s_trunc.c (1408B)
1 /* @(#)s_floor.c 5.1 93/09/24 */ 2 /* 3 * ==================================================== 4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5 * 6 * Developed at SunPro, a Sun Microsystems, Inc. business. 7 * Permission to use, copy, modify, and distribute this 8 * software is freely granted, provided that this notice 9 * is preserved. 10 * ==================================================== 11 */ 12 13 /* 14 * trunc(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 trunc(x). 20 */ 21 22 #include "math.h" 23 #include "math_private.h" 24 25 static const double huge = 1.0e300; 26 27 double 28 trunc(double x) 29 { 30 int32_t i0,i1,j0; 31 u_int32_t i,j; 32 EXTRACT_WORDS(i0,i1,x); 33 j0 = ((i0>>20)&0x7ff)-0x3ff; 34 if(j0<20) { 35 if(j0<0) { /* raise inexact if x != 0 */ 36 if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */ 37 i0 &= 0x80000000U; 38 i1 = 0; 39 } 40 } else { 41 i = (0x000fffff)>>j0; 42 if(((i0&i)|i1)==0) return x; /* x is integral */ 43 if(huge+x>0.0) { /* raise inexact flag */ 44 i0 &= (~i); i1=0; 45 } 46 } 47 } else if (j0>51) { 48 if(j0==0x400) return x+x; /* inf or NaN */ 49 else return x; /* x is integral */ 50 } else { 51 i = ((u_int32_t)(0xffffffff))>>(j0-20); 52 if((i1&i)==0) return x; /* x is integral */ 53 if(huge+x>0.0) /* raise inexact flag */ 54 i1 &= (~i); 55 } 56 INSERT_WORDS(x,i0,i1); 57 return x; 58 }