#include<stdio.h>
#include<stdlib.h>
#define TRUE 1
#define FALSE 0
#define MAX 1000
typedef struct st_tag
{
 void *baseAddr;
 int size;
 int free_flag;
 struct st_tag *next;
}node_type;
void initialize_getmemory(void);
void print_mem_info(void);
void *mymalloc(int size);
void myfree(void *xx);
node_type *hptr;
void main()
{
 int *iptr;
 initialize_getmemory();
 print_mem_info();
 iptr=(int *)mymalloc(10*sizeof(int));
 iptr[0]=10;
 iptr[1]=20;
 printf("The iptr[0]= %d addr = %u\n",iptr[0] , &iptr[0]);
 printf("The iptr[1]= %d addr = %u\n",iptr[1] , &iptr[1]);
 print_mem_info();
 printf("Try to free memory\n");
 myfree(iptr);
 print_mem_info();
}
void *mymalloc(int size)
{
 node_type *ptr=hptr;
 node_type *temp;
 int delta;
 while(ptr)
 {
  if(ptr->free_flag == TRUE && ptr->size >=size)
  {
   break;
  }
  ptr=ptr->next;
 }
 if(ptr)
 {
  temp=(node_type *)malloc(sizeof(node_type));
  temp->next=ptr->next;
  ptr->next=temp;
  delta = (int)ptr->baseAddr - (int)hptr->baseAddr;
  temp->baseAddr=(void *)((int)ptr->baseAddr + MAX - (delta + size) );
  temp->free_flag = FALSE;
  temp->size = size;
  ptr->size = ptr->size - size;
  return (void *)temp->baseAddr;
 }
 else
 {
  return (void *)NULL;
 }
}
  
void myfree(void *xx)
{
 node_type *ptr;
 node_type *temp;
 int success=FALSE;
 ptr=hptr;
 if(ptr->baseAddr==xx)
 {
  success=TRUE;
  if(ptr->next == NULL || ptr->next->free_flag == FALSE)
  {
   ptr->free_flag = TRUE;
  }
  else
  {
   ptr->free_flag = TRUE;
   ptr->size = ptr->size + ptr->next->size;
   ptr = ptr->next;
   hptr->next = ptr->next;
   free(ptr);
  }
 }
 else
 {
  while(ptr->next)
  {
   if(ptr->next->baseAddr == xx)
   {
    success=TRUE;
    if(ptr->free_flag == FALSE)
    {
     if(ptr->next->next == NULL || ptr->next->next->free_flag == FALSE)
     {
      ptr->next->free_flag = TRUE;
     }
     else
     {
      ptr=ptr->next;
      ptr->free_flag = TRUE;
      ptr->size = ptr->size  + ptr->next->size;
      temp=ptr->next;
      ptr->next = temp->next;
      free(temp);
     }
    }
    else
    {
     if(ptr->next->next == NULL || ptr->next->next->free_flag == FALSE)
     {
      ptr->size = ptr->size + ptr->next->size;
      temp=ptr->next;
      ptr->next = temp->next;
      free(temp);
     }
     else
     {
      ptr->size = ptr->size + ptr->next->size + ptr->next->next->size;
      temp=ptr->next;
      ptr->next = temp->next->next;
      free(temp->next);
      free(temp);
     }
    }
   
    break;
   }
   ptr=ptr->next;
  }
 }
 if(success == FALSE)
 {
  printf("Unable to free the memory\n");
 }
}
 
void initialize_getmemory(void)
{
 node_type *head;
 head=(node_type *)malloc(sizeof(node_type));
 head->baseAddr=(void *)malloc(MAX);
 head->size=1000;
 head->free_flag=TRUE;
 head->next=NULL;
 hptr=head;
}
void print_mem_info(void)
{
 node_type *ptr=hptr;
 while(ptr)
 {
  printf("The base address is %u\n",ptr->baseAddr);
  printf("The size is          %d\n",ptr->size);
  printf("The free_flag        %d\n\n",ptr->free_flag);
  ptr=ptr->next;
 }
}