/*====================================================================*
 -  Copyright (C) 2001 Leptonica.  All rights reserved.
 -
 -  Redistribution and use in source and binary forms, with or without
 -  modification, are permitted provided that the following conditions
 -  are met:
 -  1. Redistributions of source code must retain the above copyright
 -     notice, this list of conditions and the following disclaimer.
 -  2. Redistributions in binary form must reproduce the above
 -     copyright notice, this list of conditions and the following
 -     disclaimer in the documentation and/or other materials
 -     provided with the distribution.
 -
 -  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 -  ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 -  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 -  A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL ANY
 -  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 -  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 -  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 -  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 -  OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 -  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 -  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *====================================================================*/

#ifndef  LEPTONICA_QUEUE_H
#define  LEPTONICA_QUEUE_H

/*
 *  queue.h
 *
 *      Expandable pointer queue for arbitrary void* data.
 *
 *      The L_Queue is a fifo that implements a queue of void* pointers.
 *      It can be used to hold a queue of any type of struct.
 *
 *      Internally, it maintains two counters:
 *          nhead:  location of head (in ptrs) from the beginning
 *                  of the array.
 *          nelem:  number of ptr elements stored in the queue.
 *
 *      The element at the head of the queue, which is the next to
 *      be removed, is array[nhead].  The location at the tail of the
 *      queue to which the next element will be added is
 *      array[nhead + nelem].
 *
 *      As items are added to the queue, nelem increases.
 *      As items are removed, nhead increases and nelem decreases.
 *      Any time the tail reaches the end of the allocated array,
 *      all the pointers are shifted to the left, so that the head
 *      is at the beginning of the array.
 *      If the array becomes more than 3/4 full, it doubles in size.
 *
 *      The auxiliary stack can be used in a wrapper for re-using
 *      items popped from the queue.  It is not made by default.
 *
 *      For further implementation details, see queue.c.
 */

struct L_Queue
{
    l_int32          nalloc;     /* size of allocated ptr array            */
    l_int32          nhead;      /* location of head (in ptrs) from the    */
                                 /* beginning of the array                 */
    l_int32          nelem;      /* number of elements stored in the queue */
    void           **array;      /* ptr array                              */
    struct L_Stack  *stack;      /* auxiliary stack                        */

};
typedef struct L_Queue L_QUEUE;


#endif  /* LEPTONICA_QUEUE_H */
