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#89 in Parser implementations

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27K SLoC

Amazon Ion Rust

Crate Docs License CI Build codecov

A Rust implementation of the Amazon Ion data format.


For more information, please see our official documentation.

use ion_rs::{Element, IonResult, IonType, ion_seq};

fn main() -> IonResult<()> {

    // Read a single value from a string/slice/Vec
    let element = Element::read_one("\"Hello, world!\"")?;
    let text = element.expect_string()?;
    assert_eq!(text, "Hello, world!");

    // Read a series of values from a string/slice/Vec
    let elements = Element::read_all("1 2 3")?;
    let mut sum = 0;
    for element in elements {
        sum += element.expect_i64()?;
    assert_eq!(sum, 6);

    // Iterate over values in a file
    let ion_file = std::fs::File::open("/foo/bar/baz.ion").unwrap();
    for element in Element::iter(ion_file)? {
        println!("{}", element?)
    // Construct a sequence of Ion elements from Rust values
    let values = ion_seq!(
        Timestamp::with_ymd(2016, 5, 11).build(),

    // Write values to a buffer in generously-spaced text
    let mut text_buffer: Vec<u8> = Vec::new();
    Element::write_all_as(&values, Format::Text(TextKind::Pretty), &mut text_buffer)?;
    assert_eq!(values, Element::read_all(text_buffer)?);

    // Write values to a buffer in compact binary
    let mut binary_buffer: Vec<u8> = Vec::new();
    Element::write_all_as(&values, Format::Binary, &mut binary_buffer)?;
    assert_eq!(values, Element::read_all(binary_buffer)?);

Experimental features

The ion_rs library has a number of features that users can opt into. While the following features are complete and well-tested, their APIs are not stable and are subject to change without notice between minor versions of the library.

  1. experimental-ion-hash, an implementation of Ion Hash.
  2. experimental-reader, a streaming reader API.
  3. experimental-writer, a streaming writer API.

Features that are defined in Cargo.toml but not listed above have not been thoroughly tested.


This project uses a submodule to pull in Ion Tests and Ion Hash Tests. The easiest way to pull everything in is to clone the repository recursively:

$ git clone --recursive https://github.com/amazon-ion/ion-rust

You can also initialize the submodules as follows:

$ git submodule update --init --recursive

Building the project:

$ cargo build --all-features

Running all tests for ion-rust:

$ cargo test --all-features

Our continuous integration builds/tests, checks formatting, builds all API docs including private, and clippy linting, you will likely want to check most of these to avoid having to wait until the CI finds it:

$ ./clean-rebuild.sh


~98K SLoC