实验四 内存的分配与回收

#include <stdio.h>
#include <malloc.h> 
#include <process.h> 
#include <string.h>   
#define minisize 1   
typedef struct freeTable 
{    
char proID[6];    
int startAddr; /*空闲区起始地址*/   
int length; /*空闲区长度，单位为字节*/    
int flag; /*空闲区表登记栏标志，用"0"表示空表项，用"1"表示未分配*/   
struct freeTable *next;  
}
freeTabNode; /*空闲区表结点*/   
freeTabNode *freeTab;   
void InitFreeTab() 
{  
freeTabNode *f,*temp;    
f=(freeTabNode *)malloc(sizeof(freeTabNode));      
strcpy(f->proID,"OS");     
f->startAddr=0;     
f->length=5;f->flag=0;     
freeTab=f;
f=(freeTabNode *)malloc(sizeof(freeTabNode));;     
strcpy(f->proID,"1");     
f->startAddr=5;     
f->length=5;f->flag=0;     
freeTab->next=f;     
temp=f;   
f=(freeTabNode *)malloc(sizeof(freeTabNode));      
strcpy(f->proID,"3");     
f->startAddr=10;      
f->length=4;temp->flag=0;     
temp->next=f;  
temp=temp->next;    
f=(freeTabNode *)malloc(sizeof(freeTabNode));      
f->startAddr=14;  
f->length=12;  
f->flag=1;   
temp->next=f;
temp=temp->next;    
f=(freeTabNode *)malloc(sizeof(freeTabNode));      
strcpy(f->proID,"2");     
f->startAddr=26;     
f->length=6;f->flag=0;     
temp->next=f;temp=temp->next;      
f=(freeTabNode *)malloc(sizeof(freeTabNode));  
f->startAddr=32;  
f->length=96;  
f->flag=1;  
f->next=NULL;  
temp->next=f;  
}   
void allocate(char PName[],int PLength)
{  
freeTabNode *f,*temp;   f=freeTab;      
while(f) /*寻找空间大于PLength的最小空闲区登记项k*/  
{      
if(f->length>=PLength&&f->flag==1) break;                  
f=f->next;   
}    
if(!f)/*未找到可用空闲区，返回*/   
{     
printf("无可用空闲区\n");    
return;   
}  /*找到可用空闲区，开始分配*/   
if(f->length-PLength<=minisize)    
{    /*空闲区大小与要求分配的空间差小于minisize大小，空闲区全部分配*/    
strcpy(f->proID,PName);     
f->flag=0;  /*修改成空表目状态*/   
}   
else     
{ /*若空闲区大小与要求分配的空间差大于minisize大小，从中划出一部分分配*/       
f->length=f->length-PLength;     
temp=(freeTabNode *)malloc(sizeof(freeTabNode));        
strcpy(temp->proID,PName);     
temp->startAddr=f->startAddr+f->length;        
temp->length=PLength;    
temp->flag=0;    
temp->next=NULL;    
temp->next=f->next;     
f->next=temp;     
}
return;  
}/*主存分配函数结束*/   
void reclaim(char PName[])
{  /*回收作业名为PName的作业所占主存空间*/ 
freeTabNode *front,*rear,*temp;  
temp=freeTab;  /*寻找空闲表中对应登记项*/ 
if(strcmp(PName,"OS")==0) 
{ 
printf("ERROR!");   
return; 
}  
while((strcmp(temp->proID,PName)!=0||temp->flag==1)&&temp) 
temp=temp->next;   
if(!temp)/*在已分配表中找不到名字为PName的作业*/ 
{  
printf("找不到该作业\n"); return; 
}  /*寻找回收分区的空闲上下邻，上邻表目front，下邻表目rear*/ 
rear=temp->next; 
front=freeTab; 
while(front)  
{ 
if(front->next==temp)  
break;     
front=front->next;   
}/*找到回收分区的上邻表目*/  
if(rear==NULL)  
{  
if(front->flag==1) 
{   
front->length+=temp->length;     
front->next=NULL;
free(temp);   
}   
else temp->flag=1;  
}  
else  
{
if(front->flag==1&&rear->flag==1)            /* 上邻空闲区，下邻空闲区，三项合并*/     
{        
front->length=front->length+rear->length+temp->length;     
front->next=rear->next;  free(temp);   
free(rear);      
}      
else if(front->flag==1&&rear->flag==0)
{      /*上邻空闲区，下邻非空闲区，与上邻合并*/     
front->length+=temp->length;  
front->next=rear;  free(temp);  
}         
else  if(front->flag==0&&rear->flag==1)     /*上邻非空闲区，下邻为空闲区，与下邻合并*/      
{              
temp->length+=rear->length;             
temp->next=rear->next;       
free(rear);    
temp->flag=1;       
}                 
else             /*上下邻均为非空闲区，回收区域直接作修改*/        
temp->flag=1;
} 
}  
main( ) 
{ 
int a;  
freeTabNode *freeNode; 
char PName[6]; 
int PLength;  
InitFreeTab();   /*空闲分区表初始化：*/ 
while(1) {  
printf("**选择功能项**\n");  
printf("\t0--退出\n\t1--分配主存\n\t2--回收主存\n\t3--显示主存\n"); 
printf("选择项(0~3) :"); 
scanf("%d",&a); 
switch(a) {  
case 0: 
exit(0); /*a=0程序结束*/ 
case 1: /*a=1分配主存空间*/          
printf("要分配的作业名PName:");   
scanf("%s",PName);      
printf("\n和作业所需内存大小PLength(>1K): ");          
scanf("%d",&PLength);          
allocate(PName,PLength);/*分配主存空间*/         
break;  
case 2: /*a=2回收主存空间*/          
printf("输入要回收分区的作业名:");         
scanf("%s",PName);          
reclaim(PName);/*回收主存空间*/        
break;
case 3: /*a=3显示主存情况*/          
printf("--------------------------------------\n");      
printf("内存分区表:\n");     
printf("\t\t进程标识  起始地址  分区长度\t状态\n");          
freeNode=freeTab;   /*打印空闲区表*/   
while(freeNode)   
{       
if(freeNode->flag==1)          
printf("\t\t 空 \t%5d\t%6d\t\t 空 闲 \n",freeNode->startAddr,freeNode->length);      
else           
printf("\t\t%s\t%5d\t%6d\t\t 空 表 目 \n",freeNode->proID,freeNode->startAddr,freeNode->length);          
freeNode=freeNode->next;      
}                 
getchar();     
break;  
default:printf("没有该选项\n"); 
}/*case*/ 
}/*while*/ 
}/*main()*/