teensy-audio/play_queue.cpp

/* Audio Library for Teensy 3.X
 * Copyright (c) 2014, Paul Stoffregen, paul@pjrc.com
 *
 * Development of this audio library was funded by PJRC.COM, LLC by sales of
 * Teensy and Audio Adaptor boards.  Please support PJRC's efforts to develop
 * open source software by purchasing Teensy or other PJRC products.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice, development funding notice, and this permission
 * notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "play_queue.h"
#include "utility/dspinst.h"

bool AudioPlayQueue::available(void)
{
        if (userblock) return true;
        userblock = allocate();
        if (userblock) return true;
        return false;
}

int16_t * AudioPlayQueue::getBuffer(void)
{
	if (userblock) return userblock->data;
	while (1) {
		userblock = allocate();
		if (userblock) return userblock->data;
		yield();
	}
}

void AudioPlayQueue::playBuffer(void)
{
	uint32_t h;

	if (!userblock) return;
	h = head + 1;
	if (h >= 32) h = 0;
	while (tail == h) ; // wait until space in the queue
	queue[h] = userblock;
	head = h;
	userblock = NULL;
}

void AudioPlayQueue::update(void)
{
	audio_block_t *block;
	uint32_t t;

	t = tail;
	if (t != head) {
		if (++t >= 32) t = 0;
		block = queue[t];
		tail = t;
		transmit(block);
		release(block);
	}
}