# musli-wire
[
](https://github.com/udoprog/musli)
[
](https://crates.io/crates/musli-wire)
[
](https://docs.rs/musli-wire)
[
](https://github.com/udoprog/musli/actions?query=branch%3Amain)
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,
}
let version2 = musli_wire::to_vec(&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"),
});
```
## Configuring
To configure the behavior of the wire format you can use the [`Encoding`]
type:
```rust
use musli::{Encode, Decode};
use musli_utils::options::{self, Options, Integer};
use musli_wire::Encoding;
const OPTIONS: Options = options::new().with_integer(Integer::Fixed).build();
const CONFIG: Encoding = 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);
```
## 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