f better docs/comments in MessageBuf

Author: TheBlueMatt

lightning/src/ln/peer_channel_encryptor.rs

@@ -536,8 +536,8 @@ impl PeerChannelEncryptor {
 	}
 }
 
-/// A buffer which stores an encoded message with some padding to allow for future
-/// encryption/MACing
+/// A buffer which stores an encoded message (including the two message-type bytes) with some
+/// padding to allow for future encryption/MACing.
 pub struct MessageBuf(Vec<u8>);
 impl MessageBuf {
 	/// Creates a new buffer from an encoded message (i.e. the two message-type bytes followed by
@@ -548,6 +548,8 @@ impl MessageBuf {
 		if encoded_msg.len() > LN_MAX_MSG_LEN {
 			panic!("Attempted to encrypt message longer than 65535 bytes!");
 		}
+		// In addition to the message (continaing the two message type bytes), we also have to add
+		// the message length header (and its MAC) and the message MAC.
 		let mut res = Vec::with_capacity(encoded_msg.len() + 16*2 + 2);
 		res.resize(encoded_msg.len() + 16 + 2, 0);
 		res[16 + 2..].copy_from_slice(&encoded_msg);