JUCE/modules/juce_core/maths/juce_Random.cpp

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2016 - ROLI Ltd.

   Permission is granted to use this software under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license/

   Permission to use, copy, modify, and/or distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
   copyright notice and this permission notice appear in all copies.

   THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
   TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
   OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
   USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   OF THIS SOFTWARE.

   -----------------------------------------------------------------------------

   To release a closed-source product which uses other parts of JUCE not
   licensed under the ISC terms, commercial licenses are available: visit
   www.juce.com for more information.

  ==============================================================================
*/

Random::Random (const int64 seedValue) noexcept   : seed (seedValue)
{
}

Random::Random()  : seed (1)
{
    setSeedRandomly();
}

Random::~Random() noexcept
{
}

void Random::setSeed (const int64 newSeed) noexcept
{
    seed = newSeed;
}

void Random::combineSeed (const int64 seedValue) noexcept
{
    seed ^= nextInt64() ^ seedValue;
}

void Random::setSeedRandomly()
{
    static int64 globalSeed = 0;

    combineSeed (globalSeed ^ (int64) (pointer_sized_int) this);
    combineSeed (Time::getMillisecondCounter());
    combineSeed (Time::getHighResolutionTicks());
    combineSeed (Time::getHighResolutionTicksPerSecond());
    combineSeed (Time::currentTimeMillis());
    globalSeed ^= seed;
}

Random& Random::getSystemRandom() noexcept
{
    static Random sysRand;
    return sysRand;
}

//==============================================================================
int Random::nextInt() noexcept
{
    seed = (seed * 0x5deece66dLL + 11) & 0xffffffffffffLL;

    return (int) (seed >> 16);
}

int Random::nextInt (const int maxValue) noexcept
{
    jassert (maxValue > 0);
    return (int) ((((unsigned int) nextInt()) * (uint64) maxValue) >> 32);
}

int Random::nextInt (Range<int> range) noexcept
{
    return range.getStart() + nextInt (range.getLength());
}

int64 Random::nextInt64() noexcept
{
    return (((int64) nextInt()) << 32) | (int64) (uint64) (uint32) nextInt();
}

bool Random::nextBool() noexcept
{
    return (nextInt() & 0x40000000) != 0;
}

float Random::nextFloat() noexcept
{
    return static_cast<uint32> (nextInt()) / (std::numeric_limits<uint32>::max() + 1.0f);
}

double Random::nextDouble() noexcept
{
    return static_cast<uint32> (nextInt()) / (std::numeric_limits<uint32>::max() + 1.0);
}

BigInteger Random::nextLargeNumber (const BigInteger& maximumValue)
{
    BigInteger n;

    do
    {
        fillBitsRandomly (n, 0, maximumValue.getHighestBit() + 1);
    }
    while (n >= maximumValue);

    return n;
}

void Random::fillBitsRandomly (void* const buffer, size_t bytes)
{
    int* d = static_cast<int*> (buffer);

    for (; bytes >= sizeof (int); bytes -= sizeof (int))
        *d++ = nextInt();

    if (bytes > 0)
    {
        const int lastBytes = nextInt();
        memcpy (d, &lastBytes, bytes);
    }
}

void Random::fillBitsRandomly (BigInteger& arrayToChange, int startBit, int numBits)
{
    arrayToChange.setBit (startBit + numBits - 1, true);  // to force the array to pre-allocate space

    while ((startBit & 31) != 0 && numBits > 0)
    {
        arrayToChange.setBit (startBit++, nextBool());
        --numBits;
    }

    while (numBits >= 32)
    {
        arrayToChange.setBitRangeAsInt (startBit, 32, (unsigned int) nextInt());
        startBit += 32;
        numBits -= 32;
    }

    while (--numBits >= 0)
        arrayToChange.setBit (startBit + numBits, nextBool());
}

//==============================================================================
#if JUCE_UNIT_TESTS

class RandomTests  : public UnitTest
{
public:
    RandomTests() : UnitTest ("Random") {}

    void runTest() override
    {
        beginTest ("Random");

        Random r = getRandom();

        for (int i = 2000; --i >= 0;)
        {
            expect (r.nextDouble() >= 0.0 && r.nextDouble() < 1.0);
            expect (r.nextFloat() >= 0.0f && r.nextFloat() < 1.0f);
            expect (r.nextInt (5) >= 0 && r.nextInt (5) < 5);
            expect (r.nextInt (1) == 0);

            int n = r.nextInt (50) + 1;
            expect (r.nextInt (n) >= 0 && r.nextInt (n) < n);

            n = r.nextInt (0x7ffffffe) + 1;
            expect (r.nextInt (n) >= 0 && r.nextInt (n) < n);
        }
    }
};

static RandomTests randomTests;

#endif