# musli-wire

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Fully upgrade stable format for [Müsli] suitable for network communication.

Wire encoding is fully upgrade stable:

* ✔ Can tolerate missing fields if they are annotated with
  `#[musli(default)]`.
* ✔ Can skip over unknown fields.

This means that it's suitable as a wire format, since the data model can
evolve independently among clients. Once some clients are upgraded they will
start sending unknown fields which non-upgraded clients will be forced to
skip over for the duration of the upgrade.

```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_wire::to_buffer(&Version2 {
    name: String::from("Aristotle"),
    age: Some(62),
})?;

let version1: Version1 = musli_wire::decode(version2.as_slice())?;

assert_eq!(version1, Version1 {
    name: String::from("Aristotle"),
});
```

<br>

## Configuring

To configure the behavior of the wire format you can use the [Encoding]
type:

```rust
use musli_wire::Encoding;
use musli_wire::int::{Fixed, Variable};
use musli::{Encode, Decode};
use musli::mode::DefaultMode;

const CONFIG: Encoding<DefaultMode, Fixed, Variable, 128> = Encoding::new()
    .with_fixed_integers()
    .with_max_pack::<128>();

#[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);
```

<br>

## Implementation details

Each field is prefix *typed* with a single byte tag that allows a receiver
to figure out exactly how much should be skipped over.

Packed items are prefix-length encoded, and have a limited size. Its exact
length is defined by [MAX_INLINE_LEN] and can be modified with
[Encoding::with_max_pack].

[default encoding format]: https://docs.rs/musli-wire/latest/musli-wire/struct.Encoding.html
[MAX_INLINE_LEN]: https://docs.rs/musli-wire/latest/musli_wire/tag/constant.MAX_INLINE_LEN.html
[Müsli]: https://docs.rs/musli
[Encoding::with_max_pack]: https://docs.rs/musli-wire/latest/musli_wire/encoding/struct.Encoding.html#method.with_max_pack
[Encoding]: https://docs.rs/musli-wire/latest/musli-wire/struct.Encoding.html
