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 12 #include <sys/cdefs.h> 13 /* 14 * truncl(x) 15 * Return x rounded toward 0 to integral value 16 * Method: 17 * Bit twiddling. 18 * Exception: 19 * Inexact flag raised if x not equal to truncl(x). 20 */ 21 22 #include <float.h> 23 #include <math.h> 24 #include <stdint.h> 25 26 #include "fpmath.h" 27 28 #ifdef LDBL_IMPLICIT_NBIT 29 #define MANH_SIZE (LDBL_MANH_SIZE + 1) 30 #else 31 #define MANH_SIZE LDBL_MANH_SIZE 32 #endif 33 34 static const long double huge = 1.0e300; 35 static const float zero[] = { 0.0, -0.0 }; 36 37 long double 38 truncl(long double x) 39 { 40 union IEEEl2bits u = { .e = x }; 41 int e = u.bits.exp - LDBL_MAX_EXP + 1; 42 43 if (e < MANH_SIZE - 1) { 44 if (e < 0) { /* raise inexact if x != 0 */ 45 if (huge + x > 0.0) 46 u.e = zero[u.bits.sign]; 47 } else { 48 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1); 49 if (((u.bits.manh & m) | u.bits.manl) == 0) 50 return (x); /* x is integral */ 51 if (huge + x > 0.0) { /* raise inexact flag */ 52 u.bits.manh &= ~m; 53 u.bits.manl = 0; 54 } 55 } 56 } else if (e < LDBL_MANT_DIG - 1) { 57 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1); 58 if ((u.bits.manl & m) == 0) 59 return (x); /* x is integral */ 60 if (huge + x > 0.0) /* raise inexact flag */ 61 u.bits.manl &= ~m; 62 } 63 return (u.e); 64 } 65