/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2013 Ed Schouten <ed@FreeBSD.org>
 * 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, 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
 */

#include <uchar.h>
#include "mblocal.h"

typedef struct {
        char16_t        trail_surrogate;
        mbstate_t       c32_mbstate;
} _Char16State;

size_t
mbrtoc16_l(char16_t * __restrict pc16, const char * __restrict s, size_t n,
    mbstate_t * __restrict ps, locale_t locale)
{
        _Char16State *cs;
        char32_t c32;
        ssize_t len;

        FIX_LOCALE(locale);
        if (ps == NULL)
                ps = &(XLOCALE_CTYPE(locale)->mbrtoc16);
        cs = (_Char16State *)ps;

        /*
         * Call straight into mbrtoc32_l() if we don't need to return a
         * character value. According to the spec, if s is a null
         * pointer, the value of parameter pc16 is also ignored.
         */
        if (pc16 == NULL || s == NULL) {
                cs->trail_surrogate = 0;
                return (mbrtoc32_l(NULL, s, n, &cs->c32_mbstate, locale));
        }

        /* Return the trail surrogate from the previous invocation. */
        if (cs->trail_surrogate >= 0xdc00 && cs->trail_surrogate <= 0xdfff) {
                *pc16 = cs->trail_surrogate;
                cs->trail_surrogate = 0;
                return ((size_t)-3);
        }

        len = mbrtoc32_l(&c32, s, n, &cs->c32_mbstate, locale);
        if (len >= 0) {
                if (c32 < 0x10000) {
                        /* Fits in one UTF-16 character. */
                        *pc16 = c32;
                } else {
                        /* Split up in a surrogate pair. */
                        c32 -= 0x10000;
                        *pc16 = 0xd800 | (c32 >> 10);
                        cs->trail_surrogate = 0xdc00 | (c32 & 0x3ff);
                }
        }
        return (len);
}

size_t
mbrtoc16(char16_t * __restrict pc16, const char * __restrict s, size_t n,
    mbstate_t * __restrict ps)
{

        return (mbrtoc16_l(pc16, s, n, ps, __get_locale()));
}