Split some files and add more documentation

src/error.rs

@@ -0,0 +1,32 @@
+pub type Result<T> = std::result::Result<T, Error>;
+
+#[derive(thiserror::Error, Debug)]
+pub enum Error {
+    #[error("Device error: `{0:?}`")]
+    Device(DeviceError),
+    #[error("Other OBD2 error: `{0}`")]
+    Other(String),
+    #[error("Incorrect length (`{0}`): expected `{1}`, got `{2}`")]
+    IncorrectResponseLength(&'static str, usize, usize),
+}
+
+#[derive(Debug)]
+pub struct DeviceError(super::device::Error);
+
+impl From<super::device::Error> for Error {
+    fn from(e: super::device::Error) -> Self {
+        Error::Device(DeviceError(e))
+    }
+}
+
+impl From<std::num::ParseIntError> for Error {
+    fn from(e: std::num::ParseIntError) -> Self {
+        Error::Other(format!("invalid data recieved: {:?}", e))
+    }
+}
+
+impl From<std::string::FromUtf8Error> for Error {
+    fn from(e: std::string::FromUtf8Error) -> Self {
+        Error::Other(format!("invalid string recieved: {:?}", e))
+    }
+}