src/libm/s_scalbn.c
author Sam Lantinga <slouken@libsdl.org>
Fri, 26 Aug 2016 12:18:08 -0700
changeset 10226 cb13d22b7f09
parent 7678 286c42d7c5ed
child 11683 48bcba563d9c
permissions -rw-r--r--
Added SDL_PrivateJoystickAdded() and SDL_PrivateJoystickRemoved()
Updated the removal code to iterate over all joystick add messages instead of just the first one.
     1 /* @(#)s_scalbn.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 defined(LIBM_SCCS) && !defined(lint)
    14 static const char rcsid[] =
    15     "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $";
    16 #endif
    17 
    18 /*
    19  * scalbn (double x, int n)
    20  * scalbn(x,n) returns x* 2**n  computed by  exponent
    21  * manipulation rather than by actually performing an
    22  * exponentiation or a multiplication.
    23  */
    24 
    25 #include "math_libm.h"
    26 #include "math_private.h"
    27 
    28 libm_hidden_proto(copysign)
    29 #ifdef __STDC__
    30      static const double
    31 #else
    32      static double
    33 #endif
    34        two54 = 1.80143985094819840000e+16,      /* 0x43500000, 0x00000000 */
    35          twom54 = 5.55111512312578270212e-17,   /* 0x3C900000, 0x00000000 */
    36          huge_val = 1.0e+300, tiny = 1.0e-300;
    37 
    38 libm_hidden_proto(scalbn)
    39 #ifdef __STDC__
    40      double scalbn(double x, int n)
    41 #else
    42      double scalbn(x, n)
    43      double x;
    44      int n;
    45 #endif
    46 {
    47     int32_t k, hx, lx;
    48     EXTRACT_WORDS(hx, lx, x);
    49     k = (hx & 0x7ff00000) >> 20;        /* extract exponent */
    50     if (k == 0) {               /* 0 or subnormal x */
    51         if ((lx | (hx & 0x7fffffff)) == 0)
    52             return x;           /* +-0 */
    53         x *= two54;
    54         GET_HIGH_WORD(hx, x);
    55         k = ((hx & 0x7ff00000) >> 20) - 54;
    56         if (n < -50000)
    57             return tiny * x;    /* underflow */
    58     }
    59     if (k == 0x7ff)
    60         return x + x;           /* NaN or Inf */
    61     k = k + n;
    62     if (k > 0x7fe)
    63         return huge_val * copysign(huge_val, x);        /* overflow  */
    64     if (k > 0) {                /* normal result */
    65         SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
    66         return x;
    67     }
    68     if (k <= -54) {
    69         if (n > 50000)          /* in case integer overflow in n+k */
    70             return huge_val * copysign(huge_val, x);    /* overflow */
    71         else
    72             return tiny * copysign(tiny, x);    /* underflow */
    73     }
    74     k += 54;                    /* subnormal result */
    75     SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
    76     return x * twom54;
    77 }
    78 
    79 libm_hidden_def(scalbn)