xref: /minix3/lib/libm/src/s_trunc.c (revision 84d9c625bfea59e274550651111ae9edfdc40fbd)
12fe8fb19SBen Gras /* @(#)s_floor.c 5.1 93/09/24 */
22fe8fb19SBen Gras /*
32fe8fb19SBen Gras  * ====================================================
42fe8fb19SBen Gras  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
52fe8fb19SBen Gras  *
62fe8fb19SBen Gras  * Developed at SunPro, a Sun Microsystems, Inc. business.
72fe8fb19SBen Gras  * Permission to use, copy, modify, and distribute this
82fe8fb19SBen Gras  * software is freely granted, provided that this notice
92fe8fb19SBen Gras  * is preserved.
102fe8fb19SBen Gras  * ====================================================
112fe8fb19SBen Gras  */
122fe8fb19SBen Gras 
132fe8fb19SBen Gras #include <sys/cdefs.h>
142fe8fb19SBen Gras #if 0
152fe8fb19SBen Gras __FBSDID("$FreeBSD: src/lib/msun/src/s_trunc.c,v 1.1 2004/06/20 09:25:43 das Exp $");
162fe8fb19SBen Gras #endif
172fe8fb19SBen Gras #if defined(LIBM_SCCS) && !defined(lint)
18*84d9c625SLionel Sambuc __RCSID("$NetBSD: s_trunc.c,v 1.4 2013/11/13 12:58:11 joerg Exp $");
192fe8fb19SBen Gras #endif
202fe8fb19SBen Gras 
212fe8fb19SBen Gras /*
222fe8fb19SBen Gras  * trunc(x)
232fe8fb19SBen Gras  * Return x rounded toward 0 to integral value
242fe8fb19SBen Gras  * Method:
252fe8fb19SBen Gras  *	Bit twiddling.
262fe8fb19SBen Gras  * Exception:
272fe8fb19SBen Gras  *	Inexact flag raised if x not equal to trunc(x).
282fe8fb19SBen Gras  */
292fe8fb19SBen Gras 
302fe8fb19SBen Gras #include "math.h"
312fe8fb19SBen Gras #include "math_private.h"
322fe8fb19SBen Gras 
33*84d9c625SLionel Sambuc #ifndef __HAVE_LONG_DOUBLE
34*84d9c625SLionel Sambuc __strong_alias(_truncl, trunc)
35*84d9c625SLionel Sambuc __weak_alias(truncl, trunc)
36*84d9c625SLionel Sambuc #endif
37*84d9c625SLionel Sambuc 
382fe8fb19SBen Gras static const double huge = 1.0e300;
392fe8fb19SBen Gras 
402fe8fb19SBen Gras double
trunc(double x)412fe8fb19SBen Gras trunc(double x)
422fe8fb19SBen Gras {
432fe8fb19SBen Gras 	int32_t i0,i1,jj0;
442fe8fb19SBen Gras 	uint32_t i;
452fe8fb19SBen Gras 	EXTRACT_WORDS(i0,i1,x);
462fe8fb19SBen Gras 	jj0 = ((i0>>20)&0x7ff)-0x3ff;
472fe8fb19SBen Gras 	if(jj0<20) {
482fe8fb19SBen Gras 	    if(jj0<0) { 	/* raise inexact if x != 0 */
492fe8fb19SBen Gras 		if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
502fe8fb19SBen Gras 		    i0 &= 0x80000000U;
512fe8fb19SBen Gras 		    i1 = 0;
522fe8fb19SBen Gras 		}
532fe8fb19SBen Gras 	    } else {
542fe8fb19SBen Gras 		i = (0x000fffff)>>jj0;
552fe8fb19SBen Gras 		if(((i0&i)|i1)==0) return x; /* x is integral */
562fe8fb19SBen Gras 		if(huge+x>0.0) {	/* raise inexact flag */
572fe8fb19SBen Gras 		    i0 &= (~i); i1=0;
582fe8fb19SBen Gras 		}
592fe8fb19SBen Gras 	    }
602fe8fb19SBen Gras 	} else if (jj0>51) {
612fe8fb19SBen Gras 	    if(jj0==0x400) return x+x;	/* inf or NaN */
622fe8fb19SBen Gras 	    else return x;		/* x is integral */
632fe8fb19SBen Gras 	} else {
642fe8fb19SBen Gras 	    i = ((u_int32_t)(0xffffffff))>>(jj0-20);
652fe8fb19SBen Gras 	    if((i1&i)==0) return x;	/* x is integral */
662fe8fb19SBen Gras 	    if(huge+x>0.0)		/* raise inexact flag */
672fe8fb19SBen Gras 		i1 &= (~i);
682fe8fb19SBen Gras 	}
692fe8fb19SBen Gras 	INSERT_WORDS(x,i0,i1);
702fe8fb19SBen Gras 	return x;
712fe8fb19SBen Gras }
72