file_locking.rs
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pub mod errors;
pub mod file_ext;
#[cfg(unix)]
mod unix;
#[cfg(windows)]
mod windows;
pub use errors::{ Error, Result };
pub use file_ext::{ FileExt };
#[cfg(test)]
mod tests {
use super::*;
use std::fs::{ File, self };
use std::path::{ Path, PathBuf };
struct TestFile {
path: PathBuf,
file: File,
}
impl TestFile {
fn new<P: AsRef<Path>>(path: P) -> Result<TestFile> {
let path = path.as_ref();
let file = File::options()
.create_new(true)
.write(true)
.open(path)?;
Ok(TestFile {
path: path.to_path_buf(),
file,
})
}
}
impl Drop for TestFile {
fn drop(&mut self) {
let _ = fs::remove_file(&self.path);
}
}
#[test]
fn lock_shared_works() {
const TEST_FILE_PATH: &str = "test_lock_shared.txt";
let f = TestFile::new(TEST_FILE_PATH).expect("File should be created and opened");
let _guard = f.file.lock_shared().expect("Shared file lock should be obtained");
}
#[test]
fn lock_exclusive_works() {
const TEST_FILE_PATH: &str = "test_lock_exclusive.txt";
let f = TestFile::new(TEST_FILE_PATH).expect("File should be created and opened");
let _guard = f.file.lock_exclusive().expect("Exclusive file lock should be obtained");
}
#[test]
fn try_lock_shared_works() {
const TEST_FILE_PATH: &str = "test_try_lock_shared.txt";
let f = TestFile::new(TEST_FILE_PATH).expect("File should be created and opened");
let _guard = f.file.try_lock_shared().expect("Shared file lock should be obtained");
}
#[test]
fn try_lock_exclusive_works() {
const TEST_FILE_PATH: &str = "test_try_lock_exclusive.txt";
let f = TestFile::new(TEST_FILE_PATH).expect("File should be created and opened");
let _guard = f.file.try_lock_shared().expect("Shared file lock should be obtained");
}
#[test]
fn try_lock_shared_does_not_block() {
const TEST_FILE_PATH: &str = "test_try_lock_shared_does_not_block.txt";
let f = TestFile::new(TEST_FILE_PATH).expect("File should be created and opened");
let _guard = f.file.lock_exclusive().expect("Exclusive file lock should be obtained");
assert_shared_lock_fails(TEST_FILE_PATH);
}
#[test]
fn try_lock_exclusive_does_not_block() {
const TEST_FILE_PATH: &str = "test_try_lock_exclusive_does_not_block.txt";
let f = TestFile::new(TEST_FILE_PATH).expect("File should be created and opened");
let _guard = f.file.lock_exclusive().expect("Exclusive file lock should be obtained");
assert_exclusive_lock_fails(TEST_FILE_PATH);
}
#[test]
fn lock_guard_going_out_of_scope_releases_lock() {
const TEST_FILE_PATH: &str = "test_lock_guard_going_out_of_scope_releases_lock.txt";
let f = TestFile::new(TEST_FILE_PATH).expect("File should be created and opened");
{
let _guard = f.file.lock_exclusive().expect("Exclusive file lock should be obtained");
assert_shared_lock_fails(TEST_FILE_PATH);
}
assert_shared_lock_succeeds(TEST_FILE_PATH);
assert_exclusive_lock_succeeds(TEST_FILE_PATH);
}
fn assert_shared_lock_succeeds<P: AsRef<Path>>(path: P) {
// We need to open the file again to test exclusive locking because on Unix
// systems, locking the same file descriptor twice will result in a no-op
// for the second `flock()`
let f2 = File::options()
.read(true)
.open(path)
.expect("Second handle to the same file should be opened");
let result = f2.try_lock_shared();
match result {
Ok(_) => {},
Err(_) => panic!("Shared lock should succeed"),
}
}
fn assert_exclusive_lock_succeeds<P: AsRef<Path>>(path: P) {
// We need to open the file again to test exclusive locking because on Unix
// systems, locking the same file descriptor twice will result in a no-op
// for the second `flock()`
let f2 = File::options()
.read(true)
.open(path)
.expect("Second handle to the same file should be opened");
let result = f2.try_lock_exclusive();
match result {
Ok(_) => {},
Err(_) => panic!("Exclusive lock should succeed"),
}
}
fn assert_shared_lock_fails<P: AsRef<Path>>(path: P) {
// We need to open the file again to test exclusive locking because on Unix
// systems, locking the same file descriptor twice will result in a no-op
// for the second `flock()`
let f2 = File::options()
.read(true)
.open(path)
.expect("Second handle to the same file should be opened");
let result = f2.try_lock_shared();
match result {
Ok(_) => panic!("Second file lock should not be obtained"),
Err(Error::AlreadyLocked) => {},
Err(_) => panic!("Result of trying to obtain a second file lock should be Error::AlreadyLocked"),
}
}
fn assert_exclusive_lock_fails<P: AsRef<Path>>(path: P) {
// We need to open the file again to test exclusive locking because on Unix
// systems, locking the same file descriptor twice will result in a no-op
// for the second `flock()`
let f2 = File::options()
.read(true)
.open(path)
.expect("Second handle to the same file should be opened");
let result = f2.try_lock_exclusive();
match result {
Ok(_) => panic!("Second file lock should not be obtained"),
Err(Error::AlreadyLocked) => {},
Err(_) => panic!("Result of trying to obtain a second file lock should be Error::AlreadyLocked"),
}
}
}