存储管理 分区法内存分配算法
/***pcb.c***/
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#define MAX 32767
typedef struct node /*设置分区描述器*/
{
int address,size;
struct node *next;
}RECT;
/*函数原型*/
RECT *assignment(RECT *head,int application);
void acceptment1(RECT *head,RECT *back1);
void acceptment2(RECT *head,RECT *back1) ;
int backcheck(RECT *head,RECT *back1);
void print(RECT *head);
/*变量声明*/
RECT *head,*back,*assign1,*p;
int application1,maxblocknum;
char way;
/*主函数*/
main()
{
char choose[2];
int check;
head=(RECT*)malloc(sizeof(RECT)); /*建立可利用区表的初始状态*/
p=(RECT*)malloc(sizeof(RECT));
head->size=MAX;
head->address=0;
head->next=p;
maxblocknum=1;
p->size=MAX;
p->address=0;
p->next=NULL;
print(head); /*输出可利用表初始状态*/
printf("输入适应策略(最佳 or 最先(b/f)\n");/*选择适应策略*/
scanf("%c",&way);
do{
printf("选择1：分配或2：回收(1/2)\n");
scanf("%s",choose); /*选择分配或回收*/
if(strcmp(choose,"1")==0) /*1为分配*/
{
printf("输入申请空间大小:\n");
scanf("%d",&application1);/*输入申请空间大小*/
assign1=assignment(head,application1);/*调用分配函数*/
if(assign1->address==-1)/*分配不成功*/
printf("申请空间太大!申请失败!\n\n");
else
printf("成功!!地址=%5d\n",assign1->address); /*分配成功*/
print(head); /*输出*/
}
else
if(strcmp(choose,"2")==0) /*回收*/
{
back=(RECT*)malloc(sizeof(RECT));
printf("输入回收地址和大小!!\n");
scanf("%d%d",&back->address,&back->size);/*输入回收地址和大小*/
check=backcheck(head,back); /*检查*/
if(check==1)
{
if(tolower(way)=='f')/*首先适应算法*/
acceptment1(head,back); /*首先适应*/
else
acceptment2(head,back);/*最佳适应*/
print(head);
}
}
}while(!strcmp(choose,"1")||!strcmp(choose,"2"));
}
/*分配函数*/
RECT *assignment(RECT *head,int application)
{
RECT *after,*before,*assign;
assign=(RECT*)malloc(sizeof(RECT)); /*分配申请空间*/
assign->size=application;
assign->next=NULL;
if(application>head->size||application<=0)
assign->address=-1; /*申请无效*/
else
{
before=head;
after=head->next;
while(after->size
before=before->next;
after=after->next;
}
if(after->size==application) /*结点大小等于申请大小则完全分配*/
{
if(after->size==head->size)
maxblocknum--;
before->next=after->next;
assign->address=after->address;
free(after);
}
else
{
if(after->size==head->size) maxblocknum--;
after->size=after->size-application; /*大于申请空间则截取相应大小分配*/
assign->address=after->address+after->size;
if(tolower(way)=='b')/*如果是最佳适应，将截取后剩余结点重新回收到合适位置*/
{
before->next=after->next;
back=after;
acceptment2(head,back);
}
}
if(maxblocknum==0) /*修改最大数和头结点值*/
{
before=head;
head->size=0;
maxblocknum=1;
while(before!=NULL)
{
if(before->size>head->size)
{
head->size=before->size;
maxblocknum=1;
}
else
if(before->size==head->size)
maxblocknum++;
before=before->next;
}
}
}
assign1=assign;
return assign1; /*返回分配给用户的地址*/
}
void acceptment1(RECT *head,RECT *back1)/*首先适应*/
{
RECT *before,*after;
int insert;
before=head;
after=head->next;
insert=0;
while(!insert) /*将回收区插入空闲区表*/
{
if((after==NULL)||
((back1->address<=after->address)&&
(back1->address>=before->address)))
{
before->next=back1;
back1->next=after;
insert=1;
}
else
{
before=before->next;
after=after->next;
}
}
if(back1->address==before->address+before->size)/*与上一块合并*/
{
before->size=before->size+back1->size;
before->next=back1->next;
free(back1);
back1=before;
}
if(after!=NULL&&(after->address==back1->address+back1->size))
{ /*与下一块合并*/
back1->size=back1->size+after->size;
back1->next=after->next;
free(after);
}
if(head->size
{
head->size=back1->size;
maxblocknum=1;
}
else
if(head->size==back1->size)
maxblocknum++;
}
/*最佳适应，back1为回收结点的地址*/
void acceptment2(RECT *head,RECT *back1)
{
RECT *before,*after;
int insert ;
insert=0;
before=head;
after=head->next;
if(head->next==NULL) /*如果可利用区表为空*/
{
head->size=back1->size;
head->next=back1;
maxblocknum++;
back1->next=NULL;
}
else
{
while(after!=NULL) /*与上一块合并*/
if(back1->address==after->size+after->address)
{
before->next=after->next;
back->size=after->size+back1->size;
free(after);
after=NULL;
}
else
{
after=after->next;
before=before->next;
}
before=head;
after=head->next;
while(after!=NULL)
if
(after->address==back1->size+back1->address) /*与下一块合并*/
{
back1->size=back1->size+after->size;
before->next=after->next;
free(after);
after=NULL;
}
else
{
before=before->next;
after=after->next;
}
before=head;/*将回收结点插入到合适的位置*/
after=head->next;
do{
if(after==NULL||(after->size>back1->size))
{
before->next=back1;
back1->next=after;
insert=1;
}
else
{
before=before->next;
after=after->next;
}
}while(!insert);
if(head->size
{
head->size=back1->size;
maxblocknum++;
}
else
if(head->size==back1->size)
maxblocknum++;
}
}
void print(RECT *head) /*输出链表*/
{
RECT *before,*after;
int index,k;
before=head->next;
index=1;
if(head->next==NULL)
printf("NO part for assignment!!\n");
else
{
printf("*****索引*******地址********结束*********占用空间*****\n");
while(before!=NULL)
{
printf("----------------------------------------------------\n");
printf(" %-13d%-13d%-13d%-13d\n",index,before->address,before->address+before->size-1,before->size);
printf("----------------------------------------------------\n");
index++;
before=before->next;
}
}
}
/*检查回收块的合法性，back1为要回收的结点地址*/
int backcheck(RECT *head,RECT *back1)
{
RECT *before,*after;
int check=1;
if(back1->address<0||back1->size<0)
check=0;/*地址和大小不能为负*/
before=head->next;
while((before!=NULL)&&check)/*地址不能和空闲区表中结点出现重叠*/
if(((back1->address
&&(back1->address+back1->size>before->address))
||((back1->address>=before->address)
&&(back1->address
check=0;
else
before=before->next;
if(check==0)
printf("输入错误!!\n");
return check; /*返回检查结果*/
}