Function getRandomBits

libraries/randomHelpers/randomHelpers.cpp:199–224

n = 1..31 TODO: performance gain too low for n > 16

//  n = 1..31
//  TODO: performance gain too low for n > 16
uint32_t getRandomBits(uint8_t n) 
{
  uint32_t rv = 0;

  //  for large values of n the more straightforward approach is faster (UNO).
  if (n > 32) n = 32;
  if (n >= 20) return getRandom32() >> (32 - n);

  if (n >= __randomIdx)
  {
    if (__randomIdx > 0)
    {
      n -= __randomIdx;
      rv = __randomBuffer << n;
    }
    __randomBuffer = getRandom32();
    __randomIdx = 32;
  }
  if (n > 0)  //  more bits needed?
  {
    rv |= __randomBuffer & ((1UL << n) - 1);
    __randomBuffer >>= n;
    __randomIdx -= n;
  }
  return rv;
}


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