// write .ecc from .cod
public void EncodeECC(byte[] bytes, byte[] header, string filePath)
{
filePath = Path.ChangeExtension(filePath, FileController.ECC_EXTENSION);
Ecc a = new Ecc();
byte crc8 = a.Crc(header);
byte[] crcHeader = new byte[3] {
header[0], header[1], crc8
};
BitArray hamming = a.Hamming(bytes); // hamming bits
BitArray head = new BitArray(crcHeader); // header bits
BitArray bits8 = new BitArray(8); // aux to perform bit to byte
int tam = (crcHeader.Length * 8) + hamming.Count; // total number of bits
BitArray eccResult = new BitArray(tam);
int index = 0;
for (int i = 0; i < head.Length; i++) // add header to eccResult BitArray
{
eccResult[index++] = head[i];
}
for (int i = index, j = 0; i < tam; i++, j++) // add hamming codewords to eccResult BitArray
{
eccResult[index++] = hamming[j];
}
byte[] eccBytes = bitToByte(eccResult, tam);
File.WriteAllBytes(filePath, eccBytes);
}
// decode .ecc, check crc, write .cod
public void DecodeECC(string filePath, byte[] bytes)
{
filePath = Path.ChangeExtension(filePath, FileController.COMPRESSING_EXTENSION);
// first need to generate .cod from ecc
Ecc a = new Ecc();
byte[] header = new byte[2] {
bytes[0], bytes[1]
};
byte crc8 = a.Crc(header);
if (!crc8.Equals(bytes[2])) // check crc
{
Console.WriteLine("CRC ERROR: header is incorrect or corrupted! Ending file compressor...");
return;
}
byte[] bytesAux = new byte[bytes.Length - 3]; // remove heading
Buffer.BlockCopy(bytes, 3, bytesAux, 0, bytesAux.Length);
BitArray hammingBits = new BitArray(bytesAux);
BitArray hammingDec = a.HammingDec(hammingBits);
byte[] codedBytes = bitToByte(hammingDec, hammingDec.Length);
byte[] shiftRight = new byte[codedBytes.Length + 3]; //codedBytes
for (int i = 0; i < codedBytes.Length; i++)
{
shiftRight[(i + 3) % shiftRight.Length] = codedBytes[i];
}
shiftRight[0] = 2; // Fibonacci number
shiftRight[1] = 0; // Only for Golomb K
shiftRight[2] = crc8;
File.WriteAllBytes(filePath, shiftRight); // generate .cod
}