third_party/ulib/musl/src/stdio/ungetwc.c

#include "locale_impl.h"
#include "stdio_impl.h"
#include <ctype.h>
#include <limits.h>
#include <string.h>
#include <wchar.h>

wint_t ungetwc(wint_t c, FILE* f) {
    unsigned char mbc[MB_LEN_MAX];
    int l;
    locale_t *ploc = &CURRENT_LOCALE, loc = *ploc;

    FLOCK(f);

    if (f->mode <= 0)
        fwide(f, 1);
    *ploc = f->locale;

    if (!f->rpos)
        __toread(f);
    if (!f->rpos || c == WEOF || (l = wcrtomb((void*)mbc, c, 0)) < 0 ||
        f->rpos < f->buf - UNGET + l) {
        FUNLOCK(f);
        *ploc = loc;
        return WEOF;
    }

    if (isascii(c))
        *--f->rpos = c;
    else
        memcpy(f->rpos -= l, mbc, l);

    f->flags &= ~F_EOF;

    FUNLOCK(f);
    *ploc = loc;
    return c;
}