Add experimental support for external two-byte symbols....

src/heap.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 338 matching lines @@
       Vector<const char> str,
       PretenureFlag pretenure = NOT_TENURED);
   static Object* AllocateStringFromTwoByte(
       Vector<const uc16> str,
       PretenureFlag pretenure = NOT_TENURED);
 
   // Allocates a symbol in old space based on the character stream.
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this function does not perform a garbage collection.
-  static Object* AllocateSymbol(unibrow::CharacterStream* buffer,
-                                int chars,
-                                uint32_t length_field);
+  static inline Object* AllocateSymbol(Vector<const char> str,
+                                       int chars,
+                                       uint32_t length_field);
+
+  static Object* AllocateInternalSymbol(unibrow::CharacterStream* buffer,
+                                        int chars,
+                                        uint32_t length_field);
+
+  static Object* AllocateExternalSymbol(Vector<const char> str,
+                                        int chars);
+
 
   // Allocates and partially initializes a String.  There are two String
   // encodings: ASCII and two byte.  These functions allocate a string of the
   // given length and set its map and length fields.  The characters of the
   // string are uninitialized.
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this does not perform a garbage collection.
   static Object* AllocateRawAsciiString(
       int length,
@@ skipping 148 matching lines @@
 
   // Allocate a new external string object, which is backed by a string
   // resource that resides outside the V8 heap.
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this does not perform a garbage collection.
   static Object* AllocateExternalStringFromAscii(
       ExternalAsciiString::Resource* resource);
   static Object* AllocateExternalStringFromTwoByte(
       ExternalTwoByteString::Resource* resource);
+  static Object* AllocateExternalSymbolFromTwoByte(
+      ExternalTwoByteString::Resource* resource);
 
   // Allocates an uninitialized object.  The memory is non-executable if the
   // hardware and OS allow.
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this function does not perform a garbage collection.
   static inline Object* AllocateRaw(int size_in_bytes,
                                     AllocationSpace space,
                                     AllocationSpace retry_space);
 
@@ skipping 48 matching lines @@
   static bool GarbageCollectionGreedyCheck();
 #endif
 
   static void SetGlobalGCPrologueCallback(GCCallback callback) {
     global_gc_prologue_callback_ = callback;
   }
   static void SetGlobalGCEpilogueCallback(GCCallback callback) {
     global_gc_epilogue_callback_ = callback;
   }
 
+  static void SetExternalSymbolCallback(ExternalSymbolCallback callback) {
+    global_external_symbol_callback_ = callback;
+  }
+
   // Heap roots
 #define ROOT_ACCESSOR(type, name) static type* name() { return name##_; }
   ROOT_LIST(ROOT_ACCESSOR)
 #undef ROOT_ACCESSOR
 
 // Utility type maps
 #define STRUCT_MAP_ACCESSOR(NAME, Name, name) \
     static Map* name##_map() { return name##_map_; }
   STRUCT_LIST(STRUCT_MAP_ACCESSOR)
 #undef STRUCT_MAP_ACCESSOR
@@ skipping 239 matching lines @@
 
 #define SYMBOL_DECLARATION(name, str) static String* name##_;
   SYMBOL_LIST(SYMBOL_DECLARATION)
 #undef SYMBOL_DECLARATION
 
   // GC callback function, called before and after mark-compact GC.
   // Allocations in the callback function are disallowed.
   static GCCallback global_gc_prologue_callback_;
   static GCCallback global_gc_epilogue_callback_;
 
+  // Callback function used for allocating external symbols.
+  static ExternalSymbolCallback global_external_symbol_callback_;
+
   // Checks whether a global GC is necessary
   static GarbageCollector SelectGarbageCollector(AllocationSpace space);
 
   // Performs garbage collection
   static void PerformGarbageCollection(AllocationSpace space,
                                        GarbageCollector collector,
                                        GCTracer* tracer);
 
   // Returns either a Smi or a Number object from 'value'. If 'new_object'
   // is false, it may return a preallocated immutable object.
@@ skipping 386 matching lines @@
   int marked_count_;
 
   // The count from the end of the previous full GC.  Will be zero if there
   // was no previous full GC.
   int previous_marked_count_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_