view src/libm/s_floor.c @ 3468:789b97008d8a

My first OpenGL shader! Momma will be so proud! This shader implements the software renderer mask semantics where the source pixel is multiplied by the color and alpha modulation values and then any pixel with non-zero alpha is fully opaque. The OpenGL renderer on Mac OS X now passes all the automated render tests! :)
author Sam Lantinga <slouken@libsdl.org>
date Sat, 21 Nov 2009 05:29:31 +0000
parents 9ac6f0782dd6
children
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/* @(#)s_floor.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static const char rcsid[] =
    "$NetBSD: s_floor.c,v 1.8 1995/05/10 20:47:20 jtc Exp $";
#endif

/*
 * floor(x)
 * Return x rounded toward -inf to integral value
 * Method:
 *	Bit twiddling.
 * Exception:
 *	Inexact flag raised if x not equal to floor(x).
 */

#include "math.h"
#include "math_private.h"

#ifdef __STDC__
static const double huge_val = 1.0e300;
#else
static double huge_val = 1.0e300;
#endif

libm_hidden_proto(floor)
#ifdef __STDC__
     double floor(double x)
#else
     double floor(x)
     double x;
#endif
{
    int32_t i0, i1, j0;
    u_int32_t i, j;
    EXTRACT_WORDS(i0, i1, x);
    j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
    if (j0 < 20) {
        if (j0 < 0) {           /* raise inexact if x != 0 */
            if (huge_val + x > 0.0) {       /* return 0*sign(x) if |x|<1 */
                if (i0 >= 0) {
                    i0 = i1 = 0;
                } else if (((i0 & 0x7fffffff) | i1) != 0) {
                    i0 = 0xbff00000;
                    i1 = 0;
                }
            }
        } else {
            i = (0x000fffff) >> j0;
            if (((i0 & i) | i1) == 0)
                return x;       /* x is integral */
            if (huge_val + x > 0.0) {       /* raise inexact flag */
                if (i0 < 0)
                    i0 += (0x00100000) >> j0;
                i0 &= (~i);
                i1 = 0;
            }
        }
    } else if (j0 > 51) {
        if (j0 == 0x400)
            return x + x;       /* inf or NaN */
        else
            return x;           /* x is integral */
    } else {
        i = ((u_int32_t) (0xffffffff)) >> (j0 - 20);
        if ((i1 & i) == 0)
            return x;           /* x is integral */
        if (huge_val + x > 0.0) {   /* raise inexact flag */
            if (i0 < 0) {
                if (j0 == 20)
                    i0 += 1;
                else {
                    j = i1 + (1 << (52 - j0));
                    if (j < (u_int32_t) i1)
                        i0 += 1;        /* got a carry */
                    i1 = j;
                }
            }
            i1 &= (~i);
        }
    }
    INSERT_WORDS(x, i0, i1);
    return x;
}

libm_hidden_def(floor)