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 static const double huge = 1.0e300; 34 35 double 36 trunc(double x) 37 { 38 int32_t i0,i1,jj0; 39 uint32_t i; 40 EXTRACT_WORDS(i0,i1,x); 41 jj0 = ((i0>>20)&0x7ff)-0x3ff; 42 if(jj0<20) { 43 if(jj0<0) { /* raise inexact if x != 0 */ 44 if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */ 45 i0 &= 0x80000000U; 46 i1 = 0; 47 } 48 } else { 49 i = (0x000fffff)>>jj0; 50 if(((i0&i)|i1)==0) return x; /* x is integral */ 51 if(huge+x>0.0) { /* raise inexact flag */ 52 i0 &= (~i); i1=0; 53 } 54 } 55 } else if (jj0>51) { 56 if(jj0==0x400) return x+x; /* inf or NaN */ 57 else return x; /* x is integral */ 58 } else { 59 i = ((u_int32_t)(0xffffffff))>>(jj0-20); 60 if((i1&i)==0) return x; /* x is integral */ 61 if(huge+x>0.0) /* raise inexact flag */ 62 i1 &= (~i); 63 } 64 INSERT_WORDS(x,i0,i1); 65 return x; 66 } 67