fixp.h

   1 #ifndef ZZGO_FIXP_H
   2 #define ZZGO_FIXP_H
   3
   4 /* Tools for counting fixed-point numbers. */
   5
   6 /* We implement a simple fixed-point number type, with fixed number of
   7  * fractional binary digits after the radix point. */
   8
   9 #include <stdint.h>
  10
  11 typedef uint_fast32_t fixp_t;
  12
  13 /* We should accomodate at least 0..131072 (17bits) in the whole number
  14  * portion; assuming at least 32bit integer, that leaves us with 15-bit
  15  * fractional part. Thankfully, we need only unsigned values. */
  16 #define FIXP_BITS 15
  17
  18 #define FIXP_SCALE (1<<FIXP_BITS)
  19
  20 #define double_to_fixp(n) (nearbyint((n) * (FIXP_SCALE)))
  21 #define fixp_to_double(n) ((double) (n) / FIXP_SCALE)
  22
  23 #endif