/**************************************************************************/
/*                         File: linked_list.cc                           */
/**************************************************************************/
/* Project: Continuous Speech Recognition Search Algorithms               */
/* Author: Neeraj Deshmukh, Aravind Ganapathiraju                         */
/* Class: EE 8993 Spring 1996                        Date: March 27, 1996 */
/**************************************************************************/
 
/*========================================================================
  This file defines the generic linked list class that is used in various 
  applications in the speech recognizer
  ========================================================================*/
 
/*------------------------------------------------------------------------
  system and ISIP include files
  ------------------------------------------------------------------------*/
#include "linked_list.h"
 
/*------------------------------------------------------------------------
  forward declaration of classes
  ------------------------------------------------------------------------*/
class Linked_List;

/*========================================================================
  Linked_List
  function definitions for the generic linked list class
  ========================================================================*/
/*---------------------------
  constructors and destructor
  ---------------------------*/
// default constructor
//
Linked_List :: Linked_List (void *elem_ptr = NULL)
{
  // create members of the object
  //
  next_link_ptr   = NULL;
  prev_link_ptr   = NULL;
  element_ptr     = elem_ptr;
}

// destructor
//
Linked_List :: ~Linked_List ()
{
  // free all memory
  //
  delete [] element_ptr;
  delete next_link_ptr;
}

/*----------------------
  input / output methods
  ----------------------*/
// get element stored in link
//
void *Linked_List :: get_element_cc ()
{
  // return the element
  //
  return (element_ptr);
}

// set element at current link
//
void Linked_List :: set_element_cc (void *elem_ptr)
{
  // set the current element
  //
  element_ptr = elem_ptr;
}

/*-------------------
  linked list methods
  -------------------*/
// get the next link
//
Linked_List *Linked_List :: get_next_link_cc ()
{
  // return the next link in the list
  //
  return (next_link_ptr);
}

// get the previous link
//
Linked_List *Linked_List :: get_prev_link_cc ()
{
  // return the next link in the list
  //
  return (prev_link_ptr);
}

// add an object to list
//
Linked_List *Linked_List :: add_link_cc (void *elem_ptr)
{
  // check if this link already exists, do not duplicate it
  //
  if (find_link_cc (elem_ptr) != NULL)
    return (NULL);

  // create a new link for the given element
  //
  Linked_List *new_link_ptr = new Linked_List (elem_ptr);

  // add this at the head of the list
  //
  new_link_ptr->next_link_ptr  = next_link_ptr;
  next_link_ptr->prev_link_ptr = new_link_ptr;
  next_link_ptr                = new_link_ptr;
  new_link_ptr->prev_link_ptr  = this;

  // return the head of the linked list
  //
  return (new_link_ptr);
}

// find link with given element
//
Linked_List *Linked_List :: find_link_cc (void *elem_ptr)
{
  // traverse the linked list looking for matching element
  //
  for (Linked_List *index_ptr = this; index_ptr != NULL; 
       index_ptr = index_ptr->next_link_ptr)
    {
      // check for matching element
      //
      if (index_ptr->element_ptr == elem_ptr)
	{
	  // return link if found match
	  // 
	  return (index_ptr);
	}
    }
  
  // else return NULL
  //
  return (NULL);
}

// delete link with matching element
//
BOOL Linked_List :: remove_link_cc (void *elem_ptr)
{
  // traverse the linked list looking for matching element
  //
  for (Linked_List *index_ptr = this, *next_ptr = next_link_ptr; 
       next_ptr != NULL; index_ptr = index_ptr->next_link_ptr, 
	 next_ptr = next_ptr->next_link_ptr)
    {
      // check for matching element
      //
      if (next_ptr->element_ptr == elem_ptr)
	{
	  // delete this link and rejoin the modified list
	  //
	  index_ptr->next_link_ptr = next_ptr->next_link_ptr;
	  
	  // delete the matching link and free memory there
	  //
	  next_ptr->next_link_ptr  = NULL;
	  delete next_ptr;
	  
	  // return success
	  //
	  return (TRUE);
	}
    }
  
  // else matching element not found
  //
  return (FALSE);
}