The Android Open Source Project | b07e1d9 | 2009-03-03 19:29:30 -0800 | [diff] [blame] | 1 | |
| 2 | /* @(#)s_frexp.c 1.4 95/01/18 */ |
| 3 | /* |
| 4 | * ==================================================== |
| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| 6 | * |
| 7 | * Developed at SunSoft, a Sun Microsystems, Inc. business. |
| 8 | * Permission to use, copy, modify, and distribute this |
| 9 | * software is freely granted, provided that this notice |
| 10 | * is preserved. |
| 11 | * ==================================================== |
| 12 | */ |
| 13 | |
| 14 | /* |
| 15 | * for non-zero x |
| 16 | * x = ieee_frexp(arg,&exp); |
| 17 | * return a double fp quantity x such that 0.5 <= |x| <1.0 |
| 18 | * and the corresponding binary exponent "exp". That is |
| 19 | * arg = x*2^exp. |
| 20 | * If arg is inf, 0.0, or NaN, then ieee_frexp(arg,&exp) returns arg |
| 21 | * with *exp=0. |
| 22 | */ |
| 23 | |
| 24 | #include "fdlibm.h" |
| 25 | |
| 26 | #ifdef __STDC__ |
| 27 | static const double |
| 28 | #else |
| 29 | static double |
| 30 | #endif |
| 31 | two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */ |
| 32 | |
| 33 | #ifdef __STDC__ |
| 34 | double ieee_frexp(double x, int *eptr) |
| 35 | #else |
| 36 | double ieee_frexp(x, eptr) |
| 37 | double x; int *eptr; |
| 38 | #endif |
| 39 | { |
| 40 | int hx, ix, lx; |
| 41 | hx = __HI(x); |
| 42 | ix = 0x7fffffff&hx; |
| 43 | lx = __LO(x); |
| 44 | *eptr = 0; |
| 45 | if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */ |
| 46 | if (ix<0x00100000) { /* subnormal */ |
| 47 | x *= two54; |
| 48 | hx = __HI(x); |
| 49 | ix = hx&0x7fffffff; |
| 50 | *eptr = -54; |
| 51 | } |
| 52 | *eptr += (ix>>20)-1022; |
| 53 | hx = (hx&0x800fffff)|0x3fe00000; |
| 54 | __HI(x) = hx; |
| 55 | return x; |
| 56 | } |