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