Implement conversion traits for Model and NK_device_model

A nitrokey_sys::NK_device_model (= u32) value may correspond to a
nitrokey::Model, and vice versa.  This patch adds the appropriate From
and TryFrom implementations.

2 files changed, 31 insertions, 15 deletions

diff --git a/src/device/mod.rs b/src/device/mod.rs
index 5e15f08..a3a0255 100644
--- a/src/device/mod.rs
+++ b/src/device/mod.rs
@@ -5,6 +5,7 @@ mod pro;
 mod storage;
 mod wrapper;
 
+use std::convert::TryFrom;
 use std::fmt;
 
 use libc;
@@ -43,6 +44,30 @@ impl fmt::Display for Model {
     }
 }
 
+impl From<Model> for nitrokey_sys::NK_device_model {
+    fn from(model: Model) -> Self {
+        match model {
+            Model::Storage => nitrokey_sys::NK_device_model_NK_STORAGE,
+            Model::Pro => nitrokey_sys::NK_device_model_NK_PRO,
+        }
+    }
+}
+
+impl TryFrom<nitrokey_sys::NK_device_model> for Model {
+    type Error = Error;
+
+    fn try_from(model: nitrokey_sys::NK_device_model) -> Result<Self, Error> {
+        match model {
+            nitrokey_sys::NK_device_model_NK_DISCONNECTED => {
+                Err(CommunicationError::NotConnected.into())
+            }
+            nitrokey_sys::NK_device_model_NK_PRO => Ok(Model::Pro),
+            nitrokey_sys::NK_device_model_NK_STORAGE => Ok(Model::Storage),
+            _ => Err(Error::UnsupportedModelError),
+        }
+    }
+}
+
 /// A firmware version for a Nitrokey device.
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub struct FirmwareVersion {
@@ -428,12 +453,8 @@ pub trait Device<'a>: Authenticate<'a> + GetPasswordSafe<'a> + GenerateOtp + fmt
     }
 }
 
-fn get_connected_model() -> Option<Model> {
-    match unsafe { nitrokey_sys::NK_get_device_model() } {
-        nitrokey_sys::NK_device_model_NK_PRO => Some(Model::Pro),
-        nitrokey_sys::NK_device_model_NK_STORAGE => Some(Model::Storage),
-        _ => None,
-    }
+fn get_connected_model() -> Result<Model, Error> {
+    Model::try_from(unsafe { nitrokey_sys::NK_get_device_model() })
 }
 
 pub(crate) fn create_device_wrapper(
@@ -449,16 +470,9 @@ pub(crate) fn create_device_wrapper(
 pub(crate) fn get_connected_device(
     manager: &mut crate::Manager,
 ) -> Result<DeviceWrapper<'_>, Error> {
-    match get_connected_model() {
-        Some(model) => Ok(create_device_wrapper(manager, model)),
-        None => Err(CommunicationError::NotConnected.into()),
-    }
+    Ok(create_device_wrapper(manager, get_connected_model()?))
 }
 
 pub(crate) fn connect_enum(model: Model) -> bool {
-    let model = match model {
-        Model::Storage => nitrokey_sys::NK_device_model_NK_STORAGE,
-        Model::Pro => nitrokey_sys::NK_device_model_NK_PRO,
-    };
-    unsafe { nitrokey_sys::NK_login_enum(model) == 1 }
+    unsafe { nitrokey_sys::NK_login_enum(model.into()) == 1 }
 }
diff --git a/src/lib.rs b/src/lib.rs
index 059792d..0eb4f40 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -235,6 +235,7 @@ impl Manager {
     /// # Errors
     ///
     /// - [`NotConnected`][] if no Nitrokey device is connected
+    /// - [`UnsupportedModelError`][] if the Nitrokey device is not supported by this crate
     ///
     /// # Example
     ///
@@ -252,6 +253,7 @@ impl Manager {
     /// ```
     ///
     /// [`NotConnected`]: enum.CommunicationError.html#variant.NotConnected
+    /// [`UnsupportedModelError`]: enum.Error.html#variant.UnsupportedModelError
     pub fn connect(&mut self) -> Result<DeviceWrapper<'_>, Error> {
         if unsafe { nitrokey_sys::NK_login_auto() } == 1 {
             device::get_connected_device(self)