#include <stdio.h>
#include <stdlib.h>

 

#define mSIZE 3
#define pSIZE 8

 

static int memery[mSIZE] = {0};
static int process[pSIZE] = {0};
//static int process[pSIZE] = {2,3,2,1,5,2,4,5,3,2,5,2};
//static int process[pSIZE] = {7,10,1,2,10,3,10,4,2,3,10,3,2,1,2,10,1,7,10,1};

void build();             //生成一个随机数序列
void FIFO();               //最近最久未使用(LRU)置换算法

 

int main(int argc, char *argv[])
{
    printf("产生随机序列如下：\n");
    build();
    printf("先进先出(FIFO)页面置换算法 \n");
    FIFO();
    system("PAUSE"); 
    return 0;
}
 
void build()
{
     int i = 0;
     for(i=0; i<pSIZE; i++)
     {
              process[i] = (int)(10.0*rand()/(RAND_MAX+1.0) + 1);
              printf("%d  ",process[i]);
     }
     printf("\n");
}

void FIFO()
{
     int time[mSIZE] = {0};
     int i = 0, j = 0;
     int m = -1, n = -1;
     int max = -1,maxtime = 0;
     int count = 0;
    
     for(i = 0; i<pSIZE; i++)
     {
           //找第一个空闲的物理块
           for(j=0; j<mSIZE; j++)
           {
                    if(memery[j] == 0)
                    {
                           m = j;
                           break;
                    }
           }
          
           //找与进程相同的标号
           for(j = 0; j < mSIZE; j++)
           {
                 if(memery[j] == process[i])
                 {
                     n = j;
                 }
           }
           //找time值最大的
           for(j = 0; j < mSIZE;j++)
           {
                 if(time[j]>maxtime)
                 {
                       maxtime = time[j];
                       max = j;
                 }
           }  
          
           if(n == -1)               //不存在相同进程
           {
                if(m != -1)          //存在空闲物理块
                {
                     memery[m] = process[i];
                     time[m] = 0;
                     for(j = 0;j <= m; j++)
                     {
                           time[j]++;
                     }
                     m = -1;
                }
                else                //不存在空闲物理块
                {
                     memery[max] = process[i];
                     time[max] = 0;
                     for(j = 0;j < mSIZE; j++)
                     {
                           time[j]++;
                     }
                     max = -1;
                     maxtime = 0;
                     count++;
                }
           }
           else                    //存在相同的进程
           {
                 memery[n] = process[i];
                 for(j = 0;j < mSIZE; j++)
                 {
                       time[j]++;
                 }
                 n = -1;
           }
           for(j = 0 ;j < mSIZE; j++)
           {
                 printf("%d  ",memery[j]);
           }
           printf("\n");
     }
     printf("页面换算次数为：%d\n",count);
}