Method update

effect_delay.cpp:29–133

#include "effect_delay.h"

void AudioEffectDelay::update(void)
{
	audio_block_t *output;
	uint32_t head, tail, count, channel, index, prev, offset;
	const int16_t *src, *end;
	int16_t *dst;

	// grab incoming data and put it into the queue
	head = headindex;
	tail = tailindex;
	if (++head >= DELAY_QUEUE_SIZE) head = 0;
	if (head == tail) {
		release(queue[tail]);
		if (++tail >= DELAY_QUEUE_SIZE) tail = 0;
	}
	queue[head] = receiveReadOnly();
	headindex = head;

	// testing only.... don't allow null pointers into the queue
	// instead, fill the empty times with blocks of zeros
	//if (queue[head] == NULL) {
	//	queue[head] = allocate();
	//	if (queue[head]) {
	//		dst = queue[head]->data;
	//		end = dst + AUDIO_BLOCK_SAMPLES;
	//		do {
	//			*dst++ = 0;
	//		} while (dst < end);
	//	} else {
	//		digitalWriteFast(2, HIGH);
	//		delayMicroseconds(5);
	//		digitalWriteFast(2, LOW);
	//	}
	//}

	// discard unneeded blocks from the queue
	if (head >= tail) {
		count = head - tail;
	} else {
		count = DELAY_QUEUE_SIZE + head - tail;
	}
	if (count > maxblocks) {
		count -= maxblocks;
		do {
			release(queue[tail]);
			queue[tail] = NULL;
			if (++tail >= DELAY_QUEUE_SIZE) tail = 0;
		} while (--count > 0);
	}
	tailindex = tail;

	// transmit the delayed outputs using queue data
	for (channel = 0; channel < 8; channel++) {
		if (!(activemask & (1<<channel))) continue;
		index =  position[channel] / AUDIO_BLOCK_SAMPLES;
		offset = position[channel] % AUDIO_BLOCK_SAMPLES;
		if (head >= index) {
			index = head - index;