| /* @(#)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> |
| |
| #include <sys/types.h> |
| #include <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; |
| } |