Method update

effect_delay_ext.cpp:42–104

#define MEMBOARD_CS2_PIN 4

void AudioEffectDelayExternal::update(void)
{
	audio_block_t *block;
	uint32_t n, channel, read_offset;

	// grab incoming data and put it into the memory
	block = receiveReadOnly();
	if (memory_type >= AUDIO_MEMORY_UNDEFINED) {
		// ignore input and do nothing if undefined memory type
		release(block);
		return;
	}
	if (block) {
		if (head_offset + AUDIO_BLOCK_SAMPLES <= memory_length) {
			// a single write is enough
			write(head_offset, AUDIO_BLOCK_SAMPLES, block->data);
			head_offset += AUDIO_BLOCK_SAMPLES;
		} else {
			// write wraps across end-of-memory
			n = memory_length - head_offset;
			write(head_offset, n, block->data);
			head_offset = AUDIO_BLOCK_SAMPLES - n;
			write(0, head_offset, block->data + n);
		}
		release(block);
	} else {
		// if no input, store zeros, so later playback will
		// not be random garbage previously stored in memory
		if (head_offset + AUDIO_BLOCK_SAMPLES <= memory_length) {
			zero(head_offset, AUDIO_BLOCK_SAMPLES);
			head_offset += AUDIO_BLOCK_SAMPLES;
		} else {
			n = memory_length - head_offset;
			zero(head_offset, n);
			head_offset = AUDIO_BLOCK_SAMPLES - n;
			zero(0, head_offset);
		}
	}

	// transmit the delayed outputs
	for (channel = 0; channel < 8; channel++) {
		if (!(activemask & (1<<channel))) continue;
		block = allocate();
		if (!block) continue;
		// compute the delayed location where we read
		if (delay_length[channel] <= head_offset) {
			read_offset = head_offset - delay_length[channel];
		} else {
			read_offset = memory_length + head_offset - delay_length[channel];
		}
		if (read_offset + AUDIO_BLOCK_SAMPLES <= memory_length) {
			// a single read will do it
			read(read_offset, AUDIO_BLOCK_SAMPLES, block->data);
		} else {
			// read wraps across end-of-memory
			n = memory_length - read_offset;
			read(read_offset, n, block->data);
			read(0, AUDIO_BLOCK_SAMPLES - n, block->data + n);