frexp.c revision 132366
1132366Sdas/*- 2132366Sdas * Copyright (c) 2004 David Schultz <das@FreeBSD.ORG> 3132366Sdas * All rights reserved. 4132366Sdas * 5132366Sdas * Redistribution and use in source and binary forms, with or without 6132366Sdas * modification, are permitted provided that the following conditions 7132366Sdas * are met: 8132366Sdas * 1. Redistributions of source code must retain the above copyright 9132366Sdas * notice, this list of conditions and the following disclaimer. 10132366Sdas * 2. Redistributions in binary form must reproduce the above copyright 11132366Sdas * notice, this list of conditions and the following disclaimer in the 12132366Sdas * documentation and/or other materials provided with the distribution. 13132366Sdas * 14132366Sdas * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15132366Sdas * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16132366Sdas * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17132366Sdas * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18132366Sdas * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19132366Sdas * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20132366Sdas * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21132366Sdas * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22132366Sdas * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23132366Sdas * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24132366Sdas * SUCH DAMAGE. 25132366Sdas * 26132366Sdas * $FreeBSD: head/lib/libc/gen/frexp.c 132366 2004-07-18 21:23:39Z das $ 27132366Sdas */ 28132366Sdas 29132366Sdas#include <math.h> 30132366Sdas 31132366Sdas#include "fpmath.h" 32132366Sdas 33132366Sdasdouble 34132366Sdasfrexp(double d, int *ex) 35132366Sdas{ 36132366Sdas union IEEEd2bits u; 37132366Sdas 38132366Sdas u.d = d; 39132366Sdas switch (u.bits.exp) { 40132366Sdas case 0: /* 0 or subnormal */ 41132366Sdas if ((u.bits.manl | u.bits.manh) == 0) { 42132366Sdas *ex = 0; 43132366Sdas } else { 44132366Sdas u.d *= 0x1.0p514; 45132366Sdas *ex = u.bits.exp - 1536; 46132366Sdas u.bits.exp = 1022; 47132366Sdas } 48132366Sdas break; 49132366Sdas case 2047: /* infinity or NaN; value of *ex is unspecified */ 50132366Sdas break; 51132366Sdas default: /* normal */ 52132366Sdas *ex = u.bits.exp - 1022; 53132366Sdas u.bits.exp = 1022; 54132366Sdas break; 55132366Sdas } 56132366Sdas return (u.d); 57132366Sdas} 58