speak2erase / alox-48

Serde powered Ruby Marshal (de)serializing library

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.

alox-48's Issues

Potential licensing problems

Why is this library licensed under GPL? The GPL prevents applications that are not licensed under GPL or AGPL from linking with GPL-licensed libraries (https://www.gnu.org/licenses/gpl-faq.en.html#IfLibraryIsGPL). Usually, libraries using a copyleft license are licensed under the LGPL instead.

Implement Deserializer and Serializer for Value

Fully deserialize structs during deserialization

aloz-48 is highly dependent on structs having the exact same fields as the marshal data, otherwise it may accidentally stop prematurely and get out of sync.