fusl/src/stdio/__overflow.c

#include "stdio_impl.h"

int __overflow(FILE* f, int _c) {
  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;
  return c;
}