BuildFeed/Authentication/MongoAuth/Base32Encoding.cs

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3.8 KiB
C#
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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,
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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,
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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)
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{
returnArray[arrayIndex++] = '='; //padding
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}
}
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;
}
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//50-55 == numbers 2-7
if (value < 56 && value > 49)
{
return value - 24;
}
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//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));
}
}
}