/*
 * Copyright © 2005-2026 Rich Felker, et al.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * Imported from musl C library
 */

#include <uchar.h>
#include <wchar.h>

size_t mbrtoc16(char16_t *restrict pc16, const char *restrict s, size_t n, mbstate_t *restrict ps)
{
	static unsigned internal_state;
	if (!ps) ps = (void *)&internal_state;
	unsigned *pending = (unsigned *)ps;

	if (!s) return mbrtoc16(0, "", 1, ps);

	/* mbrtowc states for partial UTF-8 characters have the high bit set;
	 * we use nonzero states without high bit for pending surrogates. */
	if ((int)*pending > 0) {
 		if (pc16) *pc16 = *pending;
		*pending = 0;
		return -3;
	}

	wchar_t wc;
	size_t ret = mbrtowc(&wc, s, n, ps);
	if (ret <= 4) {
		if (wc >= 0x10000) {
			*pending = (wc & 0x3ff) + 0xdc00;
			wc = 0xd7c0 + (wc >> 10);
		}
		if (pc16) *pc16 = wc;
	}
	return ret;
}
