//!

//! # Overview

//!

//! Tor's primary network protocol is oriented around a set of

//! messages called "Cells".  They exist at two primary layers of the

//! protocol: the channel-cell layer, and the relay-cell layer.

//!

//! [Channel cells](chancell::ChanCell) are sent between relays, or

//! between a client and a relay, over a TLS connection.  Each of them

//! encodes a single [Channel Message](chancell::msg::ChanMsg).

//! Channel messages can affect the channel itself (such as those used

//! to negotiate and authenticate the channel), but more frequently are

//! used with respect to a given multi-hop circuit.

//!

//! Channel message that refer to a circuit do so with a channel-local

//! identifier called a [Circuit ID](chancell::CircId).  These

//! messages include CREATE2 (used to extend a circuit to a first hop)

//! and DESTROY (used to tear down a circuit).  But the most

//! frequently used channel message is RELAY, which is used to send a

//! message to a given hop along a circuit.

//!

//! Each RELAY cell is encrypted and decrypted (according to protocols

//! not implemented in this crate) until it reaches its target.  When

//! it does, it is decoded into a single [Relay

//! Message](relaycell::msg::RelayMsg).  Some of these relay messages

//! are used to manipulate circuits (e.g., by extending the circuit to

//! a new hop); others are used to manipulate anonymous data-streams

//! (by creating them, ending them, or sending data); and still others

//! are used for protocol-specific purposes (like negotiating with an

//! onion service.)

//!

//! For a list of _most_ of the cell types used in Tor, see

//! [tor-spec.txt](https://spec.torproject.org/tor-spec).  Other cell

//! types are defined in [rend-spec-v3.txt (for onion

//! services)](https://spec.torproject.org/tor-spec) and

//! [padding-spec.txt (for padding

//! negotiation)](https://spec.torproject.org/padding-spec).

//!

//! This crate is part of

//! [Arti](https://gitlab.torproject.org/tpo/core/arti/), a project to

//! implement [Tor](https://www.torproject.org/) in Rust.

//!

//! # Futureproofing note

//!

//! There are two pending proposals to remove the one-to-one

//! correspondence between relay cells and relay messages.

//!

//! [Proposal 319](https://gitlab.torproject.org/tpo/core/torspec/-/blob/master/proposals/319-wide-everything.md)

//! would add a "RELAY_FRAGMENT" command that would allow larger relay

//! messages to span multiple RELAY cells.

//!

//! [Proposal 325](https://gitlab.torproject.org/tpo/core/torspec/-/blob/master/proposals/325-packed-relay-cells.md),

//! on the other hand, would allow multiple relay messages to be

//! packed into a single RELAY cell.

//!

//! The distinction between RelayCell and RelayMsg is meant in part

//! to future-proof arti against these proposals if they are adopted.

#![deny(missing_docs)]

#![warn(noop_method_call)]

#![deny(unreachable_pub)]

#![warn(clippy::all)]

#![deny(clippy::await_holding_lock)]

#![deny(clippy::cargo_common_metadata)]

#![deny(clippy::cast_lossless)]

#![deny(clippy::checked_conversions)]

#![warn(clippy::cognitive_complexity)]

#![deny(clippy::debug_assert_with_mut_call)]

#![deny(clippy::exhaustive_enums)]

#![deny(clippy::exhaustive_structs)]

#![deny(clippy::expl_impl_clone_on_copy)]

#![deny(clippy::fallible_impl_from)]

#![deny(clippy::implicit_clone)]

#![deny(clippy::large_stack_arrays)]

#![warn(clippy::manual_ok_or)]

#![deny(clippy::missing_docs_in_private_items)]

#![deny(clippy::missing_panics_doc)]

#![warn(clippy::needless_borrow)]

#![warn(clippy::needless_pass_by_value)]

#![warn(clippy::option_option)]

#![warn(clippy::rc_buffer)]

#![deny(clippy::ref_option_ref)]

#![warn(clippy::semicolon_if_nothing_returned)]

#![warn(clippy::trait_duplication_in_bounds)]

#![deny(clippy::unnecessary_wraps)]

#![warn(clippy::unseparated_literal_suffix)]

#![deny(clippy::unwrap_used)]

pub mod chancell;

mod err;

pub mod relaycell;

pub use err::Error;

/// An error type for this crate.

pub type Result<T> = std::result::Result<T, Error>;