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 #include <sys/cdefs.h> 15 __FBSDID("$FreeBSD$"); 16 17 /* 18 * truncl(x) 19 * Return x rounded toward 0 to integral value 20 * Method: 21 * Bit twiddling. 22 * Exception: 23 * Inexact flag raised if x not equal to truncl(x). 24 */ 25 26 #include <float.h> 27 #include <math.h> 28 #include <stdint.h> 29 30 #include "fpmath.h" 31 32 #ifdef LDBL_IMPLICIT_NBIT 33 #define MANH_SIZE (LDBL_MANH_SIZE + 1) 34 #else 35 #define MANH_SIZE LDBL_MANH_SIZE 36 #endif 37 38 static const long double huge = 1.0e300; 39 static const float zero[] = { 0.0, -0.0 }; 40 41 long double 42 truncl(long double x) 43 { 44 union IEEEl2bits u = { .e = x }; 45 int e = u.bits.exp - LDBL_MAX_EXP + 1; 46 47 if (e < MANH_SIZE - 1) { 48 if (e < 0) { /* raise inexact if x != 0 */ 49 if (huge + x > 0.0) 50 u.e = zero[u.bits.sign]; 51 } else { 52 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1); 53 if (((u.bits.manh & m) | u.bits.manl) == 0) 54 return (x); /* x is integral */ 55 if (huge + x > 0.0) { /* raise inexact flag */ 56 u.bits.manh &= ~m; 57 u.bits.manl = 0; 58 } 59 } 60 } else if (e < LDBL_MANT_DIG - 1) { 61 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1); 62 if ((u.bits.manl & m) == 0) 63 return (x); /* x is integral */ 64 if (huge + x > 0.0) /* raise inexact flag */ 65 u.bits.manl &= ~m; 66 } 67 return (u.e); 68 } 69