// 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_BIGINT_H_ #define V8_OBJECTS_BIGINT_H_ #include "src/globals.h" #include "src/objects.h" #include "src/objects/heap-object.h" #include "src/utils.h" // Has to be the last include (doesn't have include guards): #include "src/objects/object-macros.h" namespace v8 { namespace internal { class BigInt; class ValueDeserializer; class ValueSerializer; // BigIntBase is just the raw data object underlying a BigInt. Use with care! // Most code should be using BigInts instead. class BigIntBase : public HeapObject { public: inline int length() const { int32_t bitfield = RELAXED_READ_INT32_FIELD(*this, kBitfieldOffset); return LengthBits::decode(static_cast<uint32_t>(bitfield)); } // For use by the GC. inline int synchronized_length() const { int32_t bitfield = ACQUIRE_READ_INT32_FIELD(*this, kBitfieldOffset); return LengthBits::decode(static_cast<uint32_t>(bitfield)); } static inline BigIntBase unchecked_cast(Object o) { return bit_cast<BigIntBase>(o); } // The maximum kMaxLengthBits that the current implementation supports // would be kMaxInt - kSystemPointerSize * kBitsPerByte - 1. // Since we want a platform independent limit, choose a nice round number // somewhere below that maximum. static const int kMaxLengthBits = 1 << 30; // ~1 billion. static const int kMaxLength = kMaxLengthBits / (kSystemPointerSize * kBitsPerByte); // Sign and length are stored in the same bitfield. Since the GC needs to be // able to read the length concurrently, the getters and setters are atomic. static const int kLengthFieldBits = 30; STATIC_ASSERT(kMaxLength <= ((1 << kLengthFieldBits) - 1)); class SignBits : public BitField<bool, 0, 1> {}; class LengthBits : public BitField<int, SignBits::kNext, kLengthFieldBits> {}; STATIC_ASSERT(LengthBits::kNext <= 32); // Layout description. #define BIGINT_FIELDS(V) \ V(kBitfieldOffset, kInt32Size) \ V(kOptionalPaddingOffset, POINTER_SIZE_PADDING(kOptionalPaddingOffset)) \ /* Header size. */ \ V(kHeaderSize, 0) \ V(kDigitsOffset, 0) DEFINE_FIELD_OFFSET_CONSTANTS(HeapObject::kHeaderSize, BIGINT_FIELDS) #undef BIGINT_FIELDS private: friend class ::v8::internal::BigInt; // MSVC wants full namespace. friend class MutableBigInt; using digit_t = uintptr_t; static const int kDigitSize = sizeof(digit_t); // kMaxLength definition assumes this: STATIC_ASSERT(kDigitSize == kSystemPointerSize); static const int kDigitBits = kDigitSize * kBitsPerByte; static const int kHalfDigitBits = kDigitBits / 2; static const digit_t kHalfDigitMask = (1ull << kHalfDigitBits) - 1; // sign() == true means negative. inline bool sign() const { int32_t bitfield = RELAXED_READ_INT32_FIELD(*this, kBitfieldOffset); return SignBits::decode(static_cast<uint32_t>(bitfield)); } inline digit_t digit(int n) const { SLOW_DCHECK(0 <= n && n < length()); return READ_UINTPTR_FIELD(*this, kDigitsOffset + n * kDigitSize); } bool is_zero() const { return length() == 0; } // Only serves to make macros happy; other code should use IsBigInt. bool IsBigIntBase() const { return true; } OBJECT_CONSTRUCTORS(BigIntBase, HeapObject); }; class FreshlyAllocatedBigInt : public BigIntBase { // This class is essentially the publicly accessible abstract version of // MutableBigInt (which is a hidden implementation detail). It serves as // the return type of Factory::NewBigInt, and makes it possible to enforce // casting restrictions: // - FreshlyAllocatedBigInt can be cast explicitly to MutableBigInt // (with MutableBigInt::Cast) for initialization. // - MutableBigInt can be cast/converted explicitly to BigInt // (with MutableBigInt::MakeImmutable); is afterwards treated as readonly. // - No accidental implicit casting is possible from BigInt to MutableBigInt // (and no explicit operator is provided either). public: inline static FreshlyAllocatedBigInt cast(Object object); inline static FreshlyAllocatedBigInt unchecked_cast(Object o) { return bit_cast<FreshlyAllocatedBigInt>(o); } // Clear uninitialized padding space. inline void clear_padding() { if (FIELD_SIZE(kOptionalPaddingOffset) != 0) { DCHECK_EQ(4, FIELD_SIZE(kOptionalPaddingOffset)); memset(reinterpret_cast<void*>(address() + kOptionalPaddingOffset), 0, FIELD_SIZE(kOptionalPaddingOffset)); } } private: // Only serves to make macros happy; other code should use IsBigInt. bool IsFreshlyAllocatedBigInt() const { return true; } OBJECT_CONSTRUCTORS(FreshlyAllocatedBigInt, BigIntBase); }; // Arbitrary precision integers in JavaScript. class BigInt : public BigIntBase { public: // Implementation of the Spec methods, see: // https://tc39.github.io/proposal-bigint/#sec-numeric-types // Sections 1.1.1 through 1.1.19. static Handle<BigInt> UnaryMinus(Isolate* isolate, Handle<BigInt> x); static MaybeHandle<BigInt> BitwiseNot(Isolate* isolate, Handle<BigInt> x); static MaybeHandle<BigInt> Exponentiate(Isolate* isolate, Handle<BigInt> base, Handle<BigInt> exponent); static MaybeHandle<BigInt> Multiply(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); static MaybeHandle<BigInt> Divide(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); static MaybeHandle<BigInt> Remainder(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); static MaybeHandle<BigInt> Add(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); static MaybeHandle<BigInt> Subtract(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); static MaybeHandle<BigInt> LeftShift(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); static MaybeHandle<BigInt> SignedRightShift(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); static MaybeHandle<BigInt> UnsignedRightShift(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); // More convenient version of "bool LessThan(x, y)". static ComparisonResult CompareToBigInt(Handle<BigInt> x, Handle<BigInt> y); static bool EqualToBigInt(BigInt x, BigInt y); static MaybeHandle<BigInt> BitwiseAnd(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); static MaybeHandle<BigInt> BitwiseXor(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); static MaybeHandle<BigInt> BitwiseOr(Isolate* isolate, Handle<BigInt> x, Handle<BigInt> y); // Other parts of the public interface. static MaybeHandle<BigInt> Increment(Isolate* isolate, Handle<BigInt> x); static MaybeHandle<BigInt> Decrement(Isolate* isolate, Handle<BigInt> x); bool ToBoolean() { return !is_zero(); } uint32_t Hash() { // TODO(jkummerow): Improve this. At least use length and sign. return is_zero() ? 0 : ComputeLongHash(static_cast<uint64_t>(digit(0))); } bool IsNegative() const { return sign(); } static bool EqualToString(Isolate* isolate, Handle<BigInt> x, Handle<String> y); static bool EqualToNumber(Handle<BigInt> x, Handle<Object> y); static ComparisonResult CompareToString(Isolate* isolate, Handle<BigInt> x, Handle<String> y); static ComparisonResult CompareToNumber(Handle<BigInt> x, Handle<Object> y); // Exposed for tests, do not call directly. Use CompareToNumber() instead. V8_EXPORT_PRIVATE static ComparisonResult CompareToDouble(Handle<BigInt> x, double y); static Handle<BigInt> AsIntN(Isolate* isolate, uint64_t n, Handle<BigInt> x); static MaybeHandle<BigInt> AsUintN(Isolate* isolate, uint64_t n, Handle<BigInt> x); static Handle<BigInt> FromInt64(Isolate* isolate, int64_t n); static Handle<BigInt> FromUint64(Isolate* isolate, uint64_t n); static MaybeHandle<BigInt> FromWords64(Isolate* isolate, int sign_bit, int words64_count, const uint64_t* words); int64_t AsInt64(bool* lossless = nullptr); uint64_t AsUint64(bool* lossless = nullptr); int Words64Count(); void ToWordsArray64(int* sign_bit, int* words64_count, uint64_t* words); DECL_CAST(BigInt) DECL_VERIFIER(BigInt) DECL_PRINTER(BigInt) void BigIntShortPrint(std::ostream& os); inline static int SizeFor(int length) { return kHeaderSize + length * kDigitSize; } static MaybeHandle<String> ToString(Isolate* isolate, Handle<BigInt> bigint, int radix = 10, ShouldThrow should_throw = kThrowOnError); // "The Number value for x", see: // https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type // Returns a Smi or HeapNumber. static Handle<Object> ToNumber(Isolate* isolate, Handle<BigInt> x); // ECMAScript's NumberToBigInt V8_EXPORT_PRIVATE static MaybeHandle<BigInt> FromNumber( Isolate* isolate, Handle<Object> number); // ECMAScript's ToBigInt (throws for Number input) static MaybeHandle<BigInt> FromObject(Isolate* isolate, Handle<Object> obj); class BodyDescriptor; private: friend class StringToBigIntHelper; friend class ValueDeserializer; friend class ValueSerializer; // Special functions for StringToBigIntHelper: static Handle<BigInt> Zero(Isolate* isolate); static MaybeHandle<FreshlyAllocatedBigInt> AllocateFor( Isolate* isolate, int radix, int charcount, ShouldThrow should_throw, AllocationType allocation); static void InplaceMultiplyAdd(Handle<FreshlyAllocatedBigInt> x, uintptr_t factor, uintptr_t summand); static Handle<BigInt> Finalize(Handle<FreshlyAllocatedBigInt> x, bool sign); // Special functions for ValueSerializer/ValueDeserializer: uint32_t GetBitfieldForSerialization() const; static int DigitsByteLengthForBitfield(uint32_t bitfield); // Expects {storage} to have a length of at least // {DigitsByteLengthForBitfield(GetBitfieldForSerialization())}. void SerializeDigits(uint8_t* storage); V8_WARN_UNUSED_RESULT static MaybeHandle<BigInt> FromSerializedDigits( Isolate* isolate, uint32_t bitfield, Vector<const uint8_t> digits_storage, AllocationType allocation); OBJECT_CONSTRUCTORS(BigInt, BigIntBase); }; } // namespace internal } // namespace v8 #include "src/objects/object-macros-undef.h" #endif // V8_OBJECTS_BIGINT_H_