- /* Initialize if we're not already writing */
- if (!f->wend) {
- /* Fail if we're in error state or unwritable. */
- if (f->flags & (F_ERR|F_NOWR)) return EOF;
-
- /* Set byte orientation -1,0=>-1; 1=>1 */
- f->mode |= f->mode-1;
-
- /* Clear read buffer (easier than summoning nasal demons) */
- f->rpos = f->rend = f->rstop = 0;
-
- /* Activate write through the buffer */
- f->wpos = f->wbase = f->buf;
- f->wend = f->buf + f->buf_size;
- f->wstop = (f->lbf < 0) ? f->wend - 1 : 0;
- }
-
- /* Buffer can always hold at least 1 byte... */
- if (c != EOF) {
- *f->wpos++ = c;
- if (f->wpos <= f->wstop && c != f->lbf) return c;
- }
- /* ...since if the next call fails, buffer is empty. */
- if (f->write(f, f->wbase, f->wpos - f->wbase) < 0) {
- f->flags |= F_ERR;
- f->wpos = f->wbase = f->wend = f->wstop = 0;
- return EOF;
- }
-
- /* Buffer is empty so reset position to beginning */
- f->wpos = f->wbase;
-
+ unsigned char c = _c;
+ if (!f->wend && __towrite(f)) return EOF;
+ if (f->wpos < f->wend && c != f->lbf) return *f->wpos++ = c;
+ if (f->write(f, &c, 1)!=1) return EOF;