Source/JavaScriptCore/runtime/NumericStrings.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.
 */

#pragma once

#include <array>
#include <wtf/HashFunctions.h>
#include <wtf/text/WTFString.h>

namespace JSC {

class NumericStrings {
public:
    ALWAYS_INLINE const String& add(double d)
    {
        CacheEntry<double>& entry = lookup(d);
        if (d == entry.key && !entry.value.isNull())
            return entry.value;
        entry.key = d;
        entry.value = String::number(d);
        return entry.value;
    }

    ALWAYS_INLINE const String& add(int i)
    {
        if (static_cast<unsigned>(i) < cacheSize)
            return lookupSmallString(static_cast<unsigned>(i));
        CacheEntry<int>& entry = lookup(i);
        if (i == entry.key && !entry.value.isNull())
            return entry.value;
        entry.key = i;
        entry.value = String::number(i);
        return entry.value;
    }

    ALWAYS_INLINE const String& add(unsigned i)
    {
        if (i < cacheSize)
            return lookupSmallString(static_cast<unsigned>(i));
        CacheEntry<unsigned>& entry = lookup(i);
        if (i == entry.key && !entry.value.isNull())
            return entry.value;
        entry.key = i;
        entry.value = String::number(i);
        return entry.value;
    }
private:
    static const size_t cacheSize = 64;

    template<typename T>
    struct CacheEntry {
        T key;
        String value;
    };

    CacheEntry<double>& lookup(double d) { return doubleCache[WTF::FloatHash<double>::hash(d) & (cacheSize - 1)]; }
    CacheEntry<int>& lookup(int i) { return intCache[WTF::IntHash<int>::hash(i) & (cacheSize - 1)]; }
    CacheEntry<unsigned>& lookup(unsigned i) { return unsignedCache[WTF::IntHash<unsigned>::hash(i) & (cacheSize - 1)]; }
    ALWAYS_INLINE const String& lookupSmallString(unsigned i)
    {
        ASSERT(i < cacheSize);
        if (smallIntCache[i].isNull())
            smallIntCache[i] = String::number(i);
        return smallIntCache[i];
    }

    std::array<CacheEntry<double>, cacheSize> doubleCache;
    std::array<CacheEntry<int>, cacheSize> intCache;
    std::array<CacheEntry<unsigned>, cacheSize> unsignedCache;
    std::array<String, cacheSize> smallIntCache;
};

} // namespace JSC