ieee754.h

Go to the documentation of this file.

// Tencent is pleased to support the open source community by making RapidJSON
// available.
//
// 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
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the 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_