[ES6 modules] Introduce ScriptModuleHash

third_party/WebKit/Source/bindings/core/v8/ScriptModule.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ScriptModule_h
 #define ScriptModule_h
 
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/SharedPersistent.h"
 #include "core/CoreExport.h"
 #include "v8/include/v8.h"
 #include "wtf/Allocator.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class CORE_EXPORT ScriptModule final {
   DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
 
  public:
   static ScriptModule compile(v8::Isolate*,
                               const String& source,
                               const String& fileName);
 
+  // TODO(kouhei): Remove copy ctor
   ScriptModule() {}
-  ScriptModule(const ScriptModule& module) : m_module(module.m_module) {}
+  ScriptModule(WTF::HashTableDeletedValueType)
+      : m_module(WTF::HashTableDeletedValue) {}
   ~ScriptModule();
 
   bool instantiate(ScriptState*);
   void evaluate(ScriptState*);
 
+  bool isHashTableDeletedValue() const {
+    return m_module.isHashTableDeletedValue();
+  }
+
+  bool operator==(const blink::ScriptModule& other) const {
+    if (isHashTableDeletedValue() && other.isHashTableDeletedValue())
+      return true;
+
+    if (isHashTableDeletedValue() || other.isHashTableDeletedValue())
+      return false;
+
+    blink::SharedPersistent<v8::Module>* left = m_module.get();
+    blink::SharedPersistent<v8::Module>* right = other.m_module.get();
+    if (left == right)
+      return true;
+    if (!left || !right)
+      return false;
+    return *left == *right;
+  }
+
+  bool operator!=(const blink::ScriptModule& other) const {
+    return !(*this == other);
+  }
+
   bool isNull() const { return m_module->isEmpty(); }
 
  private:
   ScriptModule(v8::Isolate*, v8::Local<v8::Module>);
 
   RefPtr<SharedPersistent<v8::Module>> m_module;
+  unsigned m_identityHash = 0;

[Yuta Kitamura, 2017/04/04 06:21:51]

optional: If you really care about the space waste, you might
want to just call GetIdentityHash() every time it is requested.
That should be okay if we can assume GetIdentityHash() is fast.

[kouhei (in TOK), 2017/04/04 06:36:55]

I want to have hash work w/o ScriptState*. :/
GetIdentityHash requires v8::Isolate*

[adamk, 2017/04/05 01:01:03]

I don't understand this comment: v8::Module::GetIdentityHash() takes no
arguments. Is the problem that you'd need to create a v8::Local in order to call
the underlying GetIdentityHash() method, and that requires a v8::Isolate?

[adamk, 2017/04/05 01:09:38]

Ok, makes sense. It's too bad the API is over-restrictive in this way (it'd be
completely safe to access the hash through the persistent handle), but I guess
that's something we have to pay for now that the Persistent API is safer.

+
+  friend struct ScriptModuleHash;
+};
+
+struct ScriptModuleHash {
+  STATIC_ONLY(ScriptModuleHash);
+
+ public:
+  static unsigned hash(const blink::ScriptModule& key) {
+    return key.m_identityHash;

[Yuta Kitamura, 2017/04/04 06:21:50]

Hm. This means you use a hash value returned from V8 for
WTF::HashTable, right? I've never seen this pattern before,
but I can find no reasons why this won't work, so this should be
okay...

+  }
+
+  static bool equal(const blink::ScriptModule& a,
+                    const blink::ScriptModule& b) {
+    return a == b;
+  }
+
+  static constexpr bool safeToCompareToEmptyOrDeleted = true;
 };
 
 }  // namespace blink
 
+namespace WTF {
+
+template <>
+struct DefaultHash<blink::ScriptModule> {
+  using Hash = blink::ScriptModuleHash;
+};
+
+template <>
+struct HashTraits<blink::ScriptModule>
+    : public SimpleClassHashTraits<blink::ScriptModule> {};
+
+}  // namespace WTF
+
 #endif  // ScriptModule_h