2.96

/*
 * float-f2i.c
 */
#include <stdio.h>
#include <assert.h>
#include "float-f2i.h"

/*
 * Compute (float) f
 * If conversion cause overflow or f is NaN, return 0x80000000
 */
int float_f2i(float_bits f) {
  unsigned sig = f >> 31;
  unsigned exp = f >> 23 & 0xFF;
  unsigned frac = f & 0x7FFFFF;
  unsigned bias = 0x7F;

  int num;
  unsigned E;
  unsigned M;

  /*
   * consider positive numbers
   *
   * 0 00000000 00000000000000000000000
   *   ===>
   * 0 01111111 00000000000000000000000
   *   0 <= f < 1
   * get integer 0
   *
   * 0 01111111 00000000000000000000000
   *   ===>
   * 0 (01111111+31) 00000000000000000000000
   *   1 <= f < 2^31
   * integer round to 0
   *
   * 0 (01111111+31) 00000000000000000000000
   *   ===>
   * greater
   *   2^31 <= f < oo
   * return 0x80000000
   */
  if (exp >= 0 && exp < 0 + bias) {
    /* number less than 1 */
    num = 0;
  } else if (exp >= 31 + bias) {
    /* number overflow */
    /* or f < 0 and (int)f == INT_MIN */
    num = 0x80000000;
  } else {
    E = exp - bias;
    M = frac | 0x800000;
    if (E > 23) {
      num = M << (E - 23);
    } else {
      /* whether sig is 1 or 0, round to zero */
      num = M >> (23 - E);
    }
  }

  return sig ? -num : num;
}