Crate didbot_data 

The atproto data model, its canonical encoding, and the CIDs that names.

atproto’s records are exchanged as JSON and identified as DAG-CBOR. The two are the same data model wearing different clothes, and the identity of a record — the CID a commit signs, a link quotes and an MST keys on — is the sha-256 of the DAG-CBOR bytes. Everything downstream of that hash depends on there being exactly one such encoding per record, which is why this crate is three narrow pieces rather than a serializer:

• Value is the data model: the values that have an encoding, and nothing else. Building one from JSON is where every rejection happens.

• dag_cbor turns one into bytes, and cannot fail. It reads them back too, which is a stricter job: see dag_cbor::decode.

• Cid is the hash of those bytes, and the only string form atproto permits for it.

• mst is the fourth piece and the largest: the Merkle search tree a repository is keyed by, along with the two pure functions its shape comes from.

use didbot_data::{dag_cbor, Value};

let record = serde_json::json!({
    "$type": "com.example.thing",
    "text": "quernstone",
    "count": 1,
});
let value = Value::object_from_json(&record).expect("a data-model record");
let bytes = dag_cbor::encode(&value);
assert_eq!(dag_cbor::cid(&value), didbot_data::Cid::of_dag_cbor(&bytes));

Why this is its own crate

It sits below everything that would use it and depends on none of them. A repository needs it to name a record, a Merkle search tree needs it to key one, a commit needs it to sign one, and a CAR file needs it to frame one. The tree is here, because a tree is nothing but keys and the encoding of its own nodes; the commit and the CAR are in didbot-repo, because they need a signing key and this crate deliberately depends on nothing.

What this crate does not do

It is not a serde data format: records arrive here as serde_json::Value from an HTTP body, and a derive-driven path would only add a second way to produce bytes that must be identical to these.

The conformance suite this is held to is data-model/ in the vendored upstream vectors; see docs/conformance.md.

Re-exports

pub use cid::Cid;

pub use cid::CidError;

pub use cid::RawHasher;

pub use value::DataError;

pub use value::ErrorKind;

pub use value::Value;

Modules

cid

Content identifiers, decoded rather than glanced at.

dag_cbor

The DAG-CBOR encoding, which is the canonical form a record is hashed in.

encoding 🔒

Base32 and base64, in the two exact dialects atproto uses.

mst

The Merkle search tree a repository is keyed by.

value

The atproto data model: the values a record is made of.