/*
   mkvmerge -- utility for splicing together matroska files
   from component media subtypes

   Distributed under the GPL v2
   see the file COPYING for details
   or visit http://www.gnu.org/copyleft/gpl.html

   math helper functions

   Written by Moritz Bunkus <moritz@bunkus.org>.
*/

#include "common/common_pch.h"

#include "common/math.h"

namespace mtx::math {

uint64_t
round_to_nearest_pow2(uint64_t value) {
  uint64_t best_value = 0;
  uint64_t test_value = 1;

  while (0x8000000000000000ull >= test_value) {
    if (  (value > test_value ? value - test_value : test_value - value)
        < (value > best_value ? value - best_value : best_value - value))
      best_value = test_value;
    test_value <<= 1;
  }

  return best_value;
}

int
int_log2(uint64_t value) {
  for (int bit = 63; bit >= 0; --bit)
    if (value & (1ull << bit))
      return bit;

  return -1;
}

double
int_to_double(int64_t value) {
  if (static_cast<uint64_t>(value + value) > (0xffeull << 52))
    return static_cast<double>(NAN);
  return std::ldexp(((value & ((1ll << 52) - 1)) + (1ll << 52)) * (value >> 63 | 1), (value >> 52 & 0x7ff) - 1075);
}

int64_rational_c
clamp_values_to(int64_rational_c const &r,
                int64_t max_value) {
  auto num = r.numerator();
  auto den = r.denominator();

  if (!num || !den || ((num <= max_value) && (den <= max_value)))
    return r;

  // 333 / 1000 , clamp = 500, mul = 1/2 = 1/(max/clamp) = clamp/max

  auto mult = int64_rational_c{ max_value, std::max(num, den) };
  den       = boost::rational_cast<int64_t>(den * mult);

  return { boost::rational_cast<int64_t>(num * mult), den ? den : 1 };
}
}
