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Annotation of src/lib/libm/src/s_ceil.c, Revision 1.1

1.1     ! jtc         1:
        !             2: /* @(#)s_ceil.c 5.1 93/09/24 */
        !             3: /*
        !             4:  * ====================================================
        !             5:  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
        !             6:  *
        !             7:  * Developed at SunPro, a Sun Microsystems, Inc. business.
        !             8:  * Permission to use, copy, modify, and distribute this
        !             9:  * software is freely granted, provided that this notice
        !            10:  * is preserved.
        !            11:  * ====================================================
        !            12:  */
        !            13:
        !            14: /*
        !            15:  * ceil(x)
        !            16:  * Return x rounded toward -inf to integral value
        !            17:  * Method:
        !            18:  *     Bit twiddling.
        !            19:  * Exception:
        !            20:  *     Inexact flag raised if x not equal to ceil(x).
        !            21:  */
        !            22:
        !            23: #include "fdlibm.h"
        !            24:
        !            25: #ifdef __STDC__
        !            26: static const double one = 1.0,huge = 1.0e300;
        !            27: #else
        !            28: static double one = 1.0,huge = 1.0e300;
        !            29: #endif
        !            30:
        !            31: #ifdef __STDC__
        !            32:        double ceil(double x)
        !            33: #else
        !            34:        double ceil(x)
        !            35:        double x;
        !            36: #endif
        !            37: {
        !            38:        int i0,i1,n0,j0;
        !            39:        unsigned i,j;
        !            40:        n0 = (*((int *)&one)>>29)^1;
        !            41:        i0 =  *(n0+(int*)&x);
        !            42:        i1 =  *(1-n0+(int*)&x);
        !            43:        j0 = ((i0>>20)&0x7ff)-0x3ff;
        !            44:        if(j0<20) {
        !            45:            if(j0<0) {  /* raise inexact if x != 0 */
        !            46:                if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
        !            47:                    if(i0<0) {i0=0x80000000;i1=0;}
        !            48:                    else if((i0|i1)!=0) { i0=0x3ff00000;i1=0;}
        !            49:                }
        !            50:            } else {
        !            51:                i = (0x000fffff)>>j0;
        !            52:                if(((i0&i)|i1)==0) return x; /* x is integral */
        !            53:                if(huge+x>0.0) {        /* raise inexact flag */
        !            54:                    if(i0>0) i0 += (0x00100000)>>j0;
        !            55:                    i0 &= (~i); i1=0;
        !            56:                }
        !            57:            }
        !            58:        } else if (j0>51) {
        !            59:            if(j0==0x400) return x+x;   /* inf or NaN */
        !            60:            else return x;              /* x is integral */
        !            61:        } else {
        !            62:            i = ((unsigned)(0xffffffff))>>(j0-20);
        !            63:            if((i1&i)==0) return x;     /* x is integral */
        !            64:            if(huge+x>0.0) {            /* raise inexact flag */
        !            65:                if(i0>0) {
        !            66:                    if(j0==20) i0+=1;
        !            67:                    else {
        !            68:                        j = i1 + (1<<(52-j0));
        !            69:                        if(j<i1) i0+=1; /* got a carry */
        !            70:                        i1 = j;
        !            71:                    }
        !            72:                }
        !            73:                i1 &= (~i);
        !            74:            }
        !            75:        }
        !            76:        *(n0+(int*)&x) = i0;
        !            77:        *(1-n0+(int*)&x) = i1;
        !            78:        return x;
        !            79: }