third_party/blink/renderer/platform/wtf/math_extras.h

/*
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 *
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 * are met:
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 *    notice, this list of conditions and the following disclaimer.
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 *    notice, this list of conditions and the following disclaimer in the
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_MATH_EXTRAS_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_MATH_EXTRAS_H_

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

#include "base/check_op.h"
#include "build/build_config.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"

#if defined(COMPILER_MSVC)
// Make math.h behave like other platforms.
#define _USE_MATH_DEFINES
// Even if math.h was already included, including math.h again with
// _USE_MATH_DEFINES adds the extra defines.
#include <math.h>
#include <stdint.h>
#endif

#if BUILDFLAG(IS_OPENBSD)
#include <machine/ieee.h>
#include <sys/types.h>
#endif

constexpr double kPiDouble = M_PI;
constexpr float kPiFloat = static_cast<float>(M_PI);

constexpr double kPiOverTwoDouble = M_PI_2;
constexpr float kPiOverTwoFloat = static_cast<float>(M_PI_2);

constexpr double kPiOverFourDouble = M_PI_4;
constexpr float kPiOverFourFloat = static_cast<float>(M_PI_4);

constexpr double kTwoPiDouble = kPiDouble * 2.0;
constexpr float kTwoPiFloat = kPiFloat * 2.0f;

constexpr double Deg2rad(double d) {
  return d * (kPiDouble / 180.0);
}
constexpr double Rad2deg(double r) {
  return r * (180.0 / kPiDouble);
}
constexpr double Deg2grad(double d) {
  return d * (400.0 / 360.0);
}
constexpr double Grad2deg(double g) {
  return g * (360.0 / 400.0);
}
constexpr double Turn2deg(double t) {
  return t * 360.0;
}
constexpr double Deg2turn(double d) {
  return d * (1.0 / 360.0);
}
constexpr double Rad2grad(double r) {
  return r * (200.0 / kPiDouble);
}
constexpr double Grad2rad(double g) {
  return g * (kPiDouble / 200.0);
}
constexpr double Turn2grad(double t) {
  return t * 400;
}
constexpr double Grad2turn(double g) {
  return g * (1.0 / 400.0);
}
constexpr double Rad2turn(double r) {
  return r * (1.0 / kTwoPiDouble);
}
constexpr double Turn2rad(double t) {
  return t * kTwoPiDouble;
}

constexpr float Deg2rad(float d) {
  return d * (kPiFloat / 180.0f);
}
constexpr float Rad2deg(float r) {
  return r * (180.0f / kPiFloat);
}
constexpr float Deg2grad(float d) {
  return d * (400.0f / 360.0f);
}
constexpr float Grad2deg(float g) {
  return g * (360.0f / 400.0f);
}
constexpr float Turn2deg(float t) {
  return t * 360.0f;
}
constexpr float Deg2turn(float d) {
  return d * (1.0f / 360.0f);
}
constexpr float Rad2grad(float r) {
  return r * (200.0f / kPiFloat);
}
constexpr float Grad2rad(float g) {
  return g * (kPiFloat / 200.0f);
}
constexpr float Turn2grad(float t) {
  return t * 400;
}
constexpr float Grad2turn(float g) {
  return g * (1.0f / 400.0f);
}

constexpr double RoundHalfTowardsPositiveInfinity(double value) {
  return std::floor(value + 0.5);
}

constexpr float RoundHalfTowardsPositiveInfinity(float value) {
  return std::floor(value + 0.5f);
}

// ClampTo() is implemented by templated helper classes (to allow for partial
// template specialization) as well as several helper functions.

// This helper function can be called when we know that:
// (1) The type signednesses match so the compiler will not produce signed vs.
//     unsigned warnings
// (2) The default type promotions/conversions are sufficient to handle things
//     correctly
template <typename LimitType, typename ValueType>
inline constexpr LimitType ClampToDirectComparison(ValueType value,
                                                   LimitType min,
                                                   LimitType max) {
  if (value >= max)
    return max;
  return (value <= min) ? min : static_cast<LimitType>(value);
}

// For any floating-point limits, or integral limits smaller than int64_t, we
// can cast the limits to double without losing precision; then the only cases
// where |value| can't be represented accurately as a double are the ones where
// it's outside the limit range anyway.  So doing all comparisons as doubles
// will give correct results.
//
// In some cases, we can get better performance by using
// ClampToDirectComparison().  We use a templated class to switch between these
// two cases (instead of simply using a conditional within one function) in
// order to only compile the ClampToDirectComparison() code for cases where it
// will actually be used; this prevents the compiler from emitting warnings
// about unsafe code (even though we wouldn't actually be executing that code).
template <bool can_use_direct_comparison,
          typename LimitType,
          typename ValueType>
class ClampToNonLongLongHelper;

template <typename LimitType, typename ValueType>
class ClampToNonLongLongHelper<true, LimitType, ValueType> {
  STATIC_ONLY(ClampToNonLongLongHelper);

 public:
  static inline constexpr LimitType ClampTo(ValueType value,
                                            LimitType min,
                                            LimitType max) {
    return ClampToDirectComparison(value, min, max);
  }
};

template <typename LimitType, typename ValueType>
class ClampToNonLongLongHelper<false, LimitType, ValueType> {
  STATIC_ONLY(ClampToNonLongLongHelper);

 public:
  static inline constexpr LimitType ClampTo(ValueType value,
                                            LimitType min,
                                            LimitType max) {
    const double double_value = static_cast<double>(value);
    if (double_value >= static_cast<double>(max))
      return max;
    if (double_value <= static_cast<double>(min))
      return min;
    // If the limit type is integer, we might get better performance by
    // casting |value| (as opposed to |double_value|) to the limit type.
    return std::numeric_limits<LimitType>::is_integer
               ? static_cast<LimitType>(value)
               : static_cast<LimitType>(double_value);
  }
};

// The unspecialized version of this templated class handles clamping to
// anything other than [u]int64_t limits.  It simply uses the class above
// to toggle between the "fast" and "safe" clamp implementations.
template <typename LimitType, typename ValueType>
class ClampToHelper {
 public:
  static inline constexpr LimitType ClampTo(ValueType value,
                                            LimitType min,
                                            LimitType max) {
    // We only use ClampToDirectComparison() when the integerness and
    // signedness of the two types matches.
    //
    // If the integerness of the types doesn't match, then at best
    // ClampToDirectComparison() won't be much more efficient than the
    // cast-everything-to-double method, since we'll need to convert to
    // floating point anyway; at worst, we risk incorrect results when
    // clamping a float to a 32-bit integral type due to potential precision
    // loss.
    //
    // If the signedness doesn't match, ClampToDirectComparison() will
    // produce warnings about comparing signed vs. unsigned, which are apt
    // since negative signed values will be converted to large unsigned ones
    // and we'll get incorrect results.
    return ClampToNonLongLongHelper <
                       std::numeric_limits<LimitType>::is_integer ==
                   std::numeric_limits<ValueType>::is_integer &&
               std::numeric_limits<LimitType>::is_signed ==
                   std::numeric_limits<ValueType>::is_signed,
           LimitType, ValueType > ::ClampTo(value, min, max);
  }
};

// Clamping to [u]int64_t limits requires more care.  These may not be
// accurately representable as doubles, so instead we cast |value| to the
// limit type. But that cast is undefined if |value| is floating point and
// outside the representable range of the limit type, so we also have to check
// for that case explicitly.
template <typename ValueType>
class ClampToHelper<int64_t, ValueType> {
  STATIC_ONLY(ClampToHelper);

 public:
  static inline int64_t ClampTo(ValueType value, int64_t min, int64_t max) {
    if (!std::numeric_limits<ValueType>::is_integer) {
      if (value > 0) {
        if (static_cast<double>(value) >=
            static_cast<double>(std::numeric_limits<int64_t>::max()))
          return max;
      } else if (static_cast<double>(value) <=
                 static_cast<double>(std::numeric_limits<int64_t>::min())) {
        return min;
      }
    }
    // Note: If |value| were uint64_t it could be larger than the largest
    // int64_t, and this code would be wrong; we handle  this case with
    // a separate full specialization below.
    return ClampToDirectComparison(static_cast<int64_t>(value), min, max);
  }
};

// This specialization handles the case where the above partial specialization
// would be potentially incorrect.
template <>
class ClampToHelper<int64_t, uint64_t> {
  STATIC_ONLY(ClampToHelper);

 public:
  static inline int64_t ClampTo(uint64_t value, int64_t min, int64_t max) {
    if (max <= 0 || value >= static_cast<uint64_t>(max))
      return max;
    const int64_t long_long_value = static_cast<int64_t>(value);
    return (long_long_value <= min) ? min : long_long_value;
  }
};

// This is similar to the partial specialization that clamps to int64_t, but
// because the lower-bound check is done for integer value types as well, we
// don't need a <uint64_t, int64_t> full specialization.
template <typename ValueType>
class ClampToHelper<uint64_t, ValueType> {
  STATIC_ONLY(ClampToHelper);

 public:
  static inline uint64_t ClampTo(ValueType value, uint64_t min, uint64_t max) {
    if (value <= 0)
      return min;
    if (!std::numeric_limits<ValueType>::is_integer) {
      if (static_cast<double>(value) >=
          static_cast<double>(std::numeric_limits<uint64_t>::max()))
        return max;
    }
    return ClampToDirectComparison(static_cast<uint64_t>(value), min, max);
  }
};

template <typename T>
constexpr T DefaultMaximumForClamp() {
  return std::numeric_limits<T>::max();
}
template <typename T>
constexpr T DefaultMinimumForClamp() {
  return std::numeric_limits<T>::lowest();
}

// And, finally, the actual function for people to call.
template <typename LimitType, typename ValueType>
constexpr LimitType ClampTo(
    ValueType value,
    LimitType min = DefaultMinimumForClamp<LimitType>(),
    LimitType max = DefaultMaximumForClamp<LimitType>()) {
  // We use __builtin_isnan instead of std::isnan here because std::isnan
  // is not constexpr prior to C++23.
  DCHECK(!__builtin_isnan(static_cast<double>(value)));
  DCHECK_LE(min, max);  // This also ensures |min| and |max| aren't NaN.
  return ClampToHelper<LimitType, ValueType>::ClampTo(value, min, max);
}

template <typename LimitType, typename ValueType>
constexpr LimitType ClampToWithNaNTo0(
    ValueType value,
    LimitType min = DefaultMinimumForClamp<LimitType>(),
    LimitType max = DefaultMaximumForClamp<LimitType>()) {
  static_assert(std::numeric_limits<ValueType>::has_quiet_NaN);
  if (UNLIKELY(std::isnan(value)))
    return 0;
  return ClampTo<LimitType, ValueType>(value);
}

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

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

constexpr size_t LowestCommonMultiple(size_t a, size_t b) {
  return a && b ? a / GreatestCommonDivisor(a, b) * b : 0;
}

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_MATH_EXTRAS_H_