| The Android Open Source Project | b07e1d9 | 2009-03-03 19:29:30 -0800 | [diff] [blame] | 1 | |
| 2 | /* @(#)s_modf.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 | /* |
| 15 | * ieee_modf(double x, double *iptr) |
| 16 | * return fraction part of x, and return x's integral part in *iptr. |
| 17 | * Method: |
| 18 | * Bit twiddling. |
| 19 | * |
| 20 | * Exception: |
| 21 | * No exception. |
| 22 | */ |
| 23 | |
| 24 | #include "fdlibm.h" |
| 25 | |
| 26 | #ifdef __STDC__ |
| 27 | static const double one = 1.0; |
| 28 | #else |
| 29 | static double one = 1.0; |
| 30 | #endif |
| 31 | |
| 32 | #ifdef __STDC__ |
| 33 | double ieee_modf(double x, double *iptr) |
| 34 | #else |
| 35 | double ieee_modf(x, iptr) |
| 36 | double x,*iptr; |
| 37 | #endif |
| 38 | { |
| 39 | int i0,i1,j0; |
| 40 | unsigned i; |
| 41 | i0 = __HI(x); /* high x */ |
| 42 | i1 = __LO(x); /* low x */ |
| 43 | j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ |
| 44 | if(j0<20) { /* integer part in high x */ |
| 45 | if(j0<0) { /* |x|<1 */ |
| 46 | __HIp(iptr) = i0&0x80000000; |
| 47 | __LOp(iptr) = 0; /* *iptr = +-0 */ |
| 48 | return x; |
| 49 | } else { |
| 50 | i = (0x000fffff)>>j0; |
| 51 | if(((i0&i)|i1)==0) { /* x is integral */ |
| 52 | *iptr = x; |
| 53 | __HI(x) &= 0x80000000; |
| 54 | __LO(x) = 0; /* return +-0 */ |
| 55 | return x; |
| 56 | } else { |
| 57 | __HIp(iptr) = i0&(~i); |
| 58 | __LOp(iptr) = 0; |
| 59 | return x - *iptr; |
| 60 | } |
| 61 | } |
| 62 | } else if (j0>51) { /* no fraction part */ |
| 63 | *iptr = x*one; |
| 64 | __HI(x) &= 0x80000000; |
| 65 | __LO(x) = 0; /* return +-0 */ |
| 66 | return x; |
| 67 | } else { /* fraction part in low x */ |
| 68 | i = ((unsigned)(0xffffffff))>>(j0-20); |
| 69 | if((i1&i)==0) { /* x is integral */ |
| 70 | *iptr = x; |
| 71 | __HI(x) &= 0x80000000; |
| 72 | __LO(x) = 0; /* return +-0 */ |
| 73 | return x; |
| 74 | } else { |
| 75 | __HIp(iptr) = i0; |
| 76 | __LOp(iptr) = i1&(~i); |
| 77 | return x - *iptr; |
| 78 | } |
| 79 | } |
| 80 | } |