1 /* $NetBSD: lround.c,v 1.3 2008/04/26 23:49:50 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 2004 5 * Matthias Drochner. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <math.h> 30 #include <sys/ieee754.h> 31 #include <machine/limits.h> 32 #include "math_private.h" 33 34 #ifndef LROUNDNAME 35 #define LROUNDNAME lround 36 #define RESTYPE long int 37 #define RESTYPE_MIN LONG_MIN 38 #define RESTYPE_MAX LONG_MAX 39 #endif 40 41 #define RESTYPE_BITS (sizeof(RESTYPE) * 8) 42 43 RESTYPE 44 LROUNDNAME(double x) 45 { 46 u_int32_t i0, i1; 47 int e, s, shift; 48 RESTYPE res; 49 50 GET_HIGH_WORD(i0, x); 51 e = i0 >> 20; 52 s = (uint32_t)e >> DBL_EXPBITS; 53 e = (e & 0x7ff) - DBL_EXP_BIAS; 54 55 /* 1.0 x 2^-1 is the smallest number which can be rounded to 1 */ 56 if (e < -1) 57 return (0); 58 /* 1.0 x 2^31 (or 2^63) is already too large */ 59 if (e >= (int)RESTYPE_BITS - 1) 60 return (s ? RESTYPE_MIN : RESTYPE_MAX); /* ??? unspecified */ 61 62 /* >= 2^52 is already an exact integer */ 63 if (e < DBL_FRACBITS) { 64 /* add 0.5, extraction below will truncate */ 65 x += (s ? -0.5 : 0.5); 66 } 67 68 EXTRACT_WORDS(i0, i1, x); 69 e = ((i0 >> 20) & 0x7ff) - DBL_EXP_BIAS; 70 i0 &= 0xfffff; 71 i0 |= (1 << 20); 72 73 shift = e - DBL_FRACBITS; 74 if (shift >=0) 75 res = (shift < 32 ? (RESTYPE)i1 << shift : 0); 76 else 77 res = (shift > -32 ? i1 >> -shift : 0); 78 shift += 32; 79 if (shift >=0) 80 res |= (shift < 32 ? (RESTYPE)i0 << shift : 0); 81 else 82 res |= (shift > -32 ? i0 >> -shift : 0); 83 84 return (s ? -res : res); 85 } 86