| The Android Open Source Project | a27d2ba | 2008-10-21 07:00:00 -0700 | [diff] [blame^] | 1 | /* @(#)s_modf.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_modf.c,v 1.7 2002/05/28 18:15:04 alfred Exp $"; |
| 15 | #endif |
| 16 | |
| 17 | /* |
| 18 | * modf(double x, double *iptr) |
| 19 | * return fraction part of x, and return x's integral part in *iptr. |
| 20 | * Method: |
| 21 | * Bit twiddling. |
| 22 | * |
| 23 | * Exception: |
| 24 | * No exception. |
| 25 | */ |
| 26 | |
| 27 | #include "math.h" |
| 28 | #include "math_private.h" |
| 29 | |
| 30 | static const double one = 1.0; |
| 31 | |
| 32 | double |
| 33 | modf(double x, double *iptr) |
| 34 | { |
| 35 | int32_t i0,i1,j0; |
| 36 | u_int32_t i; |
| 37 | EXTRACT_WORDS(i0,i1,x); |
| 38 | j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ |
| 39 | if(j0<20) { /* integer part in high x */ |
| 40 | if(j0<0) { /* |x|<1 */ |
| 41 | INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */ |
| 42 | return x; |
| 43 | } else { |
| 44 | i = (0x000fffff)>>j0; |
| 45 | if(((i0&i)|i1)==0) { /* x is integral */ |
| 46 | u_int32_t high; |
| 47 | *iptr = x; |
| 48 | GET_HIGH_WORD(high,x); |
| 49 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ |
| 50 | return x; |
| 51 | } else { |
| 52 | INSERT_WORDS(*iptr,i0&(~i),0); |
| 53 | return x - *iptr; |
| 54 | } |
| 55 | } |
| 56 | } else if (j0>51) { /* no fraction part */ |
| 57 | u_int32_t high; |
| 58 | *iptr = x*one; |
| 59 | GET_HIGH_WORD(high,x); |
| 60 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ |
| 61 | return x; |
| 62 | } else { /* fraction part in low x */ |
| 63 | i = ((u_int32_t)(0xffffffff))>>(j0-20); |
| 64 | if((i1&i)==0) { /* x is integral */ |
| 65 | u_int32_t high; |
| 66 | *iptr = x; |
| 67 | GET_HIGH_WORD(high,x); |
| 68 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ |
| 69 | return x; |
| 70 | } else { |
| 71 | INSERT_WORDS(*iptr,i0,i1&(~i)); |
| 72 | return x - *iptr; |
| 73 | } |
| 74 | } |
| 75 | } |