// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
//---------------------------------------------------------------------------
//
 
//
// File: FloatUtil.cs
//
// Description: This file contains the implementation of FloatUtil, which
//              provides "fuzzy" comparison functionality for floats and
//              float-based classes and structs in our code.
//
//---------------------------------------------------------------------------
 
namespace MS.Internal
{
    internal static class FloatUtil
    {
        private const float FLT_EPSILON = 1.192092896E-07f;
        private const float FLT_MAX_PRECISION = 0x00FFFFFF;
        private const float INVERSE_FLT_MAX_PRECISION = 1.0f / FLT_MAX_PRECISION;
 
        /// <summary>
        /// AreClose
        /// </summary>
        public static bool AreClose(float a, float b)
        {
            if (a == b)
                return true;
 
            // This computes (|a-b| / (|a| + |b| + 10.0f)) < FLT_EPSILON
            float eps = ((float)Math.Abs(a) + (float)Math.Abs(b) + 10.0f) * FLT_EPSILON;
            float delta = a - b;
 
            return (-eps < delta) && (eps > delta);
        }
 
        /// <summary>
        /// IsOne
        /// </summary>
        public static bool IsOne(float a)
        {
            return (float)Math.Abs(a - 1.0f) < 10.0f * FLT_EPSILON;
        }
 
        /// <summary>
        /// IsZero
        /// </summary>
        public static bool IsZero(float a)
        {
            return (float)Math.Abs(a) < 10.0f * FLT_EPSILON;
        }
 
        /// <summary>
        /// IsCloseToDivideByZero
        /// </summary>
        public static bool IsCloseToDivideByZero(float numerator, float denominator)
        {
            // When updating this, please also update code in Arithmetic.h
            return Math.Abs(denominator) <= Math.Abs(numerator) * INVERSE_FLT_MAX_PRECISION;
        }
 
    }
}