/*
 * 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 <errno.h>
#include <wchar.h>

size_t c16rtomb(char *restrict s, char16_t c16, mbstate_t *restrict ps)
{
	static unsigned internal_state;
	if (!ps) ps = (void *)&internal_state;
	unsigned *x = (unsigned *)ps;
	wchar_t wc;

	if (!s) {
		if (*x) goto ilseq;
		return 1;
	}

	if (!*x && c16 - 0xd800u < 0x400) {
		*x = c16 - 0xd7c0 << 10;
		return 0;
	}

	if (*x) {
		if (c16 - 0xdc00u >= 0x400) goto ilseq;
		else wc = *x + c16 - 0xdc00;
		*x = 0;
	} else {
		wc = c16;
	}
	return wcrtomb(s, wc, 0);

ilseq:
	*x = 0;
	errno = EILSEQ;
	return -1;
}
