Switch to using Guid.CreateVersion7 in NpgsqlSequentialGuidValueGenerator

Closes #3574

Author: roji

src/EFCore.PG/ValueGeneration/NpgsqlSequentialGuidValueGenerator.cs

@@ -10,98 +10,16 @@ namespace Npgsql.EntityFrameworkCore.PostgreSQL.ValueGeneration;
 public class NpgsqlSequentialGuidValueGenerator : ValueGenerator<Guid>
 {
     /// <summary>
-    ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
-    ///     directly from your code. This API may change or be removed in future releases.
+    ///     Gets a value to be assigned to a property.
     /// </summary>
-    public override bool GeneratesTemporaryValues => false;
+    /// <param name="entry">The change tracking entry of the entity for which the value is being generated.</param>
+    /// <returns>The value to be assigned to a property.</returns>
+    public override Guid Next(EntityEntry entry)
+        => Guid.CreateVersion7();
 
     /// <summary>
     ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
     ///     directly from your code. This API may change or be removed in future releases.
     /// </summary>
-    public override Guid Next(EntityEntry entry) => BorrowedFromNet9.CreateVersion7(timestamp: DateTimeOffset.UtcNow);
-
-    // Code borrowed from .NET 9 should be removed as soon as the target framework includes such code
-    #region Borrowed from .NET 9
-
-#pragma warning disable IDE0007 // Use implicit type -- Avoid changes to code borrowed from BCL
-
-    // https://github.com/dotnet/runtime/blob/f402418aaed508c1d77e41b942e3978675183bfc/src/libraries/System.Private.CoreLib/src/System/Guid.cs
-    internal static class BorrowedFromNet9
-    {
-        private const byte Variant10xxMask = 0xC0;
-        private const byte Variant10xxValue = 0x80;
-
-        private const ushort VersionMask = 0xF000;
-        private const ushort Version7Value = 0x7000;
-
-        /// <summary>Creates a new <see cref="Guid" /> according to RFC 9562, following the Version 7 format.</summary>
-        /// <returns>A new <see cref="Guid" /> according to RFC 9562, following the Version 7 format.</returns>
-        /// <remarks>
-        ///     <para>This uses <see cref="DateTimeOffset.UtcNow" /> to determine the Unix Epoch timestamp source.</para>
-        ///     <para>This seeds the rand_a and rand_b sub-fields with random data.</para>
-        /// </remarks>
-        public static Guid CreateVersion7() => CreateVersion7(DateTimeOffset.UtcNow);
-
-        /// <summary>Creates a new <see cref="Guid" /> according to RFC 9562, following the Version 7 format.</summary>
-        /// <param name="timestamp">The date time offset used to determine the Unix Epoch timestamp.</param>
-        /// <returns>A new <see cref="Guid" /> according to RFC 9562, following the Version 7 format.</returns>
-        /// <exception cref="ArgumentOutOfRangeException"><paramref name="timestamp" /> represents an offset prior to <see cref="DateTimeOffset.UnixEpoch" />.</exception>
-        /// <remarks>
-        ///     <para>This seeds the rand_a and rand_b sub-fields with random data.</para>
-        /// </remarks>
-        public static Guid CreateVersion7(DateTimeOffset timestamp)
-        {
-            // NewGuid uses CoCreateGuid on Windows and Interop.GetCryptographicallySecureRandomBytes on Unix to get
-            // cryptographically-secure random bytes. We could use Interop.BCrypt.BCryptGenRandom to generate the random
-            // bytes on Windows, as is done in RandomNumberGenerator, but that's measurably slower than using CoCreateGuid.
-            // And while CoCreateGuid only generates 122 bits of randomness, the other 6 bits being for the version / variant
-            // fields, this method also needs those bits to be non-random, so we can just use NewGuid for efficiency.
-            var result = Guid.NewGuid();
-
-            // 2^48 is roughly 8925.5 years, which from the Unix Epoch means we won't
-            // overflow until around July of 10,895. So there isn't any need to handle
-            // it given that DateTimeOffset.MaxValue is December 31, 9999. However, we
-            // can't represent timestamps prior to the Unix Epoch since UUIDv7 explicitly
-            // stores a 48-bit unsigned value, so we do need to throw if one is passed in.
-
-            var unix_ts_ms = timestamp.ToUnixTimeMilliseconds();
-            ArgumentOutOfRangeException.ThrowIfNegative(unix_ts_ms, nameof(timestamp));
-
-            ref var resultClone = ref Unsafe.As<Guid, GuidDoppleganger>(ref result); // Deviation from BLC: Reinterpret Guid as our own type so that we can manipulate its private fields
-
-            Unsafe.AsRef(in resultClone._a) = (int)(unix_ts_ms >> 16);
-            Unsafe.AsRef(in resultClone._b) = (short)unix_ts_ms;
-
-            Unsafe.AsRef(in resultClone._c) = (short)(resultClone._c & ~VersionMask | Version7Value);
-            Unsafe.AsRef(in resultClone._d) = (byte)(resultClone._d & ~Variant10xxMask | Variant10xxValue);
-
-            return result;
-        }
-    }
-
-    /// <summary>
-    /// Used to manipulate the private fields of a <see cref="Guid"/> like its internal methods do, by treating a <see cref="Guid"/> as a <see cref="GuidDoppleganger"/>.
-    /// </summary>
-    [StructLayout(LayoutKind.Sequential)]
-    internal readonly struct GuidDoppleganger
-    {
-#pragma warning disable IDE1006 // Naming Styles -- Avoid further changes to code borrowed from BCL when working with the current type
-        internal readonly int _a;   // Do not rename (binary serialization)
-        internal readonly short _b; // Do not rename (binary serialization)
-        internal readonly short _c; // Do not rename (binary serialization)
-        internal readonly byte _d;  // Do not rename (binary serialization)
-        internal readonly byte _e;  // Do not rename (binary serialization)
-        internal readonly byte _f;  // Do not rename (binary serialization)
-        internal readonly byte _g;  // Do not rename (binary serialization)
-        internal readonly byte _h;  // Do not rename (binary serialization)
-        internal readonly byte _i;  // Do not rename (binary serialization)
-        internal readonly byte _j;  // Do not rename (binary serialization)
-        internal readonly byte _k;  // Do not rename (binary serialization)
-#pragma warning restore IDE1006 // Naming Styles
-    }
-
-#pragma warning restore IDE0007 // Use implicit type
-
-    #endregion
+    public override bool GeneratesTemporaryValues => false;
 }