Merge pull request #46 from dbuenor/dbueno/add-postgresql-comb-guid-g…

…enerator

Added new method for AdvancedGuidGenerator to generate CombGuid for PostgreSQL

HermaFx.Foundation.Tests/AdvancedGuidGeneratorTests.cs

@@ -15,5 +15,12 @@ public void BasicCombGuidGeneration()
 			var id = AdvancedGuidGenerator.GenerateComb();
 			Guid.Parse(id.ToString());
 		}
+
+		[Test]
+		public void BasicPostgreSQLCombGuidGeneration()
+		{
+			var id = AdvancedGuidGenerator.GenerateCombEx();
+			Guid.Parse(id.ToString());
+		}
 	}
 }

HermaFx.Foundation/Utils/AdvancedGuidGenerator.cs

@@ -6,11 +6,14 @@ public static class AdvancedGuidGenerator
 	{
 		private static readonly DateTime UnixStartTime = new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc);
 
+		// XXX: Values added for GenerateCombEx
+		// From private DateTime.TicksPerMillisecond
+		private const long TicksPerMillisecond = 10000;
+		private static DateTime MinDateTimeValue { get; } = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
+		private static int NumDateBytes = 6;
+
 		// note: Guids generated by CombGuidGenerator are only considered ascending by SQL Server which compares Guids in an unusual way
 		// to generate Guids considered ascending by MongoDB use the AscendingGuidGenerator
-
-
-
 		public static Guid GenerateComb()
 		{
 			return GenerateComb(Guid.NewGuid(), DateTime.UtcNow);
@@ -47,5 +50,74 @@ public static Guid GenerateComb(Guid id, DateTime timestamp)
 #endif
 			return new Guid(result);
 		}
+
+
+		#region GenerateCombForPostgreSQL
+		/*
+		 *	FROM: https://github.com/richardtallent/RT.Comb/blob/main/src/RT.Comb/CombProvider/PostgreSqlCombProvider.cs
+		 *
+		 *	Copyright 2015-2020 Richard S. Tallent, II
+		 *	Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files
+		 *	(the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge,
+		 *	publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to
+		 *	do so, subject to the following conditions:
+		 *	The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+		 *	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+		 *	MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+		 *	LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+		 *	CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+		 */
+
+		// IDateTimeStrategy is required to provide the bytes we need in network byte order, and that's what we want
+		// in PostgreSQL as well. However, internally, GUID bytes for Data1 and Data2 are stored in little endian
+		// order, so we need to reverse one or both of those so the bytes we want are re-reversed to the correct
+		// order by Npgsql's GUID data type handler.
+		private static void SwapByteOrderForStringOrder(byte[] input)
+		{
+			Array.Reverse(input, 0, 4);             // Swap around the first 4 bytes
+			if (input.Length == 4) return;
+			Array.Reverse(input, 4, 2);             // Swap around the next 2 bytes
+		}
+
+		// We purposefully are not using the FromUnixTimeMilliseconds and ToUnixTimeMilliseconds to remain compatible with .NET 4.5.1
+		//(long)(timestamp.ToUniversalTime() - MinDateTimeValue).TotalMilliseconds;
+		//public DateTime FromUnixTimeMilliseconds(long ms) => MinDateTimeValue.AddMilliseconds(ms);
+		private static long ToUnixTimeMilliseconds(DateTime timestamp) => (timestamp.Ticks - MinDateTimeValue.Ticks) / TicksPerMillisecond;
+
+		private static byte[] DateTimeToBytes(DateTime timestamp)
+		{
+			var ms = ToUnixTimeMilliseconds(timestamp);
+			var msBytes = BitConverter.GetBytes(ms);
+			if (BitConverter.IsLittleEndian) Array.Reverse(msBytes);
+			var result = new byte[NumDateBytes];
+			var index = msBytes.GetUpperBound(0) + 1 - NumDateBytes;
+			Array.Copy(msBytes, index, result, 0, NumDateBytes);
+			return result;
+		}
+
+		/// <summary>
+		/// Generate CombGuid specially recommended for PostgreSQL databases
+		/// </summary>
+		/// <param name="id"></param>
+		/// <param name="timestamp"></param>
+		/// <returns></returns>
+		public static Guid GenerateCombEx(Guid id, DateTime timestamp)
+		{
+			var gbytes = id.ToByteArray();
+			var dbytes = DateTimeToBytes(timestamp);
+			Array.Copy(dbytes, 0, gbytes, 0, NumDateBytes);
+			SwapByteOrderForStringOrder(gbytes);
+			return new Guid(gbytes);
+		}
+
+		/// <summary>
+		/// Generate CombGuid specially recommended for PostgreSQL databases
+		/// </summary>
+		/// <returns></returns>
+		public static Guid GenerateCombEx()
+		{
+			return GenerateCombEx(Guid.NewGuid(), DateTime.UtcNow);
+		}
+		#endregion
 	}
 }