Crate eccodes

Unofficial high-level safe Rust bindings to ecCodes library

This crate contains safe high-level bindings for ecCodes library. Bindings can be considered safe mainly because all crate structures will take ownership of the data in memory before passing the raw pointer to ecCodes. Currently only reading of GRIB files is supported.

Because of the ecCodes library API characteristics theses bindings are rather thick wrapper to make this crate safe and convenient to use.

Because ecCodes supports mainly Linux platforms, this crate is not tested on other architectures.

If you want to see more features released quicker do not hesitate to contribute and check out Github repository.

ecCodes is an open-source library for reading and writing GRIB and BUFR files developed by European Centre for Medium-Range Weather Forecasts.

Usage

Accessing GRIB files

This crate provides an access to GRIB file by creating a CodesHandle and reading messages from the file with it.

The CodesHandle can be constructed in two ways:

• The main option is to use new_from_file() function to open a file under provided path with filesystem, when copying whole file into memory is not desired or not necessary.

• Alternatively new_from_memory() function can be used to access a file that is already in memory. For example, when file is downloaded from the internet and does not need to be saved on hard drive. The file must be stored in bytes::Bytes.

Data (messages) inside the GRIB file can be accessed using the FallibleIterator by iterating over the CodesHandle.

The FallibleIterator returns a KeyedMessage structure which implements some methods to access data values. The data inside KeyedMessage is provided directly as Key or as more specific data type.

Example

// We are reading the mean sea level pressure for 4 gridpoints
// nearest to Reykjavik (64.13N, -21.89E) for 1st June 2021 00:00 UTC 
// from ERA5 Climate Reanalysis

// Open the GRIB file and create the CodesHandle
let file_path = Path::new("./data/iceland.grib");
let product_kind = ProductKind::GRIB;

let handle = CodesHandle::new_from_file(file_path, product_kind)?;

// Use iterator to get a Keyed message with shortName "msl" and typeOfLevel "surface"
// First, filter and collect the messages to get those that we want
let mut level: Vec<KeyedMessage> = handle
    .filter(|msg| {

    Ok(msg.read_key("shortName")?.value == Str("msl".to_string())
        && msg.read_key("typeOfLevel")?.value == Str("surface".to_string()))
    })
    .collect()?;

// Now unwrap and access the first and only element of resulting vector
// Find nearest modifies internal KeyedMessage fields so we need mutable reference
let level = &mut level[0];

// Get the four nearest gridpoints of Reykjavik
let nearest_gridpoints = level.find_nearest(64.13, -21.89)?;

// Print value and distance of the nearest gridpoint
println!("value: {}, distance: {}", 
    nearest_gridpoints[3].value, 
    nearest_gridpoints[3].distance);

ecCodes installation

This crate uses eccodes-sys with default options to link ecCodes. Check eccodes-sys website for more details on how it links the library.

The recommended way to install ecCodes on your computer is using your package manager. For example, on Ubuntu you can use apt-get:

$ sudo apt-get install libeccodes-dev

Alternatively, you can install the library manually from source in suitable directory following this instructions.

Then add the lib/pkgconfig directory from your ecCodes installation directory to the PKG_CONFIG_PATH environmental variable. If ecCodes have been compiled as shared library you will also need to specify LD_LIBRARY_PATH. For example:

$ export PKG_CONFIG_PATH=<your_eccodes_path>/lib/pkgconfig
$ export LD_LIBRARY_PATH=<your_eccodes_path>/lib

Features

• docs - builds the crate without linking ecCodes, particularly useful when building the documentation on docs.rs. For more details check documentation of eccodes-sys.

To build your own crate with this crate as dependency on docs.rs without linking ecCodes add following lines to your Cargo.toml

[package.metadata.docs.rs]
features = ["eccodes/docs"]

Modules

codes_handle

Main crate module containing definition of CodesHandle and all associated functions and data structures

errors

Module containing all error types used by the crate