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Annotation of src/lib/libm/src/s_trunc.c, Revision 1.2

1.1       xtraeme     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:
1.2     ! hubertf    13: #include <sys/cdefs.h>
1.1       xtraeme    14: #if 0
                     15: __FBSDID("$FreeBSD: src/lib/msun/src/s_trunc.c,v 1.1 2004/06/20 09:25:43 das Exp $");
                     16: #endif
                     17: #if defined(LIBM_SCCS) && !defined(lint)
1.2     ! hubertf    18: __RCSID("$NetBSD: s_trunc.c,v 1.1 2006/03/25 16:41:12 xtraeme Exp $");
1.1       xtraeme    19: #endif
                     20:
                     21: /*
                     22:  * trunc(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 trunc(x).
                     28:  */
                     29:
                     30: #include "math.h"
                     31: #include "math_private.h"
                     32:
                     33: static const double huge = 1.0e300;
                     34:
                     35: double
                     36: trunc(double x)
                     37: {
                     38:        int32_t i0,i1,j0;
                     39:        uint32_t i;
                     40:        EXTRACT_WORDS(i0,i1,x);
                     41:        j0 = ((i0>>20)&0x7ff)-0x3ff;
                     42:        if(j0<20) {
                     43:            if(j0<0) {  /* raise inexact if x != 0 */
                     44:                if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
                     45:                    i0 &= 0x80000000U;
                     46:                    i1 = 0;
                     47:                }
                     48:            } else {
                     49:                i = (0x000fffff)>>j0;
                     50:                if(((i0&i)|i1)==0) return x; /* x is integral */
                     51:                if(huge+x>0.0) {        /* raise inexact flag */
                     52:                    i0 &= (~i); i1=0;
                     53:                }
                     54:            }
                     55:        } else if (j0>51) {
                     56:            if(j0==0x400) return x+x;   /* inf or NaN */
                     57:            else return x;              /* x is integral */
                     58:        } else {
                     59:            i = ((u_int32_t)(0xffffffff))>>(j0-20);
                     60:            if((i1&i)==0) return x;     /* x is integral */
                     61:            if(huge+x>0.0)              /* raise inexact flag */
                     62:                i1 &= (~i);
                     63:        }
                     64:        INSERT_WORDS(x,i0,i1);
                     65:        return x;
                     66: }

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