gonzui

    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: /* LINTLIBRARY */
   14: 
   15: #if 0
   16: #include <sys/cdefs.h>
   17: __FBSDID("$FreeBSD: src/lib/msun/src/s_trunc.c,v 1.1 2004/06/20 09:25:43 das Exp $");
   18: #endif
   19: 
   20: /*
   21:  * trunc(x)
   22:  * Return x rounded toward 0 to integral value
   23:  * Method:
   24:  *      Bit twiddling.
   25:  * Exception:
   26:  *      Inexact flag raised if x not equal to trunc(x).
   27:  */
   28: 
   29: #include <sys/cdefs.h>
   30: #include <float.h>
   31: #include <math.h>
   32: 
   33: #include "math_private.h"
   34: 
   35: static const double huge = 1.0e300;
   36: 
   37: double
   38: trunc(double x)
   39: {
   40:         int32_t i0,i1,jj0;
   41:         u_int32_t i;
   42:         EXTRACT_WORDS(i0,i1,x);
   43:         jj0 = ((i0>>20)&0x7ff)-0x3ff;
   44:         if(jj0<20) {
   45:             if(jj0<0) {        /* raise inexact if x != 0 */
   46:                 if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
   47:                     i0 &= 0x80000000U;
   48:                     i1 = 0;
   49:                 }
   50:             } else {
   51:                 i = (0x000fffff)>>jj0;
   52:                 if(((i0&i)|i1)==0) return x; /* x is integral */
   53:                 if(huge+x>0.0) {      /* raise inexact flag */
   54:                     i0 &= (~i); i1=0;
   55:                 }
   56:             }
   57:         } else if (jj0>51) {
   58:             if(jj0==0x400) return x+x; /* inf or NaN */
   59:             else return x;             /* x is integral */
   60:         } else {
   61:             i = ((u_int32_t)(0xffffffff))>>(jj0-20);
   62:             if((i1&i)==0) return x;    /* x is integral */
   63:             if(huge+x>0.0)             /* raise inexact flag */
   64:                 i1 &= (~i);
   65:         }
   66:         INSERT_WORDS(x,i0,i1);
   67:         return x;
   68: }
   69: 
   70: #if     LDBL_MANT_DIG == 53
   71: #ifdef  lint
   72: /* PROTOLIB1 */
   73: long double truncl(long double);
   74: #else   /* lint */
   75: __weak_alias(truncl, trunc);
   76: #endif  /* lint */
   77: #endif  /* LDBL_MANT_DIG == 53 */