Minor improvements

* properly dispose CancellationTokenSource
* rewrite DynamicHlsController.GetSegmentLengths
* remove dead code

tests/Jellyfin.Api.Tests/Controllers/DynamicHlsControllerTests.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Collections.Generic;
+using AutoFixture;
+using AutoFixture.AutoMoq;
+using Jellyfin.Api.Controllers;
+using Jellyfin.Api.Helpers;
+using Jellyfin.Api.Models.StreamingDtos;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.MediaEncoding;
+using Moq;
+using Xunit;
+
+namespace Jellyfin.Api.Tests.Controllers
+{
+    public class DynamicHlsControllerTests
+    {
+        [Theory]
+        [MemberData(nameof(GetSegmentLengths_Success_TestData))]
+        public void GetSegmentLengths_Success(long runtimeTicks, int segmentlength, double[] expected)
+        {
+            var res = DynamicHlsController.GetSegmentLengthsInternal(runtimeTicks, segmentlength);
+            Assert.Equal(expected.Length, res.Length);
+            for (int i = 0; i < expected.Length; i++)
+            {
+                Assert.Equal(expected[i], res[i]);
+            }
+        }
+
+        public static IEnumerable<object[]> GetSegmentLengths_Success_TestData()
+        {
+            yield return new object[] { 0, 6, Array.Empty<double>() };
+            yield return new object[]
+            {
+                TimeSpan.FromSeconds(3).Ticks,
+                6,
+                new double[] { 3 }
+            };
+            yield return new object[]
+            {
+                TimeSpan.FromSeconds(6).Ticks,
+                6,
+                new double[] { 6 }
+            };
+            yield return new object[]
+            {
+                TimeSpan.FromSeconds(3.3333333).Ticks,
+                6,
+                new double[] { 3.3333333 }
+            };
+            yield return new object[]
+            {
+                TimeSpan.FromSeconds(9.3333333).Ticks,
+                6,
+                new double[] { 6, 3.3333333 }
+            };
+        }
+    }
+}