Add ConcurrentAccessError and PoisonError variants

This patch prepares the refactoring of the connection methods by
introducing the Error variants ConcurrentAccessError and PoisonError.
ConcurrentAccessError indicates that the user tried to connect to
obtain a token that is currently locked, and PoisonError indicates that
a lock has been poisoned, i. e. a thread panicked while accessing using
a token.

2 files changed, 28 insertions, 2 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7623a33..046b609 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -41,6 +41,8 @@ SPDX-License-Identifier: MIT
 - Update the `nitrokey-sys` dependency to version 3.5.0.
 - Update the `nitrokey-test` dependency to version 0.2.1 and add the
   `nitrokey-test-state` dependency in version 0.1.0.
+- Refactor connection management:
+  - Add `ConcurrentAccessError` and `PoisonError` `Error` variants.
 
 # 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 1730171..c6b19db 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -5,6 +5,7 @@ use std::error;
 use std::fmt;
 use std::os::raw;
 use std::str;
+use std::sync;
 
 use crate::device;
 
@@ -13,11 +14,15 @@ use crate::device;
 pub enum Error {
     /// An error reported by the Nitrokey device in the response packet.
     CommandError(CommandError),
-    /// A device communication.
+    /// A device communication error.
     CommunicationError(CommunicationError),
+    /// An error occurred due to concurrent access to the Nitrokey device.
+    ConcurrentAccessError,
     /// A library usage error.
     LibraryError(LibraryError),
-    /// An error that occured during random number generation.
+    /// An error that occurred due to a poisoned lock.
+    PoisonError,
+    /// An error that occurred during random number generation.
     RandError(Box<dyn error::Error>),
     /// An error that is caused by an unexpected value returned by libnitrokey.
     UnexpectedError,
@@ -65,6 +70,21 @@ impl From<str::Utf8Error> for Error {
     }
 }
 
+impl<T> From<sync::PoisonError<T>> for Error {
+    fn from(_error: sync::PoisonError<T>) -> Self {
+        Error::PoisonError
+    }
+}
+
+impl<T> From<sync::TryLockError<T>> for Error {
+    fn from(error: sync::TryLockError<T>) -> Self {
+        match error {
+            sync::TryLockError::Poisoned(err) => err.into(),
+            sync::TryLockError::WouldBlock => Error::ConcurrentAccessError,
+        }
+    }
+}
+
 impl<T: device::Device> From<(T, Error)> for Error {
     fn from((_, err): (T, Error)) -> Self {
         err
@@ -76,7 +96,9 @@ impl error::Error for Error {
         match *self {
             Error::CommandError(ref err) => Some(err),
             Error::CommunicationError(ref err) => Some(err),
+            Error::ConcurrentAccessError => None,
             Error::LibraryError(ref err) => Some(err),
+            Error::PoisonError => None,
             Error::RandError(ref err) => Some(err.as_ref()),
             Error::UnexpectedError => None,
             Error::UnknownError(_) => None,
@@ -90,7 +112,9 @@ impl fmt::Display for Error {
         match *self {
             Error::CommandError(ref err) => write!(f, "Command error: {}", err),
             Error::CommunicationError(ref err) => write!(f, "Communication error: {}", err),
+            Error::ConcurrentAccessError => write!(f, "Internal error: concurrent access"),
             Error::LibraryError(ref err) => write!(f, "Library error: {}", err),
+            Error::PoisonError => write!(f, "Internal error: poisoned lock"),
             Error::RandError(ref err) => write!(f, "RNG error: {}", err),
             Error::UnexpectedError => write!(f, "An unexpected error occurred"),
             Error::UnknownError(ref err) => write!(f, "Unknown error: {}", err),