1*05a0b428SJohn Marino /* $OpenBSD: s_scalbnl.c,v 1.3 2013/11/12 18:28:02 martynas Exp $ */
2*05a0b428SJohn Marino /* @(#)s_scalbn.c 5.1 93/09/24 */
3*05a0b428SJohn Marino /*
4*05a0b428SJohn Marino * ====================================================
5*05a0b428SJohn Marino * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6*05a0b428SJohn Marino *
7*05a0b428SJohn Marino * Developed at SunPro, a Sun Microsystems, Inc. business.
8*05a0b428SJohn Marino * Permission to use, copy, modify, and distribute this
9*05a0b428SJohn Marino * software is freely granted, provided that this notice
10*05a0b428SJohn Marino * is preserved.
11*05a0b428SJohn Marino * ====================================================
12*05a0b428SJohn Marino */
13*05a0b428SJohn Marino
14*05a0b428SJohn Marino /*
15*05a0b428SJohn Marino * scalbnl (long double x, int n)
16*05a0b428SJohn Marino * scalbnl(x,n) returns x* 2**n computed by exponent
17*05a0b428SJohn Marino * manipulation rather than by actually performing an
18*05a0b428SJohn Marino * exponentiation or a multiplication.
19*05a0b428SJohn Marino */
20*05a0b428SJohn Marino
21*05a0b428SJohn Marino /*
22*05a0b428SJohn Marino * We assume that a long double has a 15-bit exponent. On systems
23*05a0b428SJohn Marino * where long double is the same as double, scalbnl() is an alias
24*05a0b428SJohn Marino * for scalbn(), so we don't use this routine.
25*05a0b428SJohn Marino */
26*05a0b428SJohn Marino
27*05a0b428SJohn Marino #include <sys/types.h>
28*05a0b428SJohn Marino #include <machine/ieee.h>
29*05a0b428SJohn Marino #include <float.h>
30*05a0b428SJohn Marino #include <math.h>
31*05a0b428SJohn Marino
32*05a0b428SJohn Marino #if LDBL_MAX_EXP != 0x4000
33*05a0b428SJohn Marino #error "Unsupported long double format"
34*05a0b428SJohn Marino #endif
35*05a0b428SJohn Marino
36*05a0b428SJohn Marino static const long double
37*05a0b428SJohn Marino huge = 0x1p16000L,
38*05a0b428SJohn Marino tiny = 0x1p-16000L;
39*05a0b428SJohn Marino
40*05a0b428SJohn Marino long double
scalbnl(long double x,int n)41*05a0b428SJohn Marino scalbnl (long double x, int n)
42*05a0b428SJohn Marino {
43*05a0b428SJohn Marino union {
44*05a0b428SJohn Marino long double e;
45*05a0b428SJohn Marino struct ieee_ext bits;
46*05a0b428SJohn Marino } u;
47*05a0b428SJohn Marino int k;
48*05a0b428SJohn Marino u.e = x;
49*05a0b428SJohn Marino k = u.bits.ext_exp; /* extract exponent */
50*05a0b428SJohn Marino if (k==0) { /* 0 or subnormal x */
51*05a0b428SJohn Marino if ((u.bits.ext_frach
52*05a0b428SJohn Marino #ifdef EXT_FRACHMBITS
53*05a0b428SJohn Marino | u.bits.ext_frachm
54*05a0b428SJohn Marino #endif /* EXT_FRACHMBITS */
55*05a0b428SJohn Marino #ifdef EXT_FRACLMBITS
56*05a0b428SJohn Marino | u.bits.ext_fraclm
57*05a0b428SJohn Marino #endif /* EXT_FRACLMBITS */
58*05a0b428SJohn Marino | u.bits.ext_fracl)==0) return x; /* +-0 */
59*05a0b428SJohn Marino u.e *= 0x1p+128;
60*05a0b428SJohn Marino k = u.bits.ext_exp - 128;
61*05a0b428SJohn Marino if (n< -50000) return tiny*x; /*underflow*/
62*05a0b428SJohn Marino }
63*05a0b428SJohn Marino if (k==0x7fff) return x+x; /* NaN or Inf */
64*05a0b428SJohn Marino k = k+n;
65*05a0b428SJohn Marino if (k >= 0x7fff) return huge*copysignl(huge,x); /* overflow */
66*05a0b428SJohn Marino if (k > 0) /* normal result */
67*05a0b428SJohn Marino {u.bits.ext_exp = k; return u.e;}
68*05a0b428SJohn Marino if (k <= -128) {
69*05a0b428SJohn Marino if (n > 50000) /* in case integer overflow in n+k */
70*05a0b428SJohn Marino return huge*copysign(huge,x); /*overflow*/
71*05a0b428SJohn Marino else return tiny*copysign(tiny,x); /*underflow*/
72*05a0b428SJohn Marino }
73*05a0b428SJohn Marino k += 128; /* subnormal result */
74*05a0b428SJohn Marino u.bits.ext_exp = k;
75*05a0b428SJohn Marino return u.e*0x1p-128;
76*05a0b428SJohn Marino }
77*05a0b428SJohn Marino
78*05a0b428SJohn Marino long double
ldexpl(long double x,int n)79*05a0b428SJohn Marino ldexpl(long double x, int n)
80*05a0b428SJohn Marino {
81*05a0b428SJohn Marino return scalbnl(x, n);
82*05a0b428SJohn Marino }
83