allow change default transfer max size of uring file

include/ylt/thirdparty/asio/completion_condition.hpp

@@ -25,7 +25,16 @@ namespace asio {
 namespace detail {
 
 // The default maximum number of bytes to transfer in a single operation.
-enum default_max_transfer_size_t { default_max_transfer_size = 65536 };
+enum default_max_transfer_size_t 
+{
+#if defined(ASIO_HAS_FILE) \
+  && defined(ASIO_HAS_IO_URING) \
+  && defined(ASIO_SPEC_MAX_TRANSFER_SIZE)
+  default_max_transfer_size = ASIO_SPEC_MAX_TRANSFER_SIZE
+#else
+  default_max_transfer_size = 65536
+#endif
+};
 
 // Adapt result of old-style completion conditions (which had a bool result
 // where true indicated that the operation was complete).