Fixed time step loop which gives millisecond precision.

LoopExtension.cs

/*
MIT License

Copyright (c) 2023 Dmytro Osipov

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 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.
*/

namespace Blackbone.Extensions
{
    public static class Extensions
    {
        public delegate bool TickDelegate(in long time, in double delta, out bool repeat);

        public static void RunLoop(this object _, TickDelegate tickDelegate, uint rate, double duration = 0)
        {
            // prepare variables
            var startTime = DateTime.UtcNow;
            var nextUpdate = startTime;
            double delta = 0;
            ulong iterations = 0;
            
            // loop while 
            while (true)
            {
                var time = ((DateTimeOffset)nextUpdate).ToUnixTimeMilliseconds();
                
                // net event repeat block
                REPEAT:
                var run = tickDelegate(time, delta, out var repeat);
                if (repeat)
                    goto REPEAT;
                // end of repeatable block

                if (!run) break;

                // calculate timeout
                iterations++;
                
                var passedSeconds = iterations / rate; 
                var inSecTicks = iterations % rate;
                var ne = startTime + TimeSpan.FromSeconds(passedSeconds) + TimeSpan.FromSeconds((double)inSecTicks / rate);
                delta = (ne - nextUpdate).TotalMilliseconds;
                nextUpdate = ne;
                
                // check timer
                if (duration > 0 && passedSeconds > duration)
                    run = false;
                
                if (!run) break;
                
                // check how much we need to wait
                var timeToWait = nextUpdate - DateTime.UtcNow - TimeSpan.FromMilliseconds(delta);
                if (timeToWait > TimeSpan.Zero) Thread.Sleep(timeToWait);
                else Console.WriteLine("iteration took longer than needed");
            }
        }
    }
}