ssh-encoding: flatten custom derive docs

Places them in the toplevel rustdoc, rather than their own (and
otherwise empty) module

Author: tarcieri

ssh-encoding/src/derive.rs

@@ -135,6 +135,73 @@
 //!
 //! [RFC3066]: https://datatracker.ietf.org/doc/html/rfc3066
 //! [RFC4251 § 5]: https://datatracker.ietf.org/doc/html/rfc4251#section-5
+//!
+//! ## Deriving [`Decode`] and [`Encode`]
+//!
+//! The traits [`Decode`] and [`Encode`] can be derived for any struct or enum where all its fields
+//! implement [`Decode`] and [`Encode`] respectively.
+//!
+//! To use this functionality, enable the `derive` crate feature for `ssh-encoding`.
+//!
+//! ### Example
+//!
+//! Here is an example of how you could define a handful of the SSH message types:
+//!
+#![cfg_attr(all(feature = "alloc", feature = "derive"), doc = "```")]
+#![cfg_attr(not(all(feature = "alloc", feature = "derive")), doc = "```ignore")]
+//! use ssh_encoding::{Decode, Encode};
+//!
+//! #[derive(Debug, PartialEq, Encode, Decode)]
+//! #[repr(u8)]
+//! enum Message {
+//!     Disconnect {
+//!         reason_code: u32,
+//!         description: String,
+//!         language_tag: String,
+//!     } = 1,
+//!     EcdhInit {
+//!         client_public_key: Vec<u8>,
+//!     } = 30,
+//!     EcdhReply {
+//!         host_key: HostKey,
+//!         server_public_key: Vec<u8>,
+//!         #[ssh(length_prefixed)]
+//!         host_signature: HostSignature,
+//!     } = 31,
+//! }
+//!
+//! #[derive(Debug, PartialEq, Encode, Decode)]
+//! #[ssh(length_prefixed)]
+//! struct HostKey {
+//!     key_type: String,
+//!     ecdsa_curve_identifier: String,
+//!     ecdsa_public_key: Vec<u8>,
+//! }
+//!
+//! #[derive(Debug, PartialEq, Encode, Decode)]
+//! struct HostSignature {
+//!     signature_type: String,
+//!     signature: Vec<u8>,
+//! }
+//!
+//! let message = Message::EcdhReply {
+//!     host_key: HostKey {
+//!         key_type: "ecdsa-sha2-nistp256".into(),
+//!         ecdsa_curve_identifier: "nistp256".into(),
+//!         ecdsa_public_key: vec![0x01, 0x02, 0x03],
+//!     },
+//!     server_public_key: vec![0x04, 0x05, 0x06],
+//!     host_signature: HostSignature {
+//!         signature_type: "ecdsa-sha2-nistp256".into(),
+//!         signature: vec![0x07, 0x08, 0x09],
+//!     },
+//! };
+//!
+//! let encoded = message.encode_vec().unwrap();
+//! assert_eq!(&encoded[..13], &[31, 0, 0, 0, 42, 0, 0, 0, 19, 101, 99, 100, 115]);
+//! let decoded = Message::decode(&mut &encoded[..]).unwrap();
+//! assert_eq!(message, decoded);
+//! ```
 
 #[cfg(feature = "alloc")]
 #[macro_use]
@@ -180,5 +247,3 @@ pub use crate::pem::{DecodePem, EncodePem};
 
 #[cfg(feature = "derive")]
 pub use ssh_derive::{Decode, Encode};
-#[cfg(feature = "derive")]
-pub mod derive;