ieee754.h

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//
// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
//
// Licensed under the MIT License (the "License"); you may not use this file except
// in compliance with the License. You may obtain a copy of the License at
//
// http://opensource.org/licenses/MIT
//
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// specific language governing permissions and limitations under the License.

#ifndef RAPIDJSON_IEEE754_
#define RAPIDJSON_IEEE754_

#include "../rapidjson.h"

RAPIDJSON_NAMESPACE_BEGIN
namespace internal
{
class Double
{
public:
  Double()
  {
  }
  Double(double d) : d_(d)
  {
  }
  Double(uint64_t u) : u_(u)
  {
  }

  double Value() const
  {
    return d_;
  }
  uint64_t Uint64Value() const
  {
    return u_;
  }

  double NextPositiveDouble() const
  {
    RAPIDJSON_ASSERT(!Sign());
    return Double(u_ + 1).Value();
  }

  bool Sign() const
  {
    return (u_ & kSignMask) != 0;
  }
  uint64_t Significand() const
  {
    return u_ & kSignificandMask;
  }
  int Exponent() const
  {
    return static_cast<int>(((u_ & kExponentMask) >> kSignificandSize) - kExponentBias);
  }

  bool IsNan() const
  {
    return (u_ & kExponentMask) == kExponentMask && Significand() != 0;
  }
  bool IsInf() const
  {
    return (u_ & kExponentMask) == kExponentMask && Significand() == 0;
  }
  bool IsNanOrInf() const
  {
    return (u_ & kExponentMask) == kExponentMask;
  }
  bool IsNormal() const
  {
    return (u_ & kExponentMask) != 0 || Significand() == 0;
  }
  bool IsZero() const
  {
    return (u_ & (kExponentMask | kSignificandMask)) == 0;
  }

  uint64_t IntegerSignificand() const
  {
    return IsNormal() ? Significand() | kHiddenBit : Significand();
  }
  int IntegerExponent() const
  {
    return (IsNormal() ? Exponent() : kDenormalExponent) - kSignificandSize;
  }
  uint64_t ToBias() const
  {
    return (u_ & kSignMask) ? ~u_ + 1 : u_ | kSignMask;
  }

  static int EffectiveSignificandSize(int order)
  {
    if (order >= -1021)
      return 53;
    else if (order <= -1074)
      return 0;
    else
      return order + 1074;
  }

private:
  static const int kSignificandSize = 52;
  static const int kExponentBias = 0x3FF;
  static const int kDenormalExponent = 1 - kExponentBias;
  static const uint64_t kSignMask = RAPIDJSON_UINT64_C2(0x80000000, 0x00000000);
  static const uint64_t kExponentMask = RAPIDJSON_UINT64_C2(0x7FF00000, 0x00000000);
  static const uint64_t kSignificandMask = RAPIDJSON_UINT64_C2(0x000FFFFF, 0xFFFFFFFF);
  static const uint64_t kHiddenBit = RAPIDJSON_UINT64_C2(0x00100000, 0x00000000);

  union
  {
    double d_;
    uint64_t u_;
  };
};

}  // namespace internal
RAPIDJSON_NAMESPACE_END

#endif  // RAPIDJSON_IEEE754_