Write measurements¶

Mf4Writer creates MF4 files. Start with a time master, then add typed channels to its group:

use falcon_mdf::Mf4Writer;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut writer = Mf4Writer::new();
    let group = writer.add_group(&[0.0, 0.1, 0.2])?;
    group.add_channel("Speed", "km/h", &[0.0, 5.0, 10.0])?;
    group.add_channel_with_validity(
        "Boost",
        "psi",
        &[1.0, 2.0, 3.0],
        Some(&[true, false, true]),
    )?;
    writer.write_to_file("out.mf4")?;
    Ok(())
}

The writer supports integer and floating-point channels, fixed-length strings and bytes, variable-length strings and bytes, conversion rules, CA arrays, and per-sample validity. A group normally gets its own data group; add_group_in can place several channel groups in one data group.

Compression¶

By default, compressed output uses deflate. The writer can also produce transposed deflate, zstd, and LZ4 variants through set_codec; zstd and LZ4 require their corresponding crate features. The output uses the MDF 4 ##HL/##DL structure around compressed ##DZ blocks.

Edit an existing file¶

Mf4Writer::from_file_with_report loads supported channels into an editable writer and reports material it could not carry over. This is a conversion path, not a lossless rewrite of every MDF metadata block. Review the report before using the result as a replacement for the source file.

For the complete writer API, see Mf4Writer on docs.rs and the repository example.