opts may be NULL or a BSON document with additional command options:

• bucketName: A UTF-8 string used as the prefix to the GridFS "chunks" and "files" collections. Defaults to "fs". The bucket name, together with the database and suffix collections must not exceed 120 characters. See the manual for the max namespace length.

• chunkSizeBytes: An int32 representing the chunk size. Defaults to 255KB.

• writeConcern: Construct a mongoc_write_concern_t and use mongoc_write_concern_append to add the write concern to opts. See the example code for mongoc_client_write_command_with_opts.

• readConcern: Construct a mongoc_read_concern_t and use mongoc_read_concern_append to add the read concern to opts. See the example code for mongoc_client_read_command_with_opts. Read concern requires MongoDB 3.2 or later, otherwise an error is returned.