unity/crnlib/crn_math.h

// File: crn_math.h
// See Copyright Notice and license at the end of inc/crnlib.h
#pragma once

#if defined(_M_IX86) && defined(_MSC_VER)
#include <intrin.h>
#pragma intrinsic(__emulu)
unsigned __int64 __emulu(unsigned int a, unsigned int b);
#endif

namespace crnlib {
namespace math {
const float cNearlyInfinite = 1.0e+37f;

const float cDegToRad = 0.01745329252f;
const float cRadToDeg = 57.29577951f;

extern uint g_bitmasks[32];

template <typename T>
inline bool within_closed_range(T a, T b, T c) {
  return (a >= b) && (a <= c);
}

template <typename T>
inline bool within_open_range(T a, T b, T c) {
  return (a >= b) && (a < c);
}

// Yes I know these should probably be pass by ref, not val:
// http://www.stepanovpapers.com/notes.pdf
// Just don't use them on non-simple (non built-in) types!
template <typename T>
inline T minimum(T a, T b) {
  return (a < b) ? a : b;
}

template <typename T>
inline T minimum(T a, T b, T c) {
  return minimum(minimum(a, b), c);
}

template <typename T>
inline T maximum(T a, T b) {
  return (a > b) ? a : b;
}

template <typename T>
inline T maximum(T a, T b, T c) {
  return maximum(maximum(a, b), c);
}

template <typename T, typename U>
inline T lerp(T a, T b, U c) {
  return a + (b - a) * c;
}

template <typename T>
inline T clamp(T value, T low, T high) {
  return (value < low) ? low : ((value > high) ? high : value);
}

template <typename T>
inline T saturate(T value) {
  return (value < 0.0f) ? 0.0f : ((value > 1.0f) ? 1.0f : value);
}

inline int float_to_int(float f) {
  return static_cast<int>(f);
}

inline uint float_to_uint(float f) {
  return static_cast<uint>(f);
}

inline int float_to_int(double f) {
  return static_cast<int>(f);
}

inline uint float_to_uint(double f) {
  return static_cast<uint>(f);
}

inline int float_to_int_round(float f) {
  return static_cast<int>((f < 0.0f) ? -floor(-f + .5f) : floor(f + .5f));
}

inline uint float_to_uint_round(float f) {
  return static_cast<uint>((f < 0.0f) ? 0.0f : floor(f + .5f));
}

template <typename T>
inline int sign(T value) {
  return (value < 0) ? -1 : ((value > 0) ? 1 : 0);
}

template <typename T>
inline T square(T value) {
  return value * value;
}

inline bool is_power_of_2(uint32 x) {
  return x && ((x & (x - 1U)) == 0U);
}
inline bool is_power_of_2(uint64 x) {
  return x && ((x & (x - 1U)) == 0U);
}

template <typename T>
inline T align_up_value(T x, uint alignment) {
  CRNLIB_ASSERT(is_power_of_2(alignment));
  uint q = static_cast<uint>(x);
  q = (q + alignment - 1) & (~(alignment - 1));
  return static_cast<T>(q);
}

template <typename T>
inline T align_down_value(T x, uint alignment) {
  CRNLIB_ASSERT(is_power_of_2(alignment));
  uint q = static_cast<uint>(x);
  q = q & (~(alignment - 1));
  return static_cast<T>(q);
}

template <typename T>
inline T get_align_up_value_delta(T x, uint alignment) {
  return align_up_value(x, alignment) - x;
}

// From "Hackers Delight"
inline uint32 next_pow2(uint32 val) {
  val--;
  val |= val >> 16;
  val |= val >> 8;
  val |= val >> 4;
  val |= val >> 2;
  val |= val >> 1;
  return val + 1;
}

inline uint64 next_pow2(uint64 val) {
  val--;
  val |= val >> 32;
  val |= val >> 16;
  val |= val >> 8;
  val |= val >> 4;
  val |= val >> 2;
  val |= val >> 1;
  return val + 1;
}

inline uint floor_log2i(uint v) {
  uint l = 0;
  while (v > 1U) {
    v >>= 1;
    l++;
  }
  return l;
}

inline uint ceil_log2i(uint v) {
  uint l = floor_log2i(v);
  if ((l != cIntBits) && (v > (1U << l)))
    l++;
  return l;
}

// Returns the total number of bits needed to encode v.
inline uint total_bits(uint v) {
  uint l = 0;
  while (v > 0U) {
    v >>= 1;
    l++;
  }
  return l;
}

// Actually counts the number of set bits, but hey
inline uint bitmask_size(uint mask) {
  uint size = 0;
  while (mask) {
    mask &= (mask - 1U);
    size++;
  }
  return size;
}

inline uint bitmask_ofs(uint mask) {
  if (!mask)
    return 0;
  uint ofs = 0;
  while ((mask & 1U) == 0) {
    mask >>= 1U;
    ofs++;
  }
  return ofs;
}

// See Bit Twiddling Hacks (public domain)
// http://www-graphics.stanford.edu/~seander/bithacks.html
inline uint count_trailing_zero_bits(uint v) {
  uint c = 32;  // c will be the number of zero bits on the right

  static const unsigned int B[] = {0x55555555, 0x33333333, 0x0F0F0F0F, 0x00FF00FF, 0x0000FFFF};
  static const unsigned int S[] = {1, 2, 4, 8, 16};  // Our Magic Binary Numbers

  for (int i = 4; i >= 0; --i)  // unroll for more speed
  {
    if (v & B[i]) {
      v <<= S[i];
      c -= S[i];
    }
  }

  if (v) {
    c--;
  }

  return c;
}

inline uint count_leading_zero_bits(uint v) {
  uint temp;
  uint result = 32U;

  temp = (v >> 16U);
  if (temp) {
    result -= 16U;
    v = temp;
  }
  temp = (v >> 8U);
  if (temp) {
    result -= 8U;
    v = temp;
  }
  temp = (v >> 4U);
  if (temp) {
    result -= 4U;
    v = temp;
  }
  temp = (v >> 2U);
  if (temp) {
    result -= 2U;
    v = temp;
  }
  temp = (v >> 1U);
  if (temp) {
    result -= 1U;
    v = temp;
  }

  if (v & 1U)
    result--;

  return result;
}

inline uint64 emulu(uint32 a, uint32 b) {
#if defined(_M_IX86) && defined(_MSC_VER)
  return __emulu(a, b);
#else
  return static_cast<uint64>(a) * static_cast<uint64>(b);
#endif
}

double compute_entropy(const uint8* p, uint n);

void compute_lower_pow2_dim(int& width, int& height);
void compute_upper_pow2_dim(int& width, int& height);

inline bool equal_tol(float a, float b, float t) {
  return fabs(a - b) < ((maximum(fabs(a), fabs(b)) + 1.0f) * t);
}

inline bool equal_tol(double a, double b, double t) {
  return fabs(a - b) < ((maximum(fabs(a), fabs(b)) + 1.0f) * t);
}
}

}  // namespace crnlib