musli-storage

Super simple storage encoding for Müsli

The storage encoding is partially upgrade safe:

• ✔ Can tolerate missing fields if they are annotated with #[musli(default)].
• ✗ Cannot skip over extra unrecognized fields.

This means that it's suitable as a storage format, since the data model only evolves in one place. But unsuitable as a wire format since it cannot allow clients to upgrade independent of each other.

See musli-wire for a fully upgrade safe format.

use musli::{Encode, Decode};

#[derive(Debug, PartialEq, Encode, Decode)]
struct Version1 {
    name: String,
}

#[derive(Debug, PartialEq, Encode, Decode)]
struct Version2 {
    name: String,
    #[musli(default)]
    age: Option<u32>,
}

let version2 = musli_storage::to_vec(&Version2 {
    name: String::from("Aristotle"),
    age: Some(62),
})?;

assert!(musli_storage::decode::<_, Version1>(&version2[..]).is_err());

let version1 = musli_storage::to_vec(&Version1 {
    name: String::from("Aristotle"),
})?;

let version2: Version2 = musli_storage::decode(&version1[..])?;

assert_eq!(version2, Version2 {
    name: String::from("Aristotle"),
    age: None,
});

Configuring

To tweak the behavior of the storage format you can use the StorageEncoding type:

use musli_storage::{Fixed, Variable, StorageEncoding};
use musli::mode::DefaultMode;
use musli::{Encode, Decode};

const CONFIG: StorageEncoding<DefaultMode, Fixed, Variable> = StorageEncoding::new()
    .with_fixed_integers();

#[derive(Debug, PartialEq, Encode, Decode)]
struct Struct<'a> {
    name: &'a str,
    age: u32,
}

let mut out = Vec::new();

let expected = Struct {
    name: "Aristotle",
    age: 61,
};

CONFIG.encode(&mut out, &expected)?;
let actual = CONFIG.decode(&out[..])?;

assert_eq!(expected, actual);

License: MIT/Apache-2.0