sky/engine/wtf/MathExtras.h

/*
 * Copyright (C) 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
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 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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#ifndef SKY_ENGINE_WTF_MATHEXTRAS_H_
#define SKY_ENGINE_WTF_MATHEXTRAS_H_

#include <cmath>
#include <cstddef>
#include <limits>

#include "sky/engine/wtf/CPU.h"
#include "sky/engine/wtf/OperatingSystem.h"

const double piDouble = M_PI;
const float piFloat = static_cast<float>(M_PI);

const double piOverTwoDouble = M_PI_2;
const float piOverTwoFloat = static_cast<float>(M_PI_2);

const double piOverFourDouble = M_PI_4;
const float piOverFourFloat = static_cast<float>(M_PI_4);

const double twoPiDouble = piDouble * 2.0;
const float twoPiFloat = piFloat * 2.0f;

#if OS(ANDROID)
// ANDROID and MSVC's math.h does not currently supply log2 or log2f.
inline double log2(double num)
{
    // This constant is roughly M_LN2, which is not provided by default on Windows and Android.
    return log(num) / 0.693147180559945309417232121458176568;
}

inline float log2f(float num)
{
    // This constant is roughly M_LN2, which is not provided by default on Windows and Android.
    return logf(num) / 0.693147180559945309417232121458176568f;
}
#endif

inline double deg2rad(double d)  { return d * piDouble / 180.0; }
inline double rad2deg(double r)  { return r * 180.0 / piDouble; }
inline double deg2grad(double d) { return d * 400.0 / 360.0; }
inline double grad2deg(double g) { return g * 360.0 / 400.0; }
inline double turn2deg(double t) { return t * 360.0; }
inline double deg2turn(double d) { return d / 360.0; }
inline double rad2grad(double r) { return r * 200.0 / piDouble; }
inline double grad2rad(double g) { return g * piDouble / 200.0; }
inline double turn2grad(double t) { return t * 400; }
inline double grad2turn(double g) { return g / 400; }

inline float deg2rad(float d)  { return d * piFloat / 180.0f; }
inline float rad2deg(float r)  { return r * 180.0f / piFloat; }
inline float deg2grad(float d) { return d * 400.0f / 360.0f; }
inline float grad2deg(float g) { return g * 360.0f / 400.0f; }
inline float turn2deg(float t) { return t * 360.0f; }
inline float deg2turn(float d) { return d / 360.0f; }
inline float rad2grad(float r) { return r * 200.0f / piFloat; }
inline float grad2rad(float g) { return g * piFloat / 200.0f; }
inline float turn2grad(float t) { return t * 400; }
inline float grad2turn(float g) { return g / 400; }

// std::numeric_limits<T>::min() returns the smallest positive value for floating point types
template<typename T> inline T defaultMinimumForClamp() { return std::numeric_limits<T>::min(); }
template<> inline float defaultMinimumForClamp() { return -std::numeric_limits<float>::max(); }
template<> inline double defaultMinimumForClamp() { return -std::numeric_limits<double>::max(); }
template<typename T> inline T defaultMaximumForClamp() { return std::numeric_limits<T>::max(); }

template<typename T> inline T clampTo(double value, T min = defaultMinimumForClamp<T>(), T max = defaultMaximumForClamp<T>())
{
    if (value >= static_cast<double>(max))
        return max;
    if (value <= static_cast<double>(min))
        return min;
    return static_cast<T>(value);
}
template<> inline long long int clampTo(double, long long int, long long int); // clampTo does not support long long ints.

inline int clampToInteger(double value)
{
    return clampTo<int>(value);
}

inline unsigned clampToUnsigned(double value)
{
    return clampTo<unsigned>(value);
}

inline float clampToFloat(double value)
{
    return clampTo<float>(value);
}

inline int clampToPositiveInteger(double value)
{
    return clampTo<int>(value, 0);
}

inline int clampToInteger(float value)
{
    return clampTo<int>(value);
}

inline int clampToInteger(unsigned x)
{
    const unsigned intMax = static_cast<unsigned>(std::numeric_limits<int>::max());

    if (x >= intMax)
        return std::numeric_limits<int>::max();
    return static_cast<int>(x);
}

inline bool isWithinIntRange(float x)
{
    return x > static_cast<float>(std::numeric_limits<int>::min()) && x < static_cast<float>(std::numeric_limits<int>::max());
}

static size_t greatestCommonDivisor(size_t a, size_t b)
{
    return b ? greatestCommonDivisor(b, a % b) : a;
}

inline size_t lowestCommonMultiple(size_t a, size_t b)
{
    return a && b ? a / greatestCommonDivisor(a, b) * b : 0;
}

#ifndef UINT64_C
#define UINT64_C(c) c ## ull
#endif

// Calculate d % 2^{64}.
inline void doubleToInteger(double d, unsigned long long& value)
{
    if (std::isnan(d) || std::isinf(d))
        value = 0;
    else {
        // -2^{64} < fmodValue < 2^{64}.
        double fmodValue = fmod(trunc(d), std::numeric_limits<unsigned long long>::max() + 1.0);
        if (fmodValue >= 0) {
            // 0 <= fmodValue < 2^{64}.
            // 0 <= value < 2^{64}. This cast causes no loss.
            value = static_cast<unsigned long long>(fmodValue);
        } else {
            // -2^{64} < fmodValue < 0.
            // 0 < fmodValueInUnsignedLongLong < 2^{64}. This cast causes no loss.
            unsigned long long fmodValueInUnsignedLongLong = static_cast<unsigned long long>(-fmodValue);
            // -1 < (std::numeric_limits<unsigned long long>::max() - fmodValueInUnsignedLongLong) < 2^{64} - 1.
            // 0 < value < 2^{64}.
            value = std::numeric_limits<unsigned long long>::max() - fmodValueInUnsignedLongLong + 1;
        }
    }
}

namespace WTF {

inline unsigned fastLog2(unsigned i)
{
    unsigned log2 = 0;
    if (i & (i - 1))
        log2 += 1;
    if (i >> 16)
        log2 += 16, i >>= 16;
    if (i >> 8)
        log2 += 8, i >>= 8;
    if (i >> 4)
        log2 += 4, i >>= 4;
    if (i >> 2)
        log2 += 2, i >>= 2;
    if (i >> 1)
        log2 += 1;
    return log2;
}

} // namespace WTF

#endif  // SKY_ENGINE_WTF_MATHEXTRAS_H_