Trait WriteGrib2Ident

Source

pub trait WriteGrib2Ident {
    // Required methods
    fn section1_len(&self) -> usize;
    fn write_section1(&self, buf: &mut [u8]) -> Result<usize, &'static str>;
}

Expand description

A functionality to write the byte sequence of Section 1 (Identification Section) of a GRIB2 message.

§Examples

This trait is implemented for the payload struct of Section 1 (def::grib2::Section1Payload).

use grib::{TryFromSlice, def::grib2, encoder::WriteGrib2Ident};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let sect = grib2::Section1 {
        header: grib2::SectionHeader {
            len: 21,
            sect_num: 1,
        },
        payload: grib2::Section1Payload {
            centre_id: 0xffff,
            subcentre_id: 0,
            master_table_version: 29,
            local_table_version: 0,
            ref_time_significance: 0,
            ref_time: grib2::RefTime {
                year: 2026,
                month: 1,
                day: 2,
                hour: 3,
                minute: 4,
                second: 5,
            },
            prod_status: 0,
            data_type: 0,
            optional: None,
        },
    };
    let mut buf = vec![0; sect.payload.section1_len()];
    sect.payload.write_section1(&mut buf)?;
    let decoded = grib2::Section1::try_from_slice(&buf, &mut 0);
    assert_eq!(decoded, Ok(sect));

    Ok(())
}

This trait is also implemented for the byte sequence of the payload of Section 1.

use grib::{TryFromSlice, def::grib2, encoder::WriteGrib2Ident};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut input = [
        0xff, 0xff, 0x00, 0x00, 0x1d, 0x00, 0x00, 0x07, 0xea, 0x01, 0x02, 0x03, 0x04, 0x05,
        0x00, 0x00,
    ];
    let mut buf = vec![0; input.section1_len()];
    input.write_section1(&mut buf)?;

    // The output is simply the input byte sequence with a section header appended to it.
    assert_eq!(&buf[5..], input);

    let decoded = grib2::Section1::try_from_slice(&buf, &mut 0);
    let expected = Ok(grib2::Section1 {
        header: grib2::SectionHeader {
            len: 21,
            sect_num: 1,
        },
        payload: grib2::Section1Payload {
            centre_id: 0xffff,
            subcentre_id: 0,
            master_table_version: 29,
            local_table_version: 0,
            ref_time_significance: 0,
            ref_time: grib2::RefTime {
                year: 2026,
                month: 1,
                day: 2,
                hour: 3,
                minute: 4,
                second: 5,
            },
            prod_status: 0,
            data_type: 0,
            optional: None,
        },
    });
    assert_eq!(decoded, expected);

    Ok(())
}

Since no constraints can be placed on the byte sequence, write_section1 can, of course, be executed on any byte sequence; however, if it is executed on an inappropriate byte sequence, the resulting byte sequence will not be correctly interpreted as Section 1.

use grib::{TryFromSlice, def::grib2, encoder::WriteGrib2Ident};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut input = [0xff, 0xff];
    let mut buf = vec![0; input.section1_len()];
    input.write_section1(&mut buf)?;

    // The output is simply the input byte sequence with a section header appended to it.
    assert_eq!(&buf[5..], input);

    // The output cannot be correctly interpreted as Section 1.
    let decoded = grib2::Section1::try_from_slice(&buf, &mut 0);
    let expected = Err("slice length is too short");
    assert_eq!(decoded, expected);

    Ok(())
}