Add support for sqlite3_unlock_notify

Author: typeless

callback.c

@@ -0,0 +1,5 @@
+void _unlock_notify_callback(void *arg, int argc)
+{
+  extern void unlock_notify_callback(void *, int);
+  unlock_notify_callback(arg, argc);
+}

callback.go

@@ -20,6 +20,8 @@ package sqlite3
 
 void _sqlite3_result_text(sqlite3_context* ctx, const char* s);
 void _sqlite3_result_blob(sqlite3_context* ctx, const void* b, int l);
+
+void _unlock_notify_callback(void *arg, int argc);
 */
 import "C"
 
@@ -378,3 +380,34 @@ func callbackSyntheticForTests(v reflect.Value, err error) callbackArgConverter
 		return v, err
 	}
 }
+
+type unlockNotification struct {
+	notify chan struct{}
+	lock   sync.Mutex
+}
+
+//export unlock_notify_callback
+func unlock_notify_callback(pargv unsafe.Pointer, argc C.int) {
+	argv := *(*uintptr)(pargv)
+	v := (*[1 << 30]uintptr)(unsafe.Pointer(argv))
+	for i := 0; i < int(argc); i++ {
+		un := lookupHandle(v[i]).(unlockNotification)
+		un.notify <- struct{}{}
+	}
+}
+
+var notifyMutex sync.Mutex
+
+//export unlock_notify_wait
+func unlock_notify_wait(db *C.sqlite3) C.int {
+	var un unlockNotification
+	un.notify = make(chan struct{})
+	defer close(un.notify)
+
+	argv := [1]uintptr{newHandle(nil, un)}
+	if rv := C.sqlite3_unlock_notify(db, (*[0]byte)(C._unlock_notify_callback), unsafe.Pointer(&argv)); rv != C.SQLITE_OK {
+		return rv
+	}
+	<-un.notify
+	return C.SQLITE_OK
+}

sqlite3.go

@@ -21,6 +21,7 @@ package sqlite3
 #cgo CFLAGS: -DSQLITE_DISABLE_INTRINSIC
 #cgo CFLAGS: -DSQLITE_DEFAULT_WAL_SYNCHRONOUS=1
 #cgo CFLAGS: -DSQLITE_ENABLE_UPDATE_DELETE_LIMIT
+#cgo CFLAGS: -DSQLITE_ENABLE_UNLOCK_NOTIFY
 #cgo CFLAGS: -Wno-deprecated-declarations
 #cgo linux,!android CFLAGS: -DHAVE_PREAD64=1 -DHAVE_PWRITE64=1
 #ifndef USE_LIBSQLITE3
@@ -88,6 +89,100 @@ _sqlite3_step(sqlite3_stmt* stmt, long long* rowid, long long* changes)
   return rv;
 }
 
+#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
+static int
+sqlite3_step_internal(sqlite3_stmt *stmt)
+{
+  extern int unlock_notify_wait(sqlite3 *db);
+  int rv;
+  sqlite3* db = sqlite3_db_handle(stmt);
+
+  for (;;) {
+    rv = sqlite3_step(stmt);
+    if (rv!=SQLITE_LOCKED) {
+      break;
+    }
+    if (sqlite3_extended_errcode(db)!=SQLITE_LOCKED_SHAREDCACHE) {
+      break;
+    }
+    rv = unlock_notify_wait(db);
+    if (rv != SQLITE_OK) {
+      break;
+    }
+    sqlite3_reset(stmt);
+  }
+
+  return rv;
+}
+
+static int
+_sqlite3_step_internal(sqlite3_stmt* stmt, long long* rowid, long long* changes)
+{
+  extern int unlock_notify_wait(sqlite3 *db);
+  int rv;
+  sqlite3* db = sqlite3_db_handle(stmt);
+
+  for (;;) {
+    rv = _sqlite3_step(stmt, rowid, changes);
+    if (rv!=SQLITE_LOCKED) {
+      break;
+    }
+    if (sqlite3_extended_errcode(db)!=SQLITE_LOCKED_SHAREDCACHE) {
+      break;
+    }
+    rv = unlock_notify_wait(db);
+    if (rv != SQLITE_OK) {
+      break;
+    }
+    sqlite3_reset(stmt);
+  }
+
+  return rv;
+}
+
+static int
+sqlite3_prepare_v2_internal(sqlite3 *db, const char *zSql, int nBytes, sqlite3_stmt **ppStmt, const char **pzTail)
+{
+  extern int unlock_notify_wait(sqlite3 *db);
+  int rv;
+
+  for (;;) {
+    rv = sqlite3_prepare_v2(db, zSql, nBytes, ppStmt, pzTail);
+    if (rv==SQLITE_OK) {
+      break;
+    } else if (rv==SQLITE_LOCKED) {
+      rv = unlock_notify_wait(db);
+      if (rv != SQLITE_OK) {
+        break;
+      }
+    } else {
+      break;
+    }
+  }
+
+  return rv;
+}
+#else
+
+static int
+sqlite3_step_internal(sqlite3_stmt *stmt)
+{
+  return sqlite3_step(stmt);
+}
+
+static int
+_sqlite3_step_internal(sqlite3_stmt* stmt, long long* rowid, long long* changes)
+{
+  return _sqlite3_step(stmt, rowid, changes);
+}
+
+static int
+sqlite3_prepare_v2_internal(sqlite3 *db, const char *zSql, int nBytes, sqlite3_stmt **ppStmt, const char **pzTail)
+{
+  return sqlite3_prepare_v2(db, zSql, nBytes, ppStmt, pzTail);
+}
+#endif
+
 void _sqlite3_result_text(sqlite3_context* ctx, const char* s) {
   sqlite3_result_text(ctx, s, -1, &free);
 }
@@ -1637,7 +1732,7 @@ func (c *SQLiteConn) prepare(ctx context.Context, query string) (driver.Stmt, er
 	defer C.free(unsafe.Pointer(pquery))
 	var s *C.sqlite3_stmt
 	var tail *C.char
-	rv := C.sqlite3_prepare_v2(c.db, pquery, -1, &s, &tail)
+	rv := C.sqlite3_prepare_v2_internal(c.db, pquery, -1, &s, &tail)
 	if rv != C.SQLITE_OK {
 		return nil, c.lastError()
 	}
@@ -1871,7 +1966,7 @@ func (s *SQLiteStmt) exec(ctx context.Context, args []namedValue) (driver.Result
 	}
 
 	var rowid, changes C.longlong
-	rv := C._sqlite3_step(s.s, &rowid, &changes)
+	rv := C._sqlite3_step_internal(s.s, &rowid, &changes)
 	if rv != C.SQLITE_ROW && rv != C.SQLITE_OK && rv != C.SQLITE_DONE {
 		err := s.c.lastError()
 		C.sqlite3_reset(s.s)
@@ -1943,7 +2038,7 @@ func (rc *SQLiteRows) Next(dest []driver.Value) error {
 	if rc.s.closed {
 		return io.EOF
 	}
-	rv := C.sqlite3_step(rc.s.s)
+	rv := C.sqlite3_step_internal(rc.s.s)
 	if rv == C.SQLITE_DONE {
 		return io.EOF
 	}