property-details.h

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// Copyright 2012 the V8 project authors. All rights reserved.
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#ifndef V8_PROPERTY_DETAILS_H_
#define V8_PROPERTY_DETAILS_H_

#include "../include/v8.h"
#include "allocation.h"
#include "utils.h"

// Ecma-262 3rd 8.6.1
enum PropertyAttributes {
  NONE              = v8::None,
  READ_ONLY         = v8::ReadOnly,
  DONT_ENUM         = v8::DontEnum,
  DONT_DELETE       = v8::DontDelete,
  ABSENT            = 16  // Used in runtime to indicate a property is absent.
  // ABSENT can never be stored in or returned from a descriptor's attributes
  // bitfield.  It is only used as a return value meaning the attributes of
  // a non-existent property.
};


namespace v8 {
namespace internal {

class Smi;

// Type of properties.
// Order of properties is significant.
// Must fit in the BitField PropertyDetails::TypeField.
// A copy of this is in mirror-debugger.js.
enum PropertyType {
  // Only in slow mode.
  NORMAL                    = 0,
  // Only in fast mode.
  FIELD                     = 1,
  CONSTANT_FUNCTION         = 2,
  CALLBACKS                 = 3,
  // Only in lookup results, not in descriptors.
  HANDLER                   = 4,
  INTERCEPTOR               = 5,
  TRANSITION                = 6,
  // Only used as a marker in LookupResult.
  NONEXISTENT               = 7
};


// PropertyDetails captures type and attributes for a property.
// They are used both in property dictionaries and instance descriptors.
class PropertyDetails BASE_EMBEDDED {
 public:
  PropertyDetails(PropertyAttributes attributes,
                  PropertyType type,
                  int index = 0) {
    value_ = TypeField::encode(type)
        | AttributesField::encode(attributes)
        | DictionaryStorageField::encode(index);

    ASSERT(type == this->type());
    ASSERT(attributes == this->attributes());
    ASSERT(index == this->dictionary_index());
  }

  int pointer() { return DescriptorPointer::decode(value_); }

  PropertyDetails set_pointer(int i) { return PropertyDetails(value_, i); }

  // Conversion for storing details as Object*.
  explicit inline PropertyDetails(Smi* smi);
  inline Smi* AsSmi();

  PropertyType type() { return TypeField::decode(value_); }

  PropertyAttributes attributes() const {
    return AttributesField::decode(value_);
  }

  int dictionary_index() {
    return DictionaryStorageField::decode(value_);
  }

  int descriptor_index() {
    return DescriptorStorageField::decode(value_);
  }

  inline PropertyDetails AsDeleted();

  static bool IsValidIndex(int index) {
    return DictionaryStorageField::is_valid(index);
  }

  bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }
  bool IsDontDelete() const { return (attributes() & DONT_DELETE) != 0; }
  bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }
  bool IsDeleted() const { return DeletedField::decode(value_) != 0;}

  // Bit fields in value_ (type, shift, size). Must be public so the
  // constants can be embedded in generated code.
  class TypeField:                public BitField<PropertyType,       0,  3> {};
  class AttributesField:          public BitField<PropertyAttributes, 3,  3> {};
  class DeletedField:             public BitField<uint32_t,           6,  1> {};
  class DictionaryStorageField:   public BitField<uint32_t,           7, 24> {};
  class DescriptorStorageField:   public BitField<uint32_t,           7, 11> {};
  class DescriptorPointer:        public BitField<uint32_t,          18, 11> {};

  static const int kInitialIndex = 1;

 private:
  PropertyDetails(int value, int pointer) {
      value_ = DescriptorPointer::update(value, pointer);
  }

  uint32_t value_;
};

} }  // namespace v8::internal

#endif  // V8_PROPERTY_DETAILS_H_