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use std::fs::{File, OpenOptions};
use std::io;
use std::mem;
use std::os::unix::prelude::*;
use std::path::Path;
#[derive(Debug)]
pub struct Lock {
file: File,
}
impl Lock {
pub fn new(p: &Path, wait: bool, create: bool, exclusive: bool) -> io::Result<Lock> {
let file = OpenOptions::new()
.read(true)
.write(true)
.create(create)
.mode(libc::S_IRWXU as u32)
.open(p)?;
let lock_type = if exclusive { libc::F_WRLCK } else { libc::F_RDLCK };
let mut flock: libc::flock = unsafe { mem::zeroed() };
flock.l_type = lock_type as libc::c_short;
flock.l_whence = libc::SEEK_SET as libc::c_short;
flock.l_start = 0;
flock.l_len = 0;
let cmd = if wait { libc::F_SETLKW } else { libc::F_SETLK };
let ret = unsafe { libc::fcntl(file.as_raw_fd(), cmd, &flock) };
if ret == -1 { Err(io::Error::last_os_error()) } else { Ok(Lock { file }) }
}
pub fn error_unsupported(err: &io::Error) -> bool {
matches!(err.raw_os_error(), Some(libc::ENOTSUP) | Some(libc::ENOSYS))
}
}
impl Drop for Lock {
fn drop(&mut self) {
let mut flock: libc::flock = unsafe { mem::zeroed() };
flock.l_type = libc::F_UNLCK as libc::c_short;
flock.l_whence = libc::SEEK_SET as libc::c_short;
flock.l_start = 0;
flock.l_len = 0;
unsafe {
libc::fcntl(self.file.as_raw_fd(), libc::F_SETLK, &flock);
}
}
}
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