动态分区分配方式首次适应算法

动态分区分配方式首次适应算法算法思路使用动态分区分配中的数据结构和分配算法，编辑动态分区存储管理方式并实现。本程序主要采用首次适应算法的动态分区分配过程alloc()和回收过程free()。

空闲分区通过空闲分区链表来管理，在进行内存分配时，系统优先使用空闲区低端的空间，即每次分配内存空间是总是从低址部分开始进行循环，找到第一个合适的空间，便按作业所需分配的大小分配给作业。二、算法流程图检查完否？从头开始查表 Yes No与要求内存是否一致？继续查找下一个表 NoYes三、函数代码#include<iostream.h>#include<stdlib.h>#defineFree0//空闲状态#defineBusy1//已用状态#defineOK1//完成#defineERROR0//出错#defineMAX_length640//最大内存空间为640KBtypedefintStatus;typedefstructfreearea//定义一个空闲区说明表结构{ intID; longsize; longaddress; intstate;}ElemType;}//------------------首次适应算法-----------------------StatusFirst_fit(intID,intrequest)//传入作业名及申请量{ //为申请作业开辟新空间且初始化 DuLinkListtemp=(DuLinkList)malloc(sizeof(DuLNode));temp->data.ID=ID;temp->data.size=request;temp->data.state=Busy;DuLNode*p=block_first->next; while(p) { if(p->data.state==Free&&p->data.size==request) { //有大小恰好合适的空闲块 p->data.state=Busy; p->data.ID=ID; returnOK; break; } if(p->data.state==Free&&p->data.size>request) { //有空闲块能满足需求且有剩余 temp->prior=p->prior; temp->next=p; temp->data.address=p->data.address; p->prior->next=temp;p->prior=temp; p->data.address=temp->data.address+temp->data.size; p->data.size-=request; returnOK; break; } p=p->next; } returnERROR;}//-----------------------主存回收--------------------Statusfree(intID){ DuLNode*p=block_first; while(p) { if(p->data.ID==ID) { p->data.state=Free; p->data.ID=Free; if(p->prior->data.state==Free)//与前面的空闲块相连 { p->prior->data.size+=p->data.size;p->prior->next=p->next;p->next->prior=p->prior; } if(p->next->data.state==Free)//与后面的空闲块相连 { p->data.size+=p->next->data.size;if(p->next->next==NULL)p->next=NULL;else{ p->next->next->prior=p; p->next=p->next->next;} } break; } p=p->next; } cout<<"分区："<<ID<<"回收成功"<<endl; returnOK;// }//---------------显示主存分配情况------------------voidshow(){ cout<<"++++++++++++++++++++++++++++++++++++++++++++\n"; cout<<"+++++主存分配情况++++++\n"; cout<<"++++++++++++++++++++++++++++++++++++++++++++\n"; DuLNode*p=block_first->next; while(p) { cout<<"分区号："; if(p->data.ID==Free) cout<<"Free"<<endl; else cout<<p->data.ID<<endl; cout<<"起始地址："<<p->data.address; cout<<"分区大小："<<p->data.size<<"KB"; cout<<"状态："; if(p->data.state==Free) cout<<"空闲"<<endl; else cout<<"已分配"<<endl; p=p->next; }}//-----------------------主函数---------------------------voidmain(){ Initblock(); intchoice; inti; for(i=0;;i++) {cout<<"++++++++++++++++++++++++++++++++++++++++++++++++++++++++\n"; cout<<"+++++++++++++++动态分区分配方式的模拟一+++++++++++++++++\n"; cout<<"++++++++++++++++++++首次适应算法++++++++++++++++++++++++\n"; cout<<"++++++++++++++++++++++++++++++++++++++++++++\n"; cout<<"++1:分配内存2:回收内存++\n"; cout<<"++3:查看分配0:退出++\n"; cout<<"++++++++++++++++++++++++++++++++++++++++++++\n"; cout<<"请输入您的操作："; cin>>choice; if(choice==1)//分配内存 alloc(); elseif(choice==2)//内存回收 { intID; cout<<"请输入您要释放的分区号："; cin>>ID; free(ID); } elseif(choice==3)//显示主存 show(); elseif(choice==0)//退出 break; else//输入操作有误 { cout<<"输入有误，请重试！"<<endl;