/*
 *  buffer.c
 *
 *  Copyright (C) Thomas Östreich - June 2001
 *
 *  This file is part of transcode, a video stream processing tool
 *      
 *  transcode is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *   
 *  transcode is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *   
 *  You should have received a copy of the GNU General Public License
 *  along with GNU Make; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
 *
 */

#include "buffer.h"

#include <stdlib.h>
#include <unistd.h>

buffer_list_t *buffer_list_head;
buffer_list_t *buffer_list_tail;

buffer_list_t *buffer_register(int id)

{
  
  /* objectives: 
     ===========

     register new buffer

     allocate space for new buffer and establish backward reference
     
     
  */

  buffer_list_t *ptr;

  // retrive a valid pointer from the pool
  
  if((ptr = malloc(sizeof(buffer_list_t))) == NULL) return(NULL);
  
  if((ptr->data = (char *) malloc(MAX_PCM_BUFFER)) == NULL) return(NULL);
  
  ptr->status = BUFFER_EMPTY;
  
  ptr->next = NULL;
  ptr->prev = NULL;
  
  ptr->id  = id;
  
  if(buffer_list_tail != NULL)
  {
      buffer_list_tail->next = ptr;
      ptr->prev = buffer_list_tail;
  }
  
  buffer_list_tail = ptr;
  
  /* first buffer registered must set buffer_list_head */
  
  if(buffer_list_head == NULL) buffer_list_head = ptr;
  
  return(ptr);
  
}


/* ------------------------------------------------------------------ */

 
void buffer_remove(buffer_list_t *ptr)

{
  
  /* objectives: 
     ===========

     remove buffer from chained list

  */

  
  if(ptr == NULL) return;         // do nothing if null pointer

  if(ptr->prev != NULL) (ptr->prev)->next = ptr->next;
  if(ptr->next != NULL) (ptr->next)->prev = ptr->prev;
  
  if(ptr == buffer_list_tail) buffer_list_tail = ptr->prev;
  if(ptr == buffer_list_head) buffer_list_head = ptr->next;
  
  // release valid pointer to pool
  ptr->status = BUFFER_EMPTY;

  free(ptr->data);
  free(ptr);
  ptr=NULL;
  
}


/* ------------------------------------------------------------------ */


buffer_list_t *buffer_retrieve()

{

  /* objectives: 
     ===========

     get pointer to next full buffer
     
  */
  
  buffer_list_t *ptr;

  ptr = buffer_list_head;

  /* move along the chain and check for status */

  while(ptr != NULL)
    {
      if(ptr->status == BUFFER_READY) 
	{

	  return(ptr);
	}
      ptr = ptr->next;
    }
  
  return(NULL);
}

