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Annotation of src/lib/libm/src/s_ceil.c, Revision 1.6

1.1       jtc         1: /* @(#)s_ceil.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:  */
1.3       jtc        12:
                     13: #ifndef lint
1.6     ! jtc        14: static char rcsid[] = "$Id: s_ceil.c,v 1.5 1994/08/10 20:32:03 jtc Exp $";
1.3       jtc        15: #endif
1.1       jtc        16:
                     17: /*
                     18:  * ceil(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 ceil(x).
                     24:  */
                     25:
1.5       jtc        26: #include "math.h"
                     27: #include "math_private.h"
1.1       jtc        28:
                     29: #ifdef __STDC__
1.4       jtc        30: static const double huge = 1.0e300;
1.1       jtc        31: #else
1.4       jtc        32: static double huge = 1.0e300;
1.1       jtc        33: #endif
                     34:
                     35: #ifdef __STDC__
                     36:        double ceil(double x)
                     37: #else
                     38:        double ceil(x)
                     39:        double x;
                     40: #endif
                     41: {
1.6     ! jtc        42:        int32_t i0,i1,j0;
        !            43:        u_int32_t i,j;
1.5       jtc        44:        EXTRACT_WORDS(i0,i1,x);
1.1       jtc        45:        j0 = ((i0>>20)&0x7ff)-0x3ff;
                     46:        if(j0<20) {
                     47:            if(j0<0) {  /* raise inexact if x != 0 */
                     48:                if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
                     49:                    if(i0<0) {i0=0x80000000;i1=0;}
                     50:                    else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
                     51:                }
                     52:            } else {
                     53:                i = (0x000fffff)>>j0;
                     54:                if(((i0&i)|i1)==0) return x; /* x is integral */
                     55:                if(huge+x>0.0) {        /* raise inexact flag */
                     56:                    if(i0>0) i0 += (0x00100000)>>j0;
                     57:                    i0 &= (~i); i1=0;
                     58:                }
                     59:            }
                     60:        } else if (j0>51) {
                     61:            if(j0==0x400) return x+x;   /* inf or NaN */
                     62:            else return x;              /* x is integral */
                     63:        } else {
1.6     ! jtc        64:            i = ((u_int32_t)(0xffffffff))>>(j0-20);
1.1       jtc        65:            if((i1&i)==0) return x;     /* x is integral */
                     66:            if(huge+x>0.0) {            /* raise inexact flag */
                     67:                if(i0>0) {
                     68:                    if(j0==20) i0+=1;
                     69:                    else {
                     70:                        j = i1 + (1<<(52-j0));
                     71:                        if(j<i1) i0+=1; /* got a carry */
                     72:                        i1 = j;
                     73:                    }
                     74:                }
                     75:                i1 &= (~i);
                     76:            }
                     77:        }
1.5       jtc        78:        INSERT_WORDS(x,i0,i1);
1.1       jtc        79:        return x;
                     80: }