Crate musli_descriptive

A fully self-descriptive format for Müsli.

Descriptive encoding is fully upgrade stable:

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

Furthermore, it can be fully converted back and from to the Value type.

This means that it’s suitable as a wire and general interchange 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.

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_descriptive::to_vec(&Version2 {
    name: String::from("Aristotle"),
    age: Some(62),
})?;

let version1: Version1 = musli_descriptive::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:

use musli_descriptive::Encoding;
use musli::{Encode, Decode};
use musli::mode::DefaultMode;

const CONFIG: Encoding<DefaultMode> = Encoding::new();

#[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 describes exactly the type which is contained in the field.

Re-exports

• pub use self::encoding::to_vec;
• pub use self::encoding::to_writer;
• pub use self::encoding::decode;
• pub use self::encoding::encode;
• pub use self::encoding::from_slice;
• pub use self::encoding::to_fixed_bytes;
• pub use self::encoding::Encoding;

Modules

• allocator
  Trait used to govern allocations. Trait used to handle individual buffer allocations.
• buffered_writer
  A writer which buffers the writes before it outputs it into the backing storage.
• context
  Helper types to set up a basic Müsli Context.
• encoding
  Module that defines Encoding whith allows for customization of the encoding format, and the DEFAULT encoding configuration.
• fixed_bytes
  A container which can store up to a fixed number of uninitialized bytes on the stack and read into and from it.
• int
  Traits and utilities for dealing with integers.
• reader
  Trait for governing how a particular source of bytes is read.
• str
  Functions for working with strings. The exported implementations change depending on if the simdutf8 feature is enabled.
• tag
  Type flags available for musli-wire.
• wrap
  Helpers for integrating musli with I/O types like std::io and std::io::Write.
• writer
  Trait for governing how a particular sink of bytes is written to.

Structs

• Error
  Error raised during descriptive encoding.

Type Aliases

• Result
  Convenient result alias for use with musli_descriptive.