fiff_data_ref.h File Reference

External-data reference record describing type, endianness, size and offset of an out-of-file FIFF payload. More...

#include "fiff_global.h"
#include <QtGlobal>

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Classes
class	FIFFLIB::FiffDataRef
	External data reference: type, endian, byte size and offset into an external FIFF payload file. More...

Namespaces
namespace	FIFFLIB
	FIFF file I/O, in-memory data structures and high-level readers/writers.

Typedefs
typedef FiffDataRef	FIFFLIB::fiffDataRefRec
	Backward-compatible typedef for the old fiffDataRefRec struct.
typedef FiffDataRef *	FIFFLIB::fiffDataRef
	Backward-compatible pointer typedef for the old fiffDataRef pointer.

Detailed Description

External-data reference record describing type, endianness, size and offset of an out-of-file FIFF payload.

SPDX-License-Identifier: BSD-3-Clause Copyright (c) 2026 MNE-CPP Authors

Author

Christoph Dinh chris.nosp@m.toph.nosp@m..dinh.nosp@m.@mne.nosp@m.-cpp..nosp@m.org

Since

2.0.0

Date

February 2026

A FIFF_REF_ROLE / FIFF_DATA_REF tag carries a small fixed-size record (the original fiffDataRefRec, 24 bytes: two 32-bit ints followed by two 64-bit offsets) that points at a payload living in a separate file rather than inline in the FIFF tag stream. This is how the Neuromag acquisition system splits very long recordings across multiple physical files while keeping a single logical FIFF tree, and how MNE-Python's mne.io.Raw chains .fif fragments through the next_fname mechanism. FiffDataRef is the in-memory representation of that record; FiffDataRef::storageSize matches the on-disk size exactly so FiffStream can stream the data ref directly into a buffer with no per-field marshalling.

Definition in file fiff_data_ref.h.