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

__attribute__((__noinline__))
static size_t c8rtomb_slow(char *__restrict s, unsigned char c8, mbstate_t *__restrict st)
{
	// We need an internal state different from mbrtowc.
	static mbstate_t internal_state;
	if (!st) st = &internal_state;
	wchar_t wc;

	// mbrtowc has return values -2, -1, 0, 1.
	size_t res = mbrtowc(&wc, (char const*)&c8, 1, st);
	switch (res) {
	// our implementation of wcrtomb ignores the state
	case  1: res = wcrtomb(s, wc, 0); break;
	case  0: res = 1; if (s) *s = 0;  break;
	}
	return res;
}

static size_t __c8rtomb(char *__restrict s, unsigned char c8, mbstate_t *__restrict st)
{
        if (st && !*(unsigned*)st && (c8 < 0x80)) {
		if (s) *s = c8;
		return 1;
	}
	return c8rtomb_slow(s, c8, st);
}

weak_alias(__c8rtomb, c8rtomb);