diff --git a/tests/ImageSharp.Tests/Common/NumericsTests.cs b/tests/ImageSharp.Tests/Common/NumericsTests.cs new file mode 100644 index 0000000000..29eae6d488 --- /dev/null +++ b/tests/ImageSharp.Tests/Common/NumericsTests.cs @@ -0,0 +1,73 @@ +// Copyright (c) Six Labors. +// Licensed under the Apache License, Version 2.0. + +using System; +using Xunit; +using Xunit.Abstractions; + +namespace SixLabors.ImageSharp.Tests.Common +{ + public class NumericsTests + { + private ITestOutputHelper Output { get; } + + public NumericsTests(ITestOutputHelper output) + { + this.Output = output; + } + + private static int Log2_ReferenceImplementation(uint value) + { + int n = 0; + while ((value >>= 1) != 0) + { + ++n; + } + + return n; + } + + [Fact] + public void Log2_ZeroConvention() + { + uint value = 0; + int expected = 0; + int actual = Numerics.Log2(value); + + Assert.True(expected == actual, $"Expected: {expected}, Actual: {actual}"); + } + + [Fact] + public void Log2_PowersOfTwo() + { + for (int i = 0; i < sizeof(int) * 8; i++) + { + // from 2^0 to 2^32 + uint value = (uint)(1 << i); + int expected = i; + int actual = Numerics.Log2(value); + + Assert.True(expected == actual, $"Expected: {expected}, Actual: {actual}"); + } + } + + [Theory] + [InlineData(1, 100)] + [InlineData(2, 100)] + public void Log2_RandomValues(int seed, int count) + { + var rng = new Random(seed); + byte[] bytes = new byte[4]; + + for (int i = 0; i < count; i++) + { + rng.NextBytes(bytes); + uint value = BitConverter.ToUInt32(bytes, 0); + int expected = Log2_ReferenceImplementation(value); + int actual = Numerics.Log2(value); + + Assert.True(expected == actual, $"Expected: {expected}, Actual: {actual}"); + } + } + } +}