Long live QRandomGenerator

This class provides a reasonably-secure random number generator that
does not need seeding. That is quite unlike qrand(), which requires a
seed and is low-quality (definitely not secure).

This class is also like std::random_device, but better. It provides an
operator() like std::random_device, but unlike that, it also provides a
way to fill a buffer with random data, not just one 32-bit quantity.
It's also stateless.

Finally, it also implements std::seed_seq-like generate(). It obeys the
standard requirement of the range (32-bit) but not that of the algorithm
(if you wanted that, you'd use std::seed_seq itself). Instead,
generate() fills with pure random data.

Change-Id: Icd0e0d4b27cb4e5eb892fffd14b4e3ba9ea04da8
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 727 insertions, 0 deletions

diff --git a/src/corelib/global/qrandom.cpp b/src/corelib/global/qrandom.cpp
new file mode 100644
index 0000000000..74fdf9f318
--- /dev/null
+++ b/src/corelib/global/qrandom.cpp
@@ -0,0 +1,727 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 Intel Corporation.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+// for rand_s
+#define _CRT_RAND_S
+
+#include "qrandom.h"
+#include "qrandom_p.h"
+
+#if QT_HAS_INCLUDE(<random>)
+#  include <random>
+#endif
+
+#ifdef Q_OS_UNIX
+#  include <fcntl.h>
+#  include <private/qcore_unix_p.h>
+#else
+#  include <qt_windows.h>
+
+// RtlGenRandom is not exported by its name in advapi32.dll, but as SystemFunction036
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/aa387694(v=vs.85).aspx
+// Implementation inspired on https://hg.mozilla.org/mozilla-central/file/722fdbff1efc/security/nss/lib/freebl/win_rand.c#l146
+// Argument why this is safe to use: https://bugzilla.mozilla.org/show_bug.cgi?id=504270
+extern "C" {
+DECLSPEC_IMPORT BOOLEAN WINAPI SystemFunction036(PVOID RandomBuffer, ULONG RandomBufferLength);
+}
+#endif
+
+QT_BEGIN_NAMESPACE
+
+namespace {
+#ifdef Q_OS_UNIX
+class SystemRandom
+{
+    static QBasicAtomicInt s_fdp1;  // "file descriptor plus 1"
+    static int openDevice();
+    SystemRandom() {}
+    ~SystemRandom();
+public:
+    enum { EfficientBufferFill = true };
+    static qssize_t fillBuffer(void *buffer, qssize_t count);
+};
+QBasicAtomicInt SystemRandom::s_fdp1 = Q_BASIC_ATOMIC_INITIALIZER(0);
+
+SystemRandom::~SystemRandom()
+{
+    int fd = s_fdp1.loadAcquire() - 1;
+    if (fd >= 0)
+        qt_safe_close(fd);
+}
+
+int SystemRandom::openDevice()
+{
+    int fd = s_fdp1.loadAcquire() - 1;
+    if (fd != -1)
+        return fd;
+
+    fd = qt_safe_open("/dev/urandom", O_RDONLY);
+    if (fd == -1)
+        fd = qt_safe_open("/dev/random", O_RDONLY | O_NONBLOCK);
+    if (fd == -1) {
+        // failed on both, set to -2 so we won't try again
+        fd = -2;
+    }
+
+    int opened_fdp1;
+    if (s_fdp1.testAndSetOrdered(0, fd + 1, opened_fdp1)) {
+        if (fd >= 0) {
+            static const SystemRandom closer;
+            Q_UNUSED(closer);
+        }
+        return fd;
+    }
+
+    // failed, another thread has opened the file descriptor
+    if (fd >= 0)
+        qt_safe_close(fd);
+    return opened_fdp1 - 1;
+}
+
+qssize_t SystemRandom::fillBuffer(void *buffer, qssize_t count)
+{
+    int fd = openDevice();
+    if (Q_UNLIKELY(fd < 0))
+        return 0;
+
+    qint64 n = qt_safe_read(fd, buffer, count);
+    return qMax<qssize_t>(n, 0);        // ignore any errors
+}
+#endif // Q_OS_UNIX
+
+#if defined(Q_OS_WIN) && !defined(Q_OS_WINRT)
+class SystemRandom
+{
+public:
+    enum { EfficientBufferFill = true };
+    static qssize_t fillBuffer(void *buffer, qssize_t count)
+    {
+        auto RtlGenRandom = SystemFunction036;
+        return RtlGenRandom(buffer, ULONG(count)) ? count: 0;
+    }
+};
+#elif defined(Q_OS_WINRT)
+class SystemRandom
+{
+public:
+    enum { EfficientBufferFill = false };
+    static qssize_t fillBuffer(void *, qssize_t)
+    {
+        // always use the fallback
+        return 0;
+    }
+};
+#endif // Q_OS_WINRT
+} // unnamed namespace
+
+#if defined(Q_OS_WIN)
+static void fallback_update_seed(unsigned) {}
+static void fallback_fill(quint32 *ptr, qssize_t left) Q_DECL_NOTHROW
+{
+    // on Windows, rand_s is a high-quality random number generator
+    // and it requires no seeding
+    std::generate(ptr, ptr + left, []() {
+        unsigned value;
+        rand_s(&value);
+        return value;
+    });
+}
+#elif QT_HAS_INCLUDE(<chrono>)
+static QBasicAtomicInteger<unsigned> seed = Q_BASIC_ATOMIC_INITIALIZER(0U);
+static void fallback_update_seed(unsigned value)
+{
+    // Update the seed to be used for the fallback mechansim, if we need to.
+    // We can't use QtPrivate::QHashCombine here because that is not an atomic
+    // operation. A simple XOR will have to do then.
+    seed.fetchAndXorRelaxed(value);
+}
+
+static void fallback_fill(quint32 *ptr, qssize_t left) Q_DECL_NOTHROW
+{
+    Q_ASSERT(left);
+
+    // this is highly inefficient, we should save the generator across calls...
+    std::mt19937 generator(seed.load());
+    std::generate(ptr, ptr + left, generator);
+
+    fallback_update_seed(*ptr);
+}
+#else
+static void fallback_update_seed(unsigned) {}
+static Q_NORETURN void fallback_fill(quint32 *, qssize_t)
+{
+    qFatal("Random number generator failed and no high-quality backup available");
+}
+#endif
+
+static void fill_internal(quint32 *buffer, qssize_t count)
+{
+    if (Q_UNLIKELY(uint(qt_randomdevice_control) & SetRandomData)) {
+        uint value = uint(qt_randomdevice_control) & RandomDataMask;
+        std::fill_n(buffer, count, value);
+        return;
+    }
+
+    qssize_t filled = 0;
+    if (uint(qt_randomdevice_control) & SkipSystemRNG) == 0) {
+        qssize_t bytesFilled =
+                SystemRandom::fillBuffer(buffer + filled, (count - filled) * qssize_t(sizeof(*buffer)));
+        filled += bytesFilled / qssize_t(sizeof(*buffer));
+    }
+    if (filled)
+        fallback_update_seed(*buffer);
+
+    if (Q_UNLIKELY(filled != count)) {
+        // failed to fill the entire buffer, try the faillback mechanism
+        fallback_fill(buffer + filled, count - filled);
+    }
+}
+
+static Q_NEVER_INLINE void fill(void *buffer, void *bufferEnd)
+{
+    struct ThreadState {
+        enum {
+            DesiredBufferByteSize = 32,
+            BufferCount = DesiredBufferByteSize / sizeof(quint32)
+        };
+        quint32 buffer[BufferCount];
+        int idx = BufferCount;
+    };
+
+    // Verify that the pointers are properly aligned for 32-bit
+    Q_ASSERT(quintptr(buffer) % sizeof(quint32) == 0);
+    Q_ASSERT(quintptr(bufferEnd) % sizeof(quint32) == 0);
+
+    quint32 *ptr = reinterpret_cast<quint32 *>(buffer);
+    quint32 * const end = reinterpret_cast<quint32 *>(bufferEnd);
+
+#if defined(Q_COMPILER_THREAD_LOCAL)
+    if (SystemRandom::EfficientBufferFill && (end - ptr) < ThreadState::BufferCount
+            && uint(qt_randomdevice_control) == 0) {
+        thread_local ThreadState state;
+        qssize_t itemsAvailable = ThreadState::BufferCount - state.idx;
+
+        // copy as much as we already have
+        qssize_t itemsToCopy = qMin(qssize_t(end - ptr), itemsAvailable);
+        memcpy(ptr, state.buffer + state.idx, size_t(itemsToCopy) * sizeof(*ptr));
+        ptr += itemsToCopy;
+
+        if (ptr != end) {
+            // refill the buffer and try again
+            fill_internal(state.buffer, ThreadState::BufferCount);
+            state.idx = 0;
+
+            itemsToCopy = end - ptr;
+            memcpy(ptr, state.buffer + state.idx, size_t(itemsToCopy) * sizeof(*ptr));
+            ptr = end;
+        }
+
+        // erase what we copied and advance
+#  ifdef Q_OS_WIN
+        // Microsoft recommends this
+        SecureZeroMemory(state.buffer + state.idx, size_t(itemsToCopy) * sizeof(*ptr));
+#  else
+        // We're quite confident the compiler will not optimize this out because
+        // we're writing to a thread-local buffer
+        memset(state.buffer + state.idx, 0, size_t(itemsToCopy) * sizeof(*ptr));
+#  endif
+        state.idx += itemsToCopy;
+    }
+#endif // Q_COMPILER_THREAD_LOCAL && !QT_BOOTSTRAPPED
+
+    if (ptr != end) {
+        // fill directly in the user buffer
+        fill_internal(ptr, end - ptr);
+    }
+}
+
+/**
+    \class QRandomGenerator
+    \inmodule QtCore
+    \since 5.10
+
+    \brief The QRandomGenerator class allows one to obtain random values from a
+    high-quality, seed-less Random Number Generator.
+
+    QRandomGenerator may be used to generate random values from a high-quality
+    random number generator. Unlike qrand(), QRandomGenerator does not need to be
+    seeded. That also means it is not possible to force it to produce a
+    reliable sequence, which may be needed for debugging.
+
+    The class can generate 32-bit or 64-bit quantities, or fill an array of
+    those. The most common way of generating new values is to call the get32(),
+    get64() or fillRange() functions. One would use it as:
+
+    \code
+        quint32 value = QRandomGenerator::get32();
+    \endcode
+
+    Additionally, it provides a floating-point function getReal() that returns
+    a number in the range [0, 1) (that is, inclusive of zero and exclusive of
+    1). There's also a set of convenience functions that facilitate obtaininga
+    random number in a bounded, integral range.
+
+    \section1 Frequency and entropy exhaustion
+
+    QRandomGenerator does not need to be seeded and instead uses operating system
+    or hardware facilities to generate random numbers. On some systems and with
+    certain hardware, those facilities are true Random Number Generators.
+    However, if they are true RNGs, those facilities have finite entropy source
+    and thus may fail to produce any results if the entropy pool is exhausted.
+
+    If that happens, first the operating system then QRandomGenerator will fall
+    back to Pseudo Random Number Generators of decreasing qualities (Qt's
+    fallback generator being the simplest). Therefore, QRandomGenerator should
+    not be used for high-frequency random number generation, lest the entropy
+    pool become empty. As a rule of thumb, this class should not be called upon
+    to generate more than a kilobyte per second of random data (note: this may
+    vary from system to system).
+
+    If an application needs true RNG data in bulk, it should use the operating
+    system facilities (such as \c{/dev/random} on Unix systems) directly and
+    wait for entropy to become available. If true RNG is not required,
+    applications should instead use a PRNG engines and can use QRandomGenerator to
+    seed those.
+
+    \section1 Standard C++ Library compatibility
+
+    QRandomGenerator is modeled after
+    \c{\l{http://en.cppreference.com/w/cpp/numeric/random/random_device}{std::random_device}}
+    and may be used in almost all contexts that the Standard Library can.
+    QRandomGenerator attempts to use either the same engine that backs
+    \c{std::random_device} or a better one. Note that \c{std::random_device} is
+    also allowed to fail if the source entropy pool becomes exhausted, in which
+    case it will throw an exception. QRandomGenerator never throws, but may abort
+    program execution instead.
+
+    Like the Standard Library class, QRandomGenerator can be used to seed Standard
+    Library deterministic random engines from \c{<random>}, such as the
+    Mersenne Twister. Unlike \c{std::random_device}, QRandomGenerator also
+    implements the API of
+    \c{\l{http://en.cppreference.com/w/cpp/numeric/random/seed_seq}{std::seed_seq}},
+    allowing it to seed the deterministic engines directly.
+
+    The following code can be used to create and seed the
+    implementation-defined default deterministic PRNG, then use it to fill a
+    block range:
+
+    \code
+        QRandomGenerator rd;
+        std::default_random_engine rng(rd);
+        std::generate(block.begin(), block.end(), rng);
+
+        // equivalent to:
+        for (auto &v : block)
+            v = rng();
+    \endcode
+
+    QRandomGenerator is also compatible with the uniform distribution classes
+    \c{std::uniform_int_distribution} and \c{std:uniform_real_distribution}, as
+    well as the free function \c{std::generate_canonical}. For example, the
+    following code may be used to generate a floating-point number in the range
+    [1, 2.5):
+
+    \code
+        QRandomGenerator64 rd;
+        std::uniform_real_distribution dist(1, 2.5);
+        return dist(rd);
+    \endcode
+
+    Note the use of the QRandomGenerator64 class instead of QRandomGenerator to
+    obtain 64 bits of random data in a single call, though it is not required
+    to make the algorithm work (the Standard Library functions will make as
+    many calls as required to obtain enough bits of random data for the desired
+    range).
+
+    \sa QRandomGenerator64, qrand()
+ */
+
+/**
+    \fn QRandomGenerator::QRandomGenerator()
+    \internal
+    Defaulted constructor, does nothing.
+ */
+
+/**
+    \typedef QRandomGenerator::result_type
+
+    A typedef to the type that operator()() returns. That is, quint32.
+
+    \sa operator()()
+ */
+
+/**
+    \fn result_type QRandomGenerator::operator()()
+
+    Generates a 32-bit random quantity and returns it.
+
+    \sa QRandomGenerator::get32(), QRandomGenerator::get64()
+ */
+
+/**
+    \fn double QRandomGenerator::entropy() const
+
+    Returns the estimate of the entropy in the random generator source.
+
+    This function exists to comply with the Standard Library requirements for
+    \c{\l{http://en.cppreference.com/w/cpp/numeric/random/random_device}{std::random_device}}
+    but it does not and cannot ever work. It is not possible to obtain a
+    reliable entropy value in a shared entropy pool in a multi-tasking system,
+    as other processes or threads may use that entropy. Any value non-zero
+    value that this function could return would be obsolete by the time the
+    user code reached it.
+
+    Since QRandomGenerator attempts to use a hardware Random Number Generator,
+    this function always returns 0.0.
+ */
+
+/**
+    \fn result_type QRandomGenerator::min()
+
+    Returns the minimum value that QRandomGenerator may ever generate. That is, 0.
+
+    \sa max(), QRandomGenerator64::max()
+ */
+
+/**
+    \fn result_type QRandomGenerator::max()
+
+    Returns the maximum value that QRandomGenerator may ever generate. That is,
+    \c {std::numeric_limits<result_type>::max()}.
+
+    \sa min(), QRandomGenerator64::max()
+ */
+
+/**
+    \fn void QRandomGenerator::generate(ForwardIterator begin, ForwardIterator end)
+
+    Generates 32-bit quantities and stores them in the range between \a begin
+    and \a end. This function is equivalent to (and is implemented as):
+
+    \code
+        std::generate(begin, end, []() { return get32(); });
+    \endcode
+
+    This function complies with the requirements for the function
+    \c{\l{http://en.cppreference.com/w/cpp/numeric/random/seed_seq/generate}{std::seed_seq::generate}},
+    which requires unsigned 32-bit integer values.
+
+    Note that if the [begin, end) range refers to an area that can store more
+    than 32 bits per element, the elements will still be initialized with only
+    32 bits of data. Any other bits will be zero. To fill the range with 64 bit
+    quantities, one can write:
+
+    \code
+        std::generate(begin, end, []() { return get64(); });
+    \endcode
+
+    If the range refers to contiguous memory (such as an array or the data from
+    a QVector), the fillRange() function may be used too.
+
+    \sa fillRange()
+ */
+
+/**
+    \fn void QRandomGenerator::generate(quint32 *begin, quint32 *end)
+    \overload
+    \internal
+
+    Same as the other overload, but more efficiently fills \a begin to \a end.
+ */
+
+/**
+    \fn void QRandomGenerator::fillRange(UInt *buffer, qssize_t count)
+
+    Generates \a count 32- or 64-bit quantities (depending on the type \c UInt)
+    and stores them in the buffer pointed by \a buffer. This is the most
+    efficient way to obtain more than one quantity at a time, as it reduces the
+    number of calls into the Random Number Generator source.
+
+    For example, to fill a vector of 16 entries with random values, one may
+    write:
+
+    \code
+        QVector<quint32> vector;
+        vector.resize(16);
+        QRandomGenerator::fillRange(vector.data(), vector.size());
+    \endcode
+
+    \sa generate()
+ */
+
+/**
+    \fn void QRandomGenerator::fillRange(UInt (&buffer)[N})
+
+    Generates \c N 32- or 64-bit quantities (depending on the type \c UInt) and
+    stores them in the \a buffer array. This is the most efficient way to
+    obtain more than one quantity at a time, as it reduces the number of calls
+    into the Random Number Generator source.
+
+    For example, to fill generate two 32-bit quantities, one may write:
+
+    \code
+        quint32 array[2];
+        QRandomGenerator::fillRange(array);
+    \endcode
+
+    It would have also been possible to make one call to get64() and then split
+    the two halves of the 64-bit value.
+
+    \sa generate()
+ */
+
+/**
+    \fn qreal QRandomGenerator::getReal()
+
+    Generates one random qreal in the canonical range [0, 1) (that is,
+    inclusive of zero and exclusive of 1).
+
+    This function is equivalent to:
+    \code
+        QRandomGenerator64 rd;
+        return std::generate_canonical<qreal, std::numeric_limits<qreal>::digits>(rd);
+    \endcode
+
+    The same may also be obtained by using
+    \c{\l{http://en.cppreference.com/w/cpp/numeric/random/uniform_real_distribution}{std::uniform_real_distribution}}
+    with parameters 0 and 1.
+
+    \sa get32(), get64(), bounded()
+ */
+
+/**
+    \fn qreal QRandomGenerator::bounded(qreal sup)
+
+    Generates one random qreal in the range between 0 (inclusive) and \a
+    sup (exclusive). This function is equivalent to and is implemented as:
+
+    \code
+        return getReal() * sup;
+    \endcode
+
+    \sa getReal(), bounded()
+ */
+
+/**
+    \fn quint32 QRandomGenerator::bounded(quint32 sup)
+    \overload
+
+    Generates one random 32-bit quantity in the range between 0 (inclusive) and
+    \a sup (exclusive). The same result may also be obtained by using
+    \c{\l{http://en.cppreference.com/w/cpp/numeric/random/uniform_int_distribution}{std::uniform_int_distribution}}
+    with parameters 0 and \c{sup - 1}. That class can also be used to obtain
+    quantities larger than 32 bits.
+
+    For example, to obtain a value between 0 and 255 (inclusive), one would write:
+
+    \code
+        quint32 v = QRandomGenerator::bounded(256);
+    \endcode
+
+    Naturally, the same could also be obtained by masking the result of get32()
+    to only the lower 8 bits. Either solution is as efficient.
+
+    Note that this function cannot be used to obtain values in the full 32-bit
+    range of quint32. Instead, use get32().
+
+    \sa get32(), get64(), getReal()
+ */
+
+/**
+    \fn quint32 QRandomGenerator::bounded(int sup)
+    \overload
+
+    Generates one random 32-bit quantity in the range between 0 (inclusive) and
+    \a sup (exclusive). \a sup must not be negative.
+
+    Note that this function cannot be used to obtain values in the full 32-bit
+    range of int. Instead, use get32() and cast to int.
+
+    \sa get32(), get64(), getReal()
+ */
+
+/**
+    \fn quint32 QRandomGenerator::bounded(quint32 min, quint32 sup)
+    \overload
+
+    Generates one random 32-bit quantity in the range between \a min (inclusive)
+    and \a sup (exclusive). The same result may also be obtained by using
+    \c{\l{http://en.cppreference.com/w/cpp/numeric/random/uniform_int_distribution}{std::uniform_int_distribution}}
+    with parameters \a min and \c{\a sup - 1}. That class can also be used to
+    obtain quantities larger than 32 bits.
+
+    For example, to obtain a value between 1000 (incl.) and 2000 (excl.), one
+    would write:
+
+    \code
+        quint32 v = QRandomGenerator::bounded(1000, 2000);
+    \endcode
+
+
+    Note that this function cannot be used to obtain values in the full 32-bit
+    range of quint32. Instead, use get32().
+
+    \sa get32(), get64(), getReal()
+ */
+
+/**
+    \fn quint32 QRandomGenerator::bounded(int min, int sup)
+    \overload
+
+    Generates one random 32-bit quantity in the range between \a min
+    (inclusive) and \a sup (exclusive), both of which may be negative.
+
+    Note that this function cannot be used to obtain values in the full 32-bit
+    range of int. Instead, use get32() and cast to int.
+
+    \sa get32(), get64(), getReal()
+ */
+
+/**
+    \class QRandomGenerator64
+    \inmodule QtCore
+    \since 5.10
+
+    \brief The QRandomGenerator64 class allows one to obtain 64-bit random values
+    from a high-quality, seed-less Random Number Generator.
+
+    QRandomGenerator64 is a simple adaptor class around QRandomGenerator, making the
+    QRandomGenerator::get64() function the default for operator()(), instead of the
+    function that returns 32-bit quantities. This class is intended to be used
+    in conjunction with Standard Library algorithms that need 64-bit quantities
+    instead of 32-bit ones.
+
+    In all other aspects, the class is the same. Please refer to
+    QRandomGenerator's documentation for more information.
+
+    \sa QRandomGenerator
+*/
+
+/**
+    \fn QRandomGenerator64::QRandomGenerator64()
+    \internal
+    Defaulted constructor, does nothing.
+ */
+
+/**
+    \typedef QRandomGenerator64::result_type
+
+    A typedef to the type that operator()() returns. That is, quint64.
+
+    \sa operator()()
+ */
+
+/**
+    \fn result_type QRandomGenerator64::operator()()
+
+    Generates a 64-bit random quantity and returns it.
+
+    \sa QRandomGenerator::get32(), QRandomGenerator::get64()
+ */
+
+/**
+    \fn double QRandomGenerator64::entropy() const
+
+    Returns the estimate of the entropy in the random generator source.
+
+    This function exists to comply with the Standard Library requirements for
+    \c{\l{http://en.cppreference.com/w/cpp/numeric/random/random_device}{std::random_device}}
+    but it does not and cannot ever work. It is not possible to obtain a
+    reliable entropy value in a shared entropy pool in a multi-tasking system,
+    as other processes or threads may use that entropy. Any value non-zero
+    value that this function could return would be obsolete by the time the
+    user code reached it.
+
+    Since QRandomGenerator64 attempts to use a hardware Random Number Generator,
+    this function always returns 0.0.
+ */
+
+/**
+    \fn result_type QRandomGenerator64::min()
+
+    Returns the minimum value that QRandomGenerator64 may ever generate. That is, 0.
+
+    \sa max(), QRandomGenerator::max()
+ */
+
+/**
+    \fn result_type QRandomGenerator64::max()
+
+    Returns the maximum value that QRandomGenerator64 may ever generate. That is,
+    \c {std::numeric_limits<result_type>::max()}.
+
+    \sa min(), QRandomGenerator::max()
+ */
+
+/**
+    Generates one 32-bit random value and returns it.
+
+    \sa get64(), getReal()
+ */
+quint32 QRandomGenerator::get32()
+{
+    quint32 ret;
+    fill(&ret, &ret + 1);
+    return ret;
+}
+
+/**
+    Generates one 64-bit random value and returns it.
+
+    \sa get32(), getReal(), QRandomGenerator64
+ */
+quint64 QRandomGenerator::get64()
+{
+    quint64 ret;
+    fill(&ret, &ret + 1);
+    return ret;
+}
+
+/**
+    \internal
+
+    Fills the range pointed by \a buffer and \a bufferEnd with 32-bit random
+    values. The buffer must be correctly aligned.
+ */
+void QRandomGenerator::fillRange_helper(void *buffer, void *bufferEnd)
+{
+    fill(buffer, bufferEnd);
+}
+
+QT_END_NAMESPACE