Add ExternalStringResourceBase::IsCompressible

src/factory.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/factory.h"
 
 #include "src/allocation-site-scopes.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
 #include "src/conversions.h"
@@ skipping 652 matching lines @@
 }
 
 
 MaybeHandle<String> Factory::NewExternalStringFromOneByte(
     const ExternalOneByteString::Resource* resource) {
   size_t length = resource->length();
   if (length > static_cast<size_t>(String::kMaxLength)) {
     THROW_NEW_ERROR(isolate(), NewInvalidStringLengthError(), String);
   }
 
-  Handle<Map> map = external_one_byte_string_map();
+  Handle<Map> map;
+  if (resource->isCompressible()) {
+    map = short_external_one_byte_string_map();

[Yang, 2015/12/17 11:41:53]

Please add a TODO to rename this to "uncached_external_one_byte_string_map()"
and similar for other short external string maps.
Or do the renaming in this CL.

[hajimehoshi, 2016/01/05 08:07:44]

Done.

+  } else {
+    map = external_one_byte_string_map();
+  }
   Handle<ExternalOneByteString> external_string =
       New<ExternalOneByteString>(map, NEW_SPACE);
   external_string->set_length(static_cast<int>(length));
   external_string->set_hash_field(String::kEmptyHashField);
   external_string->set_resource(resource);
 
   return external_string;
 }
 
 
 MaybeHandle<String> Factory::NewExternalStringFromTwoByte(
     const ExternalTwoByteString::Resource* resource) {
   size_t length = resource->length();
   if (length > static_cast<size_t>(String::kMaxLength)) {
     THROW_NEW_ERROR(isolate(), NewInvalidStringLengthError(), String);
   }
 
   // For small strings we check whether the resource contains only
   // one byte characters.  If yes, we use a different string map.
   static const size_t kOneByteCheckLengthLimit = 32;
   bool is_one_byte = length <= kOneByteCheckLengthLimit &&
       String::IsOneByte(resource->data(), static_cast<int>(length));
-  Handle<Map> map = is_one_byte ?
-      external_string_with_one_byte_data_map() : external_string_map();
+  Handle<Map> map;
+  if (resource->isCompressible()) {
+    map = is_one_byte ? short_external_string_with_one_byte_data_map()
+                      : short_external_string_map();
+  } else {
+    map = is_one_byte ? external_string_with_one_byte_data_map()
+                      : external_string_map();
+  }
   Handle<ExternalTwoByteString> external_string =
       New<ExternalTwoByteString>(map, NEW_SPACE);
   external_string->set_length(static_cast<int>(length));
   external_string->set_hash_field(String::kEmptyHashField);
   external_string->set_resource(resource);
 
   return external_string;
 }
 
 
@@ skipping 1612 matching lines @@
 }
 
 
 Handle<Object> Factory::ToBoolean(bool value) {
   return value ? true_value() : false_value();
 }
 
 
 }  // namespace internal
 }  // namespace v8