/*

* Copyright (C) 2019 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 <wtf/HashTraits.h>

#include <wtf/MathExtras.h>

namespace WTF {

class PrintStream;

}

namespace JSC {

using Checkpoint = uint8_t;

static constexpr Checkpoint noCheckpoints = 0;

class BytecodeIndex {

public:

BytecodeIndex() = default;

BytecodeIndex(WTF::HashTableDeletedValueType)

: m_packedBits(deletedValue().asBits())

{

}

explicit BytecodeIndex(uint32_t bytecodeOffset, Checkpoint checkpoint = noCheckpoints)

: m_packedBits(pack(bytecodeOffset, checkpoint))

{

ASSERT(*this);

}

static constexpr uint32_t numberOfCheckpoints = 4;

static_assert(hasOneBitSet(numberOfCheckpoints), "numberOfCheckpoints should be a power of 2");

static constexpr uint32_t checkpointMask = numberOfCheckpoints - 1;

static constexpr uint32_t checkpointShift = WTF::getMSBSetConstexpr(numberOfCheckpoints);

uint32_t offset() const { return m_packedBits >> checkpointShift; }

Checkpoint checkpoint() const { return m_packedBits & checkpointMask; }

uint32_t asBits() const { return m_packedBits; }

unsigned hash() const { return intHash(m_packedBits); }

static BytecodeIndex deletedValue() { return fromBits(invalidOffset - 1); }

bool isHashTableDeletedValue() const { return *this == deletedValue(); }

static BytecodeIndex fromBits(uint32_t bits);

BytecodeIndex withCheckpoint(Checkpoint checkpoint) const { return BytecodeIndex(offset(), checkpoint); }

// Comparison operators.

explicit operator bool() const { return m_packedBits != invalidOffset && m_packedBits != deletedValue().offset(); }

bool operator ==(const BytecodeIndex& other) const { return asBits() == other.asBits(); }

bool operator !=(const BytecodeIndex& other) const { return !(*this == other); }

bool operator <(const BytecodeIndex& other) const { return asBits() < other.asBits(); }

bool operator >(const BytecodeIndex& other) const { return asBits() > other.asBits(); }

bool operator <=(const BytecodeIndex& other) const { return asBits() <= other.asBits(); }

bool operator >=(const BytecodeIndex& other) const { return asBits() >= other.asBits(); }

void dump(WTF::PrintStream&) const;

private:

static constexpr uint32_t invalidOffset = std::numeric_limits<uint32_t>::max();

static uint32_t pack(uint32_t bytecodeIndex, Checkpoint);

uint32_t m_packedBits { invalidOffset };

};

inline uint32_t BytecodeIndex::pack(uint32_t bytecodeIndex, Checkpoint checkpoint)

{

ASSERT(checkpoint < numberOfCheckpoints);

ASSERT((bytecodeIndex << checkpointShift) >> checkpointShift == bytecodeIndex);

return bytecodeIndex << checkpointShift | checkpoint;

}

inline BytecodeIndex BytecodeIndex::fromBits(uint32_t bits)

{

BytecodeIndex result;

result.m_packedBits = bits;

return result;

}

struct BytecodeIndexHash {

static unsigned hash(const BytecodeIndex& key) { return key.hash(); }

static bool equal(const BytecodeIndex& a, const BytecodeIndex& b) { return a == b; }

static constexpr bool safeToCompareToEmptyOrDeleted = true;

};

} // namespace JSC

namespace WTF {

template<typename T> struct DefaultHash;

template<> struct DefaultHash<JSC::BytecodeIndex> : JSC::BytecodeIndexHash { };

template<typename T> struct HashTraits;

template<> struct HashTraits<JSC::BytecodeIndex> : SimpleClassHashTraits<JSC::BytecodeIndex> {

static constexpr bool emptyValueIsZero = false;

};

} // namespace WTF