SabreTools/SabreTools.Compression
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Add one more partial method

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Matt Nadareski
2023-09-22 22:07:38 -04:00
parent 8f098a6669
commit a58da1d8db
1 changed files with 69 additions and 1 deletions
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70
Quantum/Decoder.cs → Quantum/Decompressor.cs
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@@ -4,13 +4,81 @@ using SabreTools.Models.Compression.Quantum;
namespace SabreTools.Compression.Quantum
{
/// <see href="www.russotto.net/quantumcomp.html"/>
public class Quantum
public class Decompressor
{
/// <summary>
/// Internal bitstream to use for decompression
/// </summary>
private BitStream _bitStream;
// TODO: Figure out what these values are
private uint CS_H;
private uint CS_L;
private uint CS_C;
/// <summary>
/// Get the next symbol from a model
/// </summary>
public int GetSymbol(Model model)
{
int i;
int sym;
int freq = GetFrequency(model.Symbols[0].CumulativeFrequency);
for (i = 1; i < model.Entries; i++)
{
if (model.Symbols[i].CumulativeFrequency <= freq)
break;
}
sym = model.Symbols[i - 1].Symbol;
GetCode(model.Symbols[i - 1].CumulativeFrequency,
model.Symbols[i].CumulativeFrequency,
model.Symbols[0].CumulativeFrequency);
UpdateModel(model, i);
return sym;
}
/// <summary>
/// Get the next code based on the frequencies
/// </summary>
private int GetCode(int prevFrequency, int currentFrequency, int totalFrequency)
{
int uf;
uint range = (CS_H - CS_L) + 1;
CS_H = CS_L + (uint)((prevFrequency * range) / totalFrequency) - 1;
CS_L = CS_L + (uint)((currentFrequency * range) / totalFrequency);
while (true)
{
if ((CS_L & 0x8000) != (CS_H & 0x8000))
{
if ((CS_L & 0x4000) != 0 && (CS_H & 0x4000) == 0)
{
// Underflow case
CS_C ^= 0x4000;
CS_L &= 0x3FFF;
CS_H |= 0x4000;
}
else
{
break;
}
}
CS_L <<= 1;
CS_H = (CS_H << 1) | 1;
CS_C = (CS_C << 1) | _bitStream.ReadBit() ?? 0;
}
// TODO: Incomplete implementation?
return 0;
}
/// <summary>
/// Update the model after an encode or decode step
/// </summary>