13. b. Memory Allocation - Best Fit Allocation

13. MEMORY ALLOCATION

Aim: To develop application to illustrate memory allocation strategies.

Program:

// 2. Best Fit Allocation

#include <stdio.h>

#include<conio.h>

int Pr[10];

struct memblock

{

    int size;

    int alloc;

    int PrIndex;

    struct memblock *next;

};

struct memblock * CreateHdr()

{

    struct memblock * temp = (struct memblock*)malloc(sizeof(struct memblock));

    temp->size = 0;

    temp->alloc = 0;

    temp->PrIndex = -1;

    return temp; 

}

struct memblock * newNode(int s)

{

    struct memblock *temp = (struct memblock*)malloc(sizeof(struct memblock));

    temp->size = s;

    temp->alloc = 0;

    temp->PrIndex = -1;

    return temp; 

}

void InsertNode(struct memblock* H, struct memblock* N)

{

    struct memblock* tmp = H;

    while (tmp->next != NULL)

        tmp = tmp->next;

       

    tmp->next = N;

}

int Allocate(struct memblock* H, int s, int index)

{

    struct memblock* tmp = H;

    int newSize;

    

     struct memblock* ptr = NULL;

                  

    while (tmp->next != NULL)

    {

        tmp=tmp->next;

        if((tmp->alloc==0) && (s<=tmp->size))

        {

              ptr = tmp;

              break;

          }

     }

    

     while (tmp->next != NULL)

    {

        tmp=tmp->next;

          if((tmp->alloc==0) && (s<=tmp->size) && (ptr->size>tmp->size))

        {

              ptr = tmp;

          }

     }

         

     if(ptr!=NULL)

     {       

          newSize = ptr->size-s;

           

          ptr->size = s;

          ptr->alloc = 1;

          ptr->PrIndex = index;

           

          if(newSize!=0)

          {

              struct memblock* t = newNode(newSize);

              t->next = ptr->next;

              ptr->next=t;

          }

          return 1;

     }

    return 0;

}

void printList(struct memblock *m)

{

    printf("\nBlock size \t Process");

    while (m->next != NULL)

    {

        m = m->next;

        if(m->alloc==0)

            printf("\n   %d\t\tNot Allocated\n", m->size);

        else

            printf("\n   %d\t\tAllocated to Process P%d\n", m->size,m->PrIndex);

    }

}

int main()

{

    int Nb, Np;

    int i, j;

    int blksize;

    int ErrCode;

   

    struct memblock *Hdr = CreateHdr();

   

    printf("\nEnter Number of Memory Blocks : ");

    scanf("%d",&Nb);

   

    for(i=0;i<Nb;i++)

        {

            scanf("%d",&blksize);

           

            struct memblock *Node = newNode(blksize);

            InsertNode(Hdr, Node);

        }

   

    printf("\nEnter number of Process : ");

    scanf("%d",&Np);

   

    for(i=0;i<Np;i++)

    {

        printf("\nEnter size of Process P%d: ",i);

        scanf("%d",&Pr[i]);

    }

       

    printf("\n\n*** Before Process Memory Allocation ***\n");

    printList(Hdr);

    printf("\n\n*** After Process Memory Allocation ***\n");

    for(i = 0;i<Np;i++)

    {

        ErrCode = Allocate(Hdr, Pr[i], i);

       

        if(ErrCode==0)

            printf("Insufficient memory.  Process P%d (%d KB) has to wait.\n", i, Pr[i]);

    }

   

    printList(Hdr);

   

    return 0;

}