lib/libm/src/s_truncf.c

   1 /* @(#)s_floor.c 5.1 93/09/24 */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 #include <sys/cdefs.h>
  14 #if 0
  15 __FBSDID("$FreeBSD: src/lib/msun/src/s_truncf.c,v 1.1 2004/06/20 09:25:43 das Exp $");
  16 #endif
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 __RCSID("$NetBSD: s_truncf.c,v 1.4 2008/04/25 22:21:53 christos Exp $");
  19 #endif
  20
  21 /*
  22  * truncf(x)
  23  * Return x rounded toward 0 to integral value
  24  * Method:
  25  *      Bit twiddling.
  26  * Exception:
  27  *      Inexact flag raised if x not equal to truncf(x).
  28  */
  29
  30 #include "math.h"
  31 #include "math_private.h"
  32
  33 static const float huge = 1.0e30F;
  34
  35 float
  36 truncf(float x)
  37 {
  38         int32_t i0,jj0;
  39         uint32_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>0.0F)         /* |x|<1, so return 0*sign(x) */
  45                     i0 &= 0x80000000;
  46             } else {
  47                 i = (0x007fffff)>>jj0;
  48                 if((i0&i)==0) return x; /* x is integral */
  49                 if(huge+x>0.0F)         /* raise inexact flag */
  50                     i0 &= (~i);
  51             }
  52         } else {
  53             if(jj0==0x80) return x+x;   /* inf or NaN */
  54             else return x;              /* x is integral */
  55         }
  56         SET_FLOAT_WORD(x,i0);
  57         return x;
  58 }