WIP: Introduce CompressibleString

third_party/WebKit/Source/bindings/core/v8/V8ValueCache.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 66 matching lines @@
 
     WebCoreStringResource16* stringResource = new WebCoreStringResource16(string);
     v8::Local<v8::String> newString;
     if (!v8::String::NewExternalTwoByte(isolate, stringResource).ToLocal(&newString)) {
         delete stringResource;
         return v8::String::Empty(isolate);
     }
     return newString;
 }
 
+static v8::Local<v8::String> makeExternalString(v8::Isolate* isolate, const CompressableString& string)
+{
+    if (string.is8Bit()) {
+        WebCoreCompressableStringResource8* stringResource = new WebCoreCompressableStringResource8(string);
+        v8::Local<v8::String> newString;
+        if (!v8::String::NewExternalOneByte(isolate, stringResource).ToLocal(&newString)) {
+            delete stringResource;
+            return v8::String::Empty(isolate);
+        }
+        return newString;
+    }
+
+    WebCoreCompressableStringResource16* stringResource = new WebCoreCompressableStringResource16(string);
+    v8::Local<v8::String> newString;
+    if (!v8::String::NewExternalTwoByte(isolate, stringResource).ToLocal(&newString)) {
+        delete stringResource;
+        return v8::String::Empty(isolate);
+    }
+    return newString;
+}
+
 v8::Local<v8::String> StringCache::v8ExternalStringSlow(v8::Isolate* isolate, StringImpl* stringImpl)
 {
     if (!stringImpl->length())
         return v8::String::Empty(isolate);
 
     StringCacheMapTraits::MapType::PersistentValueReference cachedV8String = m_stringCache.GetReference(stringImpl);
     if (!cachedV8String.IsEmpty()) {
         m_lastStringImpl = stringImpl;
         m_lastV8String = cachedV8String;
         return m_lastV8String.NewLocal(isolate);
     }
 
     return createStringAndInsertIntoCache(isolate, stringImpl);
 }
 
+v8::Local<v8::String> StringCache::v8ExternalStringSlow(v8::Isolate* isolate, const CompressableString& string)
+{
+    if (!string.length())
+        return v8::String::Empty(isolate);
+
+    return createStringAndInsertIntoCache(isolate, string);
+}
+
 void StringCache::setReturnValueFromStringSlow(v8::ReturnValue<v8::Value> returnValue, StringImpl* stringImpl)
 {
     if (!stringImpl->length()) {
         returnValue.SetEmptyString();
         return;
     }
 
     StringCacheMapTraits::MapType::PersistentValueReference cachedV8String = m_stringCache.GetReference(stringImpl);
     if (!cachedV8String.IsEmpty()) {
         m_lastStringImpl = stringImpl;
@@ skipping 17 matching lines @@
     v8::UniquePersistent<v8::String> wrapper(isolate, newString);
 
     stringImpl->ref();
     wrapper.MarkIndependent();
     m_stringCache.Set(stringImpl, wrapper.Pass(), &m_lastV8String);
     m_lastStringImpl = stringImpl;
 
     return newString;
 }
 
+v8::Local<v8::String> StringCache::createStringAndInsertIntoCache(v8::Isolate* isolate, const CompressableString& string)
+{
+    // ASSERT(!m_stringCache.Contains(stringImpl));
+    ASSERT(string.length());
+
+    v8::Local<v8::String> newString = makeExternalString(isolate, string);
+    ASSERT(!newString.IsEmpty());
+    ASSERT(newString->Length());
+
+    v8::UniquePersistent<v8::String> wrapper(isolate, newString);
+
+    // TODO(hajimehoshi): I'm not sure this ref is needed.
+    // string->ref();

[haraken, 2015/11/24 11:15:41]

This ref is needed. If you don't have the ref, who keeps the CompressableString
alive?

I guess that in your CL all the CompressableStrings are leaking because the
strings are never evicted from the V8PerIsolateData::m_compressableStrings.

+    wrapper.MarkIndependent();
+    // m_stringCache.Set(stringImpl, wrapper.Pass(), &m_lastV8String);

[haraken, 2015/11/24 11:15:41]

You need to put the CompressableString into the m_stringCache. Otherwise,
deref() is never called when V8 collects the wrapper of the CompressableString
(See line 34 - 56).

[hajimehoshi, 2015/11/26 10:49:13]

Hmm, I didn't know m_stringCache was the owner of String objects.

+    // m_lastStringImpl = stringImpl;
+
+    return newString;
+}
+
 void StringCache::InvalidateLastString()
 {
     m_lastStringImpl = nullptr;
     m_lastV8String.Reset();
 }
 
 } // namespace blink