From 930fdd38a62ff1d73fe1c59eaa181b2d4d6d261c Mon Sep 17 00:00:00 2001
From: hadashiA <dev@hadashikick.jp>
Date: Mon, 18 Sep 2023 18:13:38 +0900
Subject: [PATCH] Add ankerl::unordered_dense inspied hashtable

---
 .../Runtime/Internal/TypeKeyHashTable2.cs     | 149 ++++++++++++++++++
 .../Internal/TypeKeyHashTable2.cs.meta        |   3 +
 .../Assets/VContainer/Runtime/Registry.cs     |   6 +-
 3 files changed, 155 insertions(+), 3 deletions(-)
 create mode 100644 VContainer/Assets/VContainer/Runtime/Internal/TypeKeyHashTable2.cs
 create mode 100644 VContainer/Assets/VContainer/Runtime/Internal/TypeKeyHashTable2.cs.meta

diff --git a/VContainer/Assets/VContainer/Runtime/Internal/TypeKeyHashTable2.cs b/VContainer/Assets/VContainer/Runtime/Internal/TypeKeyHashTable2.cs
new file mode 100644
index 00000000..571c7682
--- /dev/null
+++ b/VContainer/Assets/VContainer/Runtime/Internal/TypeKeyHashTable2.cs
@@ -0,0 +1,149 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+
+namespace VContainer.Internal
+{
+    sealed class TypeKeyHashTable2<TValue>
+    {
+        struct Bucket
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public static uint DistAndFingerPrintFromHash(int hash)
+            {
+                return DistOne | ((uint)hash & FingerPrintMask);
+            }
+
+            public const uint DistOne = 0x00000100;
+            public const uint FingerPrintMask = 0x000000FF;
+
+            /// <summary>
+            /// upper 3 bytes: dist (distance of , also known PSL (probe sequence length))
+            /// lower 1 bytes: fingerprint (lower 1 byte of hash code)
+            /// </summary>
+            public uint DistAndFingerPrint;
+
+            /// <summary>
+            /// The index that point to the location where value is actually stored.
+            /// </summary>
+            public int EntryIndex;
+        }
+
+        readonly Bucket[] buckets;
+        readonly KeyValuePair<Type, TValue>[] entries;
+        readonly int indexFor;
+
+        int insertedEntryLength;
+
+        public TypeKeyHashTable2(KeyValuePair<Type, TValue>[] values, float loadFactor = 0.75f)
+        {
+            var initialCapacity = (int)(values.Length / loadFactor);
+
+            // make power of 2(and use mask)
+            // see: Hashing https://en.wikipedia.org/wiki/Hash_table
+            var capacity = 1;
+            while (capacity < initialCapacity)
+            {
+                capacity <<= 1;
+            }
+
+            buckets = new Bucket[capacity];
+            entries = new KeyValuePair<Type, TValue>[values.Length];
+            indexFor = buckets.Length - 1;
+
+            var entryIndex = 0;
+            foreach (var x in values)
+            {
+                Insert(x, entryIndex++);
+            }
+        }
+
+        public bool TryGet(Type key, out TValue value)
+        {
+            var hash = RuntimeHelpers.GetHashCode(key);
+            var distAndFingerPrint = Bucket.DistAndFingerPrintFromHash(hash);
+            var bucketIndex = hash & indexFor;
+            ref var bucket = ref buckets[bucketIndex];
+
+            while (true)
+            {
+                if (distAndFingerPrint == bucket.DistAndFingerPrint)
+                {
+                    // compare key
+                    ref var entry = ref entries[bucket.EntryIndex];
+                    if (key == entry.Key)
+                    {
+                        value = entry.Value;
+                        return true;
+                    }
+                }
+                else if (distAndFingerPrint > bucket.DistAndFingerPrint)
+                {
+                    // not found
+                    value = default;
+                    return false;
+                }
+                distAndFingerPrint += Bucket.DistOne;
+                NextBucketIndex(ref bucketIndex);
+                bucket = ref buckets[bucketIndex];
+            }
+
+        }
+
+        void Insert(KeyValuePair<Type, TValue> entry, int entryIndex)
+        {
+            var hash = RuntimeHelpers.GetHashCode(entry.Key);
+            var distAndFingerPrint = Bucket.DistAndFingerPrintFromHash(hash);
+            var bucketIndex = hash & indexFor;
+
+            // robin food hashing
+            while (distAndFingerPrint <= buckets[bucketIndex].DistAndFingerPrint)
+            {
+                // key already exists
+                if (distAndFingerPrint == buckets[bucketIndex].DistAndFingerPrint &&
+                    entry.Key == entries[buckets[bucketIndex].EntryIndex].Key)
+                {
+                    throw new InvalidOperationException($"The key already exists: {entry.Key}");
+                }
+
+                //
+                NextBucketIndex(ref bucketIndex);
+                distAndFingerPrint += Bucket.DistOne; //
+            }
+
+            entries[entryIndex] = entry;
+            SetBucketAt(bucketIndex, new Bucket
+            {
+                DistAndFingerPrint = distAndFingerPrint,
+                EntryIndex = entryIndex
+            });
+        }
+
+        /// <summary>
+        ///
+        /// </summary>
+        /// <param name="bucket"></param>
+        /// <param name="i"></param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        void SetBucketAt(int i, Bucket bucket)
+        {
+            while (buckets[i].DistAndFingerPrint != 0)
+            {
+                // swap
+                (buckets[i], bucket) = (bucket, buckets[i]);
+                bucket.DistAndFingerPrint += Bucket.DistOne;
+                NextBucketIndex(ref i);
+            }
+            buckets[i] = bucket;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        void NextBucketIndex(ref int i)
+        {
+            if (++i >= buckets.Length)
+            {
+                i = 0;
+            }
+        }
+    }
+}
diff --git a/VContainer/Assets/VContainer/Runtime/Internal/TypeKeyHashTable2.cs.meta b/VContainer/Assets/VContainer/Runtime/Internal/TypeKeyHashTable2.cs.meta
new file mode 100644
index 00000000..8794f0d0
--- /dev/null
+++ b/VContainer/Assets/VContainer/Runtime/Internal/TypeKeyHashTable2.cs.meta
@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: 9c311a30613d4728b2b891e770db92f7
+timeCreated: 1695016383
\ No newline at end of file
diff --git a/VContainer/Assets/VContainer/Runtime/Registry.cs b/VContainer/Assets/VContainer/Runtime/Registry.cs
index 4e42e418..9f8b7bc1 100644
--- a/VContainer/Assets/VContainer/Runtime/Registry.cs
+++ b/VContainer/Assets/VContainer/Runtime/Registry.cs
@@ -9,7 +9,7 @@ public sealed class Registry
         [ThreadStatic]
         static IDictionary<Type, Registration> buildBuffer = new Dictionary<Type, Registration>(128);
 
-        readonly FixedTypeKeyHashtable<Registration> hashTable;
+        readonly TypeKeyHashTable2<Registration> hashTable;
 
         public static Registry Build(Registration[] registrations)
         {
@@ -40,7 +40,7 @@ public static Registry Build(Registration[] registrations)
                 }
             }
 
-            var hashTable = new FixedTypeKeyHashtable<Registration>(buildBuffer.ToArray());
+            var hashTable = new TypeKeyHashTable2<Registration>(buildBuffer.ToArray());
             return new Registry(hashTable);
         }
 
@@ -95,7 +95,7 @@ static void AddCollectionToBuildBuffer(IDictionary<Type, Registration> buf, Regi
             }
         }
 
-        Registry(FixedTypeKeyHashtable<Registration> hashTable)
+        Registry(TypeKeyHashTable2<Registration> hashTable)
         {
             this.hashTable = hashTable;
         }