diff options
Diffstat (limited to 'libm/src/s_scalbn.c')
-rw-r--r-- | libm/src/s_scalbn.c | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/libm/src/s_scalbn.c b/libm/src/s_scalbn.c new file mode 100644 index 0000000..6218c11 --- /dev/null +++ b/libm/src/s_scalbn.c @@ -0,0 +1,79 @@ +/* @(#)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. + * ==================================================== + */ + +#ifndef lint +static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_scalbn.c,v 1.11 2005/03/07 21:27:37 das 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 <sys/cdefs.h> +#include <float.h> + +#include "math.h" +#include "math_private.h" + +static const double +two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ +twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ +huge = 1.0e+300, +tiny = 1.0e-300; + +double +scalbn (double x, int n) +{ + 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*copysign(huge,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*copysign(huge,x); /*overflow*/ + else return tiny*copysign(tiny,x); /*underflow*/ + k += 54; /* subnormal result */ + SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); + return x*twom54; +} + +// this is normally in FreeBSD's libc. +double +ldexp (double x, int n) +{ + return scalbn(x,n); +} + +#if (LDBL_MANT_DIG == 53) //XXX: brian FIXME __weak_reference doesn work +long double ldexpl (long double x, int n) { + return scalbn((double)x,n); +} +long double scalbnl (long double x, int n) { + return scalbn((double)x,n); +} +__weak_reference(scalbn, ldexpl); +__weak_reference(scalbn, scalbnl); +#endif |