Merge pull request #349 from gwenn/unlock-notify

Unlock notify

.travis.yml

@@ -38,6 +38,7 @@ script:
   - cargo test --features serde_json
   - cargo test --features bundled
   - cargo test --features sqlcipher
+  - cargo test --features "unlock_notify bundled"
   - cargo test --features "backup blob chrono functions hooks limits load_extension serde_json trace"
   - cargo test --features "backup blob chrono functions hooks limits load_extension serde_json trace buildtime_bindgen"
   - cargo test --features "backup blob chrono functions hooks limits load_extension serde_json trace bundled"

Cargo.toml

@@ -28,6 +28,7 @@ buildtime_bindgen = ["libsqlite3-sys/buildtime_bindgen"]
 limits = []
 hooks = []
 sqlcipher = ["libsqlite3-sys/sqlcipher"]
+unlock_notify = ["libsqlite3-sys/unlock_notify"]
 
 [dependencies]
 time = "0.1.0"

libsqlite3-sys/Cargo.toml

@@ -21,6 +21,8 @@ min_sqlite_version_3_6_23 = ["pkg-config", "vcpkg"]
 min_sqlite_version_3_7_3 = ["pkg-config", "vcpkg"]
 min_sqlite_version_3_7_4 = ["pkg-config", "vcpkg"]
 min_sqlite_version_3_7_16 = ["pkg-config", "vcpkg"]
+# sqlite3_unlock_notify >= 3.6.12
+unlock_notify = []
 
 [build-dependencies]
 bindgen = { version = "0.36", optional = true }

libsqlite3-sys/build.rs

@@ -18,8 +18,8 @@ mod build {
         fs::copy("sqlite3/bindgen_bundled_version.rs", out_path)
             .expect("Could not copy bindings to output directory");
 
-        cc::Build::new()
-            .file("sqlite3/sqlite3.c")
+        let mut cfg = cc::Build::new();
+        cfg.file("sqlite3/sqlite3.c")
             .flag("-DSQLITE_CORE")
             .flag("-DSQLITE_DEFAULT_FOREIGN_KEYS=1")
             .flag("-DSQLITE_ENABLE_API_ARMOR")
@@ -38,8 +38,11 @@ mod build {
             .flag("-DSQLITE_SOUNDEX")
             .flag("-DSQLITE_THREADSAFE=1")
             .flag("-DSQLITE_USE_URI")
-            .flag("-DHAVE_USLEEP=1")
-            .compile("libsqlite3.a");
+            .flag("-DHAVE_USLEEP=1");
+        if cfg!(feature = "unlock_notify") {
+            cfg.flag("-DSQLITE_ENABLE_UNLOCK_NOTIFY");
+        }
+        cfg.compile("libsqlite3.a");
     }
 }
 

src/lib.rs

@@ -125,6 +125,7 @@ pub mod limits;
 mod hooks;
 #[cfg(feature = "hooks")]
 pub use hooks::*;
+mod unlock_notify;
 
 // Number of cached prepared statements we'll hold on to.
 const STATEMENT_CACHE_DEFAULT_CAPACITY: usize = 16;
@@ -862,16 +863,40 @@ impl InnerConnection {
         }
         let mut c_stmt: *mut ffi::sqlite3_stmt = unsafe { mem::uninitialized() };
         let c_sql = try!(str_to_cstring(sql));
-        let r = unsafe {
         let len_with_nul = (sql.len() + 1) as c_int;
-            ffi::sqlite3_prepare_v2(self.db(),
+        let r = unsafe {
+            if cfg!(feature = "unlock_notify") {
+                let mut rc;
+                loop {
+                    rc = ffi::sqlite3_prepare_v2(
+                        self.db(),
                         c_sql.as_ptr(),
                         len_with_nul,
                         &mut c_stmt,
-                                    ptr::null_mut())
+                        ptr::null_mut(),
+                    );
+                    if !unlock_notify::is_locked(self.db, rc) {
+                        break;
+                    }
+                    rc = unlock_notify::wait_for_unlock_notify(self.db);
+                    if rc != ffi::SQLITE_OK {
+                        break;
+                    }
+                }
+                rc
+            } else {
+                ffi::sqlite3_prepare_v2(
+                    self.db(),
+                    c_sql.as_ptr(),
+                    len_with_nul,
+                    &mut c_stmt,
+                    ptr::null_mut(),
+                )
+            }
         };
-        self.decode_result(r)
-            .map(|_| Statement::new(conn, RawStatement::new(c_stmt)))
+        self.decode_result(r).map(|_| {
+            Statement::new(conn, RawStatement::new(c_stmt))
+        })
     }
 
     fn changes(&mut self) -> c_int {

src/raw_statement.rs

@@ -2,6 +2,7 @@ use std::ffi::CStr;
 use std::ptr;
 use std::os::raw::c_int;
 use super::ffi;
+use super::unlock_notify;
 
 // Private newtype for raw sqlite3_stmts that finalize themselves when dropped.
 #[derive(Debug)]
@@ -29,8 +30,25 @@ impl RawStatement {
     }
 
     pub fn step(&self) -> c_int {
+        if cfg!(feature = "unlock_notify") {
+            let db = unsafe { ffi::sqlite3_db_handle(self.0) };
+            let mut rc;
+            loop {
+                rc = unsafe { ffi::sqlite3_step(self.0) };
+                if !unlock_notify::is_locked(db, rc) {
+                    break;
+                }
+                rc = unlock_notify::wait_for_unlock_notify(db);
+                if rc != ffi::SQLITE_OK {
+                    break;
+                }
+                self.reset();
+            }
+            rc
+        } else {
             unsafe { ffi::sqlite3_step(self.0) }
         }
+    }
 
     pub fn reset(&self) -> c_int {
         unsafe { ffi::sqlite3_reset(self.0) }

src/unlock_notify.rs

@@ -0,0 +1,129 @@
+//! [Unlock Notification](http://sqlite.org/unlock_notify.html)
+
+#[cfg(feature = "unlock_notify")]
+use std::sync::{Condvar, Mutex};
+use std::os::raw::c_int;
+#[cfg(feature = "unlock_notify")]
+use std::os::raw::c_void;
+
+use ffi;
+
+#[cfg(feature = "unlock_notify")]
+struct UnlockNotification {
+    cond: Condvar,      // Condition variable to wait on
+    mutex: Mutex<bool>, // Mutex to protect structure
+}
+
+#[cfg(feature = "unlock_notify")]
+impl UnlockNotification {
+    fn new() -> UnlockNotification {
+        UnlockNotification {
+            cond: Condvar::new(),
+            mutex: Mutex::new(false),
+        }
+    }
+
+    fn fired(&mut self) {
+        *self.mutex.lock().unwrap() = true;
+        self.cond.notify_one();
+    }
+
+    fn wait(&mut self) {
+        let mut fired = self.mutex.lock().unwrap();
+        while !*fired {
+            fired = self.cond.wait(fired).unwrap();
+        }
+    }
+}
+
+/// This function is an unlock-notify callback
+#[cfg(feature = "unlock_notify")]
+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, n_arg as usize);
+    for arg in args {
+        let un: &mut UnlockNotification = &mut *(*arg as *mut UnlockNotification);
+        un.fired();
+    }
+}
+
+#[cfg(feature = "unlock_notify")]
+pub fn is_locked(db: *mut ffi::sqlite3, rc: c_int) -> bool {
+    rc == ffi::SQLITE_LOCKED_SHAREDCACHE || (rc & 0xFF) == ffi::SQLITE_LOCKED && unsafe {
+        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 fn wait_for_unlock_notify(db: *mut ffi::sqlite3) -> c_int {
+    let mut un = UnlockNotification::new();
+    /* Register for an unlock-notify callback. */
+    let rc = unsafe {
+        ffi::sqlite3_unlock_notify(
+            db,
+            Some(unlock_notify_cb),
+            &mut un as *mut 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(not(feature = "unlock_notify"))]
+pub fn is_locked(_db: *mut ffi::sqlite3, _rc: c_int) -> bool {
+    unreachable!()
+}
+
+#[cfg(not(feature = "unlock_notify"))]
+pub fn wait_for_unlock_notify(_db: *mut ffi::sqlite3) -> c_int {
+    unreachable!()
+}
+
+#[cfg(feature = "unlock_notify")]
+#[cfg(test)]
+mod test {
+    use std::sync::mpsc::sync_channel;
+    use std::thread;
+    use std::time;
+    use {Connection, OpenFlags, Result, Transaction, TransactionBehavior};
+
+    #[test]
+    fn test_unlock_notify() {
+        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).unwrap();
+        db1.execute_batch("CREATE TABLE foo (x)").unwrap();
+        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: Result<i64> = db1.query_row("SELECT x FROM foo", &[], |r| r.get(0));
+        assert_eq!(42i64, the_answer.unwrap());
+        child.join().unwrap();
+    }
+}