cleanup unlock_notify code a bit

src/inner_connection.rs

@@ -13,7 +13,6 @@ use super::{Connection, InterruptHandle, OpenFlags, Result};
 use crate::error::{error_from_handle, error_from_sqlite_code, Error};
 use crate::raw_statement::RawStatement;
 use crate::statement::Statement;
-use crate::unlock_notify;
 use crate::version::version_number;
 
 pub struct InnerConnection {
@@ -223,8 +222,19 @@ impl InnerConnection {
         let mut c_stmt = ptr::null_mut();
         let (c_sql, len, _) = str_for_sqlite(sql.as_bytes())?;
         let mut c_tail = ptr::null();
+        #[cfg(not(feature = "unlock_notify"))]
         let r = unsafe {
-            if cfg!(feature = "unlock_notify") {
+            ffi::sqlite3_prepare_v2(
+                self.db(),
+                c_sql,
+                len,
+                &mut c_stmt as *mut *mut ffi::sqlite3_stmt,
+                &mut c_tail as *mut *const c_char,
+            )
+        };
+        #[cfg(feature = "unlock_notify")]
+        let r = unsafe {
+            use crate::unlock_notify;
             let mut rc;
             loop {
                 rc = ffi::sqlite3_prepare_v2(
@@ -243,15 +253,6 @@ impl InnerConnection {
                 }
             }
             rc
-            } else {
-                ffi::sqlite3_prepare_v2(
-                    self.db(),
-                    c_sql,
-                    len,
-                    &mut c_stmt as *mut *mut ffi::sqlite3_stmt,
-                    &mut c_tail as *mut *const c_char,
-                )
-            }
         };
         // If there is an error, *ppStmt is set to NULL.
         self.decode_result(r)?;

src/lib.rs

@@ -125,6 +125,7 @@ mod statement;
 pub mod trace;
 mod transaction;
 pub mod types;
+#[cfg(feature = "unlock_notify")]
 mod unlock_notify;
 mod version;
 #[cfg(feature = "vtab")]

src/raw_statement.rs

@@ -1,5 +1,4 @@
 use super::ffi;
-use super::unlock_notify;
 use super::StatementStatus;
 #[cfg(feature = "modern_sqlite")]
 use crate::util::SqliteMallocString;
@@ -101,25 +100,38 @@ impl RawStatement {
         }
     }
 
-    #[cfg_attr(not(feature = "unlock_notify"), inline)]
+    #[inline]
+    #[cfg(not(feature = "unlock_notify"))]
     pub fn step(&self) -> c_int {
-        if cfg!(feature = "unlock_notify") {
+        unsafe { ffi::sqlite3_step(self.ptr) }
-            let db = unsafe { ffi::sqlite3_db_handle(self.ptr) };
-            let mut rc;
-            loop {
-                rc = unsafe { ffi::sqlite3_step(self.ptr) };
-                if unsafe { !unlock_notify::is_locked(db, rc) } {
-                    break;
     }
-                rc = unsafe { unlock_notify::wait_for_unlock_notify(db) };
+
+    #[cfg(feature = "unlock_notify")]
+    pub fn step(&self) -> c_int {
+        use crate::unlock_notify;
+        let mut db = core::ptr::null_mut::<ffi::sqlite3>();
+        loop {
+            unsafe {
+                let mut rc = ffi::sqlite3_step(self.ptr);
+                // Bail out early for success and errors unrelated to locking. We
+                // still need check `is_locked` after this, but checking now lets us
+                // avoid one or two (admittedly cheap) calls into SQLite that we
+                // don't need to make.
+                if (rc & 0xff) != ffi::SQLITE_LOCKED {
+                    break rc;
+                }
+                if db.is_null() {
+                    db = ffi::sqlite3_db_handle(self.ptr);
+                }
+                if !unlock_notify::is_locked(db, rc) {
+                    break rc;
+                }
+                rc = unlock_notify::wait_for_unlock_notify(db);
                 if rc != ffi::SQLITE_OK {
-                    break;
+                    break rc;
                 }
                 self.reset();
             }
-            rc
-        } else {
-            unsafe { ffi::sqlite3_step(self.ptr) }
         }
     }
 

src/unlock_notify.rs

@@ -1,22 +1,17 @@
 //! [Unlock Notification](http://sqlite.org/unlock_notify.html)
 
 use std::os::raw::c_int;
-#[cfg(feature = "unlock_notify")]
 use std::os::raw::c_void;
-#[cfg(feature = "unlock_notify")]
 use std::panic::catch_unwind;
-#[cfg(feature = "unlock_notify")]
 use std::sync::{Condvar, Mutex};
 
 use crate::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")]
 #[allow(clippy::mutex_atomic)]
 impl UnlockNotification {
     fn new() -> UnlockNotification {
@@ -27,21 +22,25 @@ impl UnlockNotification {
     }
 
     fn fired(&self) {
-        let mut flag = self.mutex.lock().unwrap();
+        let mut flag = unpoison(self.mutex.lock());
         *flag = true;
         self.cond.notify_one();
     }
 
     fn wait(&self) {
-        let mut fired = self.mutex.lock().unwrap();
+        let mut fired = unpoison(self.mutex.lock());
         while !*fired {
-            fired = self.cond.wait(fired).unwrap();
+            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
-#[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 as *const &UnlockNotification, n_arg as usize);
@@ -50,7 +49,6 @@ unsafe extern "C" fn unlock_notify_cb(ap_arg: *mut *mut c_void, n_arg: c_int) {
     }
 }
 
-#[cfg(feature = "unlock_notify")]
 pub unsafe fn is_locked(db: *mut ffi::sqlite3, rc: c_int) -> bool {
     rc == ffi::SQLITE_LOCKED_SHAREDCACHE
         || (rc & 0xFF) == ffi::SQLITE_LOCKED
@@ -87,17 +85,6 @@ pub unsafe fn wait_for_unlock_notify(db: *mut ffi::sqlite3) -> c_int {
     rc
 }
 
-#[cfg(not(feature = "unlock_notify"))]
-pub unsafe fn is_locked(_db: *mut ffi::sqlite3, _rc: c_int) -> bool {
-    unreachable!()
-}
-
-#[cfg(not(feature = "unlock_notify"))]
-pub unsafe fn wait_for_unlock_notify(_db: *mut ffi::sqlite3) -> c_int {
-    unreachable!()
-}
-
-#[cfg(feature = "unlock_notify")]
 #[cfg(test)]
 mod test {
     use crate::{Connection, OpenFlags, Result, Transaction, TransactionBehavior};