/*

 * Copyright (C) 2007, 2008 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.

 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of

 *     its contributors may be used to endorse or promote products derived

 *     from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY APPLE 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 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 SymbolTable_h

#define SymbolTable_h

#include "JSObject.h"

#include "UString.h"

#include <wtf/AlwaysInline.h>

namespace JSC {

    static ALWAYS_INLINE int missingSymbolMarker() { return std::numeric_limits<int>::max(); }

    // The bit twiddling in this class assumes that every register index is a

    // reasonably small positive or negative number, and therefore has its high

    // four bits all set or all unset.

    struct SymbolTableEntry {

        SymbolTableEntry()

            : m_bits(0)

        {

        }

        SymbolTableEntry(int index)

        {

            ASSERT(isValidIndex(index));

            pack(index, false, false);

        }

        SymbolTableEntry(int index, unsigned attributes)

        {

            ASSERT(isValidIndex(index));

            pack(index, attributes & ReadOnly, attributes & DontEnum);

        }

        bool isNull() const

        {

            return !m_bits;

        }

        int getIndex() const

        {

            return m_bits >> FlagBits;

        }

        unsigned getAttributes() const

        {

            unsigned attributes = 0;

            if (m_bits & ReadOnlyFlag)

                attributes |= ReadOnly;

            if (m_bits & DontEnumFlag)

                attributes |= DontEnum;

            return attributes;

        }

        void setAttributes(unsigned attributes)

        {

            pack(getIndex(), attributes & ReadOnly, attributes & DontEnum);

        }

        bool isReadOnly() const

        {

            return m_bits & ReadOnlyFlag;

        }

    private:

        static const unsigned ReadOnlyFlag = 0x1;

        static const unsigned DontEnumFlag = 0x2;

        static const unsigned NotNullFlag = 0x4;

        static const unsigned FlagBits = 3;

        void pack(int index, bool readOnly, bool dontEnum)

        {

            m_bits = (index << FlagBits) | NotNullFlag;

            if (readOnly)

                m_bits |= ReadOnlyFlag;

            if (dontEnum)

                m_bits |= DontEnumFlag;

        }

        bool isValidIndex(int index)

        {

            return ((index << FlagBits) >> FlagBits) == index;

        }

        int m_bits;

    };

    struct SymbolTableIndexHashTraits {

        typedef SymbolTableEntry TraitType;

        static SymbolTableEntry emptyValue() { return SymbolTableEntry(); }

        static const bool emptyValueIsZero = true;

        static const bool needsDestruction = false;

    };

    typedef HashMap<RefPtr<UString::Rep>, SymbolTableEntry, IdentifierRepHash, HashTraits<RefPtr<UString::Rep> >, SymbolTableIndexHashTraits> SymbolTable;

    class SharedSymbolTable : public SymbolTable, public RefCounted<SharedSymbolTable> {

    public:

        static PassRefPtr<SharedSymbolTable> create() { return adoptRef(new SharedSymbolTable); }

    private:

        SharedSymbolTable() { }

    };

} // namespace JSC

#endif // SymbolTable_h