可变分区分配算法

实验目的本实验主要让大家熟悉内存的各种分配和回收。通过本实验，帮助大家理解不同的存储管理方式下，如何实现内存空间的分配与回收。实验内容确定内存空间分配表；采用最先适应算法完成内存空间的分配和回收；编写主函数对所做工作进行测试。设计思路先创建好空闲分区表，用户输入作业的所需分配的空间大小，从表头依次查询空闲分区表，若有适合该作业的空闲分区，则将该空闲分区分配与作业相同大小的分区给作业，若无则需等待，然后将空闲分区表按始地址从小到大顺序进行排列。带作业执行完后，释放该分区，再将空闲分区表按始地址从小到大顺序进行排列。关键代码#include<stdio.h>#defineN5 //空闲区块数typedefstructfreearea(intstartaddress;//空闲分区始址intsize; //空闲分区长度intstate; 〃标志位，0表示空，1表示未分配freearea;freeareafreeblock[N]={{87,18,1},{115,25,1},{154,102,1},{300,30,0},{600,100,1}};//给作业分配主存空间函数intalloc(intapplysize)(inti,flag=0;〃用来标识是否有满足作业的空闲空间，1表示有，0表示无for(i=0;i<N;i++)(if(freeblock[i].state==1&&freeblock[i].size>applysize)(freeblock[i].startaddress二freeblock[i].startaddress+applysize;freeblock[i].size二freeblock[i].size-applysize;flag=1;returnfreeblock[i].startaddress-applysize;}if(freeblock[i].state==1&&freeblock[i].size==applysize)(freeblock[i].state=0;flag=1;returnfreeblock[i].startaddress;}}if(flag==0)return-1;}voidsetfree()(intaddress,size;intflag1=0,flag2=0,flag3=0;//flag1:表示回收区是否有下邻空闲区；flag2:表示回收区是否有上下邻空闲区；flag3:表示回收区是否有上邻空闲区；inti,j;printf("请输入要释放区域的起始地址:\n");scanf("%d",&address);printf("请输入要释放区域的大小：\n");scanf("%d",&size);for(i=0;i<N;i++)(if(freeblock[i].startaddress==address+size&&freeblock[i].state==1)//回收区有下邻空闲区(size=size+freeblock[i].size;〃向下合并空闲区flag1=1;for(j=0;j<N;j++)if(freeblock[j].startaddress+freeblock[j].size==address &&freeblock[j].state==1)(freeblock[i].state=0;freeblock[j].size=freeblock[j].size+size;//向上合并空闲区flag2=1; 〃回收区有上下邻空闲区break;}if(flag2==0)//回收区无上邻空闲区(freeblock[i].startaddress=address;freeblock[i].size二size;break;}}if(flag1==0) //回收区无下邻空闲区，检查其是否有上邻空闲区(for(i=0;i<N;i++)if(freeblock[i].startaddress+freeblock[i].size==address &&freeblock[i].state==1)(freeblock[i].size二freeblock[i].size+size;flag3=1;break;}if(flag3==0)//回收区无上邻空闲区for(j=0;j<N;j++)if(freeblock[j].state==0)〃将释放区放入空表目中(freeblock[j].startaddress二address;freeblock[j].size二size;freeblock[j].state=1;break;}}}voidadjust()(inti,j;freeareatemp;//中间变量for(i=0;i<N;i++) //将空闲区按始地址顺序在表中排列for(j=0;j<N;j++)if(freeblock[j].startaddress>freeblock[j+1].startaddress)(temp.startaddress=freeblock[j].startaddress;temp.size=freeblock[j].size;temp.state=freeblock[j].state;freeblock[j].startaddress=freeblock[j+1].startaddress;freeblock[j].size=freeblock[j+1].size;freeblock[j].state=freeblock[j+1].state;freeblock[j+1].startaddress=temp.startaddress;freeblock[j+1].size二temp.size;freeblock[j+1].state二temp.state;}for(i=0;i<N;i++)/*将空表目放在表后面*/for(j=0;j<N;j++)if(freeblock[j].state==0&&freeblock[j+1].state==1)(temp.startaddress二freeblock[j].startaddress;temp.size二freeblock[j].size;temp.state二freeblock[j].state;freeblock[j].startaddress二freeblock[j+1].startaddress;freeblock[j].size二freeblock[j+1].size;freeblock[j].state二freeblock[j+1].state;freeblock[j+1].startaddress二temp.startaddress;freeblock[j+1].size二temp.size;freeblock[j+1].state二temp.state;}}〃打印空闲分区表voidprint()(inti;printf("|start(始址)|size(长度)|state(标志位)|\n〃)；for(i=0;i<N;i++)(printf("| %8d | %8d | %8d\n”,freeblock[i].startaddress,freeblock[i].size,freeblock[i].state);}}main()(intapplysize,staAddress;charchoice;printf("\n是否有作业需要分配空间？(yorn:)\n");choice=getchar();while(choice=='y')(printf("\n空闲分区表为:\n");adjust();print();printf("\n请输入需分配的空间大小：\n");scanf(〃％d〃，&applysize);staAddress二alloc(applysize);adjust();printf("\n经过分配后，空闲分配表为：\n");print();if(staAddress==-1)(printf("没有合适的空闲区，请等待！")；}else(printf("\n该作业在已分配表中的始址为：％d\n”,staA