Add Dart_Null, Dart_True, and Dart_False.

runtime/vm/dart_api_state.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_DART_API_STATE_H_
 #define VM_DART_API_STATE_H_
 
 #include "include/dart_api.h"
 
 #include "vm/dart_api_impl.h"
@@ skipping 54 matching lines @@
  private:
   LocalHandle() { }
   ~LocalHandle() { }
 
   RawObject* raw_;
   DISALLOW_ALLOCATION();  // Allocated through AllocateHandle methods.
   DISALLOW_COPY_AND_ASSIGN(LocalHandle);
 };
 
 
+// A distinguished callback which indicates that a persistent handle
+// should not be deleted from the dart api.
+void ProtectedHandleCallback();
+
+
 // Implementation of persistent handles which are handed out through the
 // dart API.
 class PersistentHandle {
  public:
   enum {
     StrongReference = 0,
     WeakReference,
   };
 
   // Accessors.
   RawObject* raw() const { return raw_; }
   void set_raw(const LocalHandle& ref) { raw_ = ref.raw(); }
   void set_raw(const Object& object) { raw_ = object.raw(); }
   static intptr_t raw_offset() { return OFFSET_OF(PersistentHandle, raw_); }
   void* callback() const { return callback_; }
   void set_callback(void* value) { callback_ = value; }
   intptr_t type() const { return type_; }
   void set_type(intptr_t value) { type_ = value; }
 
+  // Some handles are protected from being freed via the external dart api.
+  bool IsProtected() {
+    return callback() == &ProtectedHandleCallback;
+  }
+
  private:
   friend class PersistentHandles;
 
   PersistentHandle() { }
   ~PersistentHandle() { }
 
   // Overload the callback_ field as a next pointer when adding freed
   // handles to the free list.
   PersistentHandle* Next() {
     return reinterpret_cast<PersistentHandle*>(callback_);
@@ skipping 146 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(ApiLocalScope);
 };
 
 
 // Implementation of the API State used in dart api for maintaining
 // local scopes, persistent handles etc. These are setup on a per isolate
 // basis and destroyed when the isolate is shutdown.
 class ApiState {
  public:
-  ApiState() : top_scope_(NULL), true_(NULL) { }
+  ApiState() : top_scope_(NULL), null_(NULL), true_(NULL), false_(NULL) { }
   ~ApiState() {
     while (top_scope_ != NULL) {
       ApiLocalScope* scope = top_scope_;
       top_scope_ = top_scope_->previous();
       delete scope;
     }
+    if (null_ != NULL) {
+      persistent_handles().FreeHandle(null_);
+      null_ = NULL;
+    }
     if (true_ != NULL) {
       persistent_handles().FreeHandle(true_);
       true_ = NULL;
     }
+    if (false_ != NULL) {
+      persistent_handles().FreeHandle(false_);
+      false_ = NULL;
+    }
   }
 
   // Accessors.
   ApiLocalScope* top_scope() const { return top_scope_; }
   void set_top_scope(ApiLocalScope* value) { top_scope_ = value; }
   PersistentHandles& persistent_handles() { return persistent_handles_; }
 
   void UnwindScopes(uword sp) {
     while (top_scope_ != NULL && top_scope_->stack_marker() < sp) {
       ApiLocalScope* scope = top_scope_;
@@ skipping 39 matching lines @@
   }
   int ZoneSizeInBytes() const {
     int total = 0;
     ApiLocalScope* scope = top_scope_;
     while (scope != NULL) {
       total += scope->zone().SizeInBytes();
       scope = scope->previous();
     }
     return total;
   }
+  PersistentHandle* Null() {
+    if (null_ == NULL) {
+      Zone zone;  // Setup a VM zone as we are creating some handles.
+      HandleScope scope;  // Setup a VM handle scope.
+
+      Object& null_object = Object::Handle();
+      null_ = persistent_handles().AllocateHandle();
+      null_->set_raw(null_object);
+      null_->set_callback(reinterpret_cast<void*>(&ProtectedHandleCallback));
+    }
+    return null_;
+  }
   PersistentHandle* True() {
     if (true_ == NULL) {
       Zone zone;  // Setup a VM zone as we are creating some handles.
       HandleScope scope;  // Setup a VM handle scope.
 
       const Object& true_object = Object::Handle(Bool::True());
       true_ = persistent_handles().AllocateHandle();
       true_->set_raw(true_object);
+      true_->set_callback(reinterpret_cast<void*>(&ProtectedHandleCallback));
     }
     return true_;
   }
+  PersistentHandle* False() {
+    if (false_ == NULL) {
+      Zone zone;  // Setup a VM zone as we are creating some handles.
+      HandleScope scope;  // Setup a VM handle scope.
+
+      const Object& false_object = Object::Handle(Bool::False());
+      false_ = persistent_handles().AllocateHandle();
+      false_->set_raw(false_object);
+      false_->set_callback(reinterpret_cast<void*>(&ProtectedHandleCallback));
+    }
+    return false_;
+  }
 
  private:
   PersistentHandles persistent_handles_;
   ApiLocalScope* top_scope_;
 
-  // A persistent handle to the "True" object.
+  // Persistent handles to important objects.
+  PersistentHandle* null_;
   PersistentHandle* true_;
+  PersistentHandle* false_;
 
   DISALLOW_COPY_AND_ASSIGN(ApiState);
 };
 
 }  // namespace dart
 
 #endif  // VM_DART_API_STATE_H_