string_bytes: export GetExternalParts

The method is useful elsewhere when needing to check if external and
grab data.

src/string_bytes.cc

@@ -230,12 +230,13 @@ size_t hex_decode(char* buf,
 }
 
 
-bool GetExternalParts(Handle<Value> val, const char** data, size_t* len) {
+bool StringBytes::GetExternalParts(Handle<Value> val,
+                                   const char** data,
+                                   size_t* len) {
   if (Buffer::HasInstance(val)) {
     *data = Buffer::Data(val);
     *len = Buffer::Length(val);
     return true;
-
   }
 
   assert(val->IsString());

src/string_bytes.h

@@ -44,6 +44,12 @@ class StringBytes {
   // very much slower for UTF-8
   static size_t Size(v8::Handle<v8::Value> val, enum encoding enc);
 
+  // If the string is external then assign external properties to data and len,
+  // then return true. If not return false.
+  static bool GetExternalParts(v8::Handle<v8::Value> val,
+                               const char** data,
+                               size_t* len);
+
   // Write the bytes from the string or buffer into the char*
   // returns the number of bytes written, which will always be
   // <= buflen.  Use StorageSize/Size first to know how much