src/third_party/blink/Source/bindings/core/v8/V8ValueCache.h

/*
 * 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
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef V8ValueCache_h
#define V8ValueCache_h

#include "bindings/core/v8/V8PersistentValueMap.h"
#include "wtf/HashMap.h"
#include "wtf/RefPtr.h"
#include "wtf/text/AtomicString.h"
#include "wtf/text/WTFString.h"
#include <v8.h>

namespace blink {

class StringCacheMapTraits : public V8PersistentValueMapTraits<StringImpl*, v8::String, true> {
public:
    // Weak traits:
    typedef StringImpl WeakCallbackDataType;
    typedef v8::PersistentValueMap<StringImpl*, v8::String, StringCacheMapTraits> MapType;

    static WeakCallbackDataType* WeakCallbackParameter(
        MapType* map, StringImpl* key, v8::Local<v8::String>& value) { return key; }
    static void DisposeCallbackData(WeakCallbackDataType* callbackData) { }

    static MapType* MapFromWeakCallbackData(
        const v8::WeakCallbackData<v8::String, WeakCallbackDataType>&);

    static StringImpl* KeyFromWeakCallbackData(
        const v8::WeakCallbackData<v8::String, WeakCallbackDataType>& data)
    {
        return data.GetParameter();
    }

    static void Dispose(v8::Isolate*, v8::UniquePersistent<v8::String> value, StringImpl* key);
};


class StringCache {
public:
    StringCache(v8::Isolate* isolate) : m_stringCache(isolate) { }
    ~StringCache();

    v8::Handle<v8::String> v8ExternalString(StringImpl* stringImpl, v8::Isolate* isolate)
    {
        ASSERT(stringImpl);
        if (m_lastStringImpl.get() == stringImpl)
            return m_lastV8String.NewLocal(isolate);
        return v8ExternalStringSlow(isolate, stringImpl);
    }

    void setReturnValueFromString(v8::ReturnValue<v8::Value> returnValue, StringImpl* stringImpl)
    {
        ASSERT(stringImpl);
        if (m_lastStringImpl.get() == stringImpl)
            m_lastV8String.SetReturnValue(returnValue);
        else
            setReturnValueFromStringSlow(returnValue, stringImpl);
    }

    friend class StringCacheMapTraits;

private:
    v8::Handle<v8::String> v8ExternalStringSlow(v8::Isolate*, StringImpl*);
    void setReturnValueFromStringSlow(v8::ReturnValue<v8::Value>, StringImpl*);
    v8::Local<v8::String> createStringAndInsertIntoCache(v8::Isolate*, StringImpl*);
    void InvalidateLastString();

    StringCacheMapTraits::MapType m_stringCache;
    StringCacheMapTraits::MapType::PersistentValueReference m_lastV8String;

    // Note: RefPtr is a must as we cache by StringImpl* equality, not identity
    // hence lastStringImpl might be not a key of the cache (in sense of identity)
    // and hence it's not refed on addition.
    RefPtr<StringImpl> m_lastStringImpl;
};

} // namespace blink

#endif // V8ValueCache_h