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//! # hdlc-rust //! Rust implementation of a High-level Data Link Control (HDLC) library //! //! ## Usage //! //! ### Encode packet //! ```rust //!extern crate hdlc; //! use hdlc::{SpecialChars, encode}; //! //! let msg: Vec<u8> = vec![0x01, 0x50, 0x00, 0x00, 0x00, 0x05, 0x80, 0x09]; //! let cmp: Vec<u8> = vec![126, 1, 80, 0, 0, 0, 5, 128, 9, 126];; //! let chars = SpecialChars::default(); //! //! let result = encode(msg, chars); //! //! assert!(result.is_ok()); //! assert_eq!(result.unwrap(), cmp); //! ``` //! //! ### Custom Special Characters //! ```rust //!extern crate hdlc; //! use hdlc::{SpecialChars, encode}; //! //! let msg: Vec<u8> = vec![0x01, 0x7E, 0x70, 0x7D, 0x00, 0x05, 0x80, 0x09]; //! let cmp: Vec<u8> = vec![0x71, 1, 126, 112, 80, 125, 0, 5, 128, 9, 0x71]; //! let chars = SpecialChars::new(0x71, 0x70, 0x51, 0x50); //! //! let result = encode(msg, chars); //! //! assert!(result.is_ok()); //! assert_eq!(result.unwrap(), cmp) //! ``` //! //! ### Decode packet //! ```rust //! extern crate hdlc; //! use hdlc::{SpecialChars, decode}; //! //! let chars = SpecialChars::default(); //! let msg: Vec<u8> = vec![ //! chars.fend, 0x01, 0x50, 0x00, 0x00, 0x00, 0x05, 0x80, 0x09, chars.fend, //! ]; //! let cmp: Vec<u8> = vec![1, 80, 0, 0, 0, 5, 128, 9]; //! //! let result = decode(msg, chars); //! //! assert!(result.is_ok()); //! assert_eq!(result.unwrap(), cmp); //! ``` #![deny(missing_docs)] use std::collections::HashSet; use std::default::Default; use std::error::Error; use std::fmt; use std::io; use std::io::Result; /// Sync byte that wraps the data packet pub const FEND: u8 = 0x7E; /// Substitution character pub const FESC: u8 = 0x7D; /// Substituted for FEND pub const TFEND: u8 = 0x5E; /// Substituted for FESC pub const TFESC: u8 = 0x5D; /// Frame structure holds data to help decode packets struct Frame { last_was_fesc: u8, last_was_fend: u8, sync: u8, } impl Frame { /// Creates a new Frame structure for decoding a packet fn new() -> Frame { Frame { last_was_fesc: 0, last_was_fend: 0, sync: 0, } } } /// Special Character structure for holding the encode and decode values /// /// # Default /// /// FEND = 0x7E; /// FESC = 0x7D; /// TFEND = 0x5E; /// TFESC = 0x5D; #[derive(Debug)] pub struct SpecialChars { /// Frame END. Byte that marks the beginning and end of a packet pub fend: u8, /// Frame ESCape. Byte that marks the start of a swap byte pub fesc: u8, /// Trade Frame END. Byte that is substituted for the FEND byte pub tfend: u8, /// Trade Frame ESCape. Byte that is substituted for the FESC byte pub tfesc: u8, } impl Default for SpecialChars { /// Creates the default SpecialChars structure for encoding/decoding a packet fn default() -> SpecialChars { SpecialChars { fend: FEND, fesc: FESC, tfend: TFEND, tfesc: TFESC, } } } impl SpecialChars { /// Creates a new SpecialChars structure for encoding/decoding a packet pub fn new(fend: u8, fesc: u8, tfend: u8, tfesc: u8) -> SpecialChars { SpecialChars { fend, fesc, tfend, tfesc, } } } /// Produces unescaped message without `FEND` characters. /// /// Inputs: *Vec<u8>*: a vector of the bytes you want to decode /// Inputs: *SpecialChars*: the special characters you want to swap /// /// Returns: Decoded output message as `Result<Vec<u8>>` /// /// Safety: Checks special characters for duplicates /// /// Error: "Duplicate special character". If any of the `SpecialChars` are duplicate, throw an error /// /// Todo: Catch more errors, like an incomplete packet /// /// # Example /// ```rust /// extern crate hdlc; /// let chars = hdlc::SpecialChars::default(); /// let input: Vec<u8> = vec![ 0x7E, 0x01, 0x50, 0x00, 0x00, 0x00, 0x05, 0x80, 0x09, 0x7E]; /// let op_vec = hdlc::decode(input.to_vec(), chars); /// ``` pub fn decode(input: Vec<u8>, s_chars: SpecialChars) -> Result<Vec<u8>> { let mut set = HashSet::new(); if !set.insert(s_chars.fend) || !set.insert(s_chars.fesc) || !set.insert(s_chars.tfend) || !set.insert(s_chars.tfesc) { return Err(io::Error::new( io::ErrorKind::Other, HDLCError::DuplicateSpecialChar, )); } let mut frame: Frame = Frame::new(); let mut output: Vec<u8> = Vec::with_capacity(input.len()); for byte in input { // Handle the special escape characters if frame.last_was_fesc > 0 { if byte == s_chars.tfesc { output.push(s_chars.fesc); } else if byte == s_chars.tfend { output.push(s_chars.fend); } frame.last_was_fesc = 0 } else { // Match based on the special characters, but struct fields are not patterns and cant match if byte == s_chars.fend { // If we are already synced, this is the closing sync char if frame.sync > 0 { return Ok(output); // Todo: Maybe save for a 2nd message? } else { frame.sync = 1; } frame.last_was_fend = 0; } else if byte == s_chars.fesc { frame.last_was_fesc = 1; } else { if frame.sync > 0 { frame.last_was_fend = 0; output.push(byte); } } } } Ok(output) } /// Produces escaped and FEND surrounded message. /// /// Inputs: *Vec<u8>*: A vector of the bytes you want to encode /// Inputs: *SpecialChars*: The special characters you want to swap /// /// Returns: Decoded output message as `Result<Vec<u8>>` /// /// Safety: Checks special characters for duplicates /// /// Error: "Duplicate special character". If any of the `SpecialChars` are duplicate, throw an error /// /// Todo: Catch more errors, like an incomplete packet /// /// # Example /// ```rust /// extern crate hdlc; /// let chars = hdlc::SpecialChars::default(); /// let input: Vec<u8> = vec![0x01, 0x50, 0x00, 0x00, 0x00, 0x05, 0x80, 0x09]; /// let op_vec = hdlc::encode(input.to_vec(), chars); /// ``` pub fn encode(data: Vec<u8>, s_chars: SpecialChars) -> Result<Vec<u8>> { // Safety check to make sure the special character values are all unique let mut set = HashSet::new(); if !set.insert(s_chars.fend) || !set.insert(s_chars.fesc) || !set.insert(s_chars.tfend) || !set.insert(s_chars.tfesc) { return Err(io::Error::new( io::ErrorKind::Other, HDLCError::DuplicateSpecialChar, )); } let mut output = Vec::with_capacity(data.len() * 2); // *2 is the max size it can be if EVERY char is swapped // As of 4/24/18 Stuct fields are not patterns and cannot be match arms. for i in data { if i == s_chars.fend { output.push(s_chars.fesc); output.push(s_chars.tfend); } else if i == s_chars.fesc { output.push(s_chars.fesc); output.push(s_chars.tfesc); } else { output.push(i); } } // Wrap the message in FENDs and return Ok(wrap_fend(output, s_chars.fend)) } fn wrap_fend(mut data: Vec<u8>, fend: u8) -> Vec<u8> { let mut output = Vec::with_capacity(data.len() + 2); output.push(fend); output.append(&mut data); output.push(fend); output } /// Common Error for HDLC Actions. #[derive(Debug, PartialEq)] pub enum HDLCError { /// Catches duplicate special characters. DuplicateSpecialChar, } impl fmt::Display for HDLCError { /// Formats the output for the error using the given formatter. fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match *self { HDLCError::DuplicateSpecialChar => write!(f, "Catches duplicate special characters."), } } } impl Error for HDLCError { /// Returns a short description of the error. fn description(&self) -> &str { match *self { HDLCError::DuplicateSpecialChar => "Catches duplicate special characters.", } } } /* impl fmt::Display for IridiumError { fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { match self { IridiumError::UartError { cause } => write!(f, "{}", cause), IridiumError::PoisonError => write!( f, "The mutex guarding the RockBlock connection has been poisoned." ), } } }*/