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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
  <COPYRIGHT HOLDER> 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
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*/

/*
  Code for general handling of priority Queues.
  Implementation of queues from "Algorithms in C" by Robert Sedgewick.
*/

#ifndef _queues_h
#define _queues_h

#ifdef	__cplusplus
extern "C" {
#endif

typedef struct st_queue {
  uchar **root;
  void *first_cmp_arg;
  uint elements;
  uint max_elements;
  uint offset_to_key;          /* compare is done on element+offset */
  uint offset_to_queue_pos;    /* If we want to store position in element */
  uint auto_extent;
  int max_at_top;	/* Normally 1, set to -1 if queue_top gives max */
  int  (*compare)(void *, uchar *,uchar *);
} QUEUE;

#define queue_first_element(queue) 1
#define queue_last_element(queue) (queue)->elements
#define queue_empty(queue) ((queue)->elements == 0)
#define queue_top(queue) ((queue)->root[1])
#define queue_element(queue,index) ((queue)->root[index])
#define queue_end(queue) ((queue)->root[(queue)->elements])
#define queue_replace_top(queue) _downheap(queue, 1)
#define queue_set_cmp_arg(queue, set_arg) (queue)->first_cmp_arg= set_arg
#define queue_set_max_at_top(queue, set_arg) \
  (queue)->max_at_top= set_arg ? -1 : 1
#define queue_remove_top(queue_arg) queue_remove((queue_arg), queue_first_element(queue_arg))
typedef int (*queue_compare)(void *,uchar *, uchar *);

int init_queue(QUEUE *queue,uint max_elements,uint offset_to_key,
	       my_bool max_at_top, queue_compare compare,
	       void *first_cmp_arg, uint offset_to_queue_pos,
               uint auto_extent);
int reinit_queue(QUEUE *queue,uint max_elements,uint offset_to_key,
                 my_bool max_at_top, queue_compare compare,
                 void *first_cmp_arg, uint offset_to_queue_pos,
                 uint auto_extent);
int resize_queue(QUEUE *queue, uint max_elements);
void delete_queue(QUEUE *queue);
void queue_insert(QUEUE *queue, uchar *element);
int queue_insert_safe(QUEUE *queue, uchar *element);
uchar *queue_remove(QUEUE *queue,uint idx);
void queue_replace(QUEUE *queue,uint idx);

#define queue_remove_all(queue) { (queue)->elements= 0; }
#define queue_is_full(queue) (queue->elements == queue->max_elements)
void _downheap(QUEUE *queue, uint idx);
void queue_fix(QUEUE *queue);
#define is_queue_inited(queue) ((queue)->root != 0)

#ifdef	__cplusplus
}
#endif
#endif

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