ref returns

dotnet · Sep 18, 2017 · f8129a1 · f8129a1
1 parent be119b6
commit f8129a1
Showing 1 changed file with 30 additions and 28 deletions.
diff --git a/src/mscorlib/src/System/Collections/Generic/Dictionary.cs b/src/mscorlib/src/System/Collections/Generic/Dictionary.cs
@@ -63,6 +63,8 @@ private struct Entry
             public TValue value;         // Value of entry
         }
 
+        private static Entry s_nullEntry;
+
         private int[] _buckets;
         private Entry[] _entries;
         private int _count;
@@ -196,8 +198,11 @@ public TValue this[TKey key]
         {
             get
             {
-                int i = FindEntry(key);
-                if (i >= 0) return _entries[i].value;
+                ref Entry entry = ref FindEntry(key, out bool found);
+                if (found)
+                {
+                    return entry.value;
+                }
                 ThrowHelper.ThrowKeyNotFoundException();
                 return default(TValue);
             }
@@ -221,18 +226,14 @@ void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> keyV
 
         bool ICollection<KeyValuePair<TKey, TValue>>.Contains(KeyValuePair<TKey, TValue> keyValuePair)
         {
-            int i = FindEntry(keyValuePair.Key);
-            if (i >= 0 && EqualityComparer<TValue>.Default.Equals(_entries[i].value, keyValuePair.Value))
-            {
-                return true;
-            }
-            return false;
+            ref Entry entry = ref FindEntry(keyValuePair.Key, out bool found);
+            return found && EqualityComparer<TValue>.Default.Equals(entry.value, keyValuePair.Value);
         }
 
         bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> keyValuePair)
         {
-            int i = FindEntry(keyValuePair.Key);
-            if (i >= 0 && EqualityComparer<TValue>.Default.Equals(_entries[i].value, keyValuePair.Value))
+            ref Entry entry = ref FindEntry(keyValuePair.Key, out bool found);
+            if (found && EqualityComparer<TValue>.Default.Equals(entry.value, keyValuePair.Value))
             {
                 Remove(keyValuePair.Key);
                 return true;
@@ -258,7 +259,11 @@ public void Clear()
             }
         }
 
-        public bool ContainsKey(TKey key) => FindEntry(key) >= 0;
+        public bool ContainsKey(TKey key)
+        {
+            FindEntry(key, out bool found);
+            return found;
+        }
 
         public bool ContainsValue(TValue value)
         {
@@ -331,30 +336,31 @@ public virtual void GetObjectData(SerializationInfo info, StreamingContext conte
             }
         }
 
-        private int FindEntry(TKey key)
+        private ref Entry FindEntry(TKey key, out bool found)
         {
             if (key == null)
             {
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
             }
 
-            int result = -1;
+            found = true;
             int[] buckets = _buckets;
             if (buckets != null)
             {
                 int hashCode = KeyHashCode(key);
                 Entry[] entries = _entries;
                 for (int i = buckets[hashCode % buckets.Length]; i >= 0; i = entries[i].next)
                 {
-                    if (entries[i].hashCode == hashCode && KeyEquals(entries[i].key, key))
+                    ref Entry entry = ref entries[i];
+                    if (entry.hashCode == hashCode && KeyEquals(entry.key, key))
                     {
-                        result = i;
-                        break;
+                        return ref entry;
                     }
                 }
             }
 
-            return result;
+            found = false;
+            return ref s_nullEntry;
         }
 
         private int[] Initialize(int capacity)
@@ -658,15 +664,11 @@ public bool Remove(TKey key, out TValue value)
 
         public bool TryGetValue(TKey key, out TValue value)
         {
-            int i = FindEntry(key);
-            if (i >= 0)
-            {
-                value = _entries[i].value;
-                return true;
-            }
-            value = default(TValue);
-            return false;
+            ref Entry entry = ref FindEntry(key, out bool found);
+            value = found ? entry.value : default(TValue);
+            return found;
         }
+
         public bool TryAdd(TKey key, TValue value) => TryInsert(key, value, InsertionBehavior.None);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -874,10 +876,10 @@ object IDictionary.this[object key]
             {
                 if (IsCompatibleKey(key))
                 {
-                    int i = FindEntry((TKey)key);
-                    if (i >= 0)
+                    ref Entry entry = ref FindEntry((TKey)key, out bool found);
+                    if (found)
                     {
-                        return _entries[i].value;
+                        return entry.value;
                     }
                 }
                 return null;