The Android Open Source Project | 1dc9e47 | 2009-03-03 19:28:35 -0800 | [diff] [blame] | 1 | |
| 2 | /* @(#)e_remainder.c 1.3 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 | |
Elliott Hughes | a0ee078 | 2013-01-30 19:06:37 -0800 | [diff] [blame] | 14 | #include <sys/cdefs.h> |
| 15 | __FBSDID("$FreeBSD$"); |
The Android Open Source Project | 1dc9e47 | 2009-03-03 19:28:35 -0800 | [diff] [blame] | 16 | |
| 17 | /* __ieee754_remainder(x,p) |
| 18 | * Return : |
| 19 | * returns x REM p = x - [x/p]*p as if in infinite |
| 20 | * precise arithmetic, where [x/p] is the (infinite bit) |
| 21 | * integer nearest x/p (in half way case choose the even one). |
| 22 | * Method : |
| 23 | * Based on fmod() return x-[x/p]chopped*p exactlp. |
| 24 | */ |
| 25 | |
Elliott Hughes | a0ee078 | 2013-01-30 19:06:37 -0800 | [diff] [blame] | 26 | #include <float.h> |
| 27 | |
The Android Open Source Project | 1dc9e47 | 2009-03-03 19:28:35 -0800 | [diff] [blame] | 28 | #include "math.h" |
| 29 | #include "math_private.h" |
| 30 | |
| 31 | static const double zero = 0.0; |
| 32 | |
| 33 | |
| 34 | double |
| 35 | __ieee754_remainder(double x, double p) |
| 36 | { |
| 37 | int32_t hx,hp; |
| 38 | u_int32_t sx,lx,lp; |
| 39 | double p_half; |
| 40 | |
| 41 | EXTRACT_WORDS(hx,lx,x); |
| 42 | EXTRACT_WORDS(hp,lp,p); |
| 43 | sx = hx&0x80000000; |
| 44 | hp &= 0x7fffffff; |
| 45 | hx &= 0x7fffffff; |
| 46 | |
| 47 | /* purge off exception values */ |
| 48 | if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */ |
| 49 | if((hx>=0x7ff00000)|| /* x not finite */ |
| 50 | ((hp>=0x7ff00000)&& /* p is NaN */ |
| 51 | (((hp-0x7ff00000)|lp)!=0))) |
Elliott Hughes | a0ee078 | 2013-01-30 19:06:37 -0800 | [diff] [blame] | 52 | return ((long double)x*p)/((long double)x*p); |
The Android Open Source Project | 1dc9e47 | 2009-03-03 19:28:35 -0800 | [diff] [blame] | 53 | |
| 54 | |
| 55 | if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */ |
| 56 | if (((hx-hp)|(lx-lp))==0) return zero*x; |
| 57 | x = fabs(x); |
| 58 | p = fabs(p); |
| 59 | if (hp<0x00200000) { |
| 60 | if(x+x>p) { |
| 61 | x-=p; |
| 62 | if(x+x>=p) x -= p; |
| 63 | } |
| 64 | } else { |
| 65 | p_half = 0.5*p; |
| 66 | if(x>p_half) { |
| 67 | x-=p; |
| 68 | if(x>=p_half) x -= p; |
| 69 | } |
| 70 | } |
| 71 | GET_HIGH_WORD(hx,x); |
Elliott Hughes | a0ee078 | 2013-01-30 19:06:37 -0800 | [diff] [blame] | 72 | if ((hx&0x7fffffff)==0) hx = 0; |
The Android Open Source Project | 1dc9e47 | 2009-03-03 19:28:35 -0800 | [diff] [blame] | 73 | SET_HIGH_WORD(x,hx^sx); |
| 74 | return x; |
| 75 | } |
Elliott Hughes | a0ee078 | 2013-01-30 19:06:37 -0800 | [diff] [blame] | 76 | |
| 77 | #if LDBL_MANT_DIG == 53 |
| 78 | __weak_reference(remainder, remainderl); |
| 79 | #endif |