public void Encode(int bit, double p0)
{
checked // check for int overflow
{
uint mid = Convert.ToUInt32(lo + p0 * (hi - lo));
if (bit == 1)
{
lo = mid + 1;
}
else
{
hi = mid;
}
while ((lo & msb) == (hi & msb))
{
var writeBit = (lo & msb) >> shift; // & msb is probably useless here
_targetFile.Write(writeBit);
lo = lo << 1; // shift one written bit
hi = (hi << 1) | 1; // shift one written bit and set LSB to 1
}
}
}
private void EncodeHeader(BitFile targetFile, long size)
{
string header = $"PAQ1\r\n{size}\0";
var headerBytes = Encoding.ASCII.GetBytes(header);
foreach (var headerByte in headerBytes)
{
targetFile.Write(headerByte);
}
}
private void Decompress(BitFile sourceFile, BitFile targetFile)
{
long originalSize = DecodeHeader(sourceFile);
var predictor = new Predictor();
var decoder = new ArithmeticDecoder(sourceFile);
while (targetFile.Length < originalSize)
{
double p0 = predictor.Predict();
var bit = decoder.Decode(p0);
targetFile.Write(bit);
predictor.Update((int)bit);
}
}