#include "stdio_impl.h"

static int __fflush_unlocked(FILE* f) {
  /* If writing, flush output */
  if (f->wpos > f->wbase) {
    f->write(f, 0, 0);
    if (!f->wpos)
      return EOF;
  }

  /* If reading, sync position, per POSIX */
  if (f->rpos < f->rend)
    f->seek(f, f->rpos - f->rend, SEEK_CUR);

  /* Clear read and write modes */
  f->wpos = f->wbase = f->wend = 0;
  f->rpos = f->rend = 0;

  return 0;
}

int fflush(FILE* f) {
  int r;

  if (f) {
    FLOCK(f);
    r = __fflush_unlocked(f);
    FUNLOCK(f);
    return r;
  }

  // In case of any non-canonical buffering of stderr in-process, including any buffering below
  // writev() (canonically a syscall) but above the process boundary.
  r = fflush(stderr);

  r |= fflush(stdout);

  for (f = *__ofl_lock(); f; f = f->next) {
    FLOCK(f);
    if (f->wpos > f->wbase)
      r |= __fflush_unlocked(f);
    FUNLOCK(f);
  }
  __ofl_unlock();

  return r;
}

weak_alias(__fflush_unlocked, fflush_unlocked);