diff --git a/src/lisp/s_scalbn.c b/src/lisp/s_scalbn.c new file mode 100644 index 0000000000000000000000000000000000000000..329be8b8969b9b0effd4a48909f6621efaffc06b --- /dev/null +++ b/src/lisp/s_scalbn.c @@ -0,0 +1,63 @@ + +/* @(#)s_scalbn.c 1.3 95/01/18 */ +/* + * ==================================================== + * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. + * + * Developed at SunSoft, a Sun Microsystems, Inc. business. + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + */ + +/* + * 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 "fdlibm.h" + +#ifdef __STDC__ +static const double +#else +static double +#endif +two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ +twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ +huge = 1.0e+300, +tiny = 1.0e-300; + +#ifdef __STDC__ + double scalbn (double x, int n) +#else + double scalbn (x,n) + double x; int n; +#endif +{ + int k,hx,lx; + hx = __HI(x); + lx = __LO(x); + k = (hx&0x7ff00000)>>20; /* extract exponent */ + if (k==0) { /* 0 or subnormal x */ + if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */ + x *= two54; + hx = __HI(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 */ + {__HI(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 */ + __HI(x) = (hx&0x800fffff)|(k<<20); + return x*twom54; +}