slouken@2758: /* @(#)s_floor.c 5.1 93/09/24 */
slouken@2758: /*
slouken@2758:  * ====================================================
slouken@2758:  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
slouken@2758:  *
slouken@2758:  * Developed at SunPro, a Sun Microsystems, Inc. business.
slouken@2758:  * Permission to use, copy, modify, and distribute this
slouken@2758:  * software is freely granted, provided that this notice
slouken@2758:  * is preserved.
slouken@2758:  * ====================================================
slouken@2758:  */
slouken@2758: 
slouken@2758: #if defined(LIBM_SCCS) && !defined(lint)
slouken@2758: static char rcsid[] =
slouken@2758:     "$NetBSD: s_floor.c,v 1.8 1995/05/10 20:47:20 jtc Exp $";
slouken@2758: #endif
slouken@2758: 
slouken@2758: /*
slouken@2758:  * floor(x)
slouken@2758:  * Return x rounded toward -inf to integral value
slouken@2758:  * Method:
slouken@2758:  *	Bit twiddling.
slouken@2758:  * Exception:
slouken@2758:  *	Inexact flag raised if x not equal to floor(x).
slouken@2758:  */
slouken@2758: 
slouken@2758: #include "math.h"
slouken@2758: #include "math_private.h"
slouken@2758: 
slouken@2758: #ifdef __STDC__
slouken@2758: static const double huge = 1.0e300;
slouken@2758: #else
slouken@2758: static double huge = 1.0e300;
slouken@2758: #endif
slouken@2758: 
slouken@2758: libm_hidden_proto(floor)
slouken@2758: #ifdef __STDC__
slouken@2758:      double floor(double x)
slouken@2758: #else
slouken@2758:      double floor(x)
slouken@2758:      double x;
slouken@2758: #endif
slouken@2758: {
slouken@2758:     int32_t i0, i1, j0;
slouken@2758:     u_int32_t i, j;
slouken@2758:     EXTRACT_WORDS(i0, i1, x);
slouken@2758:     j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
slouken@2758:     if (j0 < 20) {
slouken@2758:         if (j0 < 0) {           /* raise inexact if x != 0 */
slouken@2758:             if (huge + x > 0.0) {       /* return 0*sign(x) if |x|<1 */
slouken@2758:                 if (i0 >= 0) {
slouken@2758:                     i0 = i1 = 0;
slouken@2758:                 } else if (((i0 & 0x7fffffff) | i1) != 0) {
slouken@2758:                     i0 = 0xbff00000;
slouken@2758:                     i1 = 0;
slouken@2758:                 }
slouken@2758:             }
slouken@2758:         } else {
slouken@2758:             i = (0x000fffff) >> j0;
slouken@2758:             if (((i0 & i) | i1) == 0)
slouken@2758:                 return x;       /* x is integral */
slouken@2758:             if (huge + x > 0.0) {       /* raise inexact flag */
slouken@2758:                 if (i0 < 0)
slouken@2758:                     i0 += (0x00100000) >> j0;
slouken@2758:                 i0 &= (~i);
slouken@2758:                 i1 = 0;
slouken@2758:             }
slouken@2758:         }
slouken@2758:     } else if (j0 > 51) {
slouken@2758:         if (j0 == 0x400)
slouken@2758:             return x + x;       /* inf or NaN */
slouken@2758:         else
slouken@2758:             return x;           /* x is integral */
slouken@2758:     } else {
slouken@2758:         i = ((u_int32_t) (0xffffffff)) >> (j0 - 20);
slouken@2758:         if ((i1 & i) == 0)
slouken@2758:             return x;           /* x is integral */
slouken@2758:         if (huge + x > 0.0) {   /* raise inexact flag */
slouken@2758:             if (i0 < 0) {
slouken@2758:                 if (j0 == 20)
slouken@2758:                     i0 += 1;
slouken@2758:                 else {
slouken@2758:                     j = i1 + (1 << (52 - j0));
slouken@2758:                     if (j < i1)
slouken@2758:                         i0 += 1;        /* got a carry */
slouken@2758:                     i1 = j;
slouken@2758:                 }
slouken@2758:             }
slouken@2758:             i1 &= (~i);
slouken@2758:         }
slouken@2758:     }
slouken@2758:     INSERT_WORDS(x, i0, i1);
slouken@2758:     return x;
slouken@2758: }
slouken@2758: 
slouken@2758: libm_hidden_def(floor)