added contrails

src/contrail.rs

@@ -0,0 +1,34 @@
+//! Contrails are byte arrays protected by a short crc8 checksum which is enough
+//! to protect against human typing error in most cases.
+
+use crate::crc::Crc8;
+
+/// Check that the data is a valid contrail, e.g. contains a valid checksum in the
+/// first byte.
+pub fn is_valid_contrail(data: &[u8]) -> bool {
+    Crc8::calc(&data[1..]) == data[0]
+}
+
+/// Create contrail from a given bytes slice. Return vec containing a valid
+/// contrail. It is always 1 byte longer than a given data.
+pub fn create_contrail(data: &[u8]) -> Vec<u8> {
+    let mut result = Vec::with_capacity(data.len()+1);
+    result.push(Crc8::calc(&data));
+    result.extend_from_slice(&data);
+    result
+}
+
+mod tests {
+    use crate::contrail::{create_contrail, is_valid_contrail};
+
+    #[test]
+    fn test_contrail() {
+        // let a = [1,2,3,4,5];
+        let mut c = create_contrail(&[1,2,3,4,5]);
+        // println!("{}", to_dump(&c));
+        assert_eq!(c[0], 134);
+        assert_eq!(true, is_valid_contrail(&c));
+        c[1] = 2;
+        assert_eq!(false, is_valid_contrail(&c));
+    }
+}

src/lib.rs

@@ -122,6 +122,7 @@ mod error;
 mod ser;
 mod de;
 mod crc;
+mod contrail;
 
 #[cfg(test)]
 mod tests {