Initial

src/utils.rs

@@ -0,0 +1,49 @@
+use crate::enums::{FunctionCode, MessageIdentifier};
+
+pub fn calculate_checksum(length: u8, message_identifier: MessageIdentifier, function_code: FunctionCode, address: u16, data_length: u8, data: &[u8]) -> u8 {
+    let mut checksum = 0u8;
+    let [addr_hi, addr_lo] = address.to_be_bytes();
+
+    for byte in [length, message_identifier as u8, function_code as u8, data_length, addr_hi, addr_lo].iter().chain(data) {
+        checksum = checksum.wrapping_add(*byte);
+    }
+
+    checksum
+}
+
+
+
+
+
+#[cfg(test)]
+mod tests {
+    use crate::{enums::{FunctionCode, MessageIdentifier}, message::Protocol300Message, utils::calculate_checksum};
+
+    #[test]
+    fn test_check_checksum_1() {
+        let test_msg = Protocol300Message {
+            data_address: 0x5525,
+            telegram_length: 0x05,
+            function_code: FunctionCode::VirtualREAD,
+            message_identifier: MessageIdentifier::Request,
+            data_length: 0x02,
+            data: vec![],
+            checksum: 0x82,
+        };
+        assert_eq!(calculate_checksum(test_msg.telegram_length, test_msg.message_identifier, test_msg.function_code, test_msg.data_address, test_msg.data_length, &test_msg.data), 0x82);
+    }
+
+        #[test]
+    fn test_check_checksum_2() {
+        let test_msg = Protocol300Message {
+            data_address: 0x5525,
+            telegram_length: 0x07,
+            function_code: FunctionCode::VirtualREAD,
+            message_identifier: MessageIdentifier::Response,
+            data_length: 0x02,
+            data: vec![0x07, 0x01],
+            checksum: 0x8D,
+        };
+        assert_eq!(calculate_checksum(test_msg.telegram_length, test_msg.message_identifier, test_msg.function_code, test_msg.data_address, test_msg.data_length, &test_msg.data), 0x8D);
+    }
+}