# musli-storage

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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.

```rust
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 wire format you can use the [StorageEncoding]
type:

```rust
use musli_storage::StorageEncoding;
use musli_storage::{Fixed, Variable};
use musli::{Encode, Decode};

const CONFIG: StorageEncoding<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);
```

[Müsli]: https://docs.rs/musli
[default encoding format]: https://docs.rs/musli-storage/latest/musli-storage/struct.StorageEncoding.html
[StorageEncoding]: https://docs.rs/musli-storage/latest/musli-storage/struct.StorageEncoding.html

License: MIT/Apache-2.0
