Upload FastSeekWpf/Core/IndexStore.cs

FastSeekWpf/Core/IndexStore.cs

@@ -1,12 +1,7 @@
 using System;
-using System.Buffers;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
-using System.Runtime.InteropServices;
 using System.Text;
-using System.Text.Json;
-using System.Text.Json.Serialization;
 
 namespace FastSeekWpf.Core;
 
@@ -41,26 +36,33 @@ public struct IndexEntry
     public readonly FileKind Kind => IsDir ? FileKind.Directory : FileKind.File;
 }
 
+/// <summary>
+/// High-performance index store matching the Rust design:
+/// - Arena-backed name storage (List&lt;byte&gt; for O(1) append)
+/// - Parallel cached lowercase strings for zero-allocation search
+/// - Sorted ref_lookup for O(log n) parent lookups
+/// </summary>
 public class IndexStore
 {
     public List<IndexEntry> Entries = new();
-    public byte[] NameArena = Array.Empty<byte>();
-    public byte[] NameLowerArena = Array.Empty<byte>();
-    public List<(ulong fileRef, uint idx)> RefLookup = new();
+    // Arena stores UTF-8 bytes
+    public List<byte> NameArena = new();
+    public List<byte> NameLowerArena = new();
+    // Parallel string cache for hot-path search (no UTF8 decoding during search)
+    public List<string> NameCache = new();
+    public List<string> NameLowerCache = new();
+    // Sorted by file_ref for binary search
+    public List<(ulong fileRef, int idx)> RefLookup = new();
     public string DriveRoot = string.Empty;
     public List<JournalCheckpoint> Checkpoints = new();
 
     public int Count => Entries.Count;
 
-    public string Name(IndexEntry e)
-    {
-        return Encoding.UTF8.GetString(NameArena, (int)e.NameOff, e.NameLen);
-    }
+    // ---- Hot path: cached name access (zero-allocation) ----
 
-    public string NameLower(IndexEntry e)
-    {
-        return Encoding.UTF8.GetString(NameLowerArena, (int)e.NameLowerOff, e.NameLowerLen);
-    }
+    public string Name(IndexEntry e) => NameCache[Entries.IndexOf(e)];
+    public string NameAt(int i) => NameCache[i];
+    public string NameLowerAt(int i) => NameLowerCache[i];
 
     public uint? LookupIdx(ulong fileRef)
     {
@@ -68,8 +70,8 @@ public class IndexStore
         while (lo <= hi)
         {
             int mid = (lo + hi) >>> 1;
-            var (r, _) = RefLookup[mid];
-            if (r == fileRef) return RefLookup[mid].idx;
+            var r = RefLookup[mid].fileRef;
+            if (r == fileRef) return (uint)RefLookup[mid].idx;
             if (r < fileRef) lo = mid + 1;
             else hi = mid - 1;
         }
@@ -80,8 +82,8 @@ public class IndexStore
     {
         RefLookup.Clear();
         RefLookup.Capacity = Entries.Count;
-        for (uint i = 0; i < Entries.Count; i++)
-            RefLookup.Add((Entries[(int)i].FileRef, i));
+        for (int i = 0; i < Entries.Count; i++)
+            RefLookup.Add((Entries[i].FileRef, i));
         RefLookup.Sort((a, b) => a.fileRef.CompareTo(b.fileRef));
     }
 
@@ -89,9 +91,16 @@ public class IndexStore
     {
         DriveRoot = driveRoot;
         int count = scan.Records.Count;
+        Entries.Clear();
         Entries.Capacity = count;
-        var nameArenaList = new List<byte>(count * 30);
-        var nameLowerList = new List<byte>(count * 30);
+        NameArena.Clear();
+        NameArena.Capacity = count * 30;
+        NameLowerArena.Clear();
+        NameLowerArena.Capacity = count * 30;
+        NameCache.Clear();
+        NameCache.Capacity = count;
+        NameLowerCache.Clear();
+        NameLowerCache.Capacity = count;
 
         foreach (var r in scan.Records)
         {
@@ -102,13 +111,13 @@ public class IndexStore
             byte[] nameBytes = Encoding.UTF8.GetBytes(name);
             byte[] lowerBytes = Encoding.UTF8.GetBytes(nameLower);
 
-            uint nOff = (uint)nameArenaList.Count;
+            uint nOff = (uint)NameArena.Count;
             ushort nLen = (ushort)nameBytes.Length;
-            nameArenaList.AddRange(nameBytes);
+            NameArena.AddRange(nameBytes);
 
-            uint nlOff = (uint)nameLowerList.Count;
+            uint nlOff = (uint)NameLowerArena.Count;
             ushort nlLen = (ushort)lowerBytes.Length;
-            nameLowerList.AddRange(lowerBytes);
+            NameLowerArena.AddRange(lowerBytes);
 
             Entries.Add(new IndexEntry
             {
@@ -120,20 +129,32 @@ public class IndexStore
                 NameLowerLen = nlLen,
                 Flags = r.IsDir ? (byte)1 : (byte)0
             });
-        }
 
-        NameArena = nameArenaList.ToArray();
-        NameLowerArena = nameLowerList.ToArray();
+            NameCache.Add(name);
+            NameLowerCache.Add(nameLower);
+        }
     }
 
     public void Finalize()
     {
-        Entries.Sort((a, b) =>
+        // Sort by lowercase name for search
+        var indices = Enumerable.Range(0, Entries.Count).ToArray();
+        Array.Sort(indices, (a, b) => string.CompareOrdinal(NameLowerCache[a], NameLowerCache[b]));
+
+        var sortedEntries = new List<IndexEntry>(Entries.Count);
+        var sortedNames = new List<string>(Entries.Count);
+        var sortedLower = new List<string>(Entries.Count);
+
+        foreach (var i in indices)
         {
-            var sa = NameLower(a);
-            var sb = NameLower(b);
-            return string.CompareOrdinal(sa, sb);
-        });
+            sortedEntries.Add(Entries[i]);
+            sortedNames.Add(NameCache[i]);
+            sortedLower.Add(NameLowerCache[i]);
+        }
+
+        Entries = sortedEntries;
+        NameCache = sortedNames;
+        NameLowerCache = sortedLower;
         RebuildRefLookup();
     }
 
@@ -141,11 +162,11 @@ public class IndexStore
     {
         return new CacheData
         {
-            Entries = Entries.Select(e => new CachedEntry
+            Entries = Entries.Select((e, i) => new CachedEntry
             {
                 FileRef = e.FileRef,
                 ParentRef = e.ParentRef,
-                Name = Name(e),
+                Name = NameAt(i),
                 Kind = e.Kind
             }).ToList(),
             DriveRoot = DriveRoot,
@@ -162,9 +183,8 @@ public class IndexStore
             Checkpoints = new List<JournalCheckpoint>(cache.Checkpoints)
         };
         store.Entries.Capacity = count;
-
-        var nameArenaList = new List<byte>(count * 30);
-        var nameLowerList = new List<byte>(count * 30);
+        store.NameCache.Capacity = count;
+        store.NameLowerCache.Capacity = count;
 
         foreach (var c in cache.Entries)
         {
@@ -173,13 +193,13 @@ public class IndexStore
             byte[] nameBytes = Encoding.UTF8.GetBytes(c.Name);
             byte[] lowerBytes = Encoding.UTF8.GetBytes(nameLower);
 
-            uint nOff = (uint)nameArenaList.Count;
+            uint nOff = (uint)store.NameArena.Count;
             ushort nLen = (ushort)nameBytes.Length;
-            nameArenaList.AddRange(nameBytes);
+            store.NameArena.AddRange(nameBytes);
 
-            uint nlOff = (uint)nameLowerList.Count;
+            uint nlOff = (uint)store.NameLowerArena.Count;
             ushort nlLen = (ushort)lowerBytes.Length;
-            nameLowerList.AddRange(lowerBytes);
+            store.NameLowerArena.AddRange(lowerBytes);
 
             store.Entries.Add(new IndexEntry
             {
@@ -191,10 +211,11 @@ public class IndexStore
                 NameLowerLen = nlLen,
                 Flags = c.Kind == FileKind.Directory ? (byte)1 : (byte)0
             });
+
+            store.NameCache.Add(c.Name);
+            store.NameLowerCache.Add(nameLower);
         }
 
-        store.NameArena = nameArenaList.ToArray();
-        store.NameLowerArena = nameLowerList.ToArray();
         store.RebuildRefLookup();
         return store;
     }
@@ -206,18 +227,13 @@ public class IndexStore
         var nameBytes = Encoding.UTF8.GetBytes(record.Name);
         var lowerBytes = Encoding.UTF8.GetBytes(nameLower);
 
-        var nameArenaList = new List<byte>(NameArena.Length + nameBytes.Length + 64);
-        nameArenaList.AddRange(NameArena);
-        var nameLowerList = new List<byte>(NameLowerArena.Length + lowerBytes.Length + 64);
-        nameLowerList.AddRange(NameLowerArena);
-
-        uint nOff = (uint)nameArenaList.Count;
+        uint nOff = (uint)NameArena.Count;
         ushort nLen = (ushort)nameBytes.Length;
-        nameArenaList.AddRange(nameBytes);
+        NameArena.AddRange(nameBytes);
 
-        uint nlOff = (uint)nameLowerList.Count;
+        uint nlOff = (uint)NameLowerArena.Count;
         ushort nlLen = (ushort)lowerBytes.Length;
-        nameLowerList.AddRange(lowerBytes);
+        NameLowerArena.AddRange(lowerBytes);
 
         var entry = new IndexEntry
         {
@@ -230,22 +246,37 @@ public class IndexStore
             Flags = record.Kind == FileKind.Directory ? (byte)1 : (byte)0
         };
 
+        // Insert in sorted position by lowercase name
         int pos = 0;
         for (; pos < Entries.Count; pos++)
         {
-            if (string.CompareOrdinal(nameLower, NameLower(Entries[pos])) < 0)
+            if (string.CompareOrdinal(nameLower, NameLowerAt(pos)) < 0)
                 break;
         }
         Entries.Insert(pos, entry);
+        NameCache.Insert(pos, record.Name);
+        NameLowerCache.Insert(pos, nameLower);
 
-        NameArena = nameArenaList.ToArray();
-        NameLowerArena = nameLowerList.ToArray();
+        // Rebuild lookup (rare operation, acceptable)
         RebuildRefLookup();
     }
 
     public void Remove(ulong fileRef)
     {
-        Entries.RemoveAll(e => e.FileRef == fileRef);
+        int idx = -1;
+        for (int i = 0; i < Entries.Count; i++)
+        {
+            if (Entries[i].FileRef == fileRef)
+            {
+                idx = i;
+                break;
+            }
+        }
+        if (idx < 0) return;
+
+        Entries.RemoveAt(idx);
+        NameCache.RemoveAt(idx);
+        NameLowerCache.RemoveAt(idx);
         RebuildRefLookup();
     }
 
@@ -269,7 +300,9 @@ public class IndexStore
 
     public string BuildPath(ulong fileRef)
     {
-        var components = new List<string>(16);
+        // Stackalloc-friendly: use array instead of List
+        Span<string> components = stackalloc string[64];
+        int compCount = 0;
         ulong current = fileRef;
 
         for (int i = 0; i < 64; i++)
@@ -278,20 +311,19 @@ public class IndexStore
             if (idx == null) break;
 
             var entry = Entries[(int)idx];
-            components.Add(Name(entry));
+            components[compCount++] = NameAt((int)idx);
             if (entry.ParentRef == current) break;
             current = entry.ParentRef;
         }
 
-        components.Reverse();
-        var path = new StringBuilder(DriveRoot.Length + components.Sum(c => c.Length + 1));
-        path.Append(DriveRoot);
-        foreach (var comp in components)
+        var sb = new StringBuilder(DriveRoot.Length + compCount * 32);
+        sb.Append(DriveRoot);
+        for (int i = compCount - 1; i >= 0; i--)
         {
-            if (path.Length > 0 && path[path.Length - 1] != '\\' && path[path.Length - 1] != '/')
-                path.Append('\\');
-            path.Append(comp);
+            if (sb.Length > 0 && sb[sb.Length - 1] != '\\' && sb[sb.Length - 1] != '/')
+                sb.Append('\\');
+            sb.Append(components[i]);
         }
-        return path.ToString();
+        return sb.ToString();
     }
 }