weex_core/Source/include/JavaScriptCore/runtime/JSTypeInfo.h

// -*- mode: c++; c-basic-offset: 4 -*-
/*
 * Copyright (C) 2008, 2015 Apple Inc. All rights reserved.
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#pragma once

// This file would be called TypeInfo.h, but that conflicts with <typeinfo.h>
// in the STL on systems without case-sensitive file systems. 

#include "JSType.h"

namespace JSC {

class LLIntOffsetsExtractor;

static const unsigned MasqueradesAsUndefined = 1; // WebCore uses MasqueradesAsUndefined to make document.all undetectable.
static const unsigned ImplementsDefaultHasInstance = 1 << 1;
static const unsigned TypeOfShouldCallGetCallData = 1 << 2; // Need this flag if you override getCallData() and you want typeof to use this to determine if it should say "function". Currently we always set this flag when we override getCallData().
static const unsigned OverridesGetOwnPropertySlot = 1 << 3;
static const unsigned StructureIsImmortal = 1 << 5;
static const unsigned OverridesToThis = 1 << 6; // If this is false then this returns something other than 'this'. Non-object cells that are visible to JS have this set as do some exotic objects.
static const unsigned HasStaticPropertyTable = 1 << 7;

static const unsigned ImplementsHasInstance = 1 << 8;
static const unsigned OverridesGetPropertyNames = 1 << 9;
static const unsigned ProhibitsPropertyCaching = 1 << 10;
static const unsigned GetOwnPropertySlotIsImpure = 1 << 11;
static const unsigned NewImpurePropertyFiresWatchpoints = 1 << 12;
static const unsigned IsImmutablePrototypeExoticObject = 1 << 13;
static const unsigned GetOwnPropertySlotIsImpureForPropertyAbsence = 1 << 14;
static const unsigned InterceptsGetOwnPropertySlotByIndexEvenWhenLengthIsNotZero = 1 << 15;

class TypeInfo {
public:
    typedef uint8_t InlineTypeFlags;
    typedef uint16_t OutOfLineTypeFlags;

    TypeInfo(JSType type, unsigned flags = 0)
        : TypeInfo(type, flags & 0xff, flags >> 8)
    {
        ASSERT(!(flags >> 24));
    }

    TypeInfo(JSType type, InlineTypeFlags inlineTypeFlags, OutOfLineTypeFlags outOfLineTypeFlags)
        : m_type(type)
        , m_flags(inlineTypeFlags)
        , m_flags2(outOfLineTypeFlags)
    {
    }

    JSType type() const { return static_cast<JSType>(m_type); }
    bool isObject() const { return isObject(type()); }
    static bool isObject(JSType type) { return type >= ObjectType; }
    bool isFinalObject() const { return type() == FinalObjectType; }
    bool isNumberObject() const { return type() == NumberObjectType; }

    unsigned flags() const { return (static_cast<unsigned>(m_flags2) << 8) | static_cast<unsigned>(m_flags); }
    bool masqueradesAsUndefined() const { return isSetOnFlags1(MasqueradesAsUndefined); }
    bool implementsHasInstance() const { return isSetOnFlags2(ImplementsHasInstance); }
    bool implementsDefaultHasInstance() const { return isSetOnFlags1(ImplementsDefaultHasInstance); }
    bool typeOfShouldCallGetCallData() const { return isSetOnFlags1(TypeOfShouldCallGetCallData); }
    bool overridesGetOwnPropertySlot() const { return overridesGetOwnPropertySlot(inlineTypeFlags()); }
    static bool overridesGetOwnPropertySlot(InlineTypeFlags flags) { return flags & OverridesGetOwnPropertySlot; }
    static bool hasStaticPropertyTable(InlineTypeFlags flags) { return flags & HasStaticPropertyTable; }
    bool structureIsImmortal() const { return isSetOnFlags1(StructureIsImmortal); }
    bool overridesToThis() const { return isSetOnFlags1(OverridesToThis); }
    bool overridesGetPropertyNames() const { return isSetOnFlags2(OverridesGetPropertyNames); }
    bool prohibitsPropertyCaching() const { return isSetOnFlags2(ProhibitsPropertyCaching); }
    bool getOwnPropertySlotIsImpure() const { return isSetOnFlags2(GetOwnPropertySlotIsImpure); }
    bool getOwnPropertySlotIsImpureForPropertyAbsence() const { return isSetOnFlags2(GetOwnPropertySlotIsImpureForPropertyAbsence); }
    bool newImpurePropertyFiresWatchpoints() const { return isSetOnFlags2(NewImpurePropertyFiresWatchpoints); }
    bool isImmutablePrototypeExoticObject() const { return isSetOnFlags2(IsImmutablePrototypeExoticObject); }
    bool interceptsGetOwnPropertySlotByIndexEvenWhenLengthIsNotZero() const { return isSetOnFlags2(InterceptsGetOwnPropertySlotByIndexEvenWhenLengthIsNotZero); }

    static ptrdiff_t flagsOffset()
    {
        return OBJECT_OFFSETOF(TypeInfo, m_flags);
    }

    static ptrdiff_t typeOffset()
    {
        return OBJECT_OFFSETOF(TypeInfo, m_type);
    }

    InlineTypeFlags inlineTypeFlags() const { return m_flags; }
    OutOfLineTypeFlags outOfLineTypeFlags() const { return m_flags2; }

private:
    friend class LLIntOffsetsExtractor;

    bool isSetOnFlags1(unsigned flag) const { ASSERT(flag <= (1 << 7)); return m_flags & flag; }
    bool isSetOnFlags2(unsigned flag) const { ASSERT(flag >= (1 << 8)); return m_flags2 & (flag >> 8); }

    uint8_t m_type;
    uint8_t m_flags;
    uint16_t m_flags2;
};

} // namespace JSC