Changes

src/message.rs

@@ -1,16 +1,8 @@
 use log::{warn, error};
 
-// Use std::vec when std exists, otherwise alloc::vec
-#[cfg(feature = "std")]
-use std::vec;
-
-#[cfg(not(feature = "std"))]
 extern crate alloc;
 
-#[cfg(not(feature = "std"))]
 use alloc::vec;
-
-#[cfg(not(feature = "std"))]
 use alloc::vec::Vec;
 
 use thiserror::Error;
@@ -38,6 +30,7 @@ pub struct Protocol300Message {
 }
 
 impl Protocol300Message {
+    #[inline]
     /// Creates a new `Protocol300message` used to request data from the device
     /// 
     /// # Arguments
@@ -60,6 +53,7 @@ impl Protocol300Message {
         }
     }
 
+    #[inline]
     /// Creates a new `Protocol300message` used to write data to the device
     /// 
     /// # Arguments
@@ -86,8 +80,25 @@ impl Protocol300Message {
         })
     }
 
+    #[inline]
     /// Decode a byte string into a `Protocol300Message`
-    pub fn try_from_bytes(bytes: &[u8]) -> Result<Protocol300Message, MessageDecodingError> {
+    /// 
+    /// Tries to decode a vec of bytes into an `Protocol300Message`. Includes
+    /// checking for valid start bytes and checking the checksum to detect
+    /// transmission errors
+    /// 
+    /// # Errors
+    /// Returns a `MessageDecodingError` on failure. Can be caused by multiple
+    /// things (for details look at `MessageDecodingError`):
+    /// - Invalid Start byte
+    /// - Length does not match actual length
+    /// - Invalid values for Message Identifier or Function code
+    /// - Checksum mismatch
+    pub fn try_from_bytes(bytes: &[u8]) -> Result<Self, MessageDecodingError> {
+        if bytes.len() < 8 {
+            return Err(MessageDecodingError::VecTooShort)
+        }
+        
         if bytes[0] != 0x41 {
             return Err(MessageDecodingError::InvalidTelegramStart(bytes[0]));
         }
@@ -123,7 +134,13 @@ impl Protocol300Message {
             },
         };
 
-        let checksum = calculate_checksum(telegram_length, message_identifier, function_code, data_address, data_length, &data);
+        let checksum_calculated = calculate_checksum(telegram_length, message_identifier, function_code, data_address, data_length, &data);
+        let checksum = bytes[telegram_length as usize + 2];
+        
+        // Fail if the checksums do not match
+        if checksum != checksum_calculated {
+            return Err(MessageDecodingError::Checksum)
+        }
 
         Ok(Self {
             telegram_length,
@@ -137,6 +154,9 @@ impl Protocol300Message {
 
     }
 
+    #[must_use]
+    #[inline]
+    /// Converts a `Protocol300Message` to a vec of bytes
     pub fn to_bytes(&self) -> Vec<u8> {
         let telegram_start_byte = 0x41;
         let address_as_bytes = self.data_address.to_be_bytes();
@@ -157,13 +177,13 @@ impl Protocol300Message {
 
     }
 
-    // TODO docs and test
+    #[inline]
     /// Returns the expected length of the return telegram, include start byte but excluding ACK byte
     /// 
     /// Currently only implemented for Read and Write requests, as the rest is not needed and/or
     /// unknown behaviour
     /// 
-    /// # Errors:
+    /// # Errors
     /// - `MessageReturnLengthError` - Describes the error which occured when converting
     pub const fn get_expected_return_telegram_length(&self) -> Result<usize, MessageReturnLengthError> {
         match (self.message_identifier, self.function_code) {
@@ -213,6 +233,12 @@ pub enum MessageDecodingError {
     /// Error getting function code enum variant by number
     #[error("Function Code not valid")]
     InvalidFunctionCode(#[from] num_enum::TryFromPrimitiveError<FunctionCode>),
+    /// Checksum does not match the calculated checksum
+    #[error("Checksums do not match")]
+    Checksum,
+    /// The message vec is too short
+    #[error("The message vec is too short")]
+    VecTooShort
 }
 
 #[cfg(test)]
@@ -229,7 +255,7 @@ mod tests {
 
 
     #[test]
-    fn test_new_request_message() {
+    fn new_request_message_works() {
         let expected_message = Protocol300Message{
             telegram_length: 5,
             message_identifier: MessageIdentifier::Request,
@@ -244,7 +270,7 @@ mod tests {
     }
 
     #[test]
-    fn test_new_write_message() {
+    fn new_write_message() {
         let expected_message = Protocol300Message{
             telegram_length: 9,
             message_identifier: MessageIdentifier::Request,
@@ -259,14 +285,14 @@ mod tests {
     }
 
     #[test]
-    fn test_new_write_message_data_too_long() {
+    fn new_write_message_data_too_long() {
         let generated_message = Protocol300Message::try_new_write_message(0x0101, &vec![0x00; 300]);
         assert!(generated_message.is_err());
         assert!(matches!(generated_message.err().unwrap(), MessageCreationError::DataTooLong(_)));
     }
 
     #[test]
-    fn test_received_message_read_response_from_bytes() {
+    fn received_message_read_response_from_bytes() {
         let expected_msg = Protocol300Message{
             data_address: 0x5525,
             telegram_length: 0x09,
@@ -282,7 +308,7 @@ mod tests {
     }
 
         #[test]
-    fn test_received_message_write_response_from_bytes() {
+    fn received_message_write_response_from_bytes() {
         let expected_msg = Protocol300Message{
             data_address: 0x2101,
             telegram_length: 0x05,
@@ -298,7 +324,7 @@ mod tests {
     }
 
     #[test]
-    fn test_received_message_read_request_from_bytes() {
+    fn received_message_read_request_from_bytes() {
         let expected_msg = Protocol300Message{
             data_address: 0x5525,
             telegram_length: 0x05,
@@ -314,7 +340,7 @@ mod tests {
     }
 
     #[test]
-    fn test_received_message_write_request_from_bytes() {
+    fn received_message_write_request_from_bytes() {
         let expected_msg = Protocol300Message{
             data_address: 0x2323,
             telegram_length: 0x06,
@@ -330,7 +356,7 @@ mod tests {
     }
     // TO BYTES
     #[test]
-    fn test_received_message_write_request_to_bytes() {
+    fn received_message_write_request_to_bytes() {
         let test_msg = Protocol300Message{
             data_address: 0x2323,
             telegram_length: 0x06,
@@ -346,7 +372,7 @@ mod tests {
     }
 
     #[test]
-    fn test_received_message_read_request_to_bytes() {
+    fn received_message_read_request_to_bytes() {
         let test_msg = Protocol300Message{
             data_address: 0x5525,
             telegram_length: 0x05,
@@ -362,7 +388,7 @@ mod tests {
     }
 
     #[test]
-    fn test_received_message_write_response_to_bytes() {
+    fn received_message_write_response_to_bytes() {
         let test_msg = Protocol300Message{
             data_address: 0x2101,
             telegram_length: 0x05,
@@ -378,7 +404,7 @@ mod tests {
     }
 
     #[test]
-    fn test_received_message_read_response_to_bytes() {
+    fn received_message_read_response_to_bytes() {
         let test_msg = Protocol300Message{
             data_address: 0x5525,
             telegram_length: 0x09,
@@ -394,7 +420,7 @@ mod tests {
     }
 
     #[test]
-    fn test_expected_return_length_read() {
+    fn expected_return_length_read() {
         let expected_message = Protocol300Message{
             telegram_length: 5,
             message_identifier: MessageIdentifier::Request,
@@ -408,7 +434,7 @@ mod tests {
     }
 
     #[test]
-    fn test_expected_return_length_write() {
+    fn expected_return_length_write() {
         let expected_message = Protocol300Message{
             telegram_length: 9,
             message_identifier: MessageIdentifier::Request,