JavaScriptCore/runtime/DateInstanceCache.h

/*
 * Copyright (C) 2009 Apple 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. ``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
 * 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 DateInstanceCache_h
#define DateInstanceCache_h

#include <wtf/DateMath.h>
#include <wtf/HashFunctions.h>
#include <wtf/PassRefPtr.h>
#include <wtf/RefCounted.h>

namespace JSC {

    extern const double NaN;

    class DateInstanceData : public RefCounted<DateInstanceData> {
    public:
        static PassRefPtr<DateInstanceData> create() { return adoptRef(new DateInstanceData); }

        double m_gregorianDateTimeCachedForMS;
        WTF::GregorianDateTime m_cachedGregorianDateTime;
        double m_gregorianDateTimeUTCCachedForMS;
        WTF::GregorianDateTime m_cachedGregorianDateTimeUTC;

    private:
        DateInstanceData()
            : m_gregorianDateTimeCachedForMS(NaN)
            , m_gregorianDateTimeUTCCachedForMS(NaN)
        {
        }
    };

    class DateInstanceCache {
    public:
        DateInstanceCache()
        {
            for (size_t i = 0; i < cacheSize; ++i)
                m_cache[i].key = NaN;
        }
        
        DateInstanceData* add(double d)
        {
            CacheEntry& entry = lookup(d);
            if (d == entry.key)
                return entry.value.get();

            entry.key = d;
            entry.value = DateInstanceData::create();
            return entry.value.get();
        }

    private:
        static const size_t cacheSize = 64;

        struct CacheEntry {
            double key;
            RefPtr<DateInstanceData> value;
        };

        CacheEntry& lookup(double d) { return m_cache[WTF::FloatHash<double>::hash(d) & (cacheSize - 1)]; }

        CacheEntry m_cache[cacheSize];
    };

} // namespace JSC

#endif // DateInstanceCache_h