88 lines
3.1 KiB
C
88 lines
3.1 KiB
C
/* snarfed from BSD common_source/floor.c:
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* Copyright (c) 1985, 1995 Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef lint
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static char sccsid[] = "@(#)floor.c 5.7 (Berkeley) 10/9/90";
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#endif /* not lint */
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#include "mathimpl.h"
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vc(L, 4503599627370496.0E0 ,0000,5c00,0000,0000, 55, 1.0) /* 2**55 */
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ic(L, 4503599627370496.0E0, 52, 1.0) /* 2**52 */
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#ifdef vccast
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#define L vccast(L)
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#endif
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/*
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* algorithm for rint(x) in pseudo-pascal form ...
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*
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* real rint(x): real x;
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* ... delivers integer nearest x in direction of prevailing rounding
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* ... mode
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* const L = (last consecutive integer)/2
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* = 2**55; for VAX D
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* = 2**52; for IEEE 754 Double
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* real s,t;
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* begin
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* if x != x then return x; ... NaN
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* if |x| >= L then return x; ... already an integer
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* s := copysign(L,x);
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* t := x + s; ... = (x+s) rounded to integer
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* return t - s
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* end;
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*
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* Note: Inexact will be signaled if x is not an integer, as is
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* customary for IEEE 754. No other signal can be emitted.
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*/
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double
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__rint(x)
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double x;
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{
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double s,t;
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const double one = 1.0;
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#if !defined(vax)&&!defined(tahoe)
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if (x != x) /* NaN */
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return (x);
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#endif /* !defined(vax)&&!defined(tahoe) */
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if (copysign(x,one) >= L) /* already an integer */
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return (x);
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s = copysign(L,x);
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t = x + s; /* x+s rounded to integer */
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return (t - s);
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}
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weak_alias (__rint, rint)
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