# 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.as_slice()).is_err());

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

let version2: Version2 = musli_storage::decode(version1.as_slice())?;

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

<br>

## Configuring

To tweak the behavior of the storage format you can use the [`Encoding`]
type:

```rust
use musli::mode::Binary;
use musli::{Encode, Decode};
use musli_utils::options::{self, Options, Integer};
use musli_storage::Encoding;

const OPTIONS: Options = options::new().with_integer(Integer::Fixed).build();
const CONFIG: Encoding<OPTIONS> = Encoding::new().with_options();

#[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);
```

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