src/libm/s_scalbn.c
author Ryan C. Gordon <icculus@icculus.org>
Fri, 12 Aug 2016 19:59:00 -0400
changeset 10266 c09f06c4e8c8
parent 7678 286c42d7c5ed
permissions -rw-r--r--
emscripten: send fake mouse events for touches, like other targets do. (This really should be handled at the higher level and not in the individual targets, but this fixes the immediate bug.)

/* @(#)s_scalbn.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static const char rcsid[] =
    "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $";
#endif

/*
 * scalbn (double x, int n)
 * scalbn(x,n) returns x* 2**n  computed by  exponent
 * manipulation rather than by actually performing an
 * exponentiation or a multiplication.
 */

#include "math_libm.h"
#include "math_private.h"

libm_hidden_proto(copysign)
#ifdef __STDC__
     static const double
#else
     static double
#endif
       two54 = 1.80143985094819840000e+16,      /* 0x43500000, 0x00000000 */
         twom54 = 5.55111512312578270212e-17,   /* 0x3C900000, 0x00000000 */
         huge_val = 1.0e+300, tiny = 1.0e-300;

libm_hidden_proto(scalbn)
#ifdef __STDC__
     double scalbn(double x, int n)
#else
     double scalbn(x, n)
     double x;
     int n;
#endif
{
    int32_t k, hx, lx;
    EXTRACT_WORDS(hx, lx, x);
    k = (hx & 0x7ff00000) >> 20;        /* extract exponent */
    if (k == 0) {               /* 0 or subnormal x */
        if ((lx | (hx & 0x7fffffff)) == 0)
            return x;           /* +-0 */
        x *= two54;
        GET_HIGH_WORD(hx, x);
        k = ((hx & 0x7ff00000) >> 20) - 54;
        if (n < -50000)
            return tiny * x;    /* underflow */
    }
    if (k == 0x7ff)
        return x + x;           /* NaN or Inf */
    k = k + n;
    if (k > 0x7fe)
        return huge_val * copysign(huge_val, x);        /* overflow  */
    if (k > 0) {                /* normal result */
        SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
        return x;
    }
    if (k <= -54) {
        if (n > 50000)          /* in case integer overflow in n+k */
            return huge_val * copysign(huge_val, x);    /* overflow */
        else
            return tiny * copysign(tiny, x);    /* underflow */
    }
    k += 54;                    /* subnormal result */
    SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
    return x * twom54;
}

libm_hidden_def(scalbn)