MathUtils added

Recyclable.Collections/MathUtils.cs

@@ -0,0 +1,42 @@
+using System.Runtime.CompilerServices;
+
+namespace Recyclable.Collections
+{
+	public static class MathUtils
+	{
+		private static long[] Pow2 = new long[]
+		{
+			1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384,
+			32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304,
+			8388608, 16777216, 33554432, 67108864, 134217728, 268435456,
+			536870912, 1073741824, 2147483648
+		};
+
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		public static bool IsPow2(int value) => Array.BinarySearch(Pow2, value) >= 0;
+
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		public static int GetPow2Shift(int value) => Array.BinarySearch(Pow2, value);
+
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		public static long DivMod(long number, int divider, out long remainder)
+		{
+			if (number >= divider << 4)
+			{
+				return Math.DivRem(number, divider, out remainder);
+			}
+			else
+			{
+				int result = 0;
+				remainder = number;
+				while (remainder >= divider)
+				{
+					remainder -= divider;
+					result++;
+				}
+
+				return result;
+			}
+		}
+	}
+}

Recyclable.CollectionsTests/MathUtilsTests.cs

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+using FluentAssertions;
+using Recyclable.Collections;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Recyclable.CollectionsTests
+{
+	public class MathUtilsTests
+	{
+		[Theory]
+		[InlineData(int.MaxValue / 1024, int.MaxValue / 10 / 1024)]
+		public void DivMod(long testNumber, int blockSize)
+		{
+			for (var testCase = testNumber; testCase >= 0; testCase--)
+			{
+				// Prepare
+				var expectedResult = testCase / blockSize;
+				var expectedRemainder = testCase % blockSize;
+
+				// Act
+				var actualResult = MathUtils.DivMod(testCase, blockSize, out long actualRemainder);
+
+				// Validate
+				_ = actualResult.Should().Be(expectedResult);
+				_ = actualRemainder.Should().Be(expectedRemainder);
+			}
+		}
+	}
+}