salmanoff/commonLibs/attachmentSupport/stimulusBuffer.cpp

#include <boostAsioLinkageFix.h>
#include <iostream>
#include <config.h>
#include <componentThread.h>
#include <boost/asio/io_service.hpp>
#include <boost/asio/deadline_timer.hpp>
#include <boost/system/error_code.hpp>
#include <spinLock.h>
#include <asynchronousBridge.h>
#include <user/stimulusBuffer.h>

namespace smo {
namespace stim_buff {

void StimulusBuffer::stop()
{
	shouldContinue.store(false);

	// Set up a timeout bridge using the io_service
	boost::asio::deadline_timer delayTimer(ioService);
	AsynchronousBridge bridge(ioService);

	// Set up the delay to let in-flight operation finish
	delayTimer.expires_from_now(
		boost::posix_time::milliseconds(getStopDelayMs()));

	delayTimer.async_wait(
		[&bridge](const boost::system::error_code& error)
		{
			(void)error;

			// Always signal complete, whether timeout expired or was cancelled
			bridge.setAsyncOperationComplete();
		});

	bridge.waitForAsyncOperationCompleteOrIoServiceStopped();

	std::cout << __func__ << ": Stopped stimulus buffer for device "
		<< deviceAttachmentSpec.deviceSelector << std::endl;

	// After delay, cancel timer and perform cleanup
	timer.cancel();
}

void StimulusBuffer::scheduleNextTimeout(int delayMs)
{
	if (!shouldContinue.load())
		{ return; }

	// Schedule the next timeout using the provided delay
	timer.expires_from_now(
		boost::posix_time::milliseconds(delayMs));

	timer.async_wait(
		std::bind(
			&StimulusBuffer::onTimeout, this, std::placeholders::_1));
}

void StimulusBuffer::onTimeout(const boost::system::error_code& error)
{
	// Timer was cancelled, which is expected when stopping
	if (error == boost::asio::error::operation_aborted) {
		return;
	}

	if (error)
	{
		std::cerr << "StimulusBuffer: Timer error: " << error.message()
			<< std::endl;
		return;
	}

	if (!shouldContinue.load())
		{ return; }

	/**	EXPLANATION:
	 * We need to ensure that there's only ever one stimframe being produced
	 * during any CONFIG_STIMBUFF_FRAME_PERIOD_MS period. To guarantee this, we
	 * use a spinlock.
	 *
	 * When a new frame is to be produced, the async producer will first acquire
	 * the frameAssemblyLimiter spinlock. This way, when the next timeout is
	 * fired it can check whether its predecessor stimframe has finished being
	 * produced. If the preceding stimframe is still being produced, then we'll
	 * sleep for CONFIG_STIMBUFF_FRAME_RETRY_DELAY_MS ms before trying again.
	 */
	int nextWakeupDelayMs;
	if (frameAssemblyRateLimiter.tryAcquire())
		{ nextWakeupDelayMs = CONFIG_STIMBUFF_FRAME_PERIOD_MS; }
	else
		{ nextWakeupDelayMs = CONFIG_STIMBUFF_FRAME_RETRY_DELAY_MS; }

	// Call the derived class's frame production handler
	stimFrameProductionTimesliceInd();
	// Note: The lock should be released when frame production completes

	// Schedule next timeout with the pre-determined duration
	scheduleNextTimeout(nextWakeupDelayMs);
}

} // namespace stim_buff
} // namespace smo