scale.h

tinyos-2.x.rar

#ifndef SCALE_H
#define SCALE_H

/*
 * Multiply x by a/b while avoiding overflow when possible. Requires that
 * a*b <= max value of from_t, and assumes unsigned arithmetic. 
 *
 * @param x Number to scale
 * @param a Numerator of scaling value
 * @param b Denominator of scaling value
 * @return x * a/b
 */
inline uint32_t scale32(uint32_t x, uint32_t a, uint32_t b) 
{
  uint32_t x_over_b = x / b;
  uint32_t x_mod_b = x % b;

  x_mod_b *= a; // on a separate line just in case some compiler goes weird
  return x_over_b * a + x_mod_b / b;
}

#endif