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//! # sensirion-hdlc //! Only frames the data. Rust implementation of Sensirion High-level Data Link Control (HDLC) //! library. //! //! ## Usage //! //! ### Encode packet //! ```rust //! extern crate sensirion_hdlc; //! use sensirion_hdlc::{SpecialChars, encode}; //! //! let msg = [0x01, 0x50, 0x00, 0x00, 0x00, 0x05, 0x80, 0x09, 0x20]; //! let cmp = [0x7E, 0x01, 0x50, 0x00, 0x00, 0x00, 0x05, 0x80, 0x09, 0x20, 0x7E]; //! //! let result = encode(&msg, SpecialChars::default()).unwrap(); //! //! assert_eq!(result[0..result.len()], cmp); //! ``` //! //! ### Custom Special Characters //! ```rust //! extern crate sensirion_hdlc; //! use sensirion_hdlc::{SpecialChars, encode}; //! //! let msg = [0x01, 0x7E, 0x70, 0x50, 0x00, 0x05, 0x80, 0x09, 0xe2]; //! let cmp = [0x71, 0x01, 0x7E, 0x70, 0x50, 0x50, 0x00, 0x05, 0x80, 0x09, 0xe2, 0x71]; //! let chars = SpecialChars::new(0x71, 0x70, 0x51, 0x50, 0x11, 0x31, 0x13, 0x33).unwrap(); //! //! let result = encode(&msg, chars).unwrap(); //! //! assert_eq!(result[0..result.len()], cmp) //! ``` //! //! ### Decode packet //! ```rust //! extern crate sensirion_hdlc; //! use sensirion_hdlc::{SpecialChars, decode}; //! //! let chars = SpecialChars::default(); //! let msg = [ //! chars.fend, 0x01, 0x50, 0x00, 0x00, 0x00, 0x05, 0x80, 0x29, chars.fend, //! ]; //! let cmp = [0x01, 0x50, 0x00, 0x00, 0x00, 0x05, 0x80, 0x29]; //! //! let result = decode(&msg, chars).unwrap(); //! //! assert_eq!(result[0..result.len()], cmp); //! ``` #![no_std] #![deny(missing_docs)] use arrayvec::ArrayVec; /// Special Character structure for holding the encode and decode values. /// /// # Default /// /// * **FEND** = 0x7E; /// * **FESC** = 0x7D; /// * **TFEND** = 0x5E; /// * **TFESC** = 0x5D; /// * **OB1** = 0x11; /// * **TFOB1** = 0x31; /// * **OB2** = 0x13; /// * **TFOB2** = 0x33; #[derive(Debug, Copy, Clone)] 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, /// Original Byte 1. Byte that will be substituted for the TFOB1 byte pub ob1: u8, /// Trade Frame ESCape. Byte that is substituted for the Original Byte 1 pub tfob1: u8, /// Original Byte 2. Byte that is substituted for the TFOB2 byte pub ob2: u8, /// Trade Frame Origina Byte 2. Byte that is substituted for the Original Byte 2 pub tfob2: u8, } impl Default for SpecialChars { /// Creates the default SpecialChars structure for encoding/decoding a packet fn default() -> SpecialChars { SpecialChars { fend: 0x7E, fesc: 0x7D, tfend: 0x5E, tfesc: 0x5D, ob1: 0x11, tfob1: 0x31, ob2: 0x13, tfob2: 0x33, } } } impl SpecialChars { /// Creates a new SpecialChars structure for encoding/decoding a packet #[allow(clippy::too_many_arguments)] pub fn new( fend: u8, fesc: u8, tfend: u8, tfesc: u8, ob1: u8, tfob1: u8, ob2: u8, tfob2: u8, ) -> Result<SpecialChars, HDLCError> { // Safety check to make sure the special character values are all unique let values: [u8; 8] = [fend, fesc, tfend, tfesc, ob1, tfob1, ob2, tfob2]; for i in 0..values.len() - 1 { if values[i + 1..].contains(&values[i]) { return Err(HDLCError::DuplicateSpecialChar); } } Ok(SpecialChars { fend, fesc, tfend, tfesc, ob1, tfob1, ob2, tfob2, }) } } /// Produces escaped (encoded) message surrounded with `FEND` /// /// # Inputs /// * **Vec<u8>**: A vector of the bytes you want to encode /// * **SpecialChars**: The special characters you want to swap /// /// # Output /// /// * **Result<ArrayVec<u8;1024>>**: Encoded output message /// /// /// # Error /// /// * **HDLCError::TooMuchData**: More than 260 bytes to be encoded /// /// # Example /// ```rust /// extern crate sensirion_hdlc; /// let chars = sensirion_hdlc::SpecialChars::default(); /// let input: Vec<u8> = vec![0x01, 0x50, 0x00, 0x00, 0x00, 0x05, 0x80, 0x09]; /// let op_vec = sensirion_hdlc::encode(&input.to_vec(), chars); /// ``` pub fn encode(data: &[u8], s_chars: SpecialChars) -> Result<ArrayVec<[u8; 1024]>, HDLCError> { if data.len() > 260 { return Err(HDLCError::TooMuchData); } // Iterator over the input that allows peeking let input_iter = data.iter(); let mut output = ArrayVec::<[_; 1024]>::new(); //Push initial FEND output.push(s_chars.fend); // Loop over every byte of the message for value in input_iter { match *value { // FEND , FESC, ob1 and ob2 val if val == s_chars.fesc => { output.push(s_chars.fesc); output.push(s_chars.tfesc); } val if val == s_chars.fend => { output.push(s_chars.fesc); output.push(s_chars.tfend); } val if val == s_chars.ob1 => { output.push(s_chars.fesc); output.push(s_chars.tfob1); } val if val == s_chars.ob2 => { output.push(s_chars.fesc); output.push(s_chars.tfob2); } // Handle any other bytes _ => output.push(*value), } } // Push final FEND output.push(s_chars.fend); Ok(output) } /// Produces unescaped (decoded) message without `FEND` characters. /// /// # Inputs /// * **Vec<u8>**: A vector of the bytes you want to decode /// * **SpecialChars**: The special characters you want to swap /// /// # Output /// /// * **Result<ArrayVec<u8;1024>>**: Decoded output message /// /// # Error /// /// * **HDLCError::TooMuchDecodedData**: More than expected 260 bytes of decoded data /// * **HDLCError::FendCharInData**: Checks to make sure the full decoded message is the full /// length. Found the `SpecialChars::fend` inside the message. /// * **HDLCError::MissingTradeChar**: Checks to make sure every frame escape character `fesc` /// is followed by either a `tfend` or a `tfesc`. /// * **HDLCError::MissingFirstFend**: Input vector is missing a first `SpecialChars::fend` /// * **HDLCError::MissingFinalFend**: Input vector is missing a final `SpecialChars::fend` /// * **HDLCError::TooFewData**: Data to decode is fewer than 4 bytes` /// * **HDLCError::TooMuchData**: Data to decode is larger than 1000 bytes` /// /// /// # Example /// ```rust /// extern crate sensirion_hdlc; /// let chars = sensirion_hdlc::SpecialChars::default(); /// let input =[ 0x7E, 0x01, 0x50, 0x00, 0x00, 0x00, 0x05, 0x80, 0x09, 0x7E]; /// let op_vec = sensirion_hdlc::decode(&input.to_vec(), chars); /// ``` pub fn decode(input: &[u8], s_chars: SpecialChars) -> Result<ArrayVec<[u8; 1024]>, HDLCError> { if input.len() < 4 { return Err(HDLCError::TooFewData); } if input.len() > 1000 { return Err(HDLCError::TooMuchData); } // Verify input begins with a FEND if input[0] != s_chars.fend { return Err(HDLCError::MissingFirstFend); } // Verify input ends with a FEND if input[input.len() - 1] != s_chars.fend { return Err(HDLCError::MissingFinalFend); } let mut output = ArrayVec::<[u8; 1024]>::new(); // Iterator over the input that allows peeking let mut input_iter = input[1..input.len() - 1].iter().peekable(); // Loop over every byte of the message while let Some(value) = input_iter.next() { match *value { // Handle a FESC val if val == s_chars.fesc => match input_iter.next() { Some(&val) if val == s_chars.tfend => output.push(s_chars.fend), Some(&val) if val == s_chars.tfesc => output.push(s_chars.fesc), Some(&val) if val == s_chars.tfob1 => output.push(s_chars.ob1), Some(&val) if val == s_chars.tfob2 => output.push(s_chars.ob2), _ => return Err(HDLCError::MissingTradeChar), }, // Handle a FEND val if val == s_chars.fend => { return Err(HDLCError::FendCharInData); } // Handle any other bytes _ => output.push(*value), } } if output.len() > 260 { return Err(HDLCError::TooMuchDecodedData); } Ok(output) } #[derive(Debug, PartialEq)] /// Common error for HDLC actions. pub enum HDLCError { /// Catches duplicate special characters. DuplicateSpecialChar, /// Catches a random sync char in the data. FendCharInData, /// Catches a random swap char, `fesc`, in the data with no `tfend` or `tfesc`. MissingTradeChar, /// No first fend on the message. MissingFirstFend, /// No final fend on the message. MissingFinalFend, /// Too much data to be converted into a SHDLC frame TooMuchData, /// Too few data to be converted from a SHDLC frame TooFewData, /// Checksum for decoded Frame is invalid InvalidChecksum, /// More than 259 bytes resulted after decoding SHDLC frame TooMuchDecodedData, } #[cfg(test)] mod tests { use super::*; #[test] fn encode_start_measumement() { let mosi_data = [0x00, 0x00, 0x02, 0x01, 0x03, 0xf9]; let expected = [0x7e, 0x00, 0x00, 0x02, 0x01, 0x03, 0xf9, 0x7e]; let encoded = encode(&mosi_data, SpecialChars::default()).unwrap(); assert_eq!(encoded[0..encoded.len()], expected); } #[test] fn encode_test() { let mosi_data = [0x00, 0x01, 0x00, 0xfe]; let expected = [0x7e, 0x00, 0x01, 0x00, 0xfe, 0x7e]; let encoded = encode(&mosi_data, SpecialChars::default()).unwrap(); assert_eq!(encoded[0..encoded.len()], expected); } #[test] fn decode_test() { let expected = [0x00, 0x01, 0x00, 0xfe]; let mosi_data = [0x7e, 0x00, 0x01, 0x00, 0xfe, 0x7e]; let encoded = decode(&mosi_data, SpecialChars::default()).unwrap(); assert_eq!(encoded[0..encoded.len()], expected); } }