Revision control
Copy as Markdown
Other Tools
use std::os::raw::c_int;
use std::os::raw::c_void;
use std::panic::catch_unwind;
use std::sync::{Condvar, Mutex};
use crate::ffi;
struct UnlockNotification {
cond: Condvar, // Condition variable to wait on
mutex: Mutex<bool>, // Mutex to protect structure
}
#[allow(clippy::mutex_atomic)]
impl UnlockNotification {
fn new() -> UnlockNotification {
UnlockNotification {
cond: Condvar::new(),
mutex: Mutex::new(false),
}
}
fn fired(&self) {
let mut flag = unpoison(self.mutex.lock());
*flag = true;
self.cond.notify_one();
}
fn wait(&self) {
let mut fired = unpoison(self.mutex.lock());
while !*fired {
fired = unpoison(self.cond.wait(fired));
}
}
}
#[inline]
fn unpoison<T>(r: Result<T, std::sync::PoisonError<T>>) -> T {
r.unwrap_or_else(std::sync::PoisonError::into_inner)
}
/// This function is an unlock-notify callback
unsafe extern "C" fn unlock_notify_cb(ap_arg: *mut *mut c_void, n_arg: c_int) {
use std::slice::from_raw_parts;
let args = from_raw_parts(ap_arg as *const &UnlockNotification, n_arg as usize);
for un in args {
drop(catch_unwind(std::panic::AssertUnwindSafe(|| un.fired())));
}
}
pub unsafe fn is_locked(db: *mut ffi::sqlite3, rc: c_int) -> bool {
rc == ffi::SQLITE_LOCKED_SHAREDCACHE
|| (rc & 0xFF) == ffi::SQLITE_LOCKED
&& ffi::sqlite3_extended_errcode(db) == ffi::SQLITE_LOCKED_SHAREDCACHE
}
/// This function assumes that an SQLite API call (either `sqlite3_prepare_v2()`
/// or `sqlite3_step()`) has just returned `SQLITE_LOCKED`. The argument is the
/// associated database connection.
///
/// This function calls `sqlite3_unlock_notify()` to register for an
/// unlock-notify callback, then blocks until that callback is delivered
/// and returns `SQLITE_OK`. The caller should then retry the failed operation.
///
/// Or, if `sqlite3_unlock_notify()` indicates that to block would deadlock
/// the system, then this function returns `SQLITE_LOCKED` immediately. In
/// this case the caller should not retry the operation and should roll
/// back the current transaction (if any).
#[cfg(feature = "unlock_notify")]
pub unsafe fn wait_for_unlock_notify(db: *mut ffi::sqlite3) -> c_int {
let un = UnlockNotification::new();
/* Register for an unlock-notify callback. */
let rc = ffi::sqlite3_unlock_notify(
db,
Some(unlock_notify_cb),
&un as *const UnlockNotification as *mut c_void,
);
debug_assert!(
rc == ffi::SQLITE_LOCKED || rc == ffi::SQLITE_LOCKED_SHAREDCACHE || rc == ffi::SQLITE_OK
);
if rc == ffi::SQLITE_OK {
un.wait();
}
rc
}
#[cfg(test)]
mod test {
use crate::{Connection, OpenFlags, Result, Transaction, TransactionBehavior};
use std::sync::mpsc::sync_channel;
use std::thread;
use std::time;
#[test]
fn test_unlock_notify() -> Result<()> {
let url = "file::memory:?cache=shared";
let flags = OpenFlags::SQLITE_OPEN_READ_WRITE | OpenFlags::SQLITE_OPEN_URI;
let db1 = Connection::open_with_flags(url, flags)?;
db1.execute_batch("CREATE TABLE foo (x)")?;
let (rx, tx) = sync_channel(0);
let child = thread::spawn(move || {
let mut db2 = Connection::open_with_flags(url, flags).unwrap();
let tx2 = Transaction::new(&mut db2, TransactionBehavior::Immediate).unwrap();
tx2.execute_batch("INSERT INTO foo VALUES (42)").unwrap();
rx.send(1).unwrap();
let ten_millis = time::Duration::from_millis(10);
thread::sleep(ten_millis);
tx2.commit().unwrap();
});
assert_eq!(tx.recv().unwrap(), 1);
let the_answer: i64 = db1.one_column("SELECT x FROM foo")?;
assert_eq!(42i64, the_answer);
child.join().unwrap();
Ok(())
}
}