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_DIY_FP_H_
michael@0: #define DOUBLE_CONVERSION_DIY_FP_H_
michael@0: 
michael@0: #include "utils.h"
michael@0: 
michael@0: namespace double_conversion {
michael@0: 
michael@0: // This "Do It Yourself Floating Point" class implements a floating-point number
michael@0: // with a uint64 significand and an int exponent. Normalized DiyFp numbers will
michael@0: // have the most significant bit of the significand set.
michael@0: // Multiplication and Subtraction do not normalize their results.
michael@0: // DiyFp are not designed to contain special doubles (NaN and Infinity).
michael@0: class DiyFp {
michael@0:  public:
michael@0:   static const int kSignificandSize = 64;
michael@0: 
michael@0:   DiyFp() : f_(0), e_(0) {}
michael@0:   DiyFp(uint64_t f, int e) : f_(f), e_(e) {}
michael@0: 
michael@0:   // this = this - other.
michael@0:   // The exponents of both numbers must be the same and the significand of this
michael@0:   // must be bigger than the significand of other.
michael@0:   // The result will not be normalized.
michael@0:   void Subtract(const DiyFp& other) {
michael@0:     ASSERT(e_ == other.e_);
michael@0:     ASSERT(f_ >= other.f_);
michael@0:     f_ -= other.f_;
michael@0:   }
michael@0: 
michael@0:   // Returns a - b.
michael@0:   // The exponents of both numbers must be the same and this must be bigger
michael@0:   // than other. The result will not be normalized.
michael@0:   static DiyFp Minus(const DiyFp& a, const DiyFp& b) {
michael@0:     DiyFp result = a;
michael@0:     result.Subtract(b);
michael@0:     return result;
michael@0:   }
michael@0: 
michael@0: 
michael@0:   // this = this * other.
michael@0:   void Multiply(const DiyFp& other);
michael@0: 
michael@0:   // returns a * b;
michael@0:   static DiyFp Times(const DiyFp& a, const DiyFp& b) {
michael@0:     DiyFp result = a;
michael@0:     result.Multiply(b);
michael@0:     return result;
michael@0:   }
michael@0: 
michael@0:   void Normalize() {
michael@0:     ASSERT(f_ != 0);
michael@0:     uint64_t f = f_;
michael@0:     int e = e_;
michael@0: 
michael@0:     // This method is mainly called for normalizing boundaries. In general
michael@0:     // boundaries need to be shifted by 10 bits. We thus optimize for this case.
michael@0:     const uint64_t k10MSBits = UINT64_2PART_C(0xFFC00000, 00000000);
michael@0:     while ((f & k10MSBits) == 0) {
michael@0:       f <<= 10;
michael@0:       e -= 10;
michael@0:     }
michael@0:     while ((f & kUint64MSB) == 0) {
michael@0:       f <<= 1;
michael@0:       e--;
michael@0:     }
michael@0:     f_ = f;
michael@0:     e_ = e;
michael@0:   }
michael@0: 
michael@0:   static DiyFp Normalize(const DiyFp& a) {
michael@0:     DiyFp result = a;
michael@0:     result.Normalize();
michael@0:     return result;
michael@0:   }
michael@0: 
michael@0:   uint64_t f() const { return f_; }
michael@0:   int e() const { return e_; }
michael@0: 
michael@0:   void set_f(uint64_t new_value) { f_ = new_value; }
michael@0:   void set_e(int new_value) { e_ = new_value; }
michael@0: 
michael@0:  private:
michael@0:   static const uint64_t kUint64MSB = UINT64_2PART_C(0x80000000, 00000000);
michael@0: 
michael@0:   uint64_t f_;
michael@0:   int e_;
michael@0: };
michael@0: 
michael@0: }  // namespace double_conversion
michael@0: 
michael@0: #endif  // DOUBLE_CONVERSION_DIY_FP_H_