lib/libm/src/s_floorf.c

   1 /* s_floorf.c -- float version of s_floor.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #include <sys/cdefs.h>
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 __RCSID("$NetBSD: s_floorf.c,v 1.8 2008/04/25 22:21:53 christos Exp $");
  19 #endif
  20
  21 /*
  22  * floorf(x)
  23  * Return x rounded toward -inf to integral value
  24  * Method:
  25  *      Bit twiddling.
  26  * Exception:
  27  *      Inexact flag raised if x not equal to floorf(x).
  28  */
  29
  30 #include "math.h"
  31 #include "math_private.h"
  32
  33 static const float huge = 1.0e30;
  34
  35 float
  36 floorf(float x)
  37 {
  38         int32_t i0,jj0;
  39         u_int32_t i;
  40         GET_FLOAT_WORD(i0,x);
  41         jj0 = ((i0>>23)&0xff)-0x7f;
  42         if(jj0<23) {
  43             if(jj0<0) {         /* raise inexact if x != 0 */
  44                 if(huge+x>(float)0.0) {/* return 0*sign(x) if |x|<1 */
  45                     if(i0>=0) {i0=0;}
  46                     else if((i0&0x7fffffff)!=0)
  47                         { i0=0xbf800000;}
  48                 }
  49             } else {
  50                 i = (0x007fffff)>>jj0;
  51                 if((i0&i)==0) return x; /* x is integral */
  52                 if(huge+x>(float)0.0) { /* raise inexact flag */
  53                     if(i0<0) i0 += (0x00800000)>>jj0;
  54                     i0 &= (~i);
  55                 }
  56             }
  57         } else {
  58             if(jj0==0x80) return x+x;   /* inf or NaN */
  59             else return x;              /* x is integral */
  60         }
  61         SET_FLOAT_WORD(x,i0);
  62         return x;
  63 }