Refactor CommandError::RngError into Error::RandError

We reserve CommandError for errors returned by the Nitrokey device.
Errors during random number generation should have their own type.

3 files changed, 12 insertions, 10 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index bbb3202..5a78724 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
   - Implement `std::error::Error` for `CommandError`.
   - Add the `Error` enum and the `Result` typedef.
   - Return `Error` instead of `CommandError` in all public functions.
+  - Move the `CommandError::RngError` variant to `Error::RandError`.
 
 # v0.3.4 (2019-01-20)
 - Fix authentication methods that assumed that `char` is signed.
diff --git a/src/error.rs b/src/error.rs
index 3f60af2..dfe1680 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -11,6 +11,8 @@ pub enum Error {
     CommandError(CommandError),
     /// Placeholder for testing.
     CommunicationError(CommunicationError),
+    /// An error that occured during random number generation.
+    RandError(rand_core::Error),
 }
 
 impl From<CommandError> for Error {
@@ -19,11 +21,18 @@ impl From<CommandError> for Error {
     }
 }
 
+impl From<rand_core::Error> for Error {
+    fn from(error: rand_core::Error) -> Self {
+        Error::RandError(error)
+    }
+}
+
 impl error::Error for Error {
     fn source(&self) -> Option<&(dyn error::Error + 'static)> {
         match *self {
             Error::CommandError(ref err) => Some(err),
             Error::CommunicationError(_) => None,
+            Error::RandError(ref err) => Some(err),
         }
     }
 }
@@ -33,6 +42,7 @@ impl fmt::Display for Error {
         match *self {
             Error::CommandError(ref err) => write!(f, "Command error: {}", err),
             Error::CommunicationError(_) => write!(f, "Placeholder"),
+            Error::RandError(ref err) => write!(f, "RNG error: {}", err),
         }
     }
 }
@@ -78,8 +88,6 @@ pub enum CommandError {
     InvalidHexString,
     /// The target buffer was smaller than the source.
     TargetBufferTooSmall,
-    /// An error occurred during random number generation.
-    RngError,
 }
 
 /// Placeholder for testing.
@@ -119,7 +127,6 @@ impl CommandError {
                 "The supplied string is not in hexadecimal format".into()
             }
             CommandError::TargetBufferTooSmall => "The target buffer is too small".into(),
-            CommandError::RngError => "An error occurred during random number generation".into(),
         }
     }
 }
@@ -153,9 +160,3 @@ impl From<raw::c_int> for CommandError {
         }
     }
 }
-
-impl From<rand_core::Error> for CommandError {
-    fn from(_error: rand_core::Error) -> Self {
-        CommandError::RngError
-    }
-}
diff --git a/src/util.rs b/src/util.rs
index 8855275..06bb854 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -71,7 +71,7 @@ pub fn get_last_error() -> Error {
 }
 
 pub fn generate_password(length: usize) -> Result<Vec<u8>, Error> {
-    let mut rng = OsRng::new().map_err(CommandError::from)?;
+    let mut rng = OsRng::new()?;
     let mut data = vec![0u8; length];
     rng.fill_bytes(&mut data[..]);
     Ok(data)