/* @(#)s_scalbn.c 5.1 93/09/24 */ /* @(#)fdlibm.h 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. * ==================================================== */ #include <sys/cdefs.h> __FBSDID("$FreeBSD$"); #include <sys/types.h> #include <machine/endian.h> #include <math.h> /* Bit fiddling routines copied from msun/src/math_private.h,v 1.15 */ #if BYTE_ORDER == BIG_ENDIAN typedef union { double value; struct { u_int32_t msw; u_int32_t lsw; } parts; } ieee_double_shape_type; #endif #if BYTE_ORDER == LITTLE_ENDIAN typedef union { double value; struct { u_int32_t lsw; u_int32_t msw; } parts; } ieee_double_shape_type; #endif /* Get two 32 bit ints from a double. */ #define EXTRACT_WORDS(ix0,ix1,d) \ do { \ ieee_double_shape_type ew_u; \ ew_u.value = (d); \ (ix0) = ew_u.parts.msw; \ (ix1) = ew_u.parts.lsw; \ } while (0) /* Get the more significant 32 bit int from a double. */ #define GET_HIGH_WORD(i,d) \ do { \ ieee_double_shape_type gh_u; \ gh_u.value = (d); \ (i) = gh_u.parts.msw; \ } while (0) /* Set the more significant 32 bits of a double from an int. */ #define SET_HIGH_WORD(d,v) \ do { \ ieee_double_shape_type sh_u; \ sh_u.value = (d); \ sh_u.parts.msw = (v); \ (d) = sh_u.value; \ } while (0) static const double two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ huge = 1.0e+300, tiny = 1.0e-300; static double _copysign(double x, double y) { u_int32_t hx,hy; GET_HIGH_WORD(hx,x); GET_HIGH_WORD(hy,y); SET_HIGH_WORD(x,(hx&0x7fffffff)|(hy&0x80000000)); return x; } double ldexp(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; }