Merge branch 'SequenceComparer' of Common/Utils into dev

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+ - Adding SequenceComparer for ordering collections of lists, arrays, etc
 
 ## [3.6.0] - 2018-06-19
 ### Added

ICD.Common.Utils.Tests/Comparers/SequenceComparerTest.cs

@@ -0,0 +1,33 @@
+using ICD.Common.Utils.Comparers;
+using NUnit.Framework;
+
+namespace ICD.Common.Utils.Tests.Comparers
+{
+	[TestFixture]
+	public sealed class SequenceComparerTest
+	{
+		[Test]
+		public void CompareTest()
+		{
+			SequenceComparer<int> comparer = new SequenceComparer<int>();
+
+			// Equal
+			int[] a = {1, 2, 3};
+			int[] b = {1, 2, 3};
+
+			Assert.AreEqual(0, comparer.Compare(a, b));
+
+			// A comes before B
+			a = new[] {1, 2};
+			b = new[] {1, 2, 3};
+
+			Assert.AreEqual(-1, comparer.Compare(a, b));
+
+			// B comes before A
+			a = new[] { 2, 2, 3 };
+			b = new[] { 1, 2, 3 };
+
+			Assert.AreEqual(1, comparer.Compare(a, b));
+		}
+	}
+}

ICD.Common.Utils/Comparers/SequenceComparer.cs

@@ -0,0 +1,66 @@
+using System;
+using System.Collections.Generic;
+
+namespace ICD.Common.Utils.Comparers
+{
+	public sealed class SequenceComparer<T> : IComparer<IEnumerable<T>>
+	{
+		private readonly IComparer<T> m_ItemComparer;
+
+		/// <summary>
+		/// Constructor.
+		/// </summary>
+		public SequenceComparer()
+			: this(Comparer<T>.Default)
+		{
+		}
+
+		/// <summary>
+		/// Constructor.
+		/// </summary>
+		/// <param name="comparer"></param>
+		public SequenceComparer(IComparer<T> comparer)
+		{
+			if (comparer == null)
+				throw new ArgumentNullException("comparer");
+
+			m_ItemComparer = comparer;
+		}
+
+		public int Compare(IEnumerable<T> x, IEnumerable<T> y)
+		{
+			if (x == null)
+				throw new ArgumentNullException("x");
+
+			if (y == null)
+				throw new ArgumentNullException("y");
+
+			using (IEnumerator<T> firstPos = x.GetEnumerator())
+			{
+				using (IEnumerator<T> secondPos = y.GetEnumerator())
+				{
+					bool hasFirst = firstPos.MoveNext();
+					bool hasSecond = secondPos.MoveNext();
+
+					while (hasFirst && hasSecond)
+					{
+						int result = m_ItemComparer.Compare(firstPos.Current, secondPos.Current);
+						if (result != 0)
+							return result;
+
+						hasFirst = firstPos.MoveNext();
+						hasSecond = secondPos.MoveNext();
+					}
+
+					if (!hasFirst && !hasSecond)
+						return 0;
+
+					if (!hasFirst)
+						return -1;
+
+					return 1;
+				}
+			}
+		}
+	}
+}