DivisorSet.BitContradiction mode added to --mersenne=bydivisor.

PerfectNumbers.Core/Persistence/BitContradictionStateRepository.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Globalization;
+using System.IO;
+using System.Text;
+using FASTER.core;
+
+namespace PerfectNumbers.Core.Persistence;
+
+/// <summary>
+/// Stores per-prime BitContradiction solver state (arbitrary string payload) using Microsoft.FASTER.Core.
+/// No LMDB migration is performed for this repository.
+/// </summary>
+public sealed class BitContradictionStateRepository : IDisposable
+{
+    private readonly FasterKV<string, string> _store;
+    private readonly IDevice _logDevice;
+    private readonly IDevice _objectLogDevice;
+    private static readonly Encoding Utf8 = Encoding.UTF8;
+
+    public string DatabasePath { get; }
+
+    public static BitContradictionStateRepository Open(string directory, string repositoryFileName = "bitcontradiction.solver.faster")
+    {
+        Directory.CreateDirectory(directory);
+        string dbPath = Path.Combine(directory, repositoryFileName);
+        return new BitContradictionStateRepository(dbPath);
+    }
+
+    private BitContradictionStateRepository(string path)
+    {
+        DatabasePath = path;
+        _logDevice = Devices.CreateLogDevice(path + ".log");
+        _objectLogDevice = Devices.CreateLogDevice(path + ".obj.log");
+        _store = new FasterKV<string, string>(
+            1L << 20,
+            new LogSettings
+            {
+                LogDevice = _logDevice,
+                ObjectLogDevice = _objectLogDevice,
+            });
+    }
+
+    public void Upsert(ulong prime, string state)
+    {
+        using var session = _store.For(new SimpleFunctions<string, string>()).NewSession<SimpleFunctions<string, string>>();
+        string keyString = prime.ToString(CultureInfo.InvariantCulture);
+        session.Upsert(keyString, state);
+        session.CompletePending(true);
+    }
+
+    public bool TryGet(ulong prime, out string? state)
+    {
+        using var session = _store.For(new SimpleFunctions<string, string>()).NewSession<SimpleFunctions<string, string>>();
+        string keyString = prime.ToString(CultureInfo.InvariantCulture);
+        if (session.Read(keyString, out string? stored).Found)
+        {
+            state = stored;
+            return true;
+        }
+
+        state = null;
+        return false;
+    }
+
+    public void Dispose()
+    {
+        _store.Dispose();
+        _logDevice.Dispose();
+        _objectLogDevice.Dispose();
+    }
+}