linux/sound/core/seq/seq_prioq.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *   ALSA sequencer Priority Queue
 *   Copyright (c) 1998-1999 by Frank van de Pol <[email protected]>
 */

#include <linux/time.h>
#include <linux/slab.h>
#include <sound/core.h>
#include "seq_timer.h"
#include "seq_prioq.h"


/* Implementation is a simple linked list for now...

   This priority queue orders the events on timestamp. For events with an
   equeal timestamp the queue behaves as a FIFO. 

   *
   *           +-------+
   *  Head --> | first |
   *           +-------+
   *                 |next
   *           +-----v-+
   *           |       |
   *           +-------+
   *                 |
   *           +-----v-+
   *           |       |
   *           +-------+
   *                 |
   *           +-----v-+
   *  Tail --> | last  |
   *           +-------+
   *

 */



/* create new prioq (constructor) */
struct snd_seq_prioq *snd_seq_prioq_new(void)
{ … }

/* delete prioq (destructor) */
void snd_seq_prioq_delete(struct snd_seq_prioq **fifo)
{ … }




/* compare timestamp between events */
/* return 1 if a >= b; 0 */
static inline int compare_timestamp(struct snd_seq_event *a,
				    struct snd_seq_event *b)
{ … }

/* compare timestamp between events */
/* return negative if a < b;
 *        zero     if a = b;
 *        positive if a > b;
 */
static inline int compare_timestamp_rel(struct snd_seq_event *a,
					struct snd_seq_event *b)
{ … }

/* enqueue cell to prioq */
int snd_seq_prioq_cell_in(struct snd_seq_prioq * f,
			  struct snd_seq_event_cell * cell)
{ … }

/* return 1 if the current time >= event timestamp */
static int event_is_ready(struct snd_seq_event *ev, void *current_time)
{ … }

/* dequeue cell from prioq */
struct snd_seq_event_cell *snd_seq_prioq_cell_out(struct snd_seq_prioq *f,
						  void *current_time)
{ … }

/* return number of events available in prioq */
int snd_seq_prioq_avail(struct snd_seq_prioq * f)
{ … }

/* remove cells matching with the condition */
static void prioq_remove_cells(struct snd_seq_prioq *f,
			       bool (*match)(struct snd_seq_event_cell *cell,
					     void *arg),
			       void *arg)
{ … }

struct prioq_match_arg { … };

static inline bool prioq_match(struct snd_seq_event_cell *cell, void *arg)
{ … }

/* remove cells for left client */
void snd_seq_prioq_leave(struct snd_seq_prioq *f, int client, int timestamp)
{ … }

struct prioq_remove_match_arg { … };

static bool prioq_remove_match(struct snd_seq_event_cell *cell, void *arg)
{ … }

/* remove cells matching remove criteria */
void snd_seq_prioq_remove_events(struct snd_seq_prioq * f, int client,
				 struct snd_seq_remove_events *info)
{ … }