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       ---
       s_floor.c (1768B)
       ---
            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 #ifndef lint
           14 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_floor.c,v 1.9 2003/07/23 04:53:46 peter Exp $";
           15 #endif
           16 
           17 /*
           18  * floor(x)
           19  * Return x rounded toward -inf to integral value
           20  * Method:
           21  *        Bit twiddling.
           22  * Exception:
           23  *        Inexact flag raised if x not equal to floor(x).
           24  */
           25 
           26 #include "math.h"
           27 #include "math_private.h"
           28 
           29 static const double huge = 1.0e300;
           30 
           31 double
           32 floor(double x)
           33 {
           34         int32_t i0,i1,j0;
           35         u_int32_t i,j;
           36         EXTRACT_WORDS(i0,i1,x);
           37         j0 = ((i0>>20)&0x7ff)-0x3ff;
           38         if(j0<20) {
           39             if(j0<0) {         /* raise inexact if x != 0 */
           40                 if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
           41                     if(i0>=0) {i0=i1=0;}
           42                     else if(((i0&0x7fffffff)|i1)!=0)
           43                         { i0=0xbff00000;i1=0;}
           44                 }
           45             } else {
           46                 i = (0x000fffff)>>j0;
           47                 if(((i0&i)|i1)==0) return x; /* x is integral */
           48                 if(huge+x>0.0) {        /* raise inexact flag */
           49                     if(i0<0) i0 += (0x00100000)>>j0;
           50                     i0 &= (~i); i1=0;
           51                 }
           52             }
           53         } else if (j0>51) {
           54             if(j0==0x400) return x+x;        /* inf or NaN */
           55             else return x;                /* x is integral */
           56         } else {
           57             i = ((u_int32_t)(0xffffffff))>>(j0-20);
           58             if((i1&i)==0) return x;        /* x is integral */
           59             if(huge+x>0.0) {                 /* raise inexact flag */
           60                 if(i0<0) {
           61                     if(j0==20) i0+=1;
           62                     else {
           63                         j = i1+(1<<(52-j0));
           64                         if(j<i1) i0 +=1 ;         /* got a carry */
           65                         i1=j;
           66                     }
           67                 }
           68                 i1 &= (~i);
           69             }
           70         }
           71         INSERT_WORDS(x,i0,i1);
           72         return x;
           73 }