Added an IsDone method for backup

Author: shuhaowu

backup.go

@@ -13,6 +13,15 @@ type Backup struct {
 	b *C.sqlite3_backup
 }
 
+func IsDone(err error) bool {
+	sqlErr, ok := err.(Error)
+	if !ok {
+		return false
+	}
+
+	return sqlErr.Code == ErrDone
+}
+
 func (c *SQLiteConn) Backup(dest string, conn *SQLiteConn, src string) (*Backup, error) {
 	destptr := C.CString(dest)
 	defer C.free(unsafe.Pointer(destptr))

error.go

@@ -45,6 +45,7 @@ var (
 	ErrNotADB     = ErrNo(26) /* File opened that is not a database file */
 	ErrNotice     = ErrNo(27) /* Notifications from sqlite3_log() */
 	ErrWarning    = ErrNo(28) /* Warnings from sqlite3_log() */
+	ErrDone       = ErrNo(101)
 )
 
 func (err ErrNo) Error() string {