/* Demonstrate use of a linked list */

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

/* Define a pointer to tcb and tcb structure */
typedef struct TCB* TCB_Pointer;
typedef struct TCB {
  TCB_Pointer pNext;
  /* whatever you need in TCB Goes here */
  int ThreadIndex; /* For example */
} Tcb;

/* define the global variables head and tail */
TCB_Pointer pHead = NULL;
TCB_Pointer pTail = NULL;

void AddTail( TCB_Pointer pThis)
{ /* Add pThis to tail of linked list */
 if (pTail != NULL)
   pTail->pNext = pThis;
 else
   pHead = pThis;
 pTail = pThis;
 pTail->pNext = NULL;
}

void SearchList( TCB_Pointer pStart)
{ /* Search the list starting at the specified starting point */
  /* If pStart is NULL, start at head */
  /* Search circularly (return to head after checking tail) */
TCB_Pointer pThis;

 if (pHead== NULL) return; // List is empty
 if (pStart == NULL) pStart = pHead; // Start from head if no starting point
 pThis = pStart;

 while(1)
   {
     /* Check whatever you want using pThis-> */
     printf("Checking node %d\n", pThis->ThreadIndex);
     pThis = pThis->pNext;
     if (pThis == NULL) pThis = pHead; /* Reset to head */
     if (pThis == pStart) return; /* Checked them all */
   }
}

int main()
{
TCB_Pointer pThis;
int         i;

  for (i = 0; i < 10; i++)
    {
      pThis = (TCB_Pointer)malloc(sizeof(*pThis));
      pThis->ThreadIndex = i; // Just debug stuff to demo
      AddTail(pThis);
      printf("Created new TCB, index %d\n", pThis->ThreadIndex);
      SearchList(pThis); // And for demonstration, show that this list is searched
    }
  // Now demonstate searching list from the head
  printf("Searchin from head\n");
  SearchList(NULL);
  
  return(0);
  
}