/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-â
âvi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :viâ
ââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ¡
â Copyright 2020 Justine Alexandra Roberts Tunney                              â
â                                                                              â
â Permission to use, copy, modify, and/or distribute this software for         â
â any purpose with or without fee is hereby granted, provided that the         â
â above copyright notice and this permission notice appear in all copies.      â
â                                                                              â
â THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                â
â WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                â
â WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             â
â AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         â
â DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        â
â PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               â
â TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             â
â PERFORMANCE OF THIS SOFTWARE.                                                â
ââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ*/
#include "libc/calls/calls.h"
#include "libc/errno.h"
#include "libc/runtime/runtime.h"
#include "libc/stdio/internal.h"
#include "libc/stdio/lock.internal.h"
#include "libc/stdio/stdio.h"
#include "libc/sysv/consts/o.h"

static inline int64_t ftello_unlocked(FILE *f) {
  int64_t pos;
  uint32_t skew;
  if (f->fd != -1) {
    if (__fflush_impl(f) == -1) return -1;
    if ((pos = lseek(f->fd, 0, SEEK_CUR)) != -1) {
      if (f->beg < f->end) pos -= f->end - f->beg;
      return pos;
    } else {
      f->state = errno == ESPIPE ? EBADF : errno;
      return -1;
    }
  } else {
    return f->beg;
  }
}

/**
 * Returns current position of stream.
 *
 * @param stream is a non-null stream handle
 * @returns current byte offset from beginning, or -1 w/ errno
 * @threadsafe
 */
int64_t ftello(FILE *f) {
  int64_t rc;
  flockfile(f);
  rc = ftello_unlocked(f);
  funlockfile(f);
  return rc;
}
