Remove extra ToString() when stringifying M3U8 metadata

TwitchDownloaderCore.Tests/ExtensionTests/StringBuilderExtensionTests.cs

@@ -0,0 +1,23 @@
+using System.Text;
+using TwitchDownloaderCore.Extensions;
+
+namespace TwitchDownloaderCore.Tests.ExtensionTests
+{
+    public class StringBuilderExtensionTests
+    {
+        [Theory]
+        [InlineData("Foo", "o", "F")]
+        [InlineData("Foo\r\n", "\r\n", "Foo")]
+        [InlineData("oo", "o", "")]
+        [InlineData("Foo", "L", "Foo")]
+        [InlineData("Foo", "oL", "F")]
+        public void CorrectlyTrimsCharacters(string baseString, string trimChars, string expectedResult)
+        {
+            var sb = new StringBuilder(baseString);
+
+            sb.TrimEnd(trimChars);
+
+            Assert.Equal(expectedResult, sb.ToString());
+        }
+    }
+}

TwitchDownloaderCore/Extensions/StringBuilderExtensions.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Text;
+
+namespace TwitchDownloaderCore.Extensions
+{
+    public static class StringBuilderExtensions
+    {
+        public static StringBuilder TrimEnd(this StringBuilder sb, ReadOnlySpan<char> trimChars)
+        {
+            var trimLength = 0;
+            while (sb.Length - trimLength > 0 && trimChars.Contains(sb[^(trimLength + 1)]))
+            {
+                trimLength++;
+            }
+
+            return sb.Remove(sb.Length - trimLength, trimLength);
+        }
+    }
+}

TwitchDownloaderCore/Tools/M3U8.cs

@@ -257,7 +257,7 @@ public override string ToString()
                     return "";
                 }
 
-                return sb.ToString().AsSpan().TrimEnd(itemSeparator).ToString();
+                return sb.TrimEnd(itemSeparator).ToString();
             }
 
             public sealed class Builder