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 // Copyright 2010 the V8 project authors. All rights reserved.

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 // modification, are permitted provided that the following conditions are

 // met:

 //

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 //       from this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

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 #ifndef DOUBLE_CONVERSION_DIY_FP_H_

 #define DOUBLE_CONVERSION_DIY_FP_H_

 #include "utils.h"

 namespace double_conversion {

 // This "Do It Yourself Floating Point" class implements a floating-point number

 // with a uint64 significand and an int exponent. Normalized DiyFp numbers will

 // have the most significant bit of the significand set.

 // Multiplication and Subtraction do not normalize their results.

 // DiyFp are not designed to contain special doubles (NaN and Infinity).

 class DiyFp {

  public:

   static const int kSignificandSize = 64;

   DiyFp() : f_(0), e_(0) {}

   DiyFp(uint64_t f, int e) : f_(f), e_(e) {}

   // this = this - other.

   // The exponents of both numbers must be the same and the significand of this

   // must be bigger than the significand of other.

   // The result will not be normalized.

   void Subtract(const DiyFp& other) {

     ASSERT(e_ == other.e_);

     ASSERT(f_ >= other.f_);

     f_ -= other.f_;

   }

   // Returns a - b.

   // The exponents of both numbers must be the same and this must be bigger

   // than other. The result will not be normalized.

   static DiyFp Minus(const DiyFp& a, const DiyFp& b) {

     DiyFp result = a;

     result.Subtract(b);

     return result;

   }

   // this = this * other.

   void Multiply(const DiyFp& other);

   // returns a * b;

   static DiyFp Times(const DiyFp& a, const DiyFp& b) {

     DiyFp result = a;

     result.Multiply(b);

     return result;

   }

   void Normalize() {

     ASSERT(f_ != 0);

     uint64_t f = f_;

     int e = e_;

     // This method is mainly called for normalizing boundaries. In general

     // boundaries need to be shifted by 10 bits. We thus optimize for this case.

     const uint64_t k10MSBits = UINT64_2PART_C(0xFFC00000, 00000000);

     while ((f & k10MSBits) == 0) {

       f <<= 10;

       e -= 10;

     }

     while ((f & kUint64MSB) == 0) {

       f <<= 1;

       e--;

     }

     f_ = f;

     e_ = e;

   }

   static DiyFp Normalize(const DiyFp& a) {

     DiyFp result = a;

     result.Normalize();

     return result;

   }

   uint64_t f() const { return f_; }

   int e() const { return e_; }

   void set_f(uint64_t new_value) { f_ = new_value; }

   void set_e(int new_value) { e_ = new_value; }

  private:

   static const uint64_t kUint64MSB = UINT64_2PART_C(0x80000000, 00000000);

   uint64_t f_;

   int e_;

 };

 }  // namespace double_conversion

 #endif  // DOUBLE_CONVERSION_DIY_FP_H_