/*-
* 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.
*/

#include <stdint.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"

static volatile const double vzero = 0;

long double
cospil(long double x)
{
       long double ax, c;
       uint64_t lx;
       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));
}