weishitu.rar_weishitu_位示图

#include <iostream.h> using namespace std; struct mapping //页号与块号对应 { int page; //页号 int mass; //块号 struct mapping *next; }; struct pagelist { int length; //页表长度 mapping *map; }; struct request { int num; //进程号 int size; //请求页面数 pagelist *plist; //页表始址 int length; //页表长度 char state; //状态,Y表示已分配，N表示未分配 struct request *next; }; request *S; //请求表 static int a[8][8]; void allot(); void back(); void reallot(); void display(); int main() { S=new request; S->next=NULL; int a; cout<<" 用位示图管理磁盘存储空间"<<endl; cout<<"1:分配磁盘"<<endl; cout<<"2:回收磁盘"<<endl; cout<<"0:退出"<<endl; while(1) { cout<<endl<<"请按键选择："; cin>>a; if(a>2||a<0) { cout<<endl<<"输入错误，请重新输入："; continue; } switch(a) { case 1: allot(); display(); break; case 2: back(); display(); break; case 0: goto end; } } end: ; } void allot() { int i,j,m=0; request *r=S,*p=new request; p->next=NULL; cout<<"请输入进程号和申请的空间大小："<<endl; cin>>p->num>>p->size; if(p->size<=0) { cout<<"申请空间大小错误."<<endl; delete p; return; } while(r->next!=NULL) //将p插到请求链表表尾 r=r->next; r->next=p; for(i=0;i<8;i++) //检查磁盘空间大小 { for(j=0;j<8;j++) if(a[i][j]==0) m++; } if(m<p->size) //磁盘空间不够时 { cout<<endl<<"磁盘空间不够."<<endl; p->length=0; p->state='N'; p->plist=0; return; } //磁盘空间够时 m=0; p->length=p->size; p->state='Y'; p->plist=new pagelist; //建立页表 p->plist->length=p->length; p->plist->map=new mapping; //建立页表与物理块的对应关系 p->plist->map->next=NULL; mapping *t=p->plist->map; cout<<"\t柱面号\t磁道号\t物理记录号"<<endl; for(i=0;i<8;i++) { for(j=0;j<8;j++) if(a[i][j]==0) { a[i][j]=1; m++; mapping *q=new mapping; q->next=NULL; q->page=m-1; q->mass=i*8+j; cout<<"第"<<m<<"块："; cout<<"\t"<<i; cout<<"\t"<<j/4; cout<<"\t"<<j%4<<endl; while(t->next!=NULL) //插到物理块与页号对应关系链表的表尾 t=t->next; t->next=q; q->next=NULL; if(m==p->size) goto end; } } end: cout<<"分配成功."<<endl<<endl; } void back() { int b; cout<<"请输入要回收磁盘空间的进程号："<<endl; cin>>b; request *p=S->next; while(p!=NULL&&p->num!=b) p=p->next; if(p==NULL) { cout<<endl<<"此进程不存在."<<endl; return; } if(p->state=='N') { cout<<endl<<"错误,此进程没有占据磁盘空间."<<endl; return; } cout<<endl<<"共回收"<<p->size<<"个物理块空间,具体情况如下:"<<endl; int i,j; cout<<endl<<" 每块字节号 位数号"<<endl; mapping *q=p->plist->map->next; for(int k=0;k<p->size;k++) { i=q->mass/8; j=q->mass%8; a[i][j]=0; cout<<"\t"<<i<<"\t"<<j<<endl; mapping *t; p->plist->map->next=q->next; t=q; q=p->plist->map->next; delete t; } if(S->next==p) S->next=p->next; else { request *r=S; while(r->next!=p) r=r->next; r->next=p->next; } delete p->plist->map; delete p->plist; delete p; reallot(); } void reallot() { int m=0; request *r=S,*p=new request; p->next=NULL; while(r->next!=NULL) { p=r->next; r=r->next; if(p->state=='N') //如果存在等待分配内存的进程 { for(int i=0;i<8;i++) //检查磁盘空间大小 { for(int j=0;j<8;j++) if(a[i][j]==0) m++; } if(m<p->size) //内存仍不够 { m=0; continue;} else { cout<<endl<<"进程"<<p->num<<"分配情况如下："<<endl; m=0; p->length=p->size; p->state='Y'; p->plist=new pagelist; //建立页表 p->plist->length=p->length; p->plist->map=new mapping; //建立页表与物理块的对应关系 p->plist->map->next=NULL; mapping *t=p->plist->map; cout<<"\t柱面号\t磁道号\t物理记录号"<<endl; for(int i=0;i<8;i++) { for(int j=0;j<8;j++) if(a[i][j]==0) { a[i][j]=1; m++; mapping *q=new mapping; q->next=NULL; q->page=m-1; q->mass=i*8+j; cout<<"第"<<m<<"块："; cout<<"\t"<<i; cout<<"\t"<<j/4; cout<<"\t"<<j%4<<endl; while(t->next!=NULL) //插到物理块与页号对应关系链表的表尾 t=t->next; t->next=q; q->next=NULL; if(m==p->size) {m=0; goto end;} } } end: cout<<"分配成功."<<endl<<endl; } } } } void display() { request *p=S->next; cout<<"进程号\t请求页面数\t页表地址\t页表长度\t状态"<<endl; while(p!=NULL) { if(p->state=='N') cout<<p->num<<"\t"<<p->size<<"\t\t"<<p->plist<<"\t\t"<<p->length<<"\t\t"<<p->state<<endl; else cout<<p->num<<"\t"<<p->size<<"\t\t"<<p->plist<<"\t"<<p->length<<"\t\t"<<p->state<<endl; p=p->next; } cout<<endl; for(int i=0;i<8;i++) { for(int j=0;j<8;j++) cout<<" "<<a[i][j]; cout<<endl; } }