The Android Open Source Project | b07e1d9 | 2009-03-03 19:29:30 -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 | |
| 14 | /* __ieee754_remainder(x,p) |
| 15 | * Return : |
| 16 | * returns x REM p = x - [x/p]*p as if in infinite |
| 17 | * precise arithmetic, where [x/p] is the (infinite bit) |
| 18 | * integer nearest x/p (in half way case choose the even one). |
| 19 | * Method : |
| 20 | * Based on ieee_fmod() return x-[x/p]chopped*p exactlp. |
| 21 | */ |
| 22 | |
| 23 | #include "fdlibm.h" |
| 24 | |
| 25 | #ifdef __STDC__ |
| 26 | static const double zero = 0.0; |
| 27 | #else |
| 28 | static double zero = 0.0; |
| 29 | #endif |
| 30 | |
| 31 | |
| 32 | #ifdef __STDC__ |
| 33 | double __ieee754_remainder(double x, double p) |
| 34 | #else |
| 35 | double __ieee754_remainder(x,p) |
| 36 | double x,p; |
| 37 | #endif |
| 38 | { |
| 39 | int hx,hp; |
| 40 | unsigned sx,lx,lp; |
| 41 | double p_half; |
| 42 | |
| 43 | hx = __HI(x); /* high word of x */ |
| 44 | lx = __LO(x); /* low word of x */ |
| 45 | hp = __HI(p); /* high word of p */ |
| 46 | lp = __LO(p); /* low word of p */ |
| 47 | sx = hx&0x80000000; |
| 48 | hp &= 0x7fffffff; |
| 49 | hx &= 0x7fffffff; |
| 50 | |
| 51 | /* purge off exception values */ |
| 52 | if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */ |
| 53 | if((hx>=0x7ff00000)|| /* x not finite */ |
| 54 | ((hp>=0x7ff00000)&& /* p is NaN */ |
| 55 | (((hp-0x7ff00000)|lp)!=0))) |
| 56 | return (x*p)/(x*p); |
| 57 | |
| 58 | |
| 59 | if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */ |
| 60 | if (((hx-hp)|(lx-lp))==0) return zero*x; |
| 61 | x = ieee_fabs(x); |
| 62 | p = ieee_fabs(p); |
| 63 | if (hp<0x00200000) { |
| 64 | if(x+x>p) { |
| 65 | x-=p; |
| 66 | if(x+x>=p) x -= p; |
| 67 | } |
| 68 | } else { |
| 69 | p_half = 0.5*p; |
| 70 | if(x>p_half) { |
| 71 | x-=p; |
| 72 | if(x>=p_half) x -= p; |
| 73 | } |
| 74 | } |
| 75 | __HI(x) ^= sx; |
| 76 | return x; |
| 77 | } |