/// <summary>
/// Updates the decoder based on the provided range.
/// </summary>
public void Decode(Range counts,
ReadBitDelegate bitReader)
{
if (counts.Low >= counts.High)
{
throw new ArgumentException("counts");
}
if (counts.Low >= RangeLimit || counts.High >= RangeLimit)
{
throw new ArgumentOutOfRangeException("counts");
}
if (bitReader == null)
{
throw new ArgumentNullException("bitReader");
}
// Update bounds -- interval open at the top => -1 for High
_range = (counts*_step + _range.Low) - BoundaryAdjust;
// e1/e2 mapping
while ((_range.High < Half) || (_range.Low >= Half))
{
bool isHighLessThanHalf = _range.High < Half; // true => emit false for lower half.
uint sub = isHighLessThanHalf ? 0 : Half;
_range = (_range - sub)*2 + BoundaryAdjust;
_buffer = (_buffer - sub)*2 + ((uint) (bitReader() ? 1 : 0));
_scale = 0;
}
// e3 mapping
while (_range.In(FirstQuarter, ThirdQuarter))
{
_scale++;
_range = (_range - FirstQuarter)*2 + BoundaryAdjust;
_buffer = 2*(_buffer - FirstQuarter) + ((uint) (bitReader() ? 1 : 0));
}
}
// total < 2^29
/// <summary>
/// Encodes the range updating the state of the encoder.
/// </summary>
public void Encode(Range counts,
uint total,
WriteBitDelegate bitWriter)
{
if (total >= RangeLimit)
{
throw new ArgumentOutOfRangeException("total");
}
if (counts.Low >= RangeLimit || counts.High >= RangeLimit)
{
throw new ArgumentOutOfRangeException("counts");
}
if (counts.Low >= counts.High)
{
throw new ArgumentException("counts");
}
if (bitWriter == null)
{
throw new ArgumentNullException("bitWriter");
}
// partition number space into single steps
_step = (_range.Length())/total; // interval open at the top => +1
// Update bounds -- interval open at the top => -1 for High.
_range = (counts*_step + _range.Low) - BoundaryAdjust;
// apply e1/e2 mapping
while ((_range.High < Half) || (_range.Low >= Half))
{
bool isHighLessThanHalf = _range.High < Half; // true => emit false for lower half.
uint sub = isHighLessThanHalf ? 0 : Half;
bitWriter(!isHighLessThanHalf);
EmitE3Mappings(bitWriter, isHighLessThanHalf);
_range = (_range - sub)*2 + BoundaryAdjust;
}
// e3
while (_range.In(FirstQuarter, ThirdQuarter))
{
// keep necessary e3 mappings in mind
_scale++;
_range = (_range - FirstQuarter)*2 + BoundaryAdjust;
}
}
