/*-
 * Copyright (c) 2017, 2023 Steven G. Kargl
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * See ../src/s_cospi.c for implementation details.
 */

#ifdef __i386__
#include <ieeefp.h>
#endif
#include <stdint.h>

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

static const double
pi_hi = 3.1415926814079285e+00, /* 0x400921fb 0x58000000 */
pi_lo =-2.7818135228334233e-08; /* 0xbe5dde97 0x3dcb3b3a */

#include "k_cospil.h"
#include "k_sinpil.h"

volatile static const double vzero = 0;

long double
cospil(long double x)
{
        long double ax, c;
        uint64_t lx, m;
        uint32_t j0;
        uint16_t hx, ix;

        EXTRACT_LDBL80_WORDS(hx, lx, x);
        ix = hx & 0x7fff;
        INSERT_LDBL80_WORDS(ax, ix, lx);

        ENTERI();

        if (ix < 0x3fff) {                      /* |x| < 1 */
                if (ix < 0x3ffd) {              /* |x| < 0.25 */
                        if (ix < 0x3fdd) {      /* |x| < 0x1p-34 */
                                if ((int)x == 0)
                                        RETURNI(1);
                        }
                        RETURNI(__kernel_cospil(ax));
                }

                if (ix < 0x3ffe)                        /* |x| < 0.5 */
                        c = __kernel_sinpil(0.5 - ax);
                else if (lx < 0xc000000000000000ull) {  /* |x| < 0.75 */
                        if (ax == 0.5)
                                RETURNI(0);
                        c = -__kernel_sinpil(ax - 0.5);
                } else
                        c = -__kernel_cospil(1 - ax);
                RETURNI(c);
        }

        if (ix < 0x403e) {                      /* 1 <= |x| < 0x1p63 */
                FFLOORL80(x, j0, ix, lx);       /* Integer part of ax. */
                ax -= x;
                EXTRACT_LDBL80_WORDS(ix, lx, ax);

                if (ix < 0x3ffe) {                      /* |x| < 0.5 */
                        if (ix < 0x3ffd)                /* |x| < 0.25 */
                                c = ix == 0 ? 1 : __kernel_cospil(ax);
                        else
                                c = __kernel_sinpil(0.5 - ax);

                } else {
                        if (lx < 0xc000000000000000ull) { /* |x| < 0.75 */
                                if (ax == 0.5)
                                        RETURNI(0);
                                c = -__kernel_sinpil(ax - 0.5);
                        } else
                                c = -__kernel_cospil(1 - ax);
                }

                if (j0 > 40)
                        x -= 0x1p40;
                if (j0 > 30)
                        x -= 0x1p30;
                j0 = (uint32_t)x;

                RETURNI(j0 & 1 ? -c : c);
        }

        if (ix >= 0x7fff)
                RETURNI(vzero / vzero);

        /*
         * For 0x1p63 <= |x| < 0x1p64 need to determine if x is an even
         * or odd integer to return t = +1 or -1.
         * For |x| >= 0x1p64, it is always an even integer, so t = 1.
         */
        RETURNI(ix >= 0x403f ? 1 : ((lx & 1) ? -1 : 1));
}