public static ulong Decode(String cypher_string)
{
int[] codeword = new int[ReedSolomon.initial_codeword.Length];
Array.Copy(ReedSolomon.initial_codeword, 0, codeword, 0, ReedSolomon.initial_codeword.Length);
int codeword_length = 0;
for (int i = 0; i < cypher_string.Length; i++)
{
int position_in_alphabet = ReedSolomon.alphabet.IndexOf(cypher_string[i]);
if (position_in_alphabet <= -1 || position_in_alphabet > ReedSolomon.alphabet.Length)
{
continue;
}
if (codeword_length > 16)
{
throw new CodewordTooLongException();
}
int codework_index = ReedSolomon.codeword_map[codeword_length];
codeword[codework_index] = position_in_alphabet;
codeword_length += 1;
}
if (codeword_length == 17 && !ReedSolomon.is_codeword_valid(codeword) || codeword_length != 17)
{
throw new CodewordInvalidException();
}
int length = ReedSolomon.base_32_length;
int[] cypher_string_32 = new int[length];
for (int i = 0; i < length; i++)
{
cypher_string_32[i] = codeword[length - i - 1];
}
StringBuilder plain_string_builder = new StringBuilder();
do
{ // base 32 to base 10 conversion
int new_length = 0;
int digit_10 = 0;
for (int i = 0; i < length; i++)
{
digit_10 = digit_10 * 32 + cypher_string_32[i];
if (digit_10 >= 10)
{
cypher_string_32[new_length] = digit_10 / 10;
digit_10 %= 10;
new_length += 1;
}
else if (new_length > 0)
{
cypher_string_32[new_length] = 0;
new_length += 1;
}
}
length = new_length;
plain_string_builder.Append((char)(digit_10 + (int)'0'));
} while (length > 0);
var str = new String(plain_string_builder.ToString().ToCharArray().Reverse().ToArray());
return(Convert.ToUInt64(str));
}
public static String Encode(ulong plain)
{
String plain_string = Convert.ToString(plain);
int length = plain_string.Length;
int[] plain_string_10 = new int[ReedSolomon.base_10_length];
for (int i = 0; i < length; i++)
{
plain_string_10[i] = (int)plain_string[i] - (int)'0';
}
int codeword_length = 0;
int[] codeword = new int[ReedSolomon.initial_codeword.Length];
do
{ // base 10 to base 32 conversion
int new_length = 0;
int digit_32 = 0;
for (int i = 0; i < length; i++)
{
digit_32 = digit_32 * 10 + plain_string_10[i];
if (digit_32 >= 32)
{
plain_string_10[new_length] = digit_32 >> 5;
digit_32 &= 31;
new_length += 1;
}
else if (new_length > 0)
{
plain_string_10[new_length] = 0;
new_length += 1;
}
}
length = new_length;
codeword[codeword_length] = digit_32;
codeword_length += 1;
} while (length > 0);
int[] p = { 0, 0, 0, 0 };
for (int i = ReedSolomon.base_32_length - 1; i >= 0; i--)
{
int fb = codeword[i] ^ p[3];
p[3] = p[2] ^ ReedSolomon.gmult(30, fb);
p[2] = p[1] ^ ReedSolomon.gmult(6, fb);
p[1] = p[0] ^ ReedSolomon.gmult(9, fb);
p[0] = ReedSolomon.gmult(17, fb);
}
Array.Copy(p, 0, codeword, ReedSolomon.base_32_length, ReedSolomon.initial_codeword.Length - ReedSolomon.base_32_length);
StringBuilder cypher_string_builder = new StringBuilder();
for (int i = 0; i < 17; i++)
{
int codework_index = ReedSolomon.codeword_map[i];
int alphabet_index = codeword[codework_index];
cypher_string_builder.Append(ReedSolomon.alphabet[alphabet_index]);
if ((i & 3) == 3 && i < 13)
{
cypher_string_builder.Append('-');
}
}
return(cypher_string_builder.ToString());
}
