SabreTools/SabreTools.Compression
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Finish update implementation

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This commit is contained in:
Matt Nadareski
2023-09-22 22:58:43 -04:00
parent a58da1d8db
commit 4684a6612c
1 changed files with 36 additions and 28 deletions
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64
Quantum/Decompressor.cs
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@@ -21,17 +21,16 @@ namespace SabreTools.Compression.Quantum
/// </summary>
public int GetSymbol(Model model)
{
int i;
int sym;
int freq = GetFrequency(model.Symbols[0].CumulativeFrequency);
int i;
for (i = 1; i < model.Entries; i++)
{
if (model.Symbols[i].CumulativeFrequency <= freq)
break;
}
sym = model.Symbols[i - 1].Symbol;
int sym = model.Symbols[i - 1].Symbol;
GetCode(model.Symbols[i - 1].CumulativeFrequency,
model.Symbols[i].CumulativeFrequency,
@@ -45,10 +44,8 @@ namespace SabreTools.Compression.Quantum
/// <summary>
/// Get the next code based on the frequencies
/// </summary>
private int GetCode(int prevFrequency, int currentFrequency, int totalFrequency)
private void 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);
@@ -74,9 +71,6 @@ namespace SabreTools.Compression.Quantum
CS_H = (CS_H << 1) | 1;
CS_C = (CS_C << 1) | _bitStream.ReadBit() ?? 0;
}
// TODO: Incomplete implementation?
return 0;
}
/// <summary>
@@ -89,12 +83,11 @@ namespace SabreTools.Compression.Quantum
{
var sym = model.Symbols[i];
sym.CumulativeFrequency += 8;
// model.TotalFrequency += 8; // TODO: Added in new model
}
// Decrement reordering time, if needed
// if (model.TotalFrequency > 3800) // TODO: Added in new model
// model.TimeToReorder--;
if (model.Symbols[0].CumulativeFrequency > 3800)
model.TimeToReorder--;
// If we haven't hit the reordering time
if (model.TimeToReorder > 0)
@@ -104,34 +97,49 @@ namespace SabreTools.Compression.Quantum
{
// Divide with truncation by 2
var sym = model.Symbols[i];
sym.CumulativeFrequency = (ushort)Math.Truncate((double)sym.CumulativeFrequency / 2);
sym.CumulativeFrequency >>= 1;
// If we are lower the next frequency
if (i != 0 && sym.CumulativeFrequency <= model.Symbols[i - 1].CumulativeFrequency)
{
sym.CumulativeFrequency = (ushort)(model.Symbols[i - 1].CumulativeFrequency + 1);
}
if (i != 0 && sym.CumulativeFrequency <= model.Symbols[i + 1].CumulativeFrequency)
sym.CumulativeFrequency = (ushort)(model.Symbols[i + 1].CumulativeFrequency + 1);
}
}
// If we hit the reordering time
else
{
// Calculate frequencies
ushort[] frequencies = new ushort[model.Entries];
// Calculate frequencies from cumulative frequencies
for (int i = 0; i < model.Entries; i++)
{
var sym = model.Symbols[i];
frequencies[i] = GetFrequency(sym.CumulativeFrequency);
frequencies[i] = (ushort)Math.Round((double)frequencies[i] / 2);
if (i != model.Entries - 1)
model.Symbols[i].CumulativeFrequency -= model.Symbols[i + 1].CumulativeFrequency;
model.Symbols[i].CumulativeFrequency++;
model.Symbols[i].CumulativeFrequency >>= 1;
}
// TODO: Finish implementation based on this statement from the docs:
// The table is then sorted by frequency (highest first) using
// an in-place selection sort (not stable!) and the cumulative
// frequencies recomputed.
// TODO: Determine if selection sort is needed
// Sort frequencies in decreasing order
for (int i = 0; i < model.Entries; i++)
{
for (int j = i + 1; j < model.Entries; j++)
{
if (model.Symbols[i].CumulativeFrequency < model.Symbols[j].CumulativeFrequency)
{
var temp = model.Symbols[i];
model.Symbols[i] = model.Symbols[j];
model.Symbols[j] = temp;
}
}
}
// Calculate cumulative frequencies from frequencies
for (int i = model.Entries - 1; i >= 0; i--)
{
if (i != model.Entries - 1)
model.Symbols[i].CumulativeFrequency += model.Symbols[i + 1].CumulativeFrequency;
}
// Reset the time to reorder
model.TimeToReorder = 50;
}
}