Add some helper Quantum methods

2026-09-22 23:05:04 +00:00 · 2023-09-22 21:59:15 -04:00
parent 8c5482a59a
commit 8f098a6669
1 changed files with 81 additions and 0 deletions
--- a/Quantum/Decoder.cs
+++ b/Quantum/Decoder.cs
@@ -0,0 +1,81 @@
+using System;
+using SabreTools.Models.Compression.Quantum;
+
+namespace SabreTools.Compression.Quantum
+{
+    /// <see href="www.russotto.net/quantumcomp.html"/> 
+    public class Quantum
+    {
+        // TODO: Figure out what these values are
+        private uint CS_H;
+        private uint CS_L;
+        private uint CS_C;
+
+        /// <summary>
+        /// Update the model after an encode or decode step
+        /// </summary>
+        private void UpdateModel(Model model, int lastUpdated)
+        {
+            // Update cumulative frequencies
+            for (int i = 0; i < lastUpdated; i++)
+            {
+                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 we haven't hit the reordering time
+            if (model.TimeToReorder > 0)
+            {
+                // Update the cumulative frequencies
+                for (int i = model.Entries - 1; i >= 0; i--)
+                {
+                    // Divide with truncation by 2
+                    var sym = model.Symbols[i];
+                    sym.CumulativeFrequency = (ushort)Math.Truncate((double)sym.CumulativeFrequency / 2);
+
+                    // 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 we hit the reordering time
+            else
+            {
+                // Calculate frequencies
+                ushort[] frequencies = new ushort[model.Entries];
+                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);
+                }
+
+                // 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
+
+                model.TimeToReorder = 50;
+            }
+        }
+
+        /// <summary>
+        /// Get the frequency of a symbol based on its total frequency
+        /// </summary>
+        private ushort GetFrequency(ushort totalFrequency)
+        {
+            ulong range = ((CS_H - CS_L) & 0xFFFF) + 1;
+            ulong frequency = ((CS_C - CS_L + 1) * totalFrequency - 1) / range;
+            return (ushort)(frequency & 0xFFFF);
+        }
+    }
+}