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36 // 3584 = 128 * 28. We can represent 2^3584 > 10^1000 accurately.
37 // This bignum can encode much bigger numbers, since it contains an
39 static const int kMaxSignificantBits = 3584;
42 void AssignUInt16(uint16_t value);
43 void AssignUInt64(uint64_t value);
44 void AssignBignum(const Bignum& other);
46 void AssignDecimalString(Vector<const char> value);
47 void AssignHexString(Vector<const char> value);
49 void AssignPowerUInt16(uint16_t base, int exponent);
51 void AddUInt16(uint16_t operand);
52 void AddUInt64(uint64_t operand);
53 void AddBignum(const Bignum& other);
54 // Precondition: this >= other.
55 void SubtractBignum(const Bignum& other);
58 void ShiftLeft(int shift_amount);
59 void MultiplyByUInt32(uint32_t factor);
60 void MultiplyByUInt64(uint64_t factor);
61 void MultiplyByPowerOfTen(int exponent);
62 void Times10() { return MultiplyByUInt32(10); }
64 // int result = this / other;
65 // this = this % other;
66 // In the worst case this function is in O(this/other).
67 uint16_t DivideModuloIntBignum(const Bignum& other);
69 bool ToHexString(char* buffer, int buffer_size) const;
71 static int Compare(const Bignum& a, const Bignum& b);
72 static bool Equal(const Bignum& a, const Bignum& b) {
73 return Compare(a, b) == 0;
75 static bool LessEqual(const Bignum& a, const Bignum& b) {
76 return Compare(a, b) <= 0;
78 static bool Less(const Bignum& a, const Bignum& b) {
79 return Compare(a, b) < 0;
81 // Returns Compare(a + b, c);
82 static int PlusCompare(const Bignum& a, const Bignum& b, const Bignum& c);
84 static bool PlusEqual(const Bignum& a, const Bignum& b, const Bignum& c) {
85 return PlusCompare(a, b, c) == 0;
88 static bool PlusLessEqual(const Bignum& a, const Bignum& b, const Bignum& c) {
89 return PlusCompare(a, b, c) <= 0;
92 static bool PlusLess(const Bignum& a, const Bignum& b, const Bignum& c) {
93 return PlusCompare(a, b, c) < 0;
97 typedef uint32_t Chunk;
98 typedef uint64_t DoubleChunk;
100 static const int kChunkSize = sizeof(Chunk) * 8;
101 static const int kDoubleChunkSize = sizeof(DoubleChunk) * 8;
102 // With bigit size of 28 we loose some bits, but a double still fits easily
103 // into two chunks, and more importantly we can use the Comba multiplication.
104 static const int kBigitSize = 28;
105 static const Chunk kBigitMask = (1 << kBigitSize) - 1;
106 // Every instance allocates kBigitLength chunks on the stack. Bignums cannot
107 // grow. There are no checks if the stack-allocated space is sufficient.
108 static const int kBigitCapacity = kMaxSignificantBits / kBigitSize;
110 void EnsureCapacity(int size) {
111 if (size > kBigitCapacity) {
115 void Align(const Bignum& other);
117 bool IsClamped() const;
119 // Requires this to have enough capacity (no tests done).
120 // Updates used_digits_ if necessary.
121 // by must be < kBigitSize.
122 void BigitsShiftLeft(int shift_amount);
123 // BigitLength includes the "hidden" digits encoded in the exponent.
124 int BigitLength() const { return used_digits_ + exponent_; }
125 Chunk BigitAt(int index) const;
126 void SubtractTimes(const Bignum& other, int factor);
128 Chunk bigits_buffer_[kBigitCapacity];
129 // A vector backed by bigits_buffer_. This way accesses to the array are
130 // checked for out-of-bounds errors.
131 Vector<Chunk> bigits_;
133 // The Bignum's value equals value(bigits_) * 2^(exponent_ * kBigitSize).
136 DISALLOW_COPY_AND_ASSIGN(Bignum);
139 } } // namespace v8::internal
141 #endif // V8_BIGNUM_H_