Fix order issue with ImmSet and ImmDict hashcodes.

xledger · Oct 8, 2024 · 88fff47 · 88fff47
1 parent 3c6b129
commit 88fff47
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Showing 4 changed files with 37 additions and 7 deletions.
diff --git a/Xledger.Collections.Test/TestImmDict.cs b/Xledger.Collections.Test/TestImmDict.cs
@@ -51,6 +51,17 @@ public void TestContains() {
         }
     }
 
+    [Fact]
+    public void TestHashCode() {
+        var items = Enumerable.Range(-100, 1_000).ToDictionary(i => i.ToString(), i => (i * i).ToString() + "A");
+        var imm = items.ToImmDict();
+        var ritems = Enumerable.Range(-100, 1_000).Reverse().ToDictionary(i => i.ToString(), i => (i * i).ToString() + "A");
+        var two = ritems.ToImmDict();
+
+        Assert.Equal(imm.GetHashCode(), two.GetHashCode());
+        Assert.True(imm == two);
+    }
+
     [Fact]
     public void TestNoOps() {
         var imm = ImmDict.Of((7, 6), (5, 4));

diff --git a/Xledger.Collections/ImmArray.cs b/Xledger.Collections/ImmArray.cs
@@ -67,7 +67,7 @@ public bool Equals(ImmArray<T> other) {
         if (this.data.Length != other.data.Length) {
             return false;
         }
-        if (this.hashComputed && other.hashComputed && GetHashCode() != other.GetHashCode()) {
+        if (this.hashComputed && other.hashComputed && this.hash != other.hash) {
             return false;
         }
 

diff --git a/Xledger.Collections/ImmDict.cs b/Xledger.Collections/ImmDict.cs
@@ -70,6 +70,9 @@ public bool Equals(ImmDict<K, V> other) {
         if (this.data.Count != other.data.Count) {
             return false;
         }
+        if (this.hashComputed && other.hashComputed && this.hash != other.hash) {
+            return false;
+        }
 
         foreach (var kvp in this.data) {
             if (!other.data.TryGetValue(kvp.Key, out var otherValue)
@@ -88,11 +91,18 @@ public bool Equals(ImmDict<K, V> other) {
     public override int GetHashCode() {
         if (!this.hashComputed) {
             var hashCode = -1487460045;
+            var hashes = new int[this.data.Count];
+            var i = 0;
             foreach (var kvp in this) {
-                var next = EqualityComparer<K>.Default.GetHashCode(kvp.Key);
-                hashCode = hashCode * -1521134295 + next;
-                next = EqualityComparer<V>.Default.GetHashCode(kvp.Value);
-                hashCode = hashCode * -1521134295 + next;
+                var next = 524287;
+                next = next * -1521134295 + EqualityComparer<K>.Default.GetHashCode(kvp.Key);
+                next = next * -1521134295 + EqualityComparer<V>.Default.GetHashCode(kvp.Value);
+                hashes[i] = next;
+                ++i;
+            }
+            Array.Sort(hashes);
+            for (i = 0; i < this.data.Count; ++i) {
+                hashCode = hashCode * -1521134295 + hashes[i];
             }
             this.hash = hashCode;
             this.hashComputed = true;

diff --git a/Xledger.Collections/ImmSet.cs b/Xledger.Collections/ImmSet.cs
@@ -84,6 +84,9 @@ public bool Equals(ImmSet<T> other) {
         if (this.data.Count != other.data.Count) {
             return false;
         }
+        if (this.hashComputed && other.hashComputed && this.hash != other.hash) {
+            return false;
+        }
 
         return this.data.SetEquals(other.data);
     }
@@ -100,9 +103,15 @@ public IEnumerator<T> GetEnumerator() {
     public override int GetHashCode() {
         if (!this.hashComputed) {
             var hashCode = 358481680;
+            var hashes = new int[this.data.Count];
+            var i = 0;
             foreach (var item in this) {
-                var next = EqualityComparer<T>.Default.GetHashCode(item);
-                hashCode = hashCode * -1521134295 + next;
+                hashes[i] = EqualityComparer<T>.Default.GetHashCode(item);
+                ++i;
+            }
+            Array.Sort(hashes);
+            for (i = 0; i < this.data.Count; ++i) {
+                hashCode = hashCode * -1521134295 + hashes[i];
             }
             this.hash = hashCode;
             this.hashComputed = true;