GuidExtensions.cs

//******************************************************************************************************
//  GuidExtensions.cs - Gbtc
//
//  Copyright © 2014, Grid Protection Alliance.  All Rights Reserved.
//
//  Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See
//  the NOTICE file distributed with this work for additional information regarding copyright ownership.
//  The GPA licenses this file to you under the MIT License (MIT), the "License"; you may
//  not use this file except in compliance with the License. You may obtain a copy of the License at:
//
//      http://www.opensource.org/licenses/MIT
//
//  Unless agreed to in writing, the subject software distributed under the License is distributed on an
//  "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the
//  License for the specific language governing permissions and limitations.
//
//  Code Modification History:
//  ----------------------------------------------------------------------------------------------------
//  05/07/2014 - Steven E. Chisholm
//       Generated original version of source code.
//
//******************************************************************************************************

using System;
using System.Runtime.CompilerServices;
using Gemstone.ArrayExtensions;

namespace Gemstone.GuidExtensions;

/// <summary>
/// Extension methods for <see cref="Guid"/>.
/// </summary>
public static unsafe class GuidExtensions
{
    #region [ Big Endian Based Encoding (RFC 4122) ]

    /// <summary>
    /// Encodes a <see cref="Guid"/> following RFC 4122.
    /// </summary>
    /// <param name="guid">The <see cref="Guid"/> to serialize.</param>
    /// <param name="buffer">Destination buffer to hold serialized <paramref name="guid"/>.</param>
    /// <param name="startingIndex">Starting index in <paramref name="buffer"/>.</param>
    /// <returns>Bytes encoded.</returns>
    public static int ToRfcBytes(this Guid guid, byte[] buffer, int startingIndex)
    {
        // Since Microsoft is not very clear how Guid.ToByteArray() performs on big endian processors
        // we are assuming that the internal structure of a Guid will always be the same. Reviewing
        // mono source code the internal structure is also the same.
        buffer.ValidateParameters(startingIndex, 16);

        byte* src = (byte*)&guid;

        fixed (byte* dst = &buffer[startingIndex])
        {
            if (BitConverter.IsLittleEndian)
            {
                // Guid._a (int)
                dst[0] = src[3];
                dst[1] = src[2];
                dst[2] = src[1];
                dst[3] = src[0];

                // Guid._b (short)
                dst[4] = src[5];
                dst[5] = src[4];

                // Guid._c (short)
                dst[6] = src[7];
                dst[7] = src[6];

                // Guid._d - Guid._k (8 bytes)
                // Since already encoded as big endian, just copy the data
                *(long*)(dst + 8) = *(long*)(src + 8);
            }
            else
            {
                // All fields are encoded big-endian, just copy
                *(long*)(dst + 0) = *(long*)(src + 0);
                *(long*)(dst + 8) = *(long*)(src + 8);
            }
        }

        return 16;
    }

    /// <summary>
    /// Encodes a <see cref="Guid"/> following RFC 4122.
    /// </summary>
    /// <param name="guid">The <see cref="Guid"/> to serialize.</param>
    /// <param name="buffer">Destination buffer to hold serialized <paramref name="guid"/>.</param>
    /// <returns>Bytes encoded.</returns>
    public static int ToRfcBytes(this Guid guid, byte* buffer)
    {
        byte* src = (byte*)&guid;

        if (BitConverter.IsLittleEndian)
        {
            // Guid._a (int)
            buffer[0] = src[3];
            buffer[1] = src[2];
            buffer[2] = src[1];
            buffer[3] = src[0];

            // Guid._b (short)
            buffer[4] = src[5];
            buffer[5] = src[4];

            // Guid._c (short)
            buffer[6] = src[7];
            buffer[7] = src[6];

            // Guid._d - Guid._k (8 bytes)
            // Since already encoded as big endian, just copy the data
            *(long*)(buffer + 8) = *(long*)(src + 8);
        }
        else
        {
            // All fields are encoded big-endian, just copy
            *(long*)(buffer + 0) = *(long*)(src + 0);
            *(long*)(buffer + 8) = *(long*)(src + 8);
        }

        return 16;
    }

    /// <summary>
    /// Encodes a <see cref="Guid"/> following RFC 4122.
    /// </summary>
    /// <param name="guid"><see cref="Guid"/> to serialize.</param>
    /// <returns>A <see cref="byte"/> array that represents a big-endian encoded <see cref="Guid"/>.</returns>
    public static byte[] ToRfcBytes(this Guid guid)
    {
        byte[] rv = new byte[16];
        guid.ToRfcBytes(rv, 0);

        return rv;
    }

    /// <summary>
    /// Decodes a <see cref="Guid"/> following RFC 4122
    /// </summary>
    /// <param name="buffer">Buffer containing a serialized big-endian encoded <see cref="Guid"/>.</param>
    /// <returns><see cref="Guid"/> deserialized from <paramref name="buffer"/>.</returns>
    public static Guid ToRfcGuid(this byte[] buffer) => buffer.ToRfcGuid(0);

    /// <summary>
    /// Decodes a <see cref="Guid"/> following RFC 4122
    /// </summary>
    /// <param name="buffer">Buffer containing a serialized big-endian encoded <see cref="Guid"/>.</param>
    /// <returns><see cref="Guid"/> deserialized from <paramref name="buffer"/>.</returns>
    public static Guid ToRfcGuid(byte* buffer)
    {
        // Since Microsoft is not very clear how Guid.ToByteArray() performs on big endian processors
        // we are assuming that the internal structure of a Guid will always be the same. Reviewing
        // mono source code the internal structure is also the same.
        Guid rv;
        byte* dst = (byte*)&rv;

        if (BitConverter.IsLittleEndian)
        {
            // Guid._a (int)
            dst[0] = buffer[3];
            dst[1] = buffer[2];
            dst[2] = buffer[1];
            dst[3] = buffer[0];

            // Guid._b (short)
            dst[4] = buffer[5];
            dst[5] = buffer[4];

            // Guid._c (short)
            dst[6] = buffer[7];
            dst[7] = buffer[6];

            // Guid._d - Guid._k (8 bytes)
            // Since already encoded as big endian, just copy the data
            *(long*)(dst + 8) = *(long*)(buffer + 8);
        }
        else
        {
            // All fields are encoded big-endian, just copy
            *(long*)(dst + 0) = *(long*)(buffer + 0);
            *(long*)(dst + 8) = *(long*)(buffer + 8);
        }

        return rv;
    }

    /// <summary>
    /// Decodes a <see cref="Guid"/> following RFC 4122
    /// </summary>
    /// <param name="buffer">Buffer containing a serialized big-endian encoded <see cref="Guid"/>.</param>
    /// <param name="startingIndex">Starting index in <paramref name="buffer"/>.</param>
    /// <returns><see cref="Guid"/> deserialized from <paramref name="buffer"/>.</returns>
    public static Guid ToRfcGuid(this byte[] buffer, int startingIndex)
    {
        buffer.ValidateParameters(startingIndex, 16);

        // Since Microsoft is not very clear how Guid.ToByteArray() performs on big endian processors
        // we are assuming that the internal structure of a Guid will always be the same. Reviewing
        // mono source code the internal structure is also the same.
        Guid rv;
        byte* dst = (byte*)&rv;

        fixed (byte* src = &buffer[startingIndex])
        {
            if (BitConverter.IsLittleEndian)
            {
                // Guid._a (int)
                dst[0] = src[3];
                dst[1] = src[2];
                dst[2] = src[1];
                dst[3] = src[0];

                // Guid._b (short)
                dst[4] = src[5];
                dst[5] = src[4];

                // Guid._c (short)
                dst[6] = src[7];
                dst[7] = src[6];

                // Guid._d - Guid._k (8 bytes)
                // Since already encoded as big endian, just copy the data
                *(long*)(dst + 8) = *(long*)(src + 8);
            }
            else
            {
                // All fields are encoded big-endian, just copy
                *(long*)(dst + 0) = *(long*)(src + 0);
                *(long*)(dst + 8) = *(long*)(src + 8);
            }

            return rv;
        }
    }

    #endregion

    #region [ Little Endian Encoding ]

    /// <summary>
    /// Gets the little endian encoded bytes of the <see cref="Guid"/>.
    /// </summary>
    /// <param name="guid">the <see cref="Guid"/> to serialize</param>
    /// <returns>A <see cref="byte"/>[] that represents a big endian encoded Guid.</returns>
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static byte[] ToLittleEndianBytes(this Guid guid)
    {
        byte[] rv = new byte[16];
        CopyLittleEndianBytes(guid, rv, 0);

        return rv;
    }

    /// <summary>
    /// Writes a <see cref="Guid"/> in Little Endian byte order.
    /// </summary>
    /// <param name="guid">the <see cref="Guid"/> to serialize</param>
    /// <param name="buffer">where to store the <paramref name="guid"/></param>
    /// <param name="startingIndex">the starting index in <paramref name="buffer"/></param>
    /// <returns>Bytes written.</returns>
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static int CopyLittleEndianBytes(this Guid guid, byte[] buffer, int startingIndex)
    {
        buffer.ValidateParameters(startingIndex, 16);

        fixed (byte* dst = &buffer[startingIndex])
            return CopyLittleEndianBytes(guid, dst);
    }

    /// <summary>
    /// Writes a <see cref="Guid"/> in Little Endian byte order.
    /// </summary>
    /// <param name="guid">the <see cref="Guid"/> to serialize</param>
    /// <param name="buffer">where to store the <paramref name="guid"/></param>
    /// <returns>Bytes written.</returns>
    public static int CopyLittleEndianBytes(this Guid guid, byte* buffer)
    {
        byte* src = (byte*)&guid;

        if (BitConverter.IsLittleEndian)
        {
            // just copy the data
            *(long*)(buffer + 0) = *(long*)(src + 0);
            *(long*)(buffer + 8) = *(long*)(src + 8);
        }
        else
        {
            // Guid._a (int)  //swap endian
            buffer[0] = src[3];
            buffer[1] = src[2];
            buffer[2] = src[1];
            buffer[3] = src[0];
            // Guid._b (short) //swap endian
            buffer[4] = src[5];
            buffer[5] = src[4];
            // Guid._c (short) //swap endian
            buffer[6] = src[7];
            buffer[7] = src[6];
            // Guid._d - Guid._k (8 bytes)
            *(long*)(buffer + 8) = *(long*)(src + 8);
        }

        return 16;
    }

    /// <summary>
    /// Reads a <see cref="Guid"/> in Little Endian byte order.
    /// </summary>
    /// <param name="buffer">where to read the <see cref="Guid"/>.</param>
    /// <returns>Decoded <see cref="Guid"/>.</returns>
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static Guid ToLittleEndianGuid(this byte[] buffer)
    {
        buffer.ValidateParameters(0, 16);

        fixed (byte* src = buffer)
            return ToLittleEndianGuid(src);
    }

    /// <summary>
    /// Mimicks the encoding that was present in LittleEndianOrder on a Little Endian CPU. 
    /// </summary>
    /// <param name="buffer">where to read the <see cref="Guid"/>.</param>
    /// <param name="startingIndex">the starting index in <paramref name="buffer"/></param>
    /// <returns>Decoded <see cref="Guid"/>.</returns>
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static Guid ToLittleEndianGuid(this byte[] buffer, int startingIndex)
    {
        buffer.ValidateParameters(startingIndex, 16);

        fixed (byte* src = &buffer[startingIndex])
            return ToLittleEndianGuid(src);
    }

    /// <summary>
    /// Reads a Guid in Little Endian byte order.
    /// </summary>
    /// <param name="buffer">where to read the <see cref="Guid"/>.</param>
    /// <returns>Decoded <see cref="Guid"/>.</returns>
    public static Guid ToLittleEndianGuid(byte* buffer)
    {
        Guid rv;
        byte* dst = (byte*)&rv;

        if (BitConverter.IsLittleEndian)
        {
            // internal stucture is correct, just copy
            *(long*)(dst + 0) = *(long*)(buffer + 0);
            *(long*)(dst + 8) = *(long*)(buffer + 8);
        }
        else
        {
            // Guid._a (int) //swap endian
            dst[0] = buffer[3];
            dst[1] = buffer[2];
            dst[2] = buffer[1];
            dst[3] = buffer[0];
            // Guid._b (short) //swap endian
            dst[4] = buffer[5];
            dst[5] = buffer[4];
            // Guid._c (short) //swap endian
            dst[6] = buffer[7];
            dst[7] = buffer[6];
            // Guid._d - Guid._k (8 bytes)
            *(long*)(dst + 8) = *(long*)(buffer + 8);
        }

        return rv;
    }

    #endregion
}