// 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.

using System.Diagnostics;
using System.Runtime.CompilerServices; // Do not remove. This is necessary for netstandard, since this file is mirrored into corefx

#if !netstandard
using Internal.Runtime.CompilerServices;
#endif

namespace System
{
    internal static partial class SpanHelpers // .T
    {
        public static int IndexOf<T>(ref T searchSpace, int searchSpaceLength, ref T value, int valueLength)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(searchSpaceLength >= 0);
            Debug.Assert(valueLength >= 0);

            if (valueLength == 0)
                return 0;  // A zero-length sequence is always treated as "found" at the start of the search space.

            T valueHead = value;
            ref T valueTail = ref Unsafe.Add(ref value, 1);
            int valueTailLength = valueLength - 1;

            int index = 0;
            for (; ; )
            {
                Debug.Assert(0 <= index && index <= searchSpaceLength); // Ensures no deceptive underflows in the computation of "remainingSearchSpaceLength".
                int remainingSearchSpaceLength = searchSpaceLength - index - valueTailLength;
                if (remainingSearchSpaceLength <= 0)
                    break;  // The unsearched portion is now shorter than the sequence we're looking for. So it can't be there.

                // Do a quick search for the first element of "value".
                int relativeIndex = IndexOf(ref Unsafe.Add(ref searchSpace, index), valueHead, remainingSearchSpaceLength);
                if (relativeIndex == -1)
                    break;
                index += relativeIndex;

                // Found the first element of "value". See if the tail matches.
                if (SequenceEqual(ref Unsafe.Add(ref searchSpace, index + 1), ref valueTail, valueTailLength))
                    return index;  // The tail matched. Return a successful find.

                index++;
            }
            return -1;
        }

        // Adapted from IndexOf(...)
        public unsafe static bool Contains<T>(ref T searchSpace, T value, int length)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(length >= 0);

            IntPtr index = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations

            if (default(T)! != null || (object)value != null) // TODO-NULLABLE: default(T) == null warning (https://github.com/dotnet/roslyn/issues/34757)
            {
                while (length >= 8)
                {
                    length -= 8;

                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 0)) ||
                        value.Equals(Unsafe.Add(ref searchSpace, index + 1)) ||
                        value.Equals(Unsafe.Add(ref searchSpace, index + 2)) ||
                        value.Equals(Unsafe.Add(ref searchSpace, index + 3)) ||
                        value.Equals(Unsafe.Add(ref searchSpace, index + 4)) ||
                        value.Equals(Unsafe.Add(ref searchSpace, index + 5)) ||
                        value.Equals(Unsafe.Add(ref searchSpace, index + 6)) ||
                        value.Equals(Unsafe.Add(ref searchSpace, index + 7)))
                    {
                        goto Found;
                    }

                    index += 8;
                }

                if (length >= 4)
                {
                    length -= 4;

                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 0)) ||
                        value.Equals(Unsafe.Add(ref searchSpace, index + 1)) ||
                        value.Equals(Unsafe.Add(ref searchSpace, index + 2)) ||
                        value.Equals(Unsafe.Add(ref searchSpace, index + 3)))
                    {
                        goto Found;
                    }

                    index += 4;
                }

                while (length > 0)
                {
                    length -= 1;

                    if (value.Equals(Unsafe.Add(ref searchSpace, index)))
                        goto Found;

                    index += 1;
                }
            }
            else
            {
                byte* len = (byte*)length;
                for (index = (IntPtr)0; index.ToPointer() < len; index += 1)
                {
                    if ((object)Unsafe.Add(ref searchSpace, index) is null)
                    {
                        goto Found;
                    }
                }
            }

            return false;

        Found:
            return true;
        }

        public static unsafe int IndexOf<T>(ref T searchSpace, T value, int length)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(length >= 0);

            IntPtr index = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
            if (default(T)! != null || (object)value != null) // TODO-NULLABLE: default(T) == null warning (https://github.com/dotnet/roslyn/issues/34757)
            {
                while (length >= 8)
                {
                    length -= 8;

                    if (value.Equals(Unsafe.Add(ref searchSpace, index)))
                        goto Found;
                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 1)))
                        goto Found1;
                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 2)))
                        goto Found2;
                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 3)))
                        goto Found3;
                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 4)))
                        goto Found4;
                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 5)))
                        goto Found5;
                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 6)))
                        goto Found6;
                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 7)))
                        goto Found7;

                    index += 8;
                }

                if (length >= 4)
                {
                    length -= 4;

                    if (value.Equals(Unsafe.Add(ref searchSpace, index)))
                        goto Found;
                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 1)))
                        goto Found1;
                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 2)))
                        goto Found2;
                    if (value.Equals(Unsafe.Add(ref searchSpace, index + 3)))
                        goto Found3;

                    index += 4;
                }

                while (length > 0)
                {
                    if (value.Equals(Unsafe.Add(ref searchSpace, index)))
                        goto Found;

                    index += 1;
                    length--;
                }
            }
            else
            {
                byte* len = (byte*)length;
                for (index = (IntPtr)0; index.ToPointer() < len; index += 1)
                {
                    if ((object)Unsafe.Add(ref searchSpace, index) is null)
                    {
                        goto Found;
                    }
                }
            }
            return -1;

        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
            return (int)(byte*)index;
        Found1:
            return (int)(byte*)(index + 1);
        Found2:
            return (int)(byte*)(index + 2);
        Found3:
            return (int)(byte*)(index + 3);
        Found4:
            return (int)(byte*)(index + 4);
        Found5:
            return (int)(byte*)(index + 5);
        Found6:
            return (int)(byte*)(index + 6);
        Found7:
            return (int)(byte*)(index + 7);
        }

        public static int IndexOfAny<T>(ref T searchSpace, T value0, T value1, int length)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(length >= 0);

            T lookUp;
            int index = 0;
            if (default(T)! != null || ((object)value0 != null && (object)value1 != null)) // TODO-NULLABLE: default(T) == null warning (https://github.com/dotnet/roslyn/issues/34757)
            {
                while ((length - index) >= 8)
                {
                    lookUp = Unsafe.Add(ref searchSpace, index);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found;
                    lookUp = Unsafe.Add(ref searchSpace, index + 1);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found1;
                    lookUp = Unsafe.Add(ref searchSpace, index + 2);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found2;
                    lookUp = Unsafe.Add(ref searchSpace, index + 3);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found3;
                    lookUp = Unsafe.Add(ref searchSpace, index + 4);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found4;
                    lookUp = Unsafe.Add(ref searchSpace, index + 5);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found5;
                    lookUp = Unsafe.Add(ref searchSpace, index + 6);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found6;
                    lookUp = Unsafe.Add(ref searchSpace, index + 7);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found7;

                    index += 8;
                }

                if ((length - index) >= 4)
                {
                    lookUp = Unsafe.Add(ref searchSpace, index);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found;
                    lookUp = Unsafe.Add(ref searchSpace, index + 1);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found1;
                    lookUp = Unsafe.Add(ref searchSpace, index + 2);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found2;
                    lookUp = Unsafe.Add(ref searchSpace, index + 3);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found3;

                    index += 4;
                }

                while (index < length)
                {
                    lookUp = Unsafe.Add(ref searchSpace, index);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found;

                    index++;
                }
            }
            else
            {
                for (index = 0; index < length; index++)
                {
                    lookUp = Unsafe.Add(ref searchSpace, index);
                    if ((object?)lookUp is null)
                    {
                        if ((object?)value0 is null || (object?)value1 is null)
                        {
                            goto Found;
                        }
                    }
                    else if (lookUp.Equals(value0) || lookUp.Equals(value1))
                    {
                        goto Found;
                    }
                }
            }

            return -1;

        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
            return index;
        Found1:
            return index + 1;
        Found2:
            return index + 2;
        Found3:
            return index + 3;
        Found4:
            return index + 4;
        Found5:
            return index + 5;
        Found6:
            return index + 6;
        Found7:
            return index + 7;
        }

        public static int IndexOfAny<T>(ref T searchSpace, T value0, T value1, T value2, int length)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(length >= 0);

            T lookUp;
            int index = 0;
            if (default(T)! != null || ((object)value0 != null && (object)value1 != null && (object)value2 != null)) // TODO-NULLABLE: default(T) == null warning (https://github.com/dotnet/roslyn/issues/34757)
            {
                while ((length - index) >= 8)
                {
                    lookUp = Unsafe.Add(ref searchSpace, index);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found;
                    lookUp = Unsafe.Add(ref searchSpace, index + 1);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found1;
                    lookUp = Unsafe.Add(ref searchSpace, index + 2);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found2;
                    lookUp = Unsafe.Add(ref searchSpace, index + 3);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found3;
                    lookUp = Unsafe.Add(ref searchSpace, index + 4);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found4;
                    lookUp = Unsafe.Add(ref searchSpace, index + 5);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found5;
                    lookUp = Unsafe.Add(ref searchSpace, index + 6);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found6;
                    lookUp = Unsafe.Add(ref searchSpace, index + 7);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found7;

                    index += 8;
                }

                if ((length - index) >= 4)
                {
                    lookUp = Unsafe.Add(ref searchSpace, index);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found;
                    lookUp = Unsafe.Add(ref searchSpace, index + 1);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found1;
                    lookUp = Unsafe.Add(ref searchSpace, index + 2);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found2;
                    lookUp = Unsafe.Add(ref searchSpace, index + 3);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found3;

                    index += 4;
                }

                while (index < length)
                {
                    lookUp = Unsafe.Add(ref searchSpace, index);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found;

                    index++;
                }
            }
            else
            {
                for (index = 0; index < length; index++)
                {
                    lookUp = Unsafe.Add(ref searchSpace, index);
                    if ((object?)lookUp is null)
                    {
                        if ((object?)value0 is null || (object?)value1 is null || (object?)value2 is null)
                        {
                            goto Found;
                        }
                    }
                    else if (lookUp.Equals(value0) || lookUp.Equals(value1) || lookUp.Equals(value2))
                    {
                        goto Found;
                    }
                }
            }
            return -1;

        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
            return index;
        Found1:
            return index + 1;
        Found2:
            return index + 2;
        Found3:
            return index + 3;
        Found4:
            return index + 4;
        Found5:
            return index + 5;
        Found6:
            return index + 6;
        Found7:
            return index + 7;
        }

        public static int IndexOfAny<T>(ref T searchSpace, int searchSpaceLength, ref T value, int valueLength)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(searchSpaceLength >= 0);
            Debug.Assert(valueLength >= 0);

            if (valueLength == 0)
                return -1;  // A zero-length set of values is always treated as "not found".

            int index = -1;
            for (int i = 0; i < valueLength; i++)
            {
                var tempIndex = IndexOf(ref searchSpace, Unsafe.Add(ref value, i), searchSpaceLength);
                if ((uint)tempIndex < (uint)index)
                {
                    index = tempIndex;
                    // Reduce space for search, cause we don't care if we find the search value after the index of a previously found value
                    searchSpaceLength = tempIndex;

                    if (index == 0)
                        break;
                }
            }
            return index;
        }

        public static int LastIndexOf<T>(ref T searchSpace, int searchSpaceLength, ref T value, int valueLength)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(searchSpaceLength >= 0);
            Debug.Assert(valueLength >= 0);

            if (valueLength == 0)
                return 0;  // A zero-length sequence is always treated as "found" at the start of the search space.

            T valueHead = value;
            ref T valueTail = ref Unsafe.Add(ref value, 1);
            int valueTailLength = valueLength - 1;

            int index = 0;
            for (; ; )
            {
                Debug.Assert(0 <= index && index <= searchSpaceLength); // Ensures no deceptive underflows in the computation of "remainingSearchSpaceLength".
                int remainingSearchSpaceLength = searchSpaceLength - index - valueTailLength;
                if (remainingSearchSpaceLength <= 0)
                    break;  // The unsearched portion is now shorter than the sequence we're looking for. So it can't be there.

                // Do a quick search for the first element of "value".
                int relativeIndex = LastIndexOf(ref searchSpace, valueHead, remainingSearchSpaceLength);
                if (relativeIndex == -1)
                    break;

                // Found the first element of "value". See if the tail matches.
                if (SequenceEqual(ref Unsafe.Add(ref searchSpace, relativeIndex + 1), ref valueTail, valueTailLength))
                    return relativeIndex;  // The tail matched. Return a successful find.

                index += remainingSearchSpaceLength - relativeIndex;
            }
            return -1;
        }

        public static int LastIndexOf<T>(ref T searchSpace, T value, int length)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(length >= 0);

            if (default(T)! != null || (object)value != null) // TODO-NULLABLE: default(T) == null warning (https://github.com/dotnet/roslyn/issues/34757)
            {
                while (length >= 8)
                {
                    length -= 8;

                    if (value.Equals(Unsafe.Add(ref searchSpace, length + 7)))
                        goto Found7;
                    if (value.Equals(Unsafe.Add(ref searchSpace, length + 6)))
                        goto Found6;
                    if (value.Equals(Unsafe.Add(ref searchSpace, length + 5)))
                        goto Found5;
                    if (value.Equals(Unsafe.Add(ref searchSpace, length + 4)))
                        goto Found4;
                    if (value.Equals(Unsafe.Add(ref searchSpace, length + 3)))
                        goto Found3;
                    if (value.Equals(Unsafe.Add(ref searchSpace, length + 2)))
                        goto Found2;
                    if (value.Equals(Unsafe.Add(ref searchSpace, length + 1)))
                        goto Found1;
                    if (value.Equals(Unsafe.Add(ref searchSpace, length)))
                        goto Found;
                }

                if (length >= 4)
                {
                    length -= 4;

                    if (value.Equals(Unsafe.Add(ref searchSpace, length + 3)))
                        goto Found3;
                    if (value.Equals(Unsafe.Add(ref searchSpace, length + 2)))
                        goto Found2;
                    if (value.Equals(Unsafe.Add(ref searchSpace, length + 1)))
                        goto Found1;
                    if (value.Equals(Unsafe.Add(ref searchSpace, length)))
                        goto Found;
                }

                while (length > 0)
                {
                    length--;

                    if (value.Equals(Unsafe.Add(ref searchSpace, length)))
                        goto Found;
                }
            }
            else
            {
                for (length--; length >= 0; length--)
                {
                    if ((object)Unsafe.Add(ref searchSpace, length) is null)
                    {
                        goto Found;
                    }
                }
            }

            return -1;

        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
            return length;
        Found1:
            return length + 1;
        Found2:
            return length + 2;
        Found3:
            return length + 3;
        Found4:
            return length + 4;
        Found5:
            return length + 5;
        Found6:
            return length + 6;
        Found7:
            return length + 7;
        }

        public static int LastIndexOfAny<T>(ref T searchSpace, T value0, T value1, int length)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(length >= 0);

            T lookUp;
            if (default(T)! != null || ((object)value0 != null && (object)value1 != null)) // TODO-NULLABLE: default(T) == null warning (https://github.com/dotnet/roslyn/issues/34757)
            {
                while (length >= 8)
                {
                    length -= 8;

                    lookUp = Unsafe.Add(ref searchSpace, length + 7);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found7;
                    lookUp = Unsafe.Add(ref searchSpace, length + 6);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found6;
                    lookUp = Unsafe.Add(ref searchSpace, length + 5);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found5;
                    lookUp = Unsafe.Add(ref searchSpace, length + 4);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found4;
                    lookUp = Unsafe.Add(ref searchSpace, length + 3);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found3;
                    lookUp = Unsafe.Add(ref searchSpace, length + 2);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found2;
                    lookUp = Unsafe.Add(ref searchSpace, length + 1);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found1;
                    lookUp = Unsafe.Add(ref searchSpace, length);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found;
                }

                if (length >= 4)
                {
                    length -= 4;

                    lookUp = Unsafe.Add(ref searchSpace, length + 3);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found3;
                    lookUp = Unsafe.Add(ref searchSpace, length + 2);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found2;
                    lookUp = Unsafe.Add(ref searchSpace, length + 1);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found1;
                    lookUp = Unsafe.Add(ref searchSpace, length);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found;
                }

                while (length > 0)
                {
                    length--;

                    lookUp = Unsafe.Add(ref searchSpace, length);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp))
                        goto Found;
                }
            }
            else
            {
                for (length--; length >= 0; length--)
                {
                    lookUp = Unsafe.Add(ref searchSpace, length);
                    if ((object?)lookUp is null)
                    {
                        if ((object?)value0 is null || (object?)value1 is null)
                        {
                            goto Found;
                        }
                    }
                    else if (lookUp.Equals(value0) || lookUp.Equals(value1))
                    {
                        goto Found;
                    }
                }
            }

            return -1;

        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
            return length;
        Found1:
            return length + 1;
        Found2:
            return length + 2;
        Found3:
            return length + 3;
        Found4:
            return length + 4;
        Found5:
            return length + 5;
        Found6:
            return length + 6;
        Found7:
            return length + 7;
        }

        public static int LastIndexOfAny<T>(ref T searchSpace, T value0, T value1, T value2, int length)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(length >= 0);

            T lookUp;
            if (default(T)! != null || ((object)value0 != null && (object)value1 != null)) // TODO-NULLABLE: default(T) == null warning (https://github.com/dotnet/roslyn/issues/34757)
            {
                while (length >= 8)
                {
                    length -= 8;

                    lookUp = Unsafe.Add(ref searchSpace, length + 7);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found7;
                    lookUp = Unsafe.Add(ref searchSpace, length + 6);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found6;
                    lookUp = Unsafe.Add(ref searchSpace, length + 5);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found5;
                    lookUp = Unsafe.Add(ref searchSpace, length + 4);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found4;
                    lookUp = Unsafe.Add(ref searchSpace, length + 3);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found3;
                    lookUp = Unsafe.Add(ref searchSpace, length + 2);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found2;
                    lookUp = Unsafe.Add(ref searchSpace, length + 1);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found1;
                    lookUp = Unsafe.Add(ref searchSpace, length);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found;
                }

                if (length >= 4)
                {
                    length -= 4;

                    lookUp = Unsafe.Add(ref searchSpace, length + 3);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found3;
                    lookUp = Unsafe.Add(ref searchSpace, length + 2);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found2;
                    lookUp = Unsafe.Add(ref searchSpace, length + 1);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found1;
                    lookUp = Unsafe.Add(ref searchSpace, length);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found;
                }

                while (length > 0)
                {
                    length--;

                    lookUp = Unsafe.Add(ref searchSpace, length);
                    if (value0.Equals(lookUp) || value1.Equals(lookUp) || value2.Equals(lookUp))
                        goto Found;
                }
            }
            else
            {
                for (length--; length >= 0; length--)
                {
                    lookUp = Unsafe.Add(ref searchSpace, length);
                    if ((object?)lookUp is null)
                    {
                        if ((object?)value0 is null || (object?)value1 is null || (object?)value2 is null)
                        {
                            goto Found;
                        }
                    }
                    else if (lookUp.Equals(value0) || lookUp.Equals(value1) || lookUp.Equals(value2))
                    {
                        goto Found;
                    }
                }
            }

            return -1;

        Found: // Workaround for https://github.com/dotnet/coreclr/issues/13549
            return length;
        Found1:
            return length + 1;
        Found2:
            return length + 2;
        Found3:
            return length + 3;
        Found4:
            return length + 4;
        Found5:
            return length + 5;
        Found6:
            return length + 6;
        Found7:
            return length + 7;
        }

        public static int LastIndexOfAny<T>(ref T searchSpace, int searchSpaceLength, ref T value, int valueLength)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(searchSpaceLength >= 0);
            Debug.Assert(valueLength >= 0);

            if (valueLength == 0)
                return -1;  // A zero-length set of values is always treated as "not found".

            int index = -1;
            for (int i = 0; i < valueLength; i++)
            {
                var tempIndex = LastIndexOf(ref searchSpace, Unsafe.Add(ref value, i), searchSpaceLength);
                if (tempIndex > index)
                    index = tempIndex;
            }
            return index;
        }

        public static bool SequenceEqual<T>(ref T first, ref T second, int length)
#nullable disable // to enable use with both T and T? for reference types due to IEquatable<T> being invariant
            where T : IEquatable<T>
#nullable restore
        {
            Debug.Assert(length >= 0);

            if (Unsafe.AreSame(ref first, ref second))
                goto Equal;

            IntPtr index = (IntPtr)0; // Use IntPtr for arithmetic to avoid unnecessary 64->32->64 truncations
            T lookUp0;
            T lookUp1;
            while (length >= 8)
            {
                length -= 8;

                lookUp0 = Unsafe.Add(ref first, index);
                lookUp1 = Unsafe.Add(ref second, index);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                lookUp0 = Unsafe.Add(ref first, index + 1);
                lookUp1 = Unsafe.Add(ref second, index + 1);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                lookUp0 = Unsafe.Add(ref first, index + 2);
                lookUp1 = Unsafe.Add(ref second, index + 2);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                lookUp0 = Unsafe.Add(ref first, index + 3);
                lookUp1 = Unsafe.Add(ref second, index + 3);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                lookUp0 = Unsafe.Add(ref first, index + 4);
                lookUp1 = Unsafe.Add(ref second, index + 4);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                lookUp0 = Unsafe.Add(ref first, index + 5);
                lookUp1 = Unsafe.Add(ref second, index + 5);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                lookUp0 = Unsafe.Add(ref first, index + 6);
                lookUp1 = Unsafe.Add(ref second, index + 6);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                lookUp0 = Unsafe.Add(ref first, index + 7);
                lookUp1 = Unsafe.Add(ref second, index + 7);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;

                index += 8;
            }

            if (length >= 4)
            {
                length -= 4;

                lookUp0 = Unsafe.Add(ref first, index);
                lookUp1 = Unsafe.Add(ref second, index);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                lookUp0 = Unsafe.Add(ref first, index + 1);
                lookUp1 = Unsafe.Add(ref second, index + 1);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                lookUp0 = Unsafe.Add(ref first, index + 2);
                lookUp1 = Unsafe.Add(ref second, index + 2);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                lookUp0 = Unsafe.Add(ref first, index + 3);
                lookUp1 = Unsafe.Add(ref second, index + 3);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;

                index += 4;
            }

            while (length > 0)
            {
                lookUp0 = Unsafe.Add(ref first, index);
                lookUp1 = Unsafe.Add(ref second, index);
                if (!(lookUp0?.Equals(lookUp1) ?? (object?)lookUp1 is null))
                    goto NotEqual;
                index += 1;
                length--;
            }

        Equal:
            return true;

        NotEqual: // Workaround for https://github.com/dotnet/coreclr/issues/13549
            return false;
        }

        public static int SequenceCompareTo<T>(ref T first, int firstLength, ref T second, int secondLength)
            where T : IComparable<T>
        {
            Debug.Assert(firstLength >= 0);
            Debug.Assert(secondLength >= 0);

            var minLength = firstLength;
            if (minLength > secondLength)
                minLength = secondLength;
            for (int i = 0; i < minLength; i++)
            {
                T lookUp = Unsafe.Add(ref second, i);
                int result = (Unsafe.Add(ref first, i)?.CompareTo(lookUp) ?? (((object?)lookUp is null) ? 0 : -1));
                if (result != 0)
                    return result;
            }
            return firstLength.CompareTo(secondLength);
        }
    }
}