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view src/libm/s_floor.c @ 3474:1edb86163d62

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Of COURSE that trick wouldn't work on all renderers. Fall back to something for now, hopefully figure out a better way to do this later. If we have to, we can use vertical line and horizontal line textures for vertical and horizontal lines, and then create custom textures for diagonal lines and software render those. It's terrible, but at least it would be pixel perfect.
author Sam Lantinga <slouken@libsdl.org>
date Sat, 21 Nov 2009 07:22:59 +0000
parents 9ac6f0782dd6
children
line wrap: on
line source

/* @(#)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)