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Annotation of src/lib/libm/src/s_trunc.c, Revision 1.1

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:
        !            13: #if 0
        !            14: #include <sys/cdefs.h>
        !            15: __FBSDID("$FreeBSD: src/lib/msun/src/s_trunc.c,v 1.1 2004/06/20 09:25:43 das Exp $");
        !            16: #endif
        !            17: #include <sys/cdefs.h>
        !            18: #if defined(LIBM_SCCS) && !defined(lint)
        !            19: __RCSID("$NetBSD$");
        !            20: #endif
        !            21:
        !            22: /*
        !            23:  * trunc(x)
        !            24:  * Return x rounded toward 0 to integral value
        !            25:  * Method:
        !            26:  *     Bit twiddling.
        !            27:  * Exception:
        !            28:  *     Inexact flag raised if x not equal to trunc(x).
        !            29:  */
        !            30:
        !            31: #include "math.h"
        !            32: #include "math_private.h"
        !            33:
        !            34: static const double huge = 1.0e300;
        !            35:
        !            36: double
        !            37: trunc(double x)
        !            38: {
        !            39:        int32_t i0,i1,j0;
        !            40:        uint32_t i;
        !            41:        EXTRACT_WORDS(i0,i1,x);
        !            42:        j0 = ((i0>>20)&0x7ff)-0x3ff;
        !            43:        if(j0<20) {
        !            44:            if(j0<0) {  /* raise inexact if x != 0 */
        !            45:                if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
        !            46:                    i0 &= 0x80000000U;
        !            47:                    i1 = 0;
        !            48:                }
        !            49:            } else {
        !            50:                i = (0x000fffff)>>j0;
        !            51:                if(((i0&i)|i1)==0) return x; /* x is integral */
        !            52:                if(huge+x>0.0) {        /* raise inexact flag */
        !            53:                    i0 &= (~i); i1=0;
        !            54:                }
        !            55:            }
        !            56:        } else if (j0>51) {
        !            57:            if(j0==0x400) return x+x;   /* inf or NaN */
        !            58:            else return x;              /* x is integral */
        !            59:        } else {
        !            60:            i = ((u_int32_t)(0xffffffff))>>(j0-20);
        !            61:            if((i1&i)==0) return x;     /* x is integral */
        !            62:            if(huge+x>0.0)              /* raise inexact flag */
        !            63:                i1 &= (~i);
        !            64:        }
        !            65:        INSERT_WORDS(x,i0,i1);
        !            66:        return x;
        !            67: }

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