Added Base64 URL Safe Data Encoder

NBitcoin.Tests/ConverterTests.cs

@@ -15,7 +15,12 @@ public class ConverterTests
 		[Trait("UnitTest", "UnitTest")]
 		public void CanConvertText()
 		{
-			string testPhrase = "é ^ç hello \"12345\"  wooorld";
+			var testPhrase = Encoding.UTF8.GetBytes("é ^ç hello \"12345\"  wooorld");
+			var rfc4648_1 = new byte[] { 0x14, 0xfb, 0x9c, 0x03, 0xd9, 0x7e };
+			var rfc4648_2 = new byte[] { 0x14, 0xfb, 0x9c, 0x03, 0xd9 };
+			var rfc4648_3 = new byte[] { 0x14, 0xfb, 0x9c, 0x03 };
+
+
 			var tests = new[]
 			{
 				new
@@ -43,6 +48,31 @@ public void CanConvertText()
 					Input = testPhrase,
 					Expected = "w6kgXsOnIGhlbGxvICIxMjM0NSIgIHdvb29ybGQ="
 				},
+				new
+				{
+					Encoder = Encoders.Base64UrlSafe,
+					Input = testPhrase,
+					Expected = "w6kgXsOnIGhlbGxvICIxMjM0NSIgIHdvb29ybGQ"
+				},
+				new
+				{
+					Encoder = Encoders.Base64UrlSafe,
+					Input = rfc4648_1,
+					Expected = "FPucA9l-"
+				},
+				new
+				{
+					Encoder = Encoders.Base64UrlSafe,
+					Input = rfc4648_2,
+					Expected = "FPucA9k"
+				},
+				new
+				{
+					Encoder = Encoders.Base64UrlSafe,
+					Input = rfc4648_3,
+					Expected = "FPucAw"
+				},
+
 				//Not yet implemented
 				//new 
 				//{
@@ -89,14 +119,13 @@ public void CanConvertText()
 
 			foreach (var test in tests)
 			{
-				var input = Encoding.UTF8.GetBytes(test.Input);
-				var encoded = test.Encoder.EncodeData(input);
+				var encoded = test.Encoder.EncodeData(test.Input);
 				Assert.Equal(test.Expected, encoded);
 
 				try
 				{
 					var decoded = test.Encoder.DecodeData(encoded);
-					AssertEx.CollectionEquals(input, decoded);
+					AssertEx.CollectionEquals(test.Input, decoded);
 				}
 				catch (NotSupportedException)
 				{

NBitcoin/DataEncoders/Base64UrlSafeEncoder.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Linq;
+
+namespace NBitcoin.DataEncoders
+{
+	public class Base64UrlSafeEncoder : DataEncoder
+	{
+		static readonly char[] padding = { '=' };
+		static readonly int paddingBoundary = 4;
+		public override byte[] DecodeData(string encoded)
+		{
+			var temp = encoded.Replace('-', '+').Replace('_', '/');
+
+			// Re-add padding if necessary
+			var remaining = temp.Length % paddingBoundary;
+			switch(remaining) {
+				case 2:
+				case 3:
+					temp += string.Concat(Enumerable.Repeat('=', paddingBoundary-remaining));
+					break;
+			}
+			return Convert.FromBase64String(temp);
+		}
+
+		public override string EncodeData(byte[] data, int offset, int count)
+		{
+			return Convert.ToBase64String(data, offset, count).Replace('+', '-').Replace('/', '_').TrimEnd(padding);
+		}
+	}
+}

NBitcoin/DataEncoders/Encoders.cs

@@ -98,6 +98,15 @@ public static DataEncoder Base64
 			}
 		}
 
+		static readonly Base64UrlSafeEncoder _Base64UrlSafe = new Base64UrlSafeEncoder();
+		public static DataEncoder Base64UrlSafe
+		{
+			get
+			{
+				return _Base64UrlSafe;
+			}
+		}
+
 		public static Bech32Encoder Bech32(string hrp)
 		{
 			return new Bech32Encoder(hrp);