www.pudn.com > MainMemAlloccate.rar > MainMemAlloc.c

/* 
  程序功能:模拟主存空间的分配与回收 
  其中空闲表为单链表，没有长度限制 
*/ 
#include  
#include  
#include  
#include  
 
#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()*/