michael@0: // Copyright 2010 the V8 project authors. All rights reserved.
michael@0: // Redistribution and use in source and binary forms, with or without
michael@0: // modification, are permitted provided that the following conditions are
michael@0: // met:
michael@0: //
michael@0: //     * Redistributions of source code must retain the above copyright
michael@0: //       notice, this list of conditions and the following disclaimer.
michael@0: //     * Redistributions in binary form must reproduce the above
michael@0: //       copyright notice, this list of conditions and the following
michael@0: //       disclaimer in the documentation and/or other materials provided
michael@0: //       with the distribution.
michael@0: //     * Neither the name of Google Inc. nor the names of its
michael@0: //       contributors may be used to endorse or promote products derived
michael@0: //       from this software without specific prior written permission.
michael@0: //
michael@0: // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0: // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0: // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
michael@0: // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
michael@0: // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
michael@0: // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
michael@0: // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
michael@0: // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
michael@0: // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
michael@0: // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
michael@0: // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0: 
michael@0: #ifndef DOUBLE_CONVERSION_BIGNUM_H_
michael@0: #define DOUBLE_CONVERSION_BIGNUM_H_
michael@0: 
michael@0: #include "utils.h"
michael@0: 
michael@0: namespace double_conversion {
michael@0: 
michael@0: class Bignum {
michael@0:  public:
michael@0:   // 3584 = 128 * 28. We can represent 2^3584 > 10^1000 accurately.
michael@0:   // This bignum can encode much bigger numbers, since it contains an
michael@0:   // exponent.
michael@0:   static const int kMaxSignificantBits = 3584;
michael@0: 
michael@0:   Bignum();
michael@0:   void AssignUInt16(uint16_t value);
michael@0:   void AssignUInt64(uint64_t value);
michael@0:   void AssignBignum(const Bignum& other);
michael@0: 
michael@0:   void AssignDecimalString(Vector<const char> value);
michael@0:   void AssignHexString(Vector<const char> value);
michael@0: 
michael@0:   void AssignPowerUInt16(uint16_t base, int exponent);
michael@0: 
michael@0:   void AddUInt16(uint16_t operand);
michael@0:   void AddUInt64(uint64_t operand);
michael@0:   void AddBignum(const Bignum& other);
michael@0:   // Precondition: this >= other.
michael@0:   void SubtractBignum(const Bignum& other);
michael@0: 
michael@0:   void Square();
michael@0:   void ShiftLeft(int shift_amount);
michael@0:   void MultiplyByUInt32(uint32_t factor);
michael@0:   void MultiplyByUInt64(uint64_t factor);
michael@0:   void MultiplyByPowerOfTen(int exponent);
michael@0:   void Times10() { return MultiplyByUInt32(10); }
michael@0:   // Pseudocode:
michael@0:   //  int result = this / other;
michael@0:   //  this = this % other;
michael@0:   // In the worst case this function is in O(this/other).
michael@0:   uint16_t DivideModuloIntBignum(const Bignum& other);
michael@0: 
michael@0:   bool ToHexString(char* buffer, int buffer_size) const;
michael@0: 
michael@0:   // Returns
michael@0:   //  -1 if a < b,
michael@0:   //   0 if a == b, and
michael@0:   //  +1 if a > b.
michael@0:   static int Compare(const Bignum& a, const Bignum& b);
michael@0:   static bool Equal(const Bignum& a, const Bignum& b) {
michael@0:     return Compare(a, b) == 0;
michael@0:   }
michael@0:   static bool LessEqual(const Bignum& a, const Bignum& b) {
michael@0:     return Compare(a, b) <= 0;
michael@0:   }
michael@0:   static bool Less(const Bignum& a, const Bignum& b) {
michael@0:     return Compare(a, b) < 0;
michael@0:   }
michael@0:   // Returns Compare(a + b, c);
michael@0:   static int PlusCompare(const Bignum& a, const Bignum& b, const Bignum& c);
michael@0:   // Returns a + b == c
michael@0:   static bool PlusEqual(const Bignum& a, const Bignum& b, const Bignum& c) {
michael@0:     return PlusCompare(a, b, c) == 0;
michael@0:   }
michael@0:   // Returns a + b <= c
michael@0:   static bool PlusLessEqual(const Bignum& a, const Bignum& b, const Bignum& c) {
michael@0:     return PlusCompare(a, b, c) <= 0;
michael@0:   }
michael@0:   // Returns a + b < c
michael@0:   static bool PlusLess(const Bignum& a, const Bignum& b, const Bignum& c) {
michael@0:     return PlusCompare(a, b, c) < 0;
michael@0:   }
michael@0:  private:
michael@0:   typedef uint32_t Chunk;
michael@0:   typedef uint64_t DoubleChunk;
michael@0: 
michael@0:   static const int kChunkSize = sizeof(Chunk) * 8;
michael@0:   static const int kDoubleChunkSize = sizeof(DoubleChunk) * 8;
michael@0:   // With bigit size of 28 we loose some bits, but a double still fits easily
michael@0:   // into two chunks, and more importantly we can use the Comba multiplication.
michael@0:   static const int kBigitSize = 28;
michael@0:   static const Chunk kBigitMask = (1 << kBigitSize) - 1;
michael@0:   // Every instance allocates kBigitLength chunks on the stack. Bignums cannot
michael@0:   // grow. There are no checks if the stack-allocated space is sufficient.
michael@0:   static const int kBigitCapacity = kMaxSignificantBits / kBigitSize;
michael@0: 
michael@0:   void EnsureCapacity(int size) {
michael@0:     if (size > kBigitCapacity) {
michael@0:       UNREACHABLE();
michael@0:     }
michael@0:   }
michael@0:   void Align(const Bignum& other);
michael@0:   void Clamp();
michael@0:   bool IsClamped() const;
michael@0:   void Zero();
michael@0:   // Requires this to have enough capacity (no tests done).
michael@0:   // Updates used_digits_ if necessary.
michael@0:   // shift_amount must be < kBigitSize.
michael@0:   void BigitsShiftLeft(int shift_amount);
michael@0:   // BigitLength includes the "hidden" digits encoded in the exponent.
michael@0:   int BigitLength() const { return used_digits_ + exponent_; }
michael@0:   Chunk BigitAt(int index) const;
michael@0:   void SubtractTimes(const Bignum& other, int factor);
michael@0: 
michael@0:   Chunk bigits_buffer_[kBigitCapacity];
michael@0:   // A vector backed by bigits_buffer_. This way accesses to the array are
michael@0:   // checked for out-of-bounds errors.
michael@0:   Vector<Chunk> bigits_;
michael@0:   int used_digits_;
michael@0:   // The Bignum's value equals value(bigits_) * 2^(exponent_ * kBigitSize).
michael@0:   int exponent_;
michael@0: 
michael@0:   DISALLOW_COPY_AND_ASSIGN(Bignum);
michael@0: };
michael@0: 
michael@0: }  // namespace double_conversion
michael@0: 
michael@0: #endif  // DOUBLE_CONVERSION_BIGNUM_H_