1// Tencent is pleased to support the open source community by making RapidJSON available.
2//
3// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
4//
5// Licensed under the MIT License (the "License"); you may not use this file except
6// in compliance with the License. You may obtain a copy of the License at
7//
8// http://opensource.org/licenses/MIT
9//
10// Unless required by applicable law or agreed to in writing, software distributed
11// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
12// CONDITIONS OF ANY KIND, either express or implied. See the License for the
13// specific language governing permissions and limitations under the License.
14
15#ifndef RAPIDJSON_IEEE754_
16#define RAPIDJSON_IEEE754_
17
18#include "../rapidjson.h"
19
20RAPIDJSON_NAMESPACE_BEGIN
21namespace internal {
22
23class Double {
24public:
25    Double() {}
26    explicit Double(double d) : d_(d) {}
27    explicit Double(uint64_t u) : u_(u) {}
28
29    double Value() const { return d_; }
30    uint64_t Uint64Value() const { return u_; }
31
32    double NextPositiveDouble() const {
33        RAPIDJSON_ASSERT(!Sign());
34        return Double(u_ + 1).Value();
35    }
36
37    bool Sign() const { return (u_ & kSignMask) != 0; }
38    uint64_t Significand() const { return u_ & kSignificandMask; }
39    int Exponent() const { return static_cast<int>(((u_ & kExponentMask) >> kSignificandSize) - kExponentBias); }
40
41    bool IsNan() const { return (u_ & kExponentMask) == kExponentMask && Significand() != 0; }
42    bool IsInf() const { return (u_ & kExponentMask) == kExponentMask && Significand() == 0; }
43    bool IsNormal() const { return (u_ & kExponentMask) != 0 || Significand() == 0; }
44    bool IsZero() const { return (u_ & (kExponentMask | kSignificandMask)) == 0; }
45
46    uint64_t IntegerSignificand() const { return IsNormal() ? Significand() | kHiddenBit : Significand(); }
47    int IntegerExponent() const { return (IsNormal() ? Exponent() : kDenormalExponent) - kSignificandSize; }
48    uint64_t ToBias() const { return (u_ & kSignMask) ? ~u_ + 1 : u_ | kSignMask; }
49
50    static unsigned EffectiveSignificandSize(int order) {
51        if (order >= -1021)
52            return 53;
53        else if (order <= -1074)
54            return 0;
55        else
56            return (unsigned)order + 1074;
57    }
58
59private:
60    static const int kSignificandSize = 52;
61    static const int kExponentBias = 0x3FF;
62    static const int kDenormalExponent = 1 - kExponentBias;
63    static const uint64_t kSignMask = RAPIDJSON_UINT64_C2(0x80000000, 0x00000000);
64    static const uint64_t kExponentMask = RAPIDJSON_UINT64_C2(0x7FF00000, 0x00000000);
65    static const uint64_t kSignificandMask = RAPIDJSON_UINT64_C2(0x000FFFFF, 0xFFFFFFFF);
66    static const uint64_t kHiddenBit = RAPIDJSON_UINT64_C2(0x00100000, 0x00000000);
67
68    union {
69        double d_;
70        uint64_t u_;
71    };
72};
73
74} // namespace internal
75RAPIDJSON_NAMESPACE_END
76
77#endif // RAPIDJSON_IEEE754_
78