/// <summary>
/// Reads a symbol using the bits retrieved with <paramref name="bitReader" />.
/// </summary>
public TSymbolType GetSymbol(ReadBitDelegate bitReader)
{
var current = (uint)_entries.Length - 1;
while (!_entries[current].IsSymbol)
{
current = _entries[current].GetChild(bitReader());
}
return(_entries[current].Symbol);
}
/// <summary>
/// Initializes the decoder by reading the first set of values for the state.
/// </summary>
/// <param name="bitReader"></param>
public void DecodeStart(ReadBitDelegate bitReader)
{
if (bitReader == null)
{
throw new ArgumentNullException("bitReader");
}
// Fill buffer with bits from the input stream
for (int i = 0; i < 31; i++) // just use the 31 least significant bits
{
_buffer = (_buffer << 1) | ((uint)(bitReader() ? 1 : 0));
}
}
/// <summary>
/// Handles reading the symbol from the symbol space (including the NotYetTransmitted sequence).
/// </summary>
private SymbolSpace GetSymbolInternal(ReadBitDelegate bitReader)
{
if (_entries.Length > 1)
{
var index = Root;
while (!_entries[index].IsLeaf)
{
index = _entries[index].GetIndex(bitReader());
}
return(_entries[index].Symbol);
}
return(SymbolSpace.NotYetTransmitted);
}
/// <summary>
/// Retrieves a symbol. If the bit sequence from <paramref name="bitReader" />
/// identifies a symbol literal, <paramref name="symbolReader" /> is called.
/// </summary>
public TSymbolType GetSymbol(ReadBitDelegate bitReader, ReadSymbolDelegate <TSymbolType> symbolReader)
{
var result = GetSymbolInternal(bitReader);
if (result.IsValid)
{
UpdateSymbolInternal(result, 1);
UpdateSymbolInternal(SymbolSpace.NotYetTransmitted, GetTweak(result.Symbol, false));
return(result.Symbol);
}
result = symbolReader();
UpdateSymbolInternal(SymbolSpace.NotYetTransmitted, GetTweak(result.Symbol, true));
UpdateSymbolInternal(result, 1);
return(result.Symbol);
}
/// <summary>
/// Decodes a symbol using the <paramref name="coder"/> with the provided
/// <paramref name="model"/>.
/// </summary>
public static TSymbolType Decode <TSymbolType>(this ArithmeticCoder coder, IModel <TSymbolType> model,
ReadBitDelegate bitReader)
where TSymbolType : struct
{
// read value
uint value = coder.DecodeTarget(model.TotalFrequencies);
// determine symbol
RangeSymbol <TSymbolType> rangeSymbol = model.Decode(value);
// adapt decoder
coder.Decode(rangeSymbol.Range, bitReader);
// update model
model.Update(rangeSymbol.Symbol);
return(rangeSymbol.Symbol);
}
/// <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));
}
}
/// <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));
}
}
/// <summary>
/// Initializes the decoder by reading the first set of values for the state.
/// </summary>
/// <param name="bitReader"></param>
public void DecodeStart(ReadBitDelegate bitReader)
{
if (bitReader == null)
{
throw new ArgumentNullException("bitReader");
}
// Fill buffer with bits from the input stream
for (int i = 0; i < 31; i++) // just use the 31 least significant bits
{
_buffer = (_buffer << 1) | ((uint) (bitReader() ? 1 : 0));
}
}
