My attempt at creating a circular loader

circularLoaderUsingEasing

void circularLoader2() {
  fill_solid(leds, NUM_LEDS, CRGB::Black);
  uint8_t uneased_startP = lerp8by8( 0, NUM_LEDS, beat8( 30, 5000 ) );  // start position, runs behind endP
  uint8_t uneased_endP   = lerp8by8( 0, NUM_LEDS, beat8( 30 ) );  // start position
  uint8_t startP = QuadraticEaseIn8( uneased_startP );
  uint8_t endP   = CubicEaseIn8( uneased_endP );
  DEBUG_PRINT(F("startP: ")) ;
  DEBUG_PRINT(startP) ;
  DEBUG_PRINT(F("\t")) ;
  DEBUG_PRINT(F("endP: ")) ;
  DEBUG_PRINT(endP) ;
  // DEBUG_PRINT(F("\t")) ;
  // DEBUG_PRINT(F("eased: ")) ;
  // DEBUG_PRINT(eased) ;
  DEBUG_PRINTLN() ;

  fillSolidRing(startP, endP, CHSV(90, 255, 255));

  FastLED.show();
}

// Uses functions from https://github.com/warrenm/AHEasing
uint8_t QuadraticEaseIn8( uint8_t p ) {
  int     i_100       = map(p, 0, NUM_LEDS, 0, 100); // Map current led p to percentage between 0 - 100
  AHFloat eased_float = QuadraticEaseInOut( (float)i_100 / (float)100); // Convert to value between 0 - 1
  int     eased_100   = (int)(eased_float * 100); // convert back to percentage
  return  map(eased_100, 0, 100, 0, NUM_LEDS);  // convert back to LED position
}

uint8_t CubicEaseIn8( uint8_t p ) {
  int     i_100       = map(p, 0, NUM_LEDS, 0, 100); // Map current led p to percentage between 0 - 100
  AHFloat eased_float = CubicEaseInOut( (float)i_100 / (float)100); // Convert to value between 0 - 1
  int     eased_100   = (int)(eased_float * 100); // convert back to percentage
  return  map(eased_100, 0, 100, 0, NUM_LEDS);  // convert back to LED position
}


// This is a little convoluted and could probably be written better :)
void fillSolidRing( int startLed, int endLed, CHSV color ) {
  // Determine actual start and actual end (normalize using custom modulo):
  int actualStart = mod(startLed + NUM_LEDS, NUM_LEDS)  ;
  int actualEnd = mod(endLed + NUM_LEDS, NUM_LEDS) ;

  // If beginning is at say 50, and end at 10, then we split the fill in 2:
  // * one from 50-59
  // * one from 0-10
  if ( actualStart > actualEnd ) {
    fill_solid(leds + actualStart, NUM_LEDS - actualStart, color);
    fill_solid(leds, actualEnd, color);
  } else {
    fill_solid(leds + actualStart, actualEnd - actualStart, color);
  }
} // end fillSolidRing()


// Custom modulo which always returns a positive number
int mod(int x, int m) {
  return (x % m + m) % m;
}