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/*
* Copyright (C) 2021 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. 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.
*/
#pragma once
#include <wtf/text/AtomStringImpl.h>
namespace JSC {
class VM;
class JSONAtomStringCache {
public:
static constexpr auto maxStringLengthForCache = 27;
static constexpr auto capacity = 256;
struct Slot {
UChar m_buffer[maxStringLengthForCache] { };
UChar m_length { 0 };
RefPtr<AtomStringImpl> m_impl;
};
static_assert(sizeof(Slot) <= 64);
using Cache = std::array<Slot, capacity>;
template<typename CharacterType>
ALWAYS_INLINE Ref<AtomStringImpl> makeIdentifier(std::span<const CharacterType> characters)
{
return make(characters);
}
ALWAYS_INLINE void clear()
{
m_cache.fill({ });
}
VM& vm() const;
private:
template<typename CharacterType>
Ref<AtomStringImpl> make(std::span<const CharacterType>);
ALWAYS_INLINE Slot& cacheSlot(UChar firstCharacter, UChar lastCharacter, UChar length)
{
unsigned hash = (firstCharacter << 6) ^ ((lastCharacter << 14) ^ firstCharacter);
hash += (hash >> 14) + (length << 14);
hash ^= hash << 14;
return m_cache[(hash + (hash >> 6)) % capacity];
}
Cache m_cache { };
};
} // namespace JSC
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