using System; namespace MongoAuth { /* Based off http://stackoverflow.com/a/7135008 */ internal static class Base32Encoding { public static byte[] ToBytes(string input) { if (string.IsNullOrEmpty(input)) { throw new ArgumentNullException(nameof(input)); } input = input.TrimEnd('='); //remove padding characters int byteCount = input.Length * 5 / 8; //this must be TRUNCATED var returnArray = new byte[byteCount]; byte curByte = 0, bitsRemaining = 8; int arrayIndex = 0; foreach (char c in input) { int cValue = CharToValue(c); int mask; 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(nameof(input)); } int charCount = (int)Math.Ceiling(input.Length / 5d) * 8; var 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 = 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.", nameof(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.", nameof(b)); } } }