Introduce the Error::UnexpectedError variant

The UnexpectedError variant is used when a libnitrokey function returns
a value that violates the function’s contract, for example if a function
returns a null pointer although it guarantees to never return null.
Previously, we returned a CommandError::Unspecified in these cases.

2 files changed, 7 insertions, 3 deletions

diff --git a/src/error.rs b/src/error.rs
index ef9b149..b27124c 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -14,6 +14,8 @@ pub enum Error {
     LibraryError(LibraryError),
     /// An error that occured during random number generation.
     RandError(rand_core::Error),
+    /// An error that is caused by an unexpected value returned by libnitrokey.
+    UnexpectedError,
     /// An unknown error returned by libnitrokey.
     Unknown(i64),
 }
@@ -63,6 +65,7 @@ impl error::Error for Error {
             Error::CommunicationError(ref err) => Some(err),
             Error::LibraryError(ref err) => Some(err),
             Error::RandError(ref err) => Some(err),
+            Error::UnexpectedError => None,
             Error::Unknown(_) => None,
         }
     }
@@ -75,6 +78,7 @@ impl fmt::Display for Error {
             Error::CommunicationError(ref err) => write!(f, "Communication error: {}", err),
             Error::LibraryError(ref err) => write!(f, "Library error: {}", err),
             Error::RandError(ref err) => write!(f, "RNG error: {}", err),
+            Error::UnexpectedError => write!(f, "An unexpected error occurred"),
             Error::Unknown(ref err) => write!(f, "Unknown error: {}", err),
         }
     }
diff --git a/src/util.rs b/src/util.rs
index 2738fce..79b8c34 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -5,7 +5,7 @@ use libc::{c_void, free};
 use rand_core::RngCore;
 use rand_os::OsRng;
 
-use crate::error::{CommandError, Error, LibraryError};
+use crate::error::{Error, LibraryError};
 
 /// Log level for libnitrokey.
 ///
@@ -36,7 +36,7 @@ pub fn owned_str_from_ptr(ptr: *const c_char) -> String {
 
 pub fn result_from_string(ptr: *const c_char) -> Result<String, Error> {
     if ptr.is_null() {
-        return Err(CommandError::Undefined.into());
+        return Err(Error::UnexpectedError);
     }
     unsafe {
         let s = owned_str_from_ptr(ptr);
@@ -65,7 +65,7 @@ pub fn get_last_result() -> Result<(), Error> {
 
 pub fn get_last_error() -> Error {
     return match get_last_result() {
-        Ok(()) => CommandError::Undefined.into(),
+        Ok(()) => Error::UnexpectedError,
         Err(err) => err,
     };
 }