| The Android Open Source Project | b07e1d9 | 2009-03-03 19:29:30 -0800 | [diff] [blame] | 1 | |
| 2 | /* @(#)s_floor.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_floor(x) |
| 16 | * Return x rounded toward -inf to integral value |
| 17 | * Method: |
| 18 | * Bit twiddling. |
| 19 | * Exception: |
| 20 | * Inexact flag raised if x not equal to ieee_floor(x). |
| 21 | */ |
| 22 | |
| 23 | #include "fdlibm.h" |
| 24 | |
| 25 | #ifdef __STDC__ |
| 26 | static const double huge = 1.0e300; |
| 27 | #else |
| 28 | static double huge = 1.0e300; |
| 29 | #endif |
| 30 | |
| 31 | #ifdef __STDC__ |
| 32 | double ieee_floor(double x) |
| 33 | #else |
| 34 | double ieee_floor(x) |
| 35 | double x; |
| 36 | #endif |
| 37 | { |
| 38 | int i0,i1,j0; |
| 39 | unsigned i,j; |
| 40 | i0 = __HI(x); |
| 41 | i1 = __LO(x); |
| 42 | j0 = ((i0>>20)&0x7ff)-0x3ff; |
| 43 | if(j0<20) { |
| 44 | if(j0<0) { /* raise inexact if x != 0 */ |
| 45 | if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ |
| 46 | if(i0>=0) {i0=i1=0;} |
| 47 | else if(((i0&0x7fffffff)|i1)!=0) |
| 48 | { i0=0xbff00000;i1=0;} |
| 49 | } |
| 50 | } else { |
| 51 | i = (0x000fffff)>>j0; |
| 52 | if(((i0&i)|i1)==0) return x; /* x is integral */ |
| 53 | if(huge+x>0.0) { /* raise inexact flag */ |
| 54 | if(i0<0) i0 += (0x00100000)>>j0; |
| 55 | i0 &= (~i); i1=0; |
| 56 | } |
| 57 | } |
| 58 | } else if (j0>51) { |
| 59 | if(j0==0x400) return x+x; /* inf or NaN */ |
| 60 | else return x; /* x is integral */ |
| 61 | } else { |
| 62 | i = ((unsigned)(0xffffffff))>>(j0-20); |
| 63 | if((i1&i)==0) return x; /* x is integral */ |
| 64 | if(huge+x>0.0) { /* raise inexact flag */ |
| 65 | if(i0<0) { |
| 66 | if(j0==20) i0+=1; |
| 67 | else { |
| 68 | j = i1+(1<<(52-j0)); |
| 69 | if(j<i1) i0 +=1 ; /* got a carry */ |
| 70 | i1=j; |
| 71 | } |
| 72 | } |
| 73 | i1 &= (~i); |
| 74 | } |
| 75 | } |
| 76 | __HI(x) = i0; |
| 77 | __LO(x) = i1; |
| 78 | return x; |
| 79 | } |