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 } 80
