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// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_OBJECTS_NAME_H_
#define V8_OBJECTS_NAME_H_
#include "src/objects.h"
#include "src/objects/heap-object.h"
#include "torque-generated/field-offsets-tq.h"
// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"
namespace v8 {
namespace internal {
// The Name abstract class captures anything that can be used as a property
// name, i.e., strings and symbols. All names store a hash value.
class Name : public HeapObject {
public:
// Get and set the hash field of the name.
inline uint32_t hash_field();
inline void set_hash_field(uint32_t value);
// Tells whether the hash code has been computed.
inline bool HasHashCode();
// Returns a hash value used for the property table
inline uint32_t Hash();
// Equality operations.
inline bool Equals(Name other);
inline static bool Equals(Isolate* isolate, Handle<Name> one,
Handle<Name> two);
// Conversion.
inline bool AsArrayIndex(uint32_t* index);
// An "interesting symbol" is a well-known symbol, like @@toStringTag,
// that's often looked up on random objects but is usually not present.
// We optimize this by setting a flag on the object's map when such
// symbol properties are added, so we can optimize lookups on objects
// that don't have the flag.
inline bool IsInterestingSymbol() const;
// If the name is private, it can only name own properties.
inline bool IsPrivate();
// If the name is a private name, it should behave like a private
// symbol but also throw on property access miss.
inline bool IsPrivateName();
inline bool IsUniqueName() const;
static inline bool ContainsCachedArrayIndex(uint32_t hash);
// Return a string version of this name that is converted according to the
// rules described in ES6 section 9.2.11.
V8_WARN_UNUSED_RESULT static MaybeHandle<String> ToFunctionName(
Isolate* isolate, Handle<Name> name);
V8_WARN_UNUSED_RESULT static MaybeHandle<String> ToFunctionName(
Isolate* isolate, Handle<Name> name, Handle<String> prefix);
DECL_CAST(Name)
DECL_PRINTER(Name)
void NameShortPrint();
int NameShortPrint(Vector<char> str);
DEFINE_FIELD_OFFSET_CONSTANTS(HeapObject::kHeaderSize,
TORQUE_GENERATED_NAME_FIELDS)
// Mask constant for checking if a name has a computed hash code
// and if it is a string that is an array index. The least significant bit
// indicates whether a hash code has been computed. If the hash code has
// been computed the 2nd bit tells whether the string can be used as an
// array index.
static const int kHashNotComputedMask = 1;
static const int kIsNotArrayIndexMask = 1 << 1;
static const int kNofHashBitFields = 2;
// Shift constant retrieving hash code from hash field.
static const int kHashShift = kNofHashBitFields;
// Only these bits are relevant in the hash, since the top two are shifted
// out.
static const uint32_t kHashBitMask = 0xffffffffu >> kHashShift;
// Array index strings this short can keep their index in the hash field.
static const int kMaxCachedArrayIndexLength = 7;
// Maximum number of characters to consider when trying to convert a string
// value into an array index.
static const int kMaxArrayIndexSize = 10;
// For strings which are array indexes the hash value has the string length
// mixed into the hash, mainly to avoid a hash value of zero which would be
// the case for the string '0'. 24 bits are used for the array index value.
static const int kArrayIndexValueBits = 24;
static const int kArrayIndexLengthBits =
kBitsPerInt - kArrayIndexValueBits - kNofHashBitFields;
STATIC_ASSERT(kArrayIndexLengthBits > 0);
STATIC_ASSERT(kMaxArrayIndexSize < (1 << kArrayIndexLengthBits));
class ArrayIndexValueBits
: public BitField<unsigned int, kNofHashBitFields, kArrayIndexValueBits> {
}; // NOLINT
class ArrayIndexLengthBits
: public BitField<unsigned int, kNofHashBitFields + kArrayIndexValueBits,
kArrayIndexLengthBits> {}; // NOLINT
// Check that kMaxCachedArrayIndexLength + 1 is a power of two so we
// could use a mask to test if the length of string is less than or equal to
// kMaxCachedArrayIndexLength.
static_assert(base::bits::IsPowerOfTwo(kMaxCachedArrayIndexLength + 1),
"(kMaxCachedArrayIndexLength + 1) must be power of two");
// When any of these bits is set then the hash field does not contain a cached
// array index.
static const unsigned int kDoesNotContainCachedArrayIndexMask =
(~static_cast<unsigned>(kMaxCachedArrayIndexLength)
<< ArrayIndexLengthBits::kShift) |
kIsNotArrayIndexMask;
// Value of empty hash field indicating that the hash is not computed.
static const int kEmptyHashField =
kIsNotArrayIndexMask | kHashNotComputedMask;
protected:
static inline bool IsHashFieldComputed(uint32_t field);
OBJECT_CONSTRUCTORS(Name, HeapObject);
};
// ES6 symbols.
class Symbol : public Name {
public:
// [name]: The print name of a symbol, or undefined if none.
DECL_ACCESSORS(name, Object)
DECL_INT_ACCESSORS(flags)
// [is_private]: Whether this is a private symbol. Private symbols can only
// be used to designate own properties of objects.
DECL_BOOLEAN_ACCESSORS(is_private)
// [is_well_known_symbol]: Whether this is a spec-defined well-known symbol,
// or not. Well-known symbols do not throw when an access check fails during
// a load.
DECL_BOOLEAN_ACCESSORS(is_well_known_symbol)
// [is_interesting_symbol]: Whether this is an "interesting symbol", which
// is a well-known symbol like @@toStringTag that's often looked up on
// random objects but is usually not present. See Name::IsInterestingSymbol()
// for a detailed description.
DECL_BOOLEAN_ACCESSORS(is_interesting_symbol)
// [is_public]: Whether this is a symbol created by Symbol.for. Calling
// Symbol.keyFor on such a symbol simply needs to return the attached name.
DECL_BOOLEAN_ACCESSORS(is_public)
// [is_private_name]: Whether this is a private name. Private names
// are the same as private symbols except they throw on missing
// property access.
//
// This also sets the is_private bit.
inline bool is_private_name() const;
inline void set_is_private_name();
DECL_CAST(Symbol)
// Dispatched behavior.
DECL_PRINTER(Symbol)
DECL_VERIFIER(Symbol)
DEFINE_FIELD_OFFSET_CONSTANTS(Name::kHeaderSize,
TORQUE_GENERATED_SYMBOL_FIELDS)
// Flags layout.
#define FLAGS_BIT_FIELDS(V, _) \
V(IsPrivateBit, bool, 1, _) \
V(IsWellKnownSymbolBit, bool, 1, _) \
V(IsPublicBit, bool, 1, _) \
V(IsInterestingSymbolBit, bool, 1, _) \
V(IsPrivateNameBit, bool, 1, _)
DEFINE_BIT_FIELDS(FLAGS_BIT_FIELDS)
#undef FLAGS_BIT_FIELDS
using BodyDescriptor = FixedBodyDescriptor<kNameOffset, kSize, kSize>;
void SymbolShortPrint(std::ostream& os);
private:
const char* PrivateSymbolToName() const;
// TODO(cbruni): remove once the new maptracer is in place.
friend class Name; // For PrivateSymbolToName.
OBJECT_CONSTRUCTORS(Symbol, Name);
};
} // namespace internal
} // namespace v8
#include "src/objects/object-macros-undef.h"
#endif // V8_OBJECTS_NAME_H_