1 /*- 2 * Copyright (c) 2007 David Schultz <das@FreeBSD.ORG> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * Derived from s_modf.c, which has the following Copyright: 27 * ==================================================== 28 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 29 * 30 * Developed at SunPro, a Sun Microsystems, Inc. business. 31 * Permission to use, copy, modify, and distribute this 32 * software is freely granted, provided that this notice 33 * is preserved. 34 * ==================================================== 35 * 36 * $FreeBSD: src/lib/msun/src/s_modfl.c,v 1.1 2007/01/07 07:54:21 das Exp $ 37 */ 38 39 #include <float.h> 40 #include <openlibm.h> 41 #include "math_private.h" 42 #include <sys/types.h> 43 44 #include "fpmath.h" 45 46 #if LDBL_MANL_SIZE > 32 47 #define MASK ((u_int64_t)-1) 48 #else 49 #define MASK ((u_int32_t)-1) 50 #endif 51 /* Return the last n bits of a word, representing the fractional part. */ 52 #define GETFRAC(bits, n) ((bits) & ~(MASK << (n))) 53 /* The number of fraction bits in manh, not counting the integer bit */ 54 #define HIBITS (LDBL_MANT_DIG - LDBL_MANL_SIZE) 55 56 static const long double zero[] = { 0.0L, -0.0L }; 57 58 DLLEXPORT long double 59 modfl(long double x, long double *iptr) 60 { 61 union IEEEl2bits ux; 62 int e; 63 64 ux.e = x; 65 e = ux.bits.exp - LDBL_MAX_EXP + 1; 66 if (e < HIBITS) { /* Integer part is in manh. */ 67 if (e < 0) { /* |x|<1 */ 68 *iptr = zero[ux.bits.sign]; 69 return (x); 70 } else { 71 if ((GETFRAC(ux.bits.manh, HIBITS - 1 - e) | 72 ux.bits.manl) == 0) { /* X is an integer. */ 73 *iptr = x; 74 return (zero[ux.bits.sign]); 75 } else { 76 /* Clear all but the top e+1 bits. */ 77 ux.bits.manh >>= HIBITS - 1 - e; 78 ux.bits.manh <<= HIBITS - 1 - e; 79 ux.bits.manl = 0; 80 *iptr = ux.e; 81 return (x - ux.e); 82 } 83 } 84 } else if (e >= LDBL_MANT_DIG - 1) { /* x has no fraction part. */ 85 *iptr = x; 86 if (x != x) /* Handle NaNs. */ 87 return (x); 88 return (zero[ux.bits.sign]); 89 } else { /* Fraction part is in manl. */ 90 if (GETFRAC(ux.bits.manl, LDBL_MANT_DIG - 1 - e) == 0) { 91 /* x is integral. */ 92 *iptr = x; 93 return (zero[ux.bits.sign]); 94 } else { 95 /* Clear all but the top e+1 bits. */ 96 ux.bits.manl >>= LDBL_MANT_DIG - 1 - e; 97 ux.bits.manl <<= LDBL_MANT_DIG - 1 - e; 98 *iptr = ux.e; 99 return (x - ux.e); 100 } 101 } 102 } 103