Avoid unnecessary dictionary lookups

fixes #8922

lib/base/dictionary.cpp

@@ -46,6 +46,27 @@ Value Dictionary::Get(const String& key) const
 	return it->second;
 }
 
+/**
+ * Retrieves a value from a dictionary.
+ *
+ * @param key The key whose value should be retrieved.
+ * @param result The value of the dictionary item (only set when the key exists)
+ * @returns true if the key exists, false otherwise.
+ */
+bool Dictionary::Get(const String& key, Value *result) const
+{
+	ASSERT(!OwnsLock());
+	ObjectLock olock(this);
+
+	std::map<String, Value>::const_iterator it = m_Data.find(key);
+
+	if (it == m_Data.end())
+		return false;
+
+	*result = it->second;
+	return true;
+}
+
 /**
  * Sets a value in the dictionary.
  *

lib/base/dictionary.hpp

@@ -56,6 +56,7 @@ public:
 	{ }
 
 	Value Get(const String& key) const;
+	bool Get(const String& key, Value *result) const;
 	void Set(const String& key, const Value& value);
 	bool Contains(const String& key) const;
 

lib/config/expression.cpp

@@ -92,8 +92,10 @@ const DebugInfo& DebuggableExpression::GetDebugInfo(void) const
 
 ExpressionResult VariableExpression::DoEvaluate(ScriptFrame& frame, DebugHint *dhint) const
 {
-	if (frame.Locals && frame.Locals->Contains(m_Variable))
-		return frame.Locals->Get(m_Variable);
+	Value value;
+
+	if (frame.Locals && frame.Locals->Get(m_Variable, &value))
+		return value;
 	else if (frame.Self.IsObject() && frame.Locals != static_cast<Object::Ptr>(frame.Self) && VMOps::HasField(frame.Self, m_Variable))
 		return VMOps::GetField(frame.Self, m_Variable, m_DebugInfo);
 	else

lib/config/vmops.hpp

@@ -46,8 +46,9 @@ class VMOps
 public:
 	static inline Value Variable(ScriptFrame& frame, const String& name, const DebugInfo& debugInfo = DebugInfo())
 	{
-		if (frame.Locals && frame.Locals->Contains(name))
-			return frame.Locals->Get(name);
+		Value value;
+		if (frame.Locals && frame.Locals->Get(name, &value))
+			return value;
 		else if (frame.Self.IsObject() && frame.Locals != static_cast<Object::Ptr>(frame.Self) && HasField(frame.Self, name))
 			return GetField(frame.Self, name, debugInfo);
 		else
@@ -244,8 +245,9 @@ public:
 		Dictionary::Ptr dict = dynamic_pointer_cast<Dictionary>(object);
 
 		if (dict) {
-			if (dict->Contains(field))
-				return dict->Get(field);
+			Value value;
+			if (dict->Get(field, &value))
+				return value;
 			else
 				return GetPrototypeField(context, field, false, debugInfo);
 		}