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 1.13 2009/02/16 01:27:36 lukem 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#ifndef __HAVE_LONG_DOUBLE 31__strong_alias(_floorl, floor) 32__weak_alias(floorl, floor) 33#endif 34 35static const double huge = 1.0e300; 36 37double 38floor(double x) 39{ 40 int32_t i0,i1,jj0; 41 u_int32_t i,j; 42 EXTRACT_WORDS(i0,i1,x); 43 jj0 = ((i0>>20)&0x7ff)-0x3ff; 44 if(jj0<20) { 45 if(jj0<0) { /* raise inexact if x != 0 */ 46 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */ 47 if(i0>=0) {i0=i1=0;} 48 else if(((i0&0x7fffffff)|i1)!=0) 49 { i0=0xbff00000;i1=0;} 50 } 51 } else { 52 i = (0x000fffff)>>jj0; 53 if(((i0&i)|i1)==0) return x; /* x is integral */ 54 if(huge+x>0.0) { /* raise inexact flag */ 55 if(i0<0) i0 += (0x00100000)>>jj0; 56 i0 &= (~i); i1=0; 57 } 58 } 59 } else if (jj0>51) { 60 if(jj0==0x400) return x+x; /* inf or NaN */ 61 else return x; /* x is integral */ 62 } else { 63 i = ((u_int32_t)(0xffffffff))>>(jj0-20); 64 if((i1&i)==0) return x; /* x is integral */ 65 if(huge+x>0.0) { /* raise inexact flag */ 66 if(i0<0) { 67 if(jj0==20) i0+=1; 68 else { 69 j = i1+(1<<(52-jj0)); 70 if(j<(u_int32_t)i1) i0 +=1 ; /* got a carry */ 71 i1=j; 72 } 73 } 74 i1 &= (~i); 75 } 76 } 77 INSERT_WORDS(x,i0,i1); 78 return x; 79} 80