pub unsafe extern "C" fn pb_default_field_callback(
istream: *mut pb_istream_t,
ostream: *mut pb_ostream_t,
field: *const pb_field_t,
) -> boolpub unsafe extern "C" fn pb_default_field_callback(
istream: *mut pb_istream_t,
ostream: *mut pb_ostream_t,
field: *const pb_field_t,
) -> bool