/* $OpenBSD: n_floor.c,v 1.13 2009/10/27 23:59:29 deraadt Exp $ */ /* $NetBSD: n_floor.c,v 1.1 1995/10/10 23:36:48 ragge Exp $ */ /* * Copyright (c) 1985, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include <sys/cdefs.h> #include <math.h> #include "mathimpl.h" static const double L = 36028797018963968.0E0; /* * floor(x) := the largest integer no larger than x; * ceil(x) := -floor(-x), for all real x. * * Note: Inexact will be signaled if x is not an integer, as is * customary for IEEE 754. No other signal can be emitted. */ double floor(double x) { volatile double y; if (isnan(x) || x >= L) /* already an even integer */ return x; else if (x < (double)0) return -ceil(-x); else { /* now 0 <= x < L */ y = L+x; /* destructive store must be forced */ y -= L; /* an integer, and |x-y| < 1 */ return x < y ? y-(double)1 : y; } } double ceil(double x) { volatile double y; if (isnan(x) || x >= L) /* already an even integer */ return x; else if (x < (double)0) return -floor(-x); else { /* now 0 <= x < L */ y = L+x; /* destructive store must be forced */ y -= L; /* an integer, and |x-y| < 1 */ return x > y ? y+(double)1 : y; } } /* * algorithm for rint(x) in pseudo-pascal form ... * * real rint(x): real x; * ... delivers integer nearest x in direction of prevailing rounding * ... mode * const L = (last consecutive integer)/2 * = 2**55; for VAX D * = 2**52; for IEEE 754 Double * real s,t; * begin * if isnan(x) then return x; ... NaN * if |x| >= L then return x; ... already an integer * s := copysign(L,x); * t := x + s; ... = (x+s) rounded to integer * return t - s * end; * * Note: Inexact will be signaled if x is not an integer, as is * customary for IEEE 754. No other signal can be emitted. */ double rint(double x) { double s; volatile double t; const double one = 1.0; if (isnan(x)) return (x); if (copysign(x, one) >= L) /* already an integer */ return (x); s = copysign(L,x); t = x + s; /* x+s rounded to integer */ return (t - s); } #ifdef __weak_alias __weak_alias(rintl, rint); #endif /* __weak_alias */