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use std::{
fs::{File, OpenOptions},
io,
ops::{Deref, DerefMut},
path::Path,
};
use thiserror::Error;
#[cfg(windows)]
mod windows;
#[cfg(unix)]
mod unix;
#[derive(Debug, Error)]
pub enum FileLockError {
#[error("the file is already locked")]
AlreadyLocked,
#[error("I/O error: {0}")]
IOError(#[from] io::Error),
}
#[derive(Copy, Clone, Eq, PartialEq, Debug)]
pub enum FileLockMode {
Exclusive,
Shared,
}
pub struct AdvisoryFileLock {
file: File,
file_lock_mode: FileLockMode,
}
impl AdvisoryFileLock {
pub fn new<P: AsRef<Path>>(
path: P,
file_lock_mode: FileLockMode,
) -> Result<Self, FileLockError> {
let is_exclusive = file_lock_mode == FileLockMode::Exclusive;
let file = OpenOptions::new()
.read(true)
.create(is_exclusive)
.write(is_exclusive)
.open(path)?;
Ok(AdvisoryFileLock {
file,
file_lock_mode,
})
}
pub fn is_shared(&self) -> bool {
self.file_lock_mode == FileLockMode::Shared
}
pub fn is_exclusive(&self) -> bool {
self.file_lock_mode == FileLockMode::Exclusive
}
pub fn lock(&mut self) -> Result<(), FileLockError> {
self.lock_impl()
}
pub fn try_lock(&mut self) -> Result<(), FileLockError> {
self.try_lock_impl()
}
pub fn unlock(&mut self) -> Result<(), FileLockError> {
self.unlock_impl()
}
}
impl Drop for AdvisoryFileLock {
fn drop(&mut self) {
if let Err(err) = self.unlock() {
log::error!(
"[AdvisoryFileLock] unlock_file failed during dropping: {}",
err
);
}
}
}
impl Deref for AdvisoryFileLock {
type Target = File;
fn deref(&self) -> &Self::Target {
&self.file
}
}
impl DerefMut for AdvisoryFileLock {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.file
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::env::temp_dir;
#[test]
fn simple_shared_lock() {
let mut test_file = temp_dir();
test_file.push("shared_lock");
File::create(&test_file).unwrap();
{
let mut f1 = AdvisoryFileLock::new(&test_file, FileLockMode::Shared).unwrap();
f1.lock().unwrap();
let mut f2 = AdvisoryFileLock::new(&test_file, FileLockMode::Shared).unwrap();
f2.lock().unwrap();
}
std::fs::remove_file(&test_file).unwrap();
}
#[test]
fn simple_exclusive_lock() {
let mut test_file = temp_dir();
test_file.push("exclusive_lock");
{
let mut f1 = AdvisoryFileLock::new(&test_file, FileLockMode::Exclusive).unwrap();
f1.lock().unwrap();
let f2 = AdvisoryFileLock::new(&test_file, FileLockMode::Exclusive)
.unwrap()
.try_lock();
assert!(f2.is_err());
}
std::fs::remove_file(&test_file).unwrap();
}
#[test]
fn simple_shared_exclusive_lock() {
let mut test_file = temp_dir();
test_file.push("shared_exclusive_lock");
File::create(&test_file).unwrap();
{
let mut f1 = AdvisoryFileLock::new(&test_file, FileLockMode::Shared).unwrap();
f1.lock().unwrap();
let mut f2 = AdvisoryFileLock::new(&test_file, FileLockMode::Exclusive).unwrap();
assert!(f2.try_lock().is_err());
}
std::fs::remove_file(&test_file).unwrap();
}
#[test]
fn simple_exclusive_shared_lock() {
let mut test_file = temp_dir();
test_file.push("exclusive_shared_lock");
{
let mut f1 = AdvisoryFileLock::new(&test_file, FileLockMode::Exclusive).unwrap();
f1.lock().unwrap();
let mut f2 = AdvisoryFileLock::new(&test_file, FileLockMode::Exclusive).unwrap();
assert!(f2.try_lock().is_err());
}
std::fs::remove_file(&test_file).unwrap();
}
}