unix.rs
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use crate::errors::{ Error, Result };
use crate::file_ext::{ FileExt };
use errno::{ Errno, errno };
use std::fs::{ File };
use std::os::raw::{ c_int };
use std::os::fd::{ AsRawFd };
impl FileExt for File {
type LockGuard = LockGuard;
fn lock_shared(&self) -> Result<Self::LockGuard> {
lock(self.as_raw_fd(), LOCK_SH)
}
fn lock_exclusive(&self) -> Result<Self::LockGuard> {
lock(self.as_raw_fd(), LOCK_EX)
}
fn try_lock_shared(&self) -> Result<Self::LockGuard> {
try_lock(self.as_raw_fd(), LOCK_SH)
}
fn try_lock_exclusive(&self) -> Result<Self::LockGuard> {
try_lock(self.as_raw_fd(), LOCK_EX)
}
}
#[derive(Debug)]
#[must_use = "Not retaining the guard object will result in the file being immediately unlocked"]
pub struct LockGuard {
fd: c_int,
}
impl Drop for LockGuard {
fn drop(&mut self) {
unsafe {
flock(self.fd, LOCK_UN);
}
}
}
fn lock(fd: c_int, mode: c_int) -> Result<LockGuard> {
let status = unsafe {
flock(fd, mode)
};
match status {
0 => Ok(LockGuard { fd }),
_ => Err(Error::LockFailed(errno())),
}
}
fn try_lock(fd: c_int, mode: c_int) -> Result<LockGuard> {
let status = unsafe {
flock(fd, mode | LOCK_NB)
};
match status {
0 => Ok(LockGuard { fd }),
_ => {
let e = errno();
if e == Errno(EAGAIN) || e == Errno(EWOULDBLOCK) {
Err(Error::AlreadyLocked)
} else {
Err(Error::LockFailed(e))
}
},
}
}
#[cfg(target_os = "linux")]
const EAGAIN: c_int = 11;
#[cfg(target_os = "macos")]
const EAGAIN: c_int = 35;
// No default value because it's better to not compile than to silently use
// an incorrect error code
// Defined because on some platforms it might not be EAGAIN, and this way
// we can just add a new `#[cfg(target_os = "...")]`
#[cfg(any(target_os = "linux", target_os = "macos"))]
const EWOULDBLOCK: c_int = EAGAIN;
const LOCK_SH: c_int = 0x01;
const LOCK_EX: c_int = 0x02;
const LOCK_NB: c_int = 0x04;
const LOCK_UN: c_int = 0x08;
extern "C" {
fn flock(fd: c_int, op: c_int) -> c_int;
}