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 0 15__FBSDID("$FreeBSD: src/lib/msun/src/s_trunc.c,v 1.1 2004/06/20 09:25:43 das Exp $"); 16#endif 17#if defined(LIBM_SCCS) && !defined(lint) 18__RCSID("$NetBSD: s_trunc.c,v 1.3 2008/04/25 22:21:53 christos Exp $"); 19#endif 20 21/* 22 * trunc(x) 23 * Return x rounded toward 0 to integral value 24 * Method: 25 * Bit twiddling. 26 * Exception: 27 * Inexact flag raised if x not equal to trunc(x). 28 */ 29 30#include "math.h" 31#include "math_private.h" 32 33#ifndef __HAVE_LONG_DOUBLE 34__strong_alias(_truncl, trunc) 35__weak_alias(truncl, trunc) 36#endif 37 38static const double huge = 1.0e300; 39 40double 41trunc(double x) 42{ 43 int32_t i0,i1,jj0; 44 uint32_t i; 45 EXTRACT_WORDS(i0,i1,x); 46 jj0 = ((i0>>20)&0x7ff)-0x3ff; 47 if(jj0<20) { 48 if(jj0<0) { /* raise inexact if x != 0 */ 49 if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */ 50 i0 &= 0x80000000U; 51 i1 = 0; 52 } 53 } else { 54 i = (0x000fffff)>>jj0; 55 if(((i0&i)|i1)==0) return x; /* x is integral */ 56 if(huge+x>0.0) { /* raise inexact flag */ 57 i0 &= (~i); i1=0; 58 } 59 } 60 } else if (jj0>51) { 61 if(jj0==0x400) return x+x; /* inf or NaN */ 62 else return x; /* x is integral */ 63 } else { 64 i = ((u_int32_t)(0xffffffff))>>(jj0-20); 65 if((i1&i)==0) return x; /* x is integral */ 66 if(huge+x>0.0) /* raise inexact flag */ 67 i1 &= (~i); 68 } 69 INSERT_WORDS(x,i0,i1); 70 return x; 71} 72