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erlang-term

Library to convert Erlang External Term Format to Rust objects, without using erlang NIFs.

Installation

[dependencies]
erlang-term = "1.1.0"

Usage

elixir -e ":erlang.term_to_binary([1,2,3,4]) |> IO.inspect()" | sed -e 's/<</[/g' | sed -e 's/>>/]/g'

Copy that over to rust

use erlang_term::Term;

let input = &[131, 107, 0, 4, 1, 2, 3, 4];
let term = Term::from_bytes(input);
assert_eq!(Ok(Term::Charlist([1, 2, 3, 4].to_vec())), term);

Or if you want more controle over the external term format:

use erlang_term::RawTerm;

let input = &[131, 107, 0, 4, 1, 2, 3, 4];

let term = RawTerm::from_bytes(input);
assert_eq!(Ok(RawTerm::String([1, 2, 3, 4].to_vec())), term);

The Term enum is more what you will find in elixir. The RawTerm enum takes the naming from the external term format spec.

This is already apparent in the above example. In Erlang a string is just a list of characters and in Elixir this is called a Charlist.

In this library I tried to split logic and convertion, so in the RawTerm there is only conversion between binary and rust enum and in the Term there is logic to convert that to a usable interface. Therefore RawTerm to binary is one-to-one and onto. But Term to RawTerm there will be information thrown away.

Features

There is an optional serde feature.

erlang-term = {version = "1.1.0", features = ["serde_impl"]}

There is an optional zlib feature, that allows the etf to be compressed. In Elixir:

:erlang.term_to_binary(t, [:compressed])
# or
:erlang.term_to_binary(t, compressed: 6)
erlang-term = {version = "1.1.0", features = ["zlib"]}

More examples

use erlang_term::RawTerm;
use std::iter::FromIterator;

let map = RawTerm::Map(vec![
    (RawTerm::SmallAtom(String::from("test")), RawTerm::SmallTuple(vec![RawTerm::SmallAtom(String::from("ok")), RawTerm::SmallInt(15)])),
    (RawTerm::SmallAtom(String::from("another_key")), RawTerm::Binary(b"this is a string".to_vec())),
    (RawTerm::SmallAtom(String::from("number")), RawTerm::Float(3.1415.into())),
]);

let binary = vec![
    131, 116, 0, 0, 0, 3, 119, 4, 116, 101, 115, 116, 104, 2, 119, 2, 111, 107, 97, 15, 119, 11, 97, 110, 111, 116, 104, 101, 114, 95, 107, 101, 121, 109, 0, 0, 0, 16, 116, 104, 105, 115, 32, 105, 115, 32, 97, 32, 115, 116, 114, 105, 110, 103, 119, 6, 110, 117, 109, 98, 101, 114, 70, 64, 9, 33, 202, 192, 131, 18, 111
];

assert_eq!(map.to_bytes(), binary);

Use Cases

  • Filter out non-data (such as references and functions) from stored etf files

  • Convert stored etf files to json

See the filter example

License: Unlicense