1 /* 2 * ==================================================== 3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 4 * 5 * Developed at SunPro, a Sun Microsystems, Inc. business. 6 * Permission to use, copy, modify, and distribute this 7 * software is freely granted, provided that this notice 8 * is preserved. 9 * ==================================================== 10 * 11 * From: @(#)s_floor.c 5.1 93/09/24 12 */ 13 14 #ifndef lint 15 static char rcsid[] = "$FreeBSD$"; 16 #endif 17 18 /* 19 * truncl(x) 20 * Return x rounded toward 0 to integral value 21 * Method: 22 * Bit twiddling. 23 * Exception: 24 * Inexact flag raised if x not equal to truncl(x). 25 */ 26 27 #include <float.h> 28 #include <math.h> 29 #include <stdint.h> 30 31 #include "fpmath.h" 32 33 #ifdef LDBL_IMPLICIT_NBIT 34 #define MANH_SIZE (LDBL_MANH_SIZE + 1) 35 #else 36 #define MANH_SIZE LDBL_MANH_SIZE 37 #endif 38 39 long double 40 truncl(long double x) 41 { 42 union IEEEl2bits u = { .e = x }; 43 int e = u.bits.exp - LDBL_MAX_EXP + 1; 44 45 if (e < MANH_SIZE - 1) { 46 if (e < 0) { /* raise inexact if x != 0 */ 47 u.e = 0.0; 48 } else { 49 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1); 50 if (((u.bits.manh & m) | u.bits.manl) == 0) 51 return (x); /* x is integral */ 52 u.bits.manh &= ~m; 53 u.bits.manl = 0; 54 } 55 } else if (e < LDBL_MANT_DIG - 1) { 56 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1); 57 if ((u.bits.manl & m) == 0) 58 return (x); /* x is integral */ 59 u.bits.manl &= ~m; 60 } 61 return (u.e); 62 } 63