Russell Brenner | 90bac25 | 2010-11-18 13:33:46 -0800 | [diff] [blame] | 1 | // Copyright 2010 the V8 project authors. All rights reserved. |
Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
Russell Brenner | 90bac25 | 2010-11-18 13:33:46 -0800 | [diff] [blame] | 4 | |
| 5 | #ifndef V8_BIGNUM_H_ |
| 6 | #define V8_BIGNUM_H_ |
| 7 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 8 | #include "src/vector.h" |
| 9 | |
Russell Brenner | 90bac25 | 2010-11-18 13:33:46 -0800 | [diff] [blame] | 10 | namespace v8 { |
| 11 | namespace internal { |
| 12 | |
| 13 | class Bignum { |
| 14 | public: |
| 15 | // 3584 = 128 * 28. We can represent 2^3584 > 10^1000 accurately. |
| 16 | // This bignum can encode much bigger numbers, since it contains an |
| 17 | // exponent. |
| 18 | static const int kMaxSignificantBits = 3584; |
| 19 | |
| 20 | Bignum(); |
| 21 | void AssignUInt16(uint16_t value); |
| 22 | void AssignUInt64(uint64_t value); |
| 23 | void AssignBignum(const Bignum& other); |
| 24 | |
| 25 | void AssignDecimalString(Vector<const char> value); |
| 26 | void AssignHexString(Vector<const char> value); |
| 27 | |
| 28 | void AssignPowerUInt16(uint16_t base, int exponent); |
| 29 | |
| 30 | void AddUInt16(uint16_t operand); |
| 31 | void AddUInt64(uint64_t operand); |
| 32 | void AddBignum(const Bignum& other); |
| 33 | // Precondition: this >= other. |
| 34 | void SubtractBignum(const Bignum& other); |
| 35 | |
| 36 | void Square(); |
| 37 | void ShiftLeft(int shift_amount); |
| 38 | void MultiplyByUInt32(uint32_t factor); |
| 39 | void MultiplyByUInt64(uint64_t factor); |
| 40 | void MultiplyByPowerOfTen(int exponent); |
| 41 | void Times10() { return MultiplyByUInt32(10); } |
| 42 | // Pseudocode: |
| 43 | // int result = this / other; |
| 44 | // this = this % other; |
| 45 | // In the worst case this function is in O(this/other). |
| 46 | uint16_t DivideModuloIntBignum(const Bignum& other); |
| 47 | |
| 48 | bool ToHexString(char* buffer, int buffer_size) const; |
| 49 | |
| 50 | static int Compare(const Bignum& a, const Bignum& b); |
| 51 | static bool Equal(const Bignum& a, const Bignum& b) { |
| 52 | return Compare(a, b) == 0; |
| 53 | } |
| 54 | static bool LessEqual(const Bignum& a, const Bignum& b) { |
| 55 | return Compare(a, b) <= 0; |
| 56 | } |
| 57 | static bool Less(const Bignum& a, const Bignum& b) { |
| 58 | return Compare(a, b) < 0; |
| 59 | } |
| 60 | // Returns Compare(a + b, c); |
| 61 | static int PlusCompare(const Bignum& a, const Bignum& b, const Bignum& c); |
| 62 | // Returns a + b == c |
| 63 | static bool PlusEqual(const Bignum& a, const Bignum& b, const Bignum& c) { |
| 64 | return PlusCompare(a, b, c) == 0; |
| 65 | } |
| 66 | // Returns a + b <= c |
| 67 | static bool PlusLessEqual(const Bignum& a, const Bignum& b, const Bignum& c) { |
| 68 | return PlusCompare(a, b, c) <= 0; |
| 69 | } |
| 70 | // Returns a + b < c |
| 71 | static bool PlusLess(const Bignum& a, const Bignum& b, const Bignum& c) { |
| 72 | return PlusCompare(a, b, c) < 0; |
| 73 | } |
Ben Murdoch | 589d697 | 2011-11-30 16:04:58 +0000 | [diff] [blame] | 74 | |
Russell Brenner | 90bac25 | 2010-11-18 13:33:46 -0800 | [diff] [blame] | 75 | private: |
| 76 | typedef uint32_t Chunk; |
| 77 | typedef uint64_t DoubleChunk; |
| 78 | |
| 79 | static const int kChunkSize = sizeof(Chunk) * 8; |
| 80 | static const int kDoubleChunkSize = sizeof(DoubleChunk) * 8; |
| 81 | // With bigit size of 28 we loose some bits, but a double still fits easily |
| 82 | // into two chunks, and more importantly we can use the Comba multiplication. |
| 83 | static const int kBigitSize = 28; |
| 84 | static const Chunk kBigitMask = (1 << kBigitSize) - 1; |
| 85 | // Every instance allocates kBigitLength chunks on the stack. Bignums cannot |
| 86 | // grow. There are no checks if the stack-allocated space is sufficient. |
| 87 | static const int kBigitCapacity = kMaxSignificantBits / kBigitSize; |
| 88 | |
| 89 | void EnsureCapacity(int size) { |
| 90 | if (size > kBigitCapacity) { |
| 91 | UNREACHABLE(); |
| 92 | } |
| 93 | } |
| 94 | void Align(const Bignum& other); |
| 95 | void Clamp(); |
| 96 | bool IsClamped() const; |
| 97 | void Zero(); |
| 98 | // Requires this to have enough capacity (no tests done). |
| 99 | // Updates used_digits_ if necessary. |
| 100 | // by must be < kBigitSize. |
| 101 | void BigitsShiftLeft(int shift_amount); |
| 102 | // BigitLength includes the "hidden" digits encoded in the exponent. |
| 103 | int BigitLength() const { return used_digits_ + exponent_; } |
| 104 | Chunk BigitAt(int index) const; |
| 105 | void SubtractTimes(const Bignum& other, int factor); |
| 106 | |
| 107 | Chunk bigits_buffer_[kBigitCapacity]; |
| 108 | // A vector backed by bigits_buffer_. This way accesses to the array are |
| 109 | // checked for out-of-bounds errors. |
| 110 | Vector<Chunk> bigits_; |
| 111 | int used_digits_; |
| 112 | // The Bignum's value equals value(bigits_) * 2^(exponent_ * kBigitSize). |
| 113 | int exponent_; |
| 114 | |
| 115 | DISALLOW_COPY_AND_ASSIGN(Bignum); |
| 116 | }; |
| 117 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 118 | } // namespace internal |
| 119 | } // namespace v8 |
Russell Brenner | 90bac25 | 2010-11-18 13:33:46 -0800 | [diff] [blame] | 120 | |
| 121 | #endif // V8_BIGNUM_H_ |