fusl/src/stdio/ungetwc.c

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

wint_t ungetwc(wint_t c, FILE* f) {
  unsigned char mbc[MB_LEN_MAX];
  int l = 1;
  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 || f->rpos < f->buf - UNGET + l || c == WEOF ||
      (!isascii(c) && (l = wctomb((void*)mbc, c)) < 0)) {
    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;
}