stgsharp/StgSharp.Mathematics/Numeric/Graphics/Vec4.cs

// -----------------------------------------------------------------------------
// file="Vec4"
// Project: StgSharp
// Copyright (c) Nitload.
// SPDX-License-Identifier: MIT
// -----------------------------------------------------------------------------

using StgSharp.HighPerformance.ProcessorAbstraction;
using StgSharp.Mathematics;
using StgSharp.Mathematics.Internal;
using StgSharp.Mathematics.Numeric;
using System;
using System.Data.Common;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace StgSharp.Mathematics.Graphics
{
    [CollectionBuilder(builderType:typeof(Vec4), methodName: nameof(Vec4.FromSpan))]
    [StructLayout(LayoutKind.Explicit, Size = 16, Pack = 16)]
    public unsafe struct Vec4 : IEquatable<Vec4>, IUnmanagedVector<Vec4>
    {

        [FieldOffset(0)] internal unsafe fixed float num[4];

        [FieldOffset(0)] internal M128 reg;

        [FieldOffset(0)] internal Vector4 vec;
        [FieldOffset(12)] public float W;

        [FieldOffset(0)] public float X;
        [FieldOffset(4)] public float Y;
        [FieldOffset(8)] public float Z;

        internal Vec4(
                 Vector4 v
        )
        {
            Unsafe.SkipInit(out X);
            Unsafe.SkipInit(out Y);
            Unsafe.SkipInit(out Z);
            Unsafe.SkipInit(out W);
            Unsafe.SkipInit(out reg);

            vec = v;
        }

        internal Vec4(
                 M128 v
        )
        {
            Unsafe.SkipInit(out X);
            Unsafe.SkipInit(out Y);
            Unsafe.SkipInit(out Z);
            Unsafe.SkipInit(out W);
            Unsafe.SkipInit(out vec);

            reg = v;
        }

        public Vec4(
               Vec3 v3,
               float w
        )
        {
            Unsafe.SkipInit(out X);
            Unsafe.SkipInit(out Y);
            Unsafe.SkipInit(out Z);
            Unsafe.SkipInit(out W);
            reg = v3.reg;
            W = w;
        }

        public Vec4(
               float x,
               float y,
               float z,
               float w
        )
        {
            vec = new Vector4(x, y, z, w);
        }

        public unsafe Vec2 XY
        {
            get => new Vec2(reg);
            set
            {
                X = value.X;
                Y = value.Y;
            }
        }

        public unsafe Vec3 XYZ
        {
            get => new Vec3(reg);
            set
            {
                float w = W;
                reg = value.reg;
                W = w;
            }
        }

        public static Vec4 One => new Vec4(1, 1, 1, 1);

        public static Vec4 Zero => new Vec4(0, 0, 0, 0);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Vec4 Add(
                           Vec4 left,
                           Vec4 right
        )
        {
            return left + right;
        }

        public ReadOnlySpan<float> AsSpan()
        {
            return MemoryMarshal.CreateReadOnlySpan(ref reg.Member<float>(0), 4);
        }

        public override bool Equals(
                             object obj
        )
        {
            return (obj is Vec4 v) && (v == this);
        }

        public static Vec4 FromSpan(
                           ReadOnlySpan<float> span
        )
        {
            if (span.Length < 4) {
                throw new ArgumentException("Span length must be at least 4.", nameof(span));
            }

            // Read 4 floats as a Vector4 in one operation without per-element copy.
            Vector4 v = MemoryMarshal.Read<Vector4>(MemoryMarshal.AsBytes(span));
            return new Vec4(v);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public ReadOnlySpan<float>.Enumerator GetEnumerator()
        {
            return AsSpan().GetEnumerator();
        }

        public override int GetHashCode()
        {
            return vec.GetHashCode();
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Vec4 Subtract(
                           Vec4 left,
                           Vec4 right
        )
        {
            return left - right;
        }

        public override string ToString()
        {
            return vec.ToString();
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Vec4 operator -(
                                    Vec4 left,
                                    Vec4 right
        )
        {
            return new Vec4(left.vec - right.vec);
        }

        public static bool operator !=(
                                    Vec4 left,
                                    Vec4 right
        )
        {
            return !(left == right);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Vec4 operator *(
                                    GraphicsMatrix mat,
                                    Vec4 vec
        )
        {
            GraphicsMatrix transpose = mat.Transpose;
            return new Vec4(Vector4.Dot(transpose.mat.colum0, vec.vec),
                            Vector4.Dot(transpose.mat.colum1, vec.vec),
                            Vector4.Dot(transpose.mat.colum2, vec.vec),
                            Vector4.Dot(transpose.mat.colum3, vec.vec));
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Vec4 operator +(
                                    Vec4 left,
                                    Vec4 right
        )
        {
            return new Vec4(left.vec + right.vec);
        }

        public static bool operator ==(
                                    Vec4 left,
                                    Vec4 right
        )
        {
            return left.vec == right.vec;
        }

        bool IEquatable<Vec4>.Equals(
                              Vec4 other
        )
        {
            return vec == other.vec;
        }

    }
}