Allow the morphing of strings to external strings to avoid having to...

src/objects.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 927 matching lines @@
  private:
   // HeapObject calls the private constructor and directly reads the value.
   friend class HeapObject;
 
   explicit MapWord(uintptr_t value) : value_(value) {}
 
   uintptr_t value_;
 
   // Bits used by the marking phase of the garbage collector.
   //
-  // The first word of a heap object is normall a map pointer. The last two
+  // The first word of a heap object is normally a map pointer. The last two
   // bits are tagged as '01' (kHeapObjectTag). We reuse the last two bits to
   // mark an object as live and/or overflowed:
   //   last bit = 0, marked as alive
   //   second bit = 1, overflowed
   // An object is only marked as overflowed when it is marked as live while
   // the marking stack is overflowed.
   static const int kMarkingBit = 0;  // marking bit
   static const int kMarkingMask = (1 << kMarkingBit);  // marking mask
   static const int kOverflowBit = 1;  // overflow bit
   static const int kOverflowMask = (1 << kOverflowBit);  // overflow mask
@@ skipping 2239 matching lines @@
   // Returns a hash value used for the property table
   inline uint32_t Hash();
 
   static uint32_t ComputeLengthAndHashField(unibrow::CharacterStream* buffer,
                                             int length);
 
   static bool ComputeArrayIndex(unibrow::CharacterStream* buffer,
                                 uint32_t* index,
                                 int length);
 
+  // Externalization.
+  bool MakeExternal(v8::String::ExternalStringResource* resource);
+  bool MakeExternal(v8::String::ExternalAsciiStringResource* resource);
+
   // Conversion.
   inline bool AsArrayIndex(uint32_t* index);
 
   // Casting.
   static inline String* cast(Object* obj);
 
   void PrintOn(FILE* out);
 
   // For use during stack traces.  Performs rudimentary sanity check.
   bool LooksValid();
@@ skipping 359 matching lines @@
   static inline ExternalAsciiString* cast(Object* obj);
 
   // Support for StringInputBuffer.
   const unibrow::byte* ExternalAsciiStringReadBlock(unsigned* remaining,
                                                     unsigned* offset,
                                                     unsigned chars);
   inline void ExternalAsciiStringReadBlockIntoBuffer(ReadBlockBuffer* buffer,
                                                      unsigned* offset,
                                                      unsigned chars);
 
+  // Identify the map for the external string/symbol with a particular length.
+  static inline Map* StringMap(int length);
+  static inline Map* SymbolMap(int length);
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalAsciiString);
 };
 
 
 // The ExternalTwoByteString class is an external string backed by a UTF-16
 // encoded string.
 class ExternalTwoByteString: public ExternalString {
  public:
   typedef v8::String::ExternalStringResource Resource;
 
   // The underlying string resource.
   inline Resource* resource();
   inline void set_resource(Resource* buffer);
 
   // Dispatched behavior.
   uint16_t ExternalTwoByteStringGet(int index);
 
   // For regexp code.
   const uint16_t* ExternalTwoByteStringGetData(unsigned start);
 
   // Casting.
   static inline ExternalTwoByteString* cast(Object* obj);
 
   // Support for StringInputBuffer.
   void ExternalTwoByteStringReadBlockIntoBuffer(ReadBlockBuffer* buffer,
                                                 unsigned* offset_ptr,
                                                 unsigned chars);
 
+  // Identify the map for the external string/symbol with a particular length.
+  static inline Map* StringMap(int length);
+  static inline Map* SymbolMap(int length);
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalTwoByteString);
 };
 
 
 // A flat string reader provides random access to the contents of a
 // string independent of the character width of the string.  The handle
 // must be valid as long as the reader is being used.
 class FlatStringReader BASE_EMBEDDED {
  public:
@@ skipping 601 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_