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
/* ============================================================
 *
 * This file is a part of digiKam project
 * https://www.digikam.org
 *
 * Date        : 2010-11-03
 * Description : Generating random numbers
 *
 * SPDX-FileCopyrightText: 2010-2011 by Marcel Wiesweg <marcel dot wiesweg at gmx dot de>
 * SPDX-FileCopyrightText: 2021      by Anjani Kumar <anjanik012 at gmail dot com>
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * ============================================================ */

#include "randomnumbergenerator.h"

// Qt includes

#include <QDateTime>
#include <QFile>
#include <QUuid>
#include <QRandomGenerator>

// C++ includes

#include <random>

namespace Digikam
{

NonDeterministicRandomData::NonDeterministicRandomData(int s)
{

#ifndef Q_OS_WIN

    {
        // Try urandom for UNIX platforms.

        QFile urandom(QLatin1String("/dev/urandom"));

        if (urandom.exists() && urandom.open(QIODevice::ReadOnly))
        {
            resize(s);

            if (urandom.read(data(), s) == s)
            {
                urandom.close();
                return;
            }

            urandom.close();
        }
    }

#endif

    /*
     * Fallback, mostly for Windows, where UUID generation
     * is supposed to be very good.
     */
    if (isEmpty())
    {
        reserve(s);

        while (size() < s)
        {
            append(QByteArray::fromHex(QUuid::createUuid()
                        .toString()
                        .remove(QLatin1Char('{'))
                        .remove(QLatin1Char('}'))
                        .remove(QLatin1Char('-'))
                        .toLatin1())
                  );
        }

        resize(s);
    }
}

// ---------------------------------------------------------------------------------

class Q_DECL_HIDDEN RandomNumberGenerator::Private
{
public:

    enum
    {
        InitialSeed = 5489  ///< guaranteed constant initial seed, do not change
    };

public:

    Private() = default;

    quint32          seed   = InitialSeed;
    QRandomGenerator engine = QRandomGenerator(InitialSeed);
};

RandomNumberGenerator::RandomNumberGenerator()
    : d(new Private)
{
}

RandomNumberGenerator::~RandomNumberGenerator()
{
    delete d;
}

quint32 RandomNumberGenerator::nonDeterministicSeed()
{
    NonDeterministicRandomData seed(sizeof(quint32));<--- Shadow variable

    return *reinterpret_cast<quint32*>(seed.data());
}

quint32 RandomNumberGenerator::timeSeed()
{
    uint seed;<--- Shadow variable
    seed = quintptr(&seed) + QDateTime::currentSecsSinceEpoch();

    return seed;
}

quint32 RandomNumberGenerator::seedNonDeterministic()
{
    d->seed = nonDeterministicSeed();
    d->engine.seed(d->seed);

    return d->seed;
}

quint32 RandomNumberGenerator::seedByTime()
{
    d->seed = timeSeed();
    d->engine.seed(d->seed);

    return d->seed;
}

void RandomNumberGenerator::seed(quint32 seed)
{
    d->seed = seed;
    d->engine.seed(seed);
}

void RandomNumberGenerator::reseed()
{
    seed(d->seed);
}

quint32 RandomNumberGenerator::currentSeed() const
{
    return d->seed;
}

int RandomNumberGenerator::number(int min, int max)
{
    std::uniform_int_distribution<int> dist(min, max);
    return dist(d->engine);
}

double RandomNumberGenerator::number(double min, double max)
{
    std::uniform_real_distribution<double> dist(min, max);
    return dist(d->engine);
}

bool RandomNumberGenerator::yesOrNo(double p)
{
    std::bernoulli_distribution dist(p);
    return dist(d->engine);
}

} // namespace Digikam