convert Value::*Value() function to return Maybe results

include/v8.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 959 matching lines @@
   void operator delete(void*, size_t);
 
   internal::Object** escape_slot_;
 };
 
 
 /**
  * A simple Maybe type, representing an object which may or may not have a
  * value.
  */
-template<class T>
-struct Maybe {
+template <class T>
+class Maybe {
+ public:
   Maybe() : has_value(false) {}
-  explicit Maybe(T t) : has_value(true), value(t) {}
-  Maybe(bool has, T t) : has_value(has), value(t) {}
+  explicit Maybe(const T& t) : has_value(true), value(t) {}
+  // TODO(dcarney): remove this constructor, it makes no sense.
+  Maybe(bool has, const T& t) : has_value(has), value(t) {}
 
+  V8_INLINE bool HasValue() const { return has_value; }
+
+  V8_WARN_UNUSED_RESULT V8_INLINE bool ToValue(T* out) const {
+    *out = has_value ? value : T();
+    return has_value;
+  }
+
+  V8_INLINE T ToValueChecked() const {
+    // TODO(dcarney): add DCHECK.
+    return value;
+  }
+
+  V8_INLINE T From(const T& default_value) const {
+    return has_value ? value : default_value;
+  }
+
+  // TODO(dcarney): make private.
   bool has_value;
   T value;
 };
 
 
 // Convenience wrapper.
 template <class T>
 inline Maybe<T> maybe(T t) {
   return Maybe<T>(t);
 }
@@ skipping 918 matching lines @@
   inline Local<Integer> ToInteger() const;
   inline Local<Uint32> ToUint32() const;
   inline Local<Int32> ToInt32() const;
 
   /**
    * Attempts to convert a string to an array index.
    * Returns an empty handle if the conversion fails.
    */
   Local<Uint32> ToArrayIndex() const;
 
+  Maybe<bool> BooleanValue(Local<Context> context) const;
+  Maybe<double> NumberValue(Local<Context> context) const;
+  Maybe<int64_t> IntegerValue(Local<Context> context) const;
+  Maybe<uint32_t> Uint32Value(Local<Context> context) const;
+  Maybe<int32_t> Int32Value(Local<Context> context) const;
+
+  // TODO(dcarney): deprecate all these.
   bool BooleanValue() const;
   double NumberValue() const;
   int64_t IntegerValue() const;
   uint32_t Uint32Value() const;
   int32_t Int32Value() const;
 
   /** JS == */
   bool Equals(Handle<Value> that) const;
   bool StrictEquals(Handle<Value> that) const;
   bool SameValue(Handle<Value> that) const;
@@ skipping 5671 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_