Banker's Algorithm Implementation in C/C++

<syntaxhighlight lang="C" name="banker_algorithm">

1. include<stdio.h>
2. include<stdlib.h>
3. include<string.h>

int max[20][20]; int allocated[20][20]; int need[20][20]; int available[20]; int n, m; int safe[20]; int issafe(); int memcp(int*, int*, int);

void print(int (*a)[20], int n, int m) {

 int i, j;
 for(i = 0; i < n; i++)
   {
     printf("\n");
   for(j = 0; j < m; j++)
     {

printf("%d\t", a[i][j]);

     }
   }

}

int main() {

 int i, j, p, request[20];
 int *avail, *alloc, *nd;
 printf("Enter the no. of processes and resources: ");
 scanf("%d%d", &n, &m);
 printf("Enter the max. need matrix\n");
 for(i = 0; i < n; i++)
   for(j = 0; j < m; j++)
     {

printf("MaxNeed[%d][%d]: ", i+1, j+1); scanf("%d", &max[i][j]);

     }
 printf("Enter the available resource vector: \n");
 for(i = 0; i < m; i++)
   {
     printf("Resource[%d]: ", i+1);
     scanf("%d", &available[i]);
   }
 printf("Enter the  allocation matrix\n");
 for(i = 0; i < n; i++)
   for(j = 0; j < m; j++)
     {
       printf("Allocated[%d][%d]: ", i+1, j+1);
       scanf("%d", &allocated[i][j]);
     }
 for(i = 0; i < n; i++)
   for(j = 0; j < m; j++)
     {
       need[i][j] = max[i][j] - allocated[i][j];
     }

 while(1)
   {
     printf("Enter the id of the requesting process: ");
     scanf("%d", &p);
     p--;
     printf("Enter the request vector\n");
     for(i = 0; i < m; i++)

{ printf("Resource[%d] :", i+1); scanf("%d", &request[i]); }

     if(isless(request, need[p]))

{ if(isless(request, available)) { avail = malloc(4*m); alloc = malloc(4*m); nd = malloc(4*m); memcp(avail,available,m); memcp(alloc,allocated[p],m); memcp(nd,need[p],m); sub(available,request); add(allocated[p],request); sub(need[p],request); // print(allocated,n,m); //print(need,n,m); if(issafe()) { printf("Request Accepted!!!\n"); } else { printf("Request Pending!!!\nSystem cannot be in safe state if the request is accepted now\n"); { memcp(available,avail,m); memcp(allocated[p],alloc,m); memcp(need[p],nd,m); } } free(avail); free(alloc); free(nd); } else { printf("Request Pending!!!\nNot enough available resources\n"); } }

     else

{ printf("Invalid request!!!\n"); }

     printf("Enter 0 to stop or any other number to continue: ");
     scanf("%d", &p);

if(!p) break;

   }

}

int memcp(int *a,int *b, int n) {

 int i;
 for(i = 0;i < n; i++)
   a[i] = b[i];

}

int isless(int *a,int *b) {

 int i;
 for(i = 0; i < m; i++)
     if(a[i] > b[i])

return 0;

 return 1;

}

int issafe() {

 int i, *work, *finish;
 char out[50];
 work = malloc(m*4);
 finish = malloc(n*4);
 memset(finish, 0, n);
 memcp(work, available, m);
 sprintf(out, "<");
 for(i = 0; i < n; i++)
   {
     if(isless(need[i], work) && !finish[i])

{ add(work, allocated[i]); finish[i] = 1; sprintf(out + strlen(out), "P%d, ", i+1); i = -1; }

   }
 printf("\n");
 for(i = 0; i < n; i++)
   if(!finish[i])
     break;
 free(work);
 free(finish);
 if(i == n)
   {
     sprintf(out + strlen(out) - 2, ">");
     printf("%s\n", out);
   return 1;
   }
 else
   return 0;

}

int add(int *a, int *b) {

 int i;
 for(i = 0; i < m; i++)
   a[i] += b[i];
 return 1;

}

int sub(int *a, int *b)
{
  int i;
  for(i = 0; i < m; i++)
    a[i] -= b[i];
  return 1;
}

</syntaxhighlight>

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