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