1 files changed, 134 insertions, 0 deletions
diff --git a/TwoStepsAuthenticator.DotnetCore/Base32Encoding.cs b/TwoStepsAuthenticator.DotnetCore/Base32Encoding.cs
new file mode 100644
index 0000000..5acb49b
--- /dev/null
+++ b/TwoStepsAuthenticator.DotnetCore/Base32Encoding.cs
@@ -0,0 +1,134 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TwoStepsAuthenticator
+{
+    // This class was found just here : http://stackoverflow.com/questions/641361/base32-decoding
+    // This file is under Creative Commons http://creativecommons.org/licenses/by-sa/2.5/
+    public class Base32Encoding
+    {
+        public static byte[] ToBytes(string input)
+        {
+            if (string.IsNullOrEmpty(input))
+            {
+                throw new ArgumentNullException("input");
+            }
+
+            input = input.TrimEnd('='); //remove padding characters
+            int byteCount = input.Length * 5 / 8; //this must be TRUNCATED
+            byte[] returnArray = new byte[byteCount];
+
+            byte curByte = 0, bitsRemaining = 8;
+            int mask = 0, arrayIndex = 0;
+
+            foreach (char c in input)
+            {
+                int cValue = CharToValue(c);
+
+                if (bitsRemaining > 5)
+                {
+                    mask = cValue << (bitsRemaining - 5);
+                    curByte = (byte)(curByte | mask);
+                    bitsRemaining -= 5;
+                }
+                else
+                {
+                    mask = cValue >> (5 - bitsRemaining);
+                    curByte = (byte)(curByte | mask);
+                    returnArray[arrayIndex++] = curByte;
+                    curByte = (byte)(cValue << (3 + bitsRemaining));
+                    bitsRemaining += 3;
+                }
+            }
+
+            //if we didn't end with a full byte
+            if (arrayIndex != byteCount)
+            {
+                returnArray[arrayIndex] = curByte;
+            }
+
+            return returnArray;
+        }
+
+        public static string ToString(byte[] input)
+        {
+            if (input == null || input.Length == 0)
+            {
+                throw new ArgumentNullException("input");
+            }
+
+            int charCount = (int)Math.Ceiling(input.Length / 5d) * 8;
+            char[] returnArray = new char[charCount];
+
+            byte nextChar = 0, bitsRemaining = 5;
+            int arrayIndex = 0;
+
+            foreach (byte b in input)
+            {
+                nextChar = (byte)(nextChar | (b >> (8 - bitsRemaining)));
+                returnArray[arrayIndex++] = ValueToChar(nextChar);
+
+                if (bitsRemaining < 4)
+                {
+                    nextChar = (byte)((b >> (3 - bitsRemaining)) & 31);
+                    returnArray[arrayIndex++] = ValueToChar(nextChar);
+                    bitsRemaining += 5;
+                }
+
+                bitsRemaining -= 3;
+                nextChar = (byte)((b << bitsRemaining) & 31);
+            }
+
+            //if we didn't end with a full char
+            if (arrayIndex != charCount)
+            {
+                returnArray[arrayIndex++] = ValueToChar(nextChar);
+                while (arrayIndex != charCount) returnArray[arrayIndex++] = '='; //padding
+            }
+
+            return new string(returnArray);
+        }
+
+        private static int CharToValue(char c)
+        {
+            int value = (int)c;
+
+            //65-90 == uppercase letters
+            if (value < 91 && value > 64)
+            {
+                return value - 65;
+            }
+            //50-55 == numbers 2-7
+            if (value < 56 && value > 49)
+            {
+                return value - 24;
+            }
+            //97-122 == lowercase letters
+            if (value < 123 && value > 96)
+            {
+                return value - 97;
+            }
+
+            throw new ArgumentException("Character is not a Base32 character.", "c");
+        }
+
+        private static char ValueToChar(byte b)
+        {
+            if (b < 26)
+            {
+                return (char)(b + 65);
+            }
+
+            if (b < 32)
+            {
+                return (char)(b + 24);
+            }
+
+            throw new ArgumentException("Byte is not a value Base32 value.", "b");
+        }
+
+    }
+}