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 * modification, are permitted provided that the following conditions
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 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
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 *    used to endorse or promote products derived from this software
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 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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/**
 * @file mavlink_stream.cpp
 * Mavlink messages stream implementation.
 *
 * @author Anton Babushkin <anton.babushkin@me.com>
 * @author Lorenz Meier <lorenz@px4.io>
 */

#include <stdlib.h>

#include "mavlink_stream.h"
#include "mavlink_main.h"

MavlinkStream::MavlinkStream(Mavlink *mavlink) :
	next(nullptr),
	_mavlink(mavlink),
	_interval(1000000),
	_last_sent(0 /* 0 means unlimited - updates on every iteration */)
{
}

MavlinkStream::~MavlinkStream() = default;

/**
 * Set messages interval in ms
 */
void
MavlinkStream::set_interval(const int interval)
{
	_interval = interval;
}

/**
 * Update subscriptions and send message if necessary
 */
int
MavlinkStream::update(const hrt_abstime t)
{
	update_data();

	// If the message has never been sent before we want
	// to send it immediately and can return right away
	if (_last_sent == 0) {
		// this will give different messages on the same run a different
		// initial timestamp which will help spacing them out
		// on the link scheduling
#ifndef __PX4_QURT
		if (send(t)) {
			_last_sent = hrt_absolute_time();
		}

#endif
		return 0;
	}

	// One of the previous iterations sent the update
	// already before the deadline
	if (_last_sent > t) {
		return -1;
	}

	int64_t dt = t - _last_sent;
	int interval = (_interval > 0) ? _interval : 0;

	if (!const_rate()) {
		interval /= _mavlink->get_rate_mult();
	}

	// Send the message if it is due or
	// if it will overrun the next scheduled send interval
	// by 30% of the interval time. This helps to avoid
	// sending a scheduled message on average slower than
	// scheduled. Doing this at 50% would risk sending
	// the message too often as the loop runtime of the app
	// needs to be accounted for as well.
	// This method is not theoretically optimal but a suitable
	// stopgap as it hits its deadlines well (0.5 Hz, 50 Hz and 250 Hz)

	if (interval == 0 || (dt > (interval - (_mavlink->get_main_loop_delay() / 10) * 3))) {
		// interval expired, send message
		bool sent = true;
#ifndef __PX4_QURT
		sent = send(t);
#endif

		// If the interval is non-zero and dt is smaller than 1.5 times the interval
		// do not use the actual time but increment at a fixed rate, so that processing delays do not
		// distort the average rate. The check of the maximum interval is done to ensure that after a
		// long time not sending anything, sending multiple messages in a short time is avoided.
		if (sent) {
			_last_sent = ((interval > 0) && ((int64_t)(1.5f * interval) > dt)) ? _last_sent + interval : t;
			return 0;

		} else {
			return -1;
		}
	}

	return -1;
}