blob: fc4e68d89d38fb9784fbb596ce5e0cf8b7dcf864 [file] [log] [blame]
// Copyright 2018 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//! This module contains all the unsafe code necessary for this crate.
use std::ffi::CString;
use std::mem::zeroed;
use std::os::unix::ffi::OsStrExt;
use std::path::Path;
use libc::{__errno_location, statvfs64, EINTR, EINVAL};
/// Gets free disk space in bytes on the filesystem that contains `path`. Returns a positive `errno`
/// on failure.
pub fn get_free_disk_space<P: AsRef<Path>>(path: P) -> Result<u64, i32> {
let path_cstr = CString::new(path.as_ref().as_os_str().as_bytes()).or(Err(EINVAL))?;
// Safe because `stats` is never accessed until after being initialized by the `statvfs64` call
// returns successfully.
let mut stats: statvfs64 = unsafe { zeroed() };
let mut errno = EINTR;
while errno == EINTR {
// Safe because a valid C-style string is passed in, along with the correct type of mutable
// pointer for returned data. The return value is also checked for errors.
unsafe {
if statvfs64(path_cstr.as_ptr(), &mut stats) == 0 {
// This clippy override is needed because the type of `stats.f_frsize` is sometimes
// `u64` depending on the target architecture.
#[cfg_attr(feature = "cargo-clippy", allow(identity_conversion))]
return Ok(stats.f_bavail.saturating_mul(u64::from(stats.f_frsize)));
errno = *__errno_location();
mod tests {
use super::*;
use libc::ENOENT;
use std::process::Command;
fn same_as_df() {
let free_bytes = get_free_disk_space(".").expect("failed to get free disk space");
let df_free_bytes = String::from_utf8(
.args(&["--output=avail", "--block-size=1", "."])
println!("get_free_disk_space reports {}", free_bytes);
println!("df reports {}", df_free_bytes);
assert!(df_free_bytes.trim().ends_with(&format!("{}", free_bytes)));
fn invalid_nul() {
assert_eq!(get_free_disk_space("./\0"), Err(EINVAL));
fn no_such_path() {