public byte[] Decrypt(string input)
{
byte newChar = 0x0;
//填充新字所缺位元數
int leaNewCharBitCounter = FixedByteCounter;
//拿來使用的位元組所剩的位元數
int reminderBitCounter = 0;
//用剩下的位元組
byte reminderByte = 0x0;
List <byte> result = new List <byte>();
//去掉padding
input = input.Replace("=", "");
byte[] byteResult = new byte[input.Length];
//把base32alphabet結果轉換成byte array
for (int k = 0; k < input.Length; k++)
{
byteResult[k] = Convert.ToByte(Base32Alphabet.IndexOf(input[k]));
}
for (int i = 0; i < byteResult.Length; i++)
{
//空出newChar所需的空間
newChar |= (reminderByte <<= (FixedByteCounter - reminderBitCounter));
//埴充newChar所缺的bit數
leaNewCharBitCounter -= reminderBitCounter;
if (leaNewCharBitCounter > FixedDrawCounter)
{
newChar |= (byte)(byteResult[i] << (leaNewCharBitCounter - FixedDrawCounter));
leaNewCharBitCounter -= FixedDrawCounter;
reminderBitCounter = 0;
}
else if (leaNewCharBitCounter == FixedDrawCounter)
{
newChar |= byteResult[i];
leaNewCharBitCounter = 0;
reminderBitCounter = 0;
}
else if (leaNewCharBitCounter < FixedDrawCounter)
{
newChar |= (byte)(byteResult[i] >> (FixedDrawCounter - leaNewCharBitCounter));
reminderBitCounter = FixedDrawCounter - leaNewCharBitCounter;
reminderByte = byteResult[i] &= Convert.ToByte(Math.Pow(2, reminderBitCounter) - 1);
leaNewCharBitCounter = 0;
}
if (leaNewCharBitCounter == 0)
{
result.Add(newChar);
newChar = 0x0;
leaNewCharBitCounter = FixedByteCounter;
}
}
return(result.ToArray());
}
/// <summary>
/// Convert <paramref name="base32String"/> string to a byte array
/// </summary>
/// <param name="base32String">Base32 string to convert - must be at least two characters</param>
public static Maybe <byte[]> FromBase32String(string base32String)
{
// Check if string is empty
if (string.IsNullOrEmpty(base32String))
{
return(Array.Empty <byte>());
}
// Convert to upper-case
var base32StringUpperCase = base32String.ToUpperInvariant();
// Prepare output byte array
var outputBytes = new byte[base32StringUpperCase.Length * OutByteSize / InByteSize];
// Check the size
if (outputBytes.Length == 0)
{
return(F.None <byte[], M.InputStringNotLongEnoughMsg>());
}
// Position in the string
var base32Position = 0;
// Offset inside the character in the string
var base32SubPosition = 0;
// Position within outputBytes array
var outputBytePosition = 0;
// The number of bits filled in the current output byte
var outputByteSubPosition = 0;
// Normally we would iterate on the input array but in this case we actually iterate on the output array
// We do it because output array doesn''t have overflow bits, while input does and it will cause output array overflow if we don''t stop in time
while (outputBytePosition < outputBytes.Length)
{
// Look up current character in the dictionary to convert it to byte
var currentBase32Byte = Base32Alphabet.IndexOf(base32StringUpperCase[base32Position]);
// Check if found
if (currentBase32Byte < 0)
{
return(F.None <byte[]>(new M.CharacterNotInBase32AlphabetMsg(base32String[base32Position])));
}
// Calculate the number of bits we can extract out of current input character to fill missing bits in the output byte
var bitsAvailableInByte = Math.Min(OutByteSize - base32SubPosition, InByteSize - outputByteSubPosition);
// Make space in the output byte
outputBytes[outputBytePosition] <<= bitsAvailableInByte;
// Extract the part of the input character and move it to the output byte
outputBytes[outputBytePosition] |= (byte)(currentBase32Byte >> (OutByteSize - (base32SubPosition + bitsAvailableInByte)));
// Update current sub-byte position
outputByteSubPosition += bitsAvailableInByte;
// Check overflow
if (outputByteSubPosition >= InByteSize)
{
// Move to the next byte
outputBytePosition++;
outputByteSubPosition = 0;
}
// Update current base32 byte completion
base32SubPosition += bitsAvailableInByte;
// Check overflow or end of input array
if (base32SubPosition >= OutByteSize)
{
// Move to the next character
base32Position++;
base32SubPosition = 0;
}
}
return(outputBytes);
}
private byte[] FromBase32String(string base32String)
{
const int InByteSize = 8;
const int OutByteSize = 5;
const string Base32Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
// Check if string is null
if (base32String == null)
{
return(null);
}
// Check if empty
else if (base32String == string.Empty)
{
return(new byte[0]);
}
// Convert to upper-case
string base32StringUpperCase = base32String.ToUpperInvariant();
// Prepare output byte array
byte[] outputBytes = new byte[base32StringUpperCase.Length * OutByteSize / InByteSize];
// Check the size
if (outputBytes.Length == 0)
{
throw new ArgumentException("Specified string is not valid Base32 format because it doesn't have enough data to construct a complete byte array");
}
// Position in the string
int base32Position = 0;
// Offset inside the character in the string
int base32SubPosition = 0;
// Position within outputBytes array
int outputBytePosition = 0;
// The number of bits filled in the current output byte
int outputByteSubPosition = 0;
// Normally we would iterate on the input array but in this case we actually iterate on the output array
// We do it because output array doesn't have overflow bits, while input does and it will cause output array overflow if we don't stop in time
while (outputBytePosition < outputBytes.Length)
{
// Look up current character in the dictionary to convert it to byte
int currentBase32Byte = Base32Alphabet.IndexOf(base32StringUpperCase[base32Position]);
// Check if found
if (currentBase32Byte < 0)
{
throw new ArgumentException(string.Format("Specified string is not valid Base32 format because character \"{0}\" does not exist in Base32 alphabet", base32String[base32Position]));
}
// Calculate the number of bits we can extract out of current input character to fill missing bits in the output byte
int bitsAvailableInByte = Math.Min(OutByteSize - base32SubPosition, InByteSize - outputByteSubPosition);
// Make space in the output byte
outputBytes[outputBytePosition] <<= bitsAvailableInByte;
// Extract the part of the input character and move it to the output byte
outputBytes[outputBytePosition] |= (byte)(currentBase32Byte >> (OutByteSize - (base32SubPosition + bitsAvailableInByte)));
// Update current sub-byte position
outputByteSubPosition += bitsAvailableInByte;
// Check overflow
if (outputByteSubPosition >= InByteSize)
{
// Move to the next byte
outputBytePosition++;
outputByteSubPosition = 0;
}
// Update current base32 byte completion
base32SubPosition += bitsAvailableInByte;
// Check overflow or end of input array
if (base32SubPosition >= OutByteSize)
{
// Move to the next character
base32Position++;
base32SubPosition = 0;
}
}
return(outputBytes);
}