summaryrefslogtreecommitdiff
path: root/src/mongo/util/safe_num.h
blob: 500429857a32693e3bd089a0926d9b2a23562b8c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249

/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the Server Side Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#pragma once

#include <iosfwd>
#include <string>

#include "mongo/db/jsobj.h"

namespace mongo {

namespace mutablebson {
class Element;
class Document;
}

/**
 * SafeNum holds and does arithmetic on a number in a safe way, handling overflow
 * and casting for the user. 32-bit integers will overflow into 64-bit integers. But
 * 64-bit integers will NOT overflow to doubles. Also, this class does NOT
 * downcast. Doubles will NOT overflow to decimal, but mixed type arithmetic with a decimal
 * will. This class should be as conservative as possible about upcasting, but
 * should never lose precision.
 *
 * This class does not throw any exceptions, so the user should call type() before
 * using a SafeNum to ensure that it is valid.  A SafeNum could be invalid
 * from creation (if, for example, a non-numeric BSONElement was passed to the
 * constructor) or due to overflow.  NAN is a valid value.
 *
 * Usage example:
 *
 *      SafeNum counter(doc["count"]);
 *
 *      SafeNum newValue = counter + 10;
 *      // check if valid
 *      if (newValue.type() == EOO) {
 *          return;
 *      }
 *      // append SafeNum to a BSONObj
 *      bsonObjBuilder.append(newValue);
 *
 */
class SafeNum {
public:
    SafeNum();
    ~SafeNum();

    //
    // construction support
    //

    // Copy ctor and assignment are allowed.
    SafeNum(const SafeNum& rhs);
    SafeNum& operator=(const SafeNum& rhs);

    // These implicit conversions are allowed.
    SafeNum(const BSONElement& element);
    SafeNum(int32_t num);
    SafeNum(int64_t num);
    SafeNum(double num);
    SafeNum(Decimal128 num);

    // Other/Implicit conversions are not allowed.
    template <typename T>
    SafeNum(T t) = delete;

    // TODO: add Paul's mutablebson::Element ctor

    //
    // comparison support
    //

    /**
     * Returns true if the numeric quantity of 'rhs' and 'this' are the same. That is,
     * an int32(10), an int64(10), a double(10), and a decimal(10) are equivalent. An
     * EOO-typed safe num is equivalent only to another EOO-typed instance. Otherwise,
     * returns false.
     */
    bool isEquivalent(const SafeNum& rhs) const;
    bool operator==(const SafeNum& rhs) const;
    bool operator!=(const SafeNum& rhs) const;

    /**
     * Returns true if 'rsh' is equivalent to 'this' (see isEquivalent) _and_ both
     * types are exactly the same. An EOO-typed safe num is never identical to
     * anything else, even another EOO-typed instance. Otherwise, returns false.
     */
    bool isIdentical(const SafeNum& rhs) const;

    //
    // arithmetic support
    //

    /**
     * Sums the 'rhs' -- right-hand side -- safe num with this, taking care of
     * upconversions and overflow (see class header).
     */
    SafeNum operator+(const SafeNum& rhs) const;
    SafeNum& operator+=(const SafeNum& rhs);

    /**
     * Multiplies the 'rhs' -- right-hand side -- safe num with this, taking care of
     * upconversions and overflow (see class header).
     */
    SafeNum operator*(const SafeNum& rhs) const;
    SafeNum& operator*=(const SafeNum& rhs);

    //
    // logical operation support. Note that these operations are only supported for
    // integral types. Attempts to apply with either side holding a double or decimal
    // value will result in an EOO typed safenum.
    //

    // Bitwise 'and' support
    SafeNum bitAnd(const SafeNum& rhs) const;
    SafeNum operator&(const SafeNum& rhs) const;
    SafeNum& operator&=(const SafeNum& rhs);

    // Bitwise 'or' support
    SafeNum bitOr(const SafeNum& rhs) const;
    SafeNum operator|(const SafeNum& rhs) const;
    SafeNum& operator|=(const SafeNum& rhs);

    // Bitwise 'xor' support
    SafeNum bitXor(const SafeNum& rhs) const;
    SafeNum operator^(const SafeNum& rhs) const;
    SafeNum& operator^=(const SafeNum& rhs);


    //
    // output support
    //

    friend class mutablebson::Element;
    friend class mutablebson::Document;

    // TODO: output to builder

    //
    // accessors
    //
    bool isValid() const;
    BSONType type() const;
    std::string debugString() const;

    //
    // Below exposed for testing purposes. Treat as private.
    //

    // Maximum integer that can be converted accuratelly into a double, assuming a
    // double precission IEEE 754 representation.
    // TODO use numeric_limits to make this portable
    static const int64_t maxIntInDouble = 9007199254740992LL;  // 2^53

private:
    // One of the following: NumberInt, NumberLong, NumberDouble, NumberDecimal, or EOO.
    BSONType _type;

    // Value of the safe num. Indeterminate if _type is EOO.
    union {
        int32_t int32Val;
        int64_t int64Val;
        double doubleVal;
        Decimal128::Value decimalVal;
    } _value;

    /**
     * Returns the sum of 'lhs' and 'rhs', taking into consideration their types. The
     * type of the result would upcast, if necessary and permitted. Otherwise, returns
     * an EOO-type instance.
     */
    static SafeNum addInternal(const SafeNum& lhs, const SafeNum& rhs);

    /**
     * Returns the product of 'lhs' and 'rhs', taking into consideration their types. The
     * type of the result would upcast, if necessary and permitted. Otherwise, returns an
     * EOO-type instance.
     */
    static SafeNum mulInternal(const SafeNum& lhs, const SafeNum& rhs);

    /** Returns the bitwise 'and' of lhs and rhs, taking into consideration their types. If
     *  the operation is invalid for the underlying types, returns an EOO instance.
     */
    static SafeNum andInternal(const SafeNum& lhs, const SafeNum& rhs);

    /** Returns the bitwise 'or' of lhs and rhs, taking into consideration their types. If
     *  the operation is invalid for the underlying types, returns an EOO instance.
     */
    static SafeNum orInternal(const SafeNum& lhs, const SafeNum& rhs);

    /** Returns the bitwise 'xor' of lhs and rhs, taking into consideration their types. If
     *  the operation is invalid for the underlying types, returns an EOO instance.
     */
    static SafeNum xorInternal(const SafeNum& lhs, const SafeNum& rhs);

    /**
     * Extracts the value of 'snum' in a int64_t format. It assumes 'snum' is an NumberInt
     * or a NumberLong.
     */
    static int64_t getInt64(const SafeNum& snum);

    /**
     * Extracts the value of 'snum' in a double format. It assumes 'snum' is a valid
     * SafeNum, i.e., that _type is not EOO.
     */
    static double getDouble(const SafeNum& snum);

    /**
     * Extracts the value of 'snum' in a Decimal128 format.  It assumes 'snum' is an
     * NumberInt, NumberDouble, or NumberLong.  Integral values are converted exactly.
     * NumberDouble is converted to 15 digits of precision, as defined in Decimal128.
     */
    static Decimal128 getDecimal(const SafeNum& snum);
};

// Convenience method for unittest code. Please use accessors otherwise.
std::ostream& operator<<(std::ostream& os, const SafeNum& snum);

}  // namespace mongo

#include "mongo/util/safe_num-inl.h"