source: azure_iot_hub/trunk/musl-1.1.18/src/math/sincos.c@ 388

/* origin: FreeBSD /usr/src/lib/msun/src/s_sin.c */
/*
 * ====================================================
 * 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.
 * ====================================================
 */

#define _GNU_SOURCE
#include "libm.h"

void sincos(double x, double *sin, double *cos)
{
        double y[2], s, c;
        uint32_t ix;
        unsigned n;

        GET_HIGH_WORD(ix, x);
        ix &= 0x7fffffff;

        /* |x| ~< pi/4 */
        if (ix <= 0x3fe921fb) {
                /* if |x| < 2**-27 * sqrt(2) */
                if (ix < 0x3e46a09e) {
                        /* raise inexact if x!=0 and underflow if subnormal */
                        FORCE_EVAL(ix < 0x00100000 ? x/0x1p120f : x+0x1p120f);
                        *sin = x;
                        *cos = 1.0;
                        return;
                }
                *sin = __sin(x, 0.0, 0);
                *cos = __cos(x, 0.0);
                return;
        }

        /* sincos(Inf or NaN) is NaN */
        if (ix >= 0x7ff00000) {
                *sin = *cos = x - x;
                return;
        }

        /* argument reduction needed */
        n = __rem_pio2(x, y);
        s = __sin(y[0], y[1], 1);
        c = __cos(y[0], y[1]);
        switch (n&3) {
        case 0:
                *sin = s;
                *cos = c;
                break;
        case 1:
                *sin = c;
                *cos = -s;
                break;
        case 2:
                *sin = -s;
                *cos = -c;
                break;
        case 3:
        default:
                *sin = -c;
                *cos = s;
                break;
        }
}