1 /*- 2 * Copyright (c) 2007 David Schultz <das (at) 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 * $FreeBSD$ 37 */ 38 39 #include <float.h> 40 #include <math.h> 41 #include <sys/types.h> 42 43 #include "fpmath.h" 44 45 #if LDBL_MANL_SIZE > 32 46 #define MASK ((uint64_t)-1) 47 #else 48 #define MASK ((uint32_t)-1) 49 #endif 50 /* Return the last n bits of a word, representing the fractional part. */ 51 #define GETFRAC(bits, n) ((bits) & ~(MASK << (n))) 52 /* The number of fraction bits in manh, not counting the integer bit */ 53 #define HIBITS (LDBL_MANT_DIG - LDBL_MANL_SIZE) 54 55 static const long double zero[] = { 0.0L, -0.0L }; 56 57 long double 58 modfl(long double x, long double *iptr) 59 { 60 union IEEEl2bits ux; 61 int e; 62 63 ux.e = x; 64 e = ux.bits.exp - LDBL_MAX_EXP + 1; 65 if (e < HIBITS) { /* Integer part is in manh. */ 66 if (e < 0) { /* |x|<1 */ 67 *iptr = zero[ux.bits.sign]; 68 return (x); 69 } else { 70 if ((GETFRAC(ux.bits.manh, HIBITS - 1 - e) | 71 ux.bits.manl) == 0) { /* X is an integer. */ 72 *iptr = x; 73 return (zero[ux.bits.sign]); 74 } else { 75 /* Clear all but the top e+1 bits. */ 76 ux.bits.manh >>= HIBITS - 1 - e; 77 ux.bits.manh <<= HIBITS - 1 - e; 78 ux.bits.manl = 0; 79 *iptr = ux.e; 80 return (x - ux.e); 81 } 82 } 83 } else if (e >= LDBL_MANT_DIG - 1) { /* x has no fraction part. */ 84 *iptr = x; 85 if (x != x) /* Handle NaNs. */ 86 return (x); 87 return (zero[ux.bits.sign]); 88 } else { /* Fraction part is in manl. */ 89 if (GETFRAC(ux.bits.manl, LDBL_MANT_DIG - 1 - e) == 0) { 90 /* x is integral. */ 91 *iptr = x; 92 return (zero[ux.bits.sign]); 93 } else { 94 /* Clear all but the top e+1 bits. */ 95 ux.bits.manl >>= LDBL_MANT_DIG - 1 - e; 96 ux.bits.manl <<= LDBL_MANT_DIG - 1 - e; 97 *iptr = ux.e; 98 return (x - ux.e); 99 } 100 } 101 } 102
