- Add functionality to morph a string into an external string

vm/object.h

 // Copyright (c) 2012, 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_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 282 matching lines @@
     return unhandled_exception_class_;
   }
   static RawClass* unwind_error_class() { return unwind_error_class_; }
   static RawClass* icdata_class() { return icdata_class_; }
   static RawClass* subtypetestcache_class() { return subtypetestcache_class_; }
 
   static RawError* Init(Isolate* isolate);
   static void InitFromSnapshot(Isolate* isolate);
   static void InitOnce();
   static void RegisterSingletonClassNames();
+  static void MakeUnusedSpaceTraversable(const Object& obj,
+                                         intptr_t original_size,
+                                         intptr_t used_size);
 
   static intptr_t InstanceSize() {
     return RoundedAllocationSize(sizeof(RawObject));
   }
 
   static const ClassId kClassId = kObjectCid;
 
   // Different kinds of type tests.
   enum TypeTestKind {
     kIsSubtypeOf = 0,
@@ skipping 3445 matching lines @@
   }
 
   bool IsExternal() const {
     return RawObject::IsExternalStringClassId(raw()->GetClassId());
   }
 
   void* GetPeer() const;
 
   void ToUTF8(uint8_t* utf8_array, intptr_t array_len) const;
 
+  // Copies the string characters into the provided external array
+  // and morphs the string object into an external string object.
+  // The remaining unused part of the original string object is marked as
+  // an Array object or a regular Object so that it can be traversed during
+  // garbage collection.
+  RawString* MakeExternal(void* array,
+                          intptr_t length,
+                          void* peer,
+                          Dart_PeerFinalizer cback) const;
+
+
   // Creates a new String object from a C string that is assumed to contain
   // UTF-8 encoded characters and '\0' is considered a termination character.
   static RawString* New(const char* cstr, Heap::Space space = Heap::kNew);
 
   // Creates a new String object from an array of UTF-8 encoded characters.
   static RawString* New(const uint8_t* utf8_array,
                         intptr_t array_len,
                         Heap::Space space = Heap::kNew);
 
   // Creates a new String object from an array of UTF-16 encoded characters.
@@ skipping 525 matching lines @@
   }
 
   void SetLength(intptr_t value) const {
     // This is only safe because we create a new Smi, which does not cause
     // heap allocation.
     raw_ptr()->length_ = Smi::New(value);
   }
 
   HEAP_OBJECT_IMPLEMENTATION(Array, Instance);
   friend class Class;
+  friend class String;
 };
 
 
 class ImmutableArray : public Array {
  public:
   static RawImmutableArray* New(intptr_t len, Heap::Space space = Heap::kNew);
 
  private:
   HEAP_OBJECT_IMPLEMENTATION(ImmutableArray, Array);
   friend class Class;
@@ skipping 1584 matching lines @@
     if (this->CharAt(i) != str.CharAt(begin_index + i)) {
       return false;
     }
   }
   return true;
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_