alox-48

alox-48 (short for aluminum oxide 48) is a crate for deserializing (soon serializing as well) Ruby's Marshal data format, using serde. It requires rust nightly as of 2/8/23 for min-specialization.

alox-48 intends to provide almost perfect round-trip deserialization, with some exceptions:

• Object links are not preserved. Object links are a way for Ruby to compact data in Marshal. They rely heavily on Ruby having a GC and thus do not map well to Rust.
• Classes and Modules are unsupported.
• Bignum is unsupported.

Why min-specialization

alox-48 uses min-specialization to extend serde in order to preserve types that may be lost in deserialization. There are a lot of data types in Marshal that do not map well to serde's data model, or rust's data model.

This includes:

• Symbols
• Userdata
• Objects
• Strings with non-utf8 encoding

It does this via the VistorExt trait:

pub trait VisitorExt<'de>: Visitor<'de> {
    fn visit_userdata<E>(self, class: &'de str, data: &'de [u8]) -> Result<Self::Value, E>
    where
        E: SerdeError;

    fn visit_object<A>(self, class: &'de str, fields: A) -> Result<Self::Value, A::Error>
    where
        A: MapAccess<'de>;

    fn visit_symbol<E>(self, sym: &'de str) -> Result<Self::Value, E>
    where
        E: SerdeError;

    fn visit_ruby_string<A>(self, str: &'de [u8], fields: A) -> Result<Self::Value, A::Error>
    where
        A: MapAccess<'de>;
}

You are free to implement this trait on any of your types. It'll only work with the deserializer from this crate, though.

Value

alox-48 provides a Value enum to work with untyped data.

pub enum Value {
    Nil,
    Bool(bool),
    Float(f64),
    Integer(i64),
    String(RbString),
    Symbol(Symbol),
    Array(RbArray),
    Hash(RbHash),
    Userdata(Userdata),
    Object(Object),
}

Value relies heavily on VistorExt to make sure types stay the same and data is not lost in deserialization.