queues.h

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   it under the terms of the GNU General Public License, version 2.0,
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   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */

#ifndef QUEUES_INCLUDED
#define QUEUES_INCLUDED

/**
  @file storage/myisam/queues.h
  Code for handling of priority queues.
  Implementation of queues from "Algorithms in C" by Robert Sedgewick.
*/

#include <stddef.h>
#include <sys/types.h>

#include "my_inttypes.h"
#include "mysql/psi/psi_memory.h"

#ifdef __cplusplus
extern "C" {
#endif

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

void _downheap(QUEUE *queue, uint idx);
void queue_fix(QUEUE *queue);

#define queue_top(queue) ((queue)->root[1])
#define queue_element(queue, index) ((queue)->root[index + 1])
#define queue_end(queue) ((queue)->root[(queue)->elements])

static inline void queue_replaced(QUEUE *queue) { _downheap(queue, 1); }

static inline void queue_set_max_at_top(QUEUE *queue, int set_arg) {
  queue->max_at_top = set_arg ? -1 : 1;
}

typedef int (*queue_compare)(void *, uchar *, uchar *);

int init_queue(QUEUE *queue, PSI_memory_key psi_key, uint max_elements,
               uint offset_to_key, bool max_at_top, queue_compare compare,
               void *first_cmp_arg);
int reinit_queue(QUEUE *queue, PSI_memory_key psi_key, uint max_elements,
                 uint offset_to_key, bool max_at_top, queue_compare compare,
                 void *first_cmp_arg);
void delete_queue(QUEUE *queue);
void queue_insert(QUEUE *queue, uchar *element);
uchar *queue_remove(QUEUE *queue, uint idx);

static inline void queue_remove_all(QUEUE *queue) { queue->elements = 0; }

static inline bool queue_is_full(QUEUE *queue) {
  return queue->elements == queue->max_elements;
}

static inline bool is_queue_inited(QUEUE *queue) {
  return queue->root != nullptr;
}

#ifdef __cplusplus
}
#endif

#endif  // QUEUES_INCLUDED