块while (cur != NULL & (char*)cur next;/temp与前段free_list相邻if (char *)prev + sizeof(struct block) + prev-length) = (char*)temp)prev-length =prev-length + sizeof(struct block) + temp-length;temp = prev;ptr = NULL;elseprev-next = temp;ptr = NULL;/free_list在比temp地址大的地方且两者相邻if (char *)tempn = (char *)cur | cur = NULL) temp-next = cur-next;temp-length = sizeof(struct block) + cur-length + temp-length;ptr = NULL;elsetemp-next = cur;ptr = NULL;void malloc_state(void)printf(free blocks:n);struct block * ptr;for (ptr = free_list; ptr != NULL; ptr = ptr-next) int i;printf(%p:, ptr);/printf(%d, ptr-length);for (int i = 0; i length; i+) printf(=);printf( );printf(n);void malloc_test(void)/定义abcdef为分配状态char* a = (char*)malloc(sizeof(char);malloc_state();char* b = (char*)malloc(sizeof(char);malloc_state();char* c = (char*)malloc(sizeof(char);malloc_state();char* d = (char*)malloc(sizeof(char);malloc_state();char* e = (char*)malloc(sizeof(char);malloc_state();char* f = (char*)malloc(sizeof(char);/按照adbfec的顺序进行释放会将所有的情况包含进去malloc_state();free(a);malloc_state();free(d);malloc_state();free(b);malloc_state();free(f);malloc_state();free(e);malloc_state();free(c);malloc_state