1 /* @(#)s_floor.c 5.1 93/09/24 */ 2 /* 3 * ==================================================== 4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5 * 6 * Developed at SunPro, a Sun Microsystems, Inc. business. 7 * Permission to use, copy, modify, and distribute this 8 * software is freely granted, provided that this notice 9 * is preserved. 10 * ==================================================== 11 */ 12 13 #include <sys/cdefs.h> 14 #if defined(LIBM_SCCS) && !defined(lint) 15 __RCSID("$NetBSD: s_floor.c,v 1.11 2002/05/26 22:01:56 wiz Exp $"); 16 #endif 17 18 /* 19 * floor(x) 20 * Return x rounded toward -inf to integral value 21 * Method: 22 * Bit twiddling. 23 * Exception: 24 * Inexact flag raised if x not equal to floor(x). 25 */ 26 27 #include "math.h" 28 #include "math_private.h" 29 30 static const double huge = 1.0e300; 31 32 double 33 floor(double x) 34 { 35 int32_t i0,i1,j0; 36 u_int32_t i,j; 37 EXTRACT_WORDS(i0,i1,x); 38 j0 = ((i0>>20)&0x7ff)-0x3ff; 39 if(j0<20) { 40 if(j0<0) { /* raise inexact if x != 0 */ 41 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ 42 if(i0>=0) {i0=i1=0;} 43 else if(((i0&0x7fffffff)|i1)!=0) 44 { i0=0xbff00000;i1=0;} 45 } 46 } else { 47 i = (0x000fffff)>>j0; 48 if(((i0&i)|i1)==0) return x; /* x is integral */ 49 if(huge+x>0.0) { /* raise inexact flag */ 50 if(i0<0) i0 += (0x00100000)>>j0; 51 i0 &= (~i); i1=0; 52 } 53 } 54 } else if (j0>51) { 55 if(j0==0x400) return x+x; /* inf or NaN */ 56 else return x; /* x is integral */ 57 } else { 58 i = ((u_int32_t)(0xffffffff))>>(j0-20); 59 if((i1&i)==0) return x; /* x is integral */ 60 if(huge+x>0.0) { /* raise inexact flag */ 61 if(i0<0) { 62 if(j0==20) i0+=1; 63 else { 64 j = i1+(1<<(52-j0)); 65 if(j<i1) i0 +=1 ; /* got a carry */ 66 i1=j; 67 } 68 } 69 i1 &= (~i); 70 } 71 } 72 INSERT_WORDS(x,i0,i1); 73 return x; 74 } 75