Refactored fast external string resource getter.

include/v8.h

 // Copyright 2012 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 1000 matching lines @@
   V8EXPORT bool Value() const;
   static inline Handle<Boolean> New(bool value);
 };
 
 
 /**
  * A JavaScript string value (ECMA-262, 4.3.17).
  */
 class String : public Primitive {
  public:
+  static const int kExternalAsciiStringType = 0x06;
+  static const int kExternalTwoByteStringType = 0x02;
   /**
    * Returns the number of characters in this string.
    */
   V8EXPORT int Length() const;
 
   /**
    * Returns the number of bytes in the UTF-8 encoded
    * representation of this string.
    */
   V8EXPORT int Utf8Length() const;
@@ skipping 143 matching lines @@
     virtual ~ExternalAsciiStringResource() {}
     /** The string data from the underlying buffer.*/
     virtual const char* data() const = 0;
     /** The number of ASCII characters in the string.*/
     virtual size_t length() const = 0;
    protected:
     ExternalAsciiStringResource() {}
   };
 
   /**
+   * Get any type of external string resource.
+   * Returns 0 if there is no external string and does not modify resource or
+   * returns either kExternalAsciiStringType or kExternalTwoByteStringType and
+   * sets the resource pointer.
+   */
+  inline int GetExternalStringResourceBase(
+      ExternalStringResourceBase*& resource) const;
+
+  /**
    * Get the ExternalStringResource for an external string.  Returns
    * NULL if IsExternal() doesn't return true.
    */
   inline ExternalStringResource* GetExternalStringResource() const;
 
   /**
    * Get the ExternalAsciiStringResource for an external ASCII string.
    * Returns NULL if IsExternalAscii() doesn't return true.
    */
   V8EXPORT const ExternalAsciiStringResource* GetExternalAsciiStringResource()
@@ skipping 142 matching lines @@
    private:
     uint16_t* str_;
     int length_;
 
     // Disallow copying and assigning.
     Value(const Value&);
     void operator=(const Value&);
   };
 
  private:
+  V8EXPORT void VerifyExternalStringResourceBase(ExternalStringResourceBase* v,
+                                                 int type) const;
   V8EXPORT void VerifyExternalStringResource(ExternalStringResource* val) const;
   V8EXPORT static void CheckCast(v8::Value* obj);
 };
 
 
 /**
  * A JavaScript number value (ECMA-262, 4.3.20)
  */
 class Number : public Primitive {
  public:
@@ skipping 2671 matching lines @@
   // the implementation of v8.
   static const int kHeapObjectMapOffset = 0;
   static const int kMapInstanceTypeOffset = 1 * kApiPointerSize + kApiIntSize;
   static const int kStringResourceOffset = 3 * kApiPointerSize;
 
   static const int kOddballKindOffset = 3 * kApiPointerSize;
   static const int kForeignAddressOffset = kApiPointerSize;
   static const int kJSObjectHeaderSize = 3 * kApiPointerSize;
   static const int kFullStringRepresentationMask = 0x07;
   static const int kExternalTwoByteRepresentationTag = 0x02;
+  static const int kExternalAsciiRepresentationTag = 0x06;
 
   static const int kIsolateStateOffset = 0;
   static const int kIsolateEmbedderDataOffset = 1 * kApiPointerSize;
   static const int kIsolateRootsOffset = 3 * kApiPointerSize;
   static const int kUndefinedValueRootIndex = 5;
   static const int kNullValueRootIndex = 7;
   static const int kTrueValueRootIndex = 8;
   static const int kFalseValueRootIndex = 9;
   static const int kEmptySymbolRootIndex = 116;
 
@@ skipping 333 matching lines @@
     result = reinterpret_cast<String::ExternalStringResource*>(value);
   } else {
     result = NULL;
   }
 #ifdef V8_ENABLE_CHECKS
   VerifyExternalStringResource(result);
 #endif
   return result;
 }
 
+int String::GetExternalStringResourceBase(
+    String::ExternalStringResourceBase*& resource) const {
+  typedef internal::Object O;
+  typedef internal::Internals I;
+  O* obj = *reinterpret_cast<O**>(const_cast<String*>(this));
+  int type = I::GetInstanceType(obj) & I::kFullStringRepresentationMask;
+  if (type == I::kExternalAsciiRepresentationTag
+      || type == I::kExternalTwoByteRepresentationTag) {
+    void* value = I::ReadField<void*>(obj, I::kStringResourceOffset);
+    resource = static_cast<String::ExternalStringResourceBase*>(value);
+#ifdef V8_ENABLE_CHECKS
+    VerifyExternalStringResourceBase(resource, type);
+#endif
+    return type;
+  } else {
+#ifdef V8_ENABLE_CHECKS
+    VerifyExternalStringResourceBase(NULL, 0);
+#endif
+    return 0;
+  }
+}
 
 bool Value::IsUndefined() const {
 #ifdef V8_ENABLE_CHECKS
   return FullIsUndefined();
 #else
   return QuickIsUndefined();
 #endif
 }
 
 bool Value::QuickIsUndefined() const {
@@ skipping 210 matching lines @@
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_