//THIS IS THE PRIORITY ALGORITHM
//display the processes manager
//write by Li Xin
//June 23,2006 
   #include<stdio.h> 
   #include<stdlib.h> 
   #include<iostream.h> 
   #define P_NUM 3 
   #define P_PRI 40 

   enum state{                       //枚舉類型，進程的三種狀態
         ready, 
         working, 
         finish 
   }; 

   struct pcb{                         //結構體，pcb的結構
         char name[4]; 
         int priority; 
         int cputime; 
         int needtime; 
         state process;
         pcb * next;
   }; 

   pcb * get_process(){                   //初始化進程
         pcb *q; 
         pcb *t; 
         pcb *p; 
         int i=0; 
         cout<<"input ProcessNames and ProcessTime"<<endl; 
         while (i<P_NUM){ 
               q=(struct pcb *)malloc(sizeof(pcb)); 
               cin>>q->name; 
               cin>>q->needtime; 
               q->cputime=0; 
               q->priority=P_PRI-q->needtime; 
               q->process=ready; 
               q->next=NULL; 
               if (i==0){ 
                     p=q; 
                     t=q; 
               } 
               else{ 
                     t->next=q; 
                     t=q; 
               } 
               i++; 
         }   
         return p; 
   } 

   void  display(pcb *p){               //顯示進程狀態
         cout<<"name"<<"    "<<"cputime"<<"    "<<"needtime"<<"    "<<"priority"<<"    "<<"state"<<endl; 
         while(p){ 
               cout<<p->name; 
               cout<<"        "; 
               cout<<p->cputime; 
               cout<<"          "; 
               cout<<p->needtime; 
               cout<<"          "; 
               cout<<p->priority; 
               cout<<"          "; 
               switch(p->process){ 
                     case ready:cout<<"ready"<<endl;break; 
                     case working:cout<<"working"<<endl;break; 
                     case finish:cout<<"finish"<<endl;break; 
               } 
               p=p->next;
         } 
         cout<<"_______________________________________________________"<<endl;
   } 

   int process_finish(pcb *q){                //判斷進程是否完成 
         int b=1; 
         while(b&&q){ 
               b=(b&&q->needtime==0); 
               q=q->next; 
         } 
         return b; 
   } 

   void cpuexe(pcb *q){                     //進程一次的運行
         pcb *t=q; 
         int c=0; 
         while(q){ 
               if (q->process!=finish){ 
                     q->process=ready; 
                     if(q->needtime==0){ 
                           q->process=finish; 
                     } 
               } 
               if(c<q->priority&&q->process!=finish){ 
                     c=q->priority; 
                     t=q; 
               } 
               q=q->next; 
         } 
         if(t->needtime!=0){ 
               t->priority-=3; 
               t->needtime--; 
               t->process=working; 
               t->cputime++; 
         } 
   } 

   void priority_cal(){                          //優先數程序
         pcb * p; 
         p=get_process(); 
         int cpu=0; 
         while(!process_finish(p)){ 
               cpu++; 
               cout<<"cputime:"<<cpu<<endl; 
               cpuexe(p); 
               display(p); 
         } 
         printf("All Processes Have Finished!");
   } 
  
   void display_menu(){                           //顯示菜單 
         cout<<"*****************THIS IS THE PRIORITY ALGORITHM******************"<<endl; 
         cout<<"                    ONLY DISPALY 3 PROCESSes!                    "<<endl;
         cout<<"                1 : ENTER                  2 : EXIT              "<<endl; 
         cout<<"*****************************************************************"<<endl; 
   } 

   void main(){ 
         display_menu(); 
         int a; 
         cin>>a; 
         switch(a){ 
                     case 1:priority_cal();break;  
                     case 2:break;  
         } 
         }