| The Android Open Source Project | 1dc9e47 | 2009-03-03 19:28:35 -0800 | [diff] [blame^] | 1 | /* @(#)s_frexp.c 5.1 93/09/24 */ |
| 2 | /* |
| 3 | * ==================================================== |
| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| 5 | * |
| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
| 7 | * Permission to use, copy, modify, and distribute this |
| 8 | * software is freely granted, provided that this notice |
| 9 | * is preserved. |
| 10 | * ==================================================== |
| 11 | */ |
| 12 | |
| 13 | #ifndef lint |
| 14 | static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_frexp.c,v 1.10 2005/03/07 21:27:37 das Exp $"; |
| 15 | #endif |
| 16 | |
| 17 | /* |
| 18 | * for non-zero x |
| 19 | * x = frexp(arg,&exp); |
| 20 | * return a double fp quantity x such that 0.5 <= |x| <1.0 |
| 21 | * and the corresponding binary exponent "exp". That is |
| 22 | * arg = x*2^exp. |
| 23 | * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg |
| 24 | * with *exp=0. |
| 25 | */ |
| 26 | |
| 27 | #include <sys/cdefs.h> |
| 28 | #include <float.h> |
| 29 | |
| 30 | #include "math.h" |
| 31 | #include "math_private.h" |
| 32 | |
| 33 | static const double |
| 34 | two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */ |
| 35 | |
| 36 | double |
| 37 | frexp(double x, int *eptr) |
| 38 | { |
| 39 | int32_t hx, ix, lx; |
| 40 | EXTRACT_WORDS(hx,lx,x); |
| 41 | ix = 0x7fffffff&hx; |
| 42 | *eptr = 0; |
| 43 | if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */ |
| 44 | if (ix<0x00100000) { /* subnormal */ |
| 45 | x *= two54; |
| 46 | GET_HIGH_WORD(hx,x); |
| 47 | ix = hx&0x7fffffff; |
| 48 | *eptr = -54; |
| 49 | } |
| 50 | *eptr += (ix>>20)-1022; |
| 51 | hx = (hx&0x800fffff)|0x3fe00000; |
| 52 | SET_HIGH_WORD(x,hx); |
| 53 | return x; |
| 54 | } |
| 55 | |
| 56 | #if (LDBL_MANT_DIG == 53) |
| 57 | __weak_reference(frexp, frexpl); |
| 58 | #endif |