s_modfl.c revision 285830
1193156Snwhitehorn/*- 2193156Snwhitehorn * Copyright (c) 2007 David Schultz <das@FreeBSD.ORG> 3193156Snwhitehorn * All rights reserved. 4193156Snwhitehorn * 5193156Snwhitehorn * Redistribution and use in source and binary forms, with or without 6193156Snwhitehorn * modification, are permitted provided that the following conditions 7193156Snwhitehorn * are met: 8193156Snwhitehorn * 1. Redistributions of source code must retain the above copyright 9193156Snwhitehorn * notice, this list of conditions and the following disclaimer. 10193156Snwhitehorn * 2. Redistributions in binary form must reproduce the above copyright 11193156Snwhitehorn * notice, this list of conditions and the following disclaimer in the 12193156Snwhitehorn * documentation and/or other materials provided with the distribution. 13193156Snwhitehorn * 14193156Snwhitehorn * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15193156Snwhitehorn * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16193156Snwhitehorn * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17193156Snwhitehorn * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18193156Snwhitehorn * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19193156Snwhitehorn * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20193156Snwhitehorn * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21193156Snwhitehorn * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22193156Snwhitehorn * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23193156Snwhitehorn * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24193156Snwhitehorn * SUCH DAMAGE. 25193156Snwhitehorn * 26227843Smarius * Derived from s_modf.c, which has the following Copyright: 27227843Smarius * ==================================================== 28227843Smarius * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 29193156Snwhitehorn * 30193156Snwhitehorn * Developed at SunPro, a Sun Microsystems, Inc. business. 31193156Snwhitehorn * Permission to use, copy, modify, and distribute this 32193156Snwhitehorn * software is freely granted, provided that this notice 33193156Snwhitehorn * is preserved. 34193156Snwhitehorn * ==================================================== 35193156Snwhitehorn * 36193156Snwhitehorn * $FreeBSD: releng/10.2/lib/msun/src/s_modfl.c 165855 2007-01-07 07:54:21Z das $ 37193156Snwhitehorn */ 38193156Snwhitehorn 39193156Snwhitehorn#include <float.h> 40193156Snwhitehorn#include <math.h> 41193156Snwhitehorn#include <sys/types.h> 42193156Snwhitehorn 43193156Snwhitehorn#include "fpmath.h" 44193156Snwhitehorn 45193156Snwhitehorn#if LDBL_MANL_SIZE > 32 46193156Snwhitehorn#define MASK ((uint64_t)-1) 47193156Snwhitehorn#else 48193156Snwhitehorn#define MASK ((uint32_t)-1) 49193156Snwhitehorn#endif 50193156Snwhitehorn/* Return the last n bits of a word, representing the fractional part. */ 51193156Snwhitehorn#define GETFRAC(bits, n) ((bits) & ~(MASK << (n))) 52193156Snwhitehorn/* The number of fraction bits in manh, not counting the integer bit */ 53193156Snwhitehorn#define HIBITS (LDBL_MANT_DIG - LDBL_MANL_SIZE) 54193156Snwhitehorn 55193156Snwhitehornstatic const long double zero[] = { 0.0L, -0.0L }; 56193156Snwhitehorn 57193156Snwhitehornlong double 58193156Snwhitehornmodfl(long double x, long double *iptr) 59193156Snwhitehorn{ 60193156Snwhitehorn union IEEEl2bits ux; 61193156Snwhitehorn int e; 62193156Snwhitehorn 63193156Snwhitehorn ux.e = x; 64193156Snwhitehorn e = ux.bits.exp - LDBL_MAX_EXP + 1; 65193156Snwhitehorn if (e < HIBITS) { /* Integer part is in manh. */ 66227843Smarius if (e < 0) { /* |x|<1 */ 67193156Snwhitehorn *iptr = zero[ux.bits.sign]; 68193156Snwhitehorn return (x); 69193156Snwhitehorn } else { 70193156Snwhitehorn if ((GETFRAC(ux.bits.manh, HIBITS - 1 - e) | 71193156Snwhitehorn ux.bits.manl) == 0) { /* X is an integer. */ 72193156Snwhitehorn *iptr = x; 73193156Snwhitehorn return (zero[ux.bits.sign]); 74193156Snwhitehorn } else { 75193156Snwhitehorn /* Clear all but the top e+1 bits. */ 76193156Snwhitehorn ux.bits.manh >>= HIBITS - 1 - e; 77193156Snwhitehorn ux.bits.manh <<= HIBITS - 1 - e; 78193156Snwhitehorn ux.bits.manl = 0; 79193156Snwhitehorn *iptr = ux.e; 80193156Snwhitehorn return (x - ux.e); 81193156Snwhitehorn } 82193156Snwhitehorn } 83193156Snwhitehorn } else if (e >= LDBL_MANT_DIG - 1) { /* x has no fraction part. */ 84193156Snwhitehorn *iptr = x; 85193156Snwhitehorn if (x != x) /* Handle NaNs. */ 86193156Snwhitehorn return (x); 87193156Snwhitehorn return (zero[ux.bits.sign]); 88193156Snwhitehorn } else { /* Fraction part is in manl. */ 89193156Snwhitehorn if (GETFRAC(ux.bits.manl, LDBL_MANT_DIG - 1 - e) == 0) { 90193156Snwhitehorn /* x is integral. */ 91193156Snwhitehorn *iptr = x; 92193156Snwhitehorn return (zero[ux.bits.sign]); 93193156Snwhitehorn } else { 94193156Snwhitehorn /* Clear all but the top e+1 bits. */ 95193156Snwhitehorn ux.bits.manl >>= LDBL_MANT_DIG - 1 - e; 96193156Snwhitehorn ux.bits.manl <<= LDBL_MANT_DIG - 1 - e; 97193156Snwhitehorn *iptr = ux.e; 98193156Snwhitehorn return (x - ux.e); 99193156Snwhitehorn } 100193156Snwhitehorn } 101193156Snwhitehorn} 102193156Snwhitehorn