From 66f22f7fb47197298702a0fefff17c81667b2739 Mon Sep 17 00:00:00 2001
From: Robin Krahl <robin.krahl@ireas.org>
Date: Thu, 7 Jun 2018 16:05:22 +0200
Subject: Implement std::fmt::Display for CommandError

The std::fmt::Display implementation provides a human-readable error
message for a CommandError.  It is intended to be used in error
messages displayed to the user.
---
 src/util.rs | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/util.rs b/src/util.rs
index 75de799..d764baa 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -3,6 +3,7 @@ use nitrokey_sys;
 use rand::{OsRng, Rng};
 use std;
 use std::ffi::{CStr, CString};
+use std::fmt;
 use std::os::raw::{c_char, c_int};
 
 /// Error types returned by Nitrokey device or by the library.
@@ -27,7 +28,7 @@ pub enum CommandError {
     NotSupported,
     /// This command is unknown.
     UnknownCommand,
-    /// AES decryptionfailed.
+    /// AES decryption failed.
     AesDecryptionFailed,
     /// An unknown error occured.
     Unknown,
@@ -114,6 +115,30 @@ pub fn get_cstring<T: Into<Vec<u8>>>(s: T) -> Result<CString, CommandError> {
     CString::new(s).or(Err(CommandError::InvalidString))
 }
 
+impl fmt::Display for CommandError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let msg = match *self {
+            CommandError::WrongCrc => "A packet with a wrong checksum has been sent or received",
+            CommandError::WrongSlot => "The given OTP slot does not exist",
+            CommandError::SlotNotProgrammed => "The given OTP slot is not programmed",
+            CommandError::WrongPassword => "The given password is wrong",
+            CommandError::NotAuthorized => {
+                "You are not authorized for this command or provided a wrong temporary password"
+            }
+            CommandError::Timestamp => "An error occured when getting or setting the time",
+            CommandError::NoName => "You did not provide a name for the OTP slot",
+            CommandError::NotSupported => "This command is not supported by this device",
+            CommandError::UnknownCommand => "This command is unknown",
+            CommandError::AesDecryptionFailed => "AES decryption failed",
+            CommandError::Unknown => "An unknown error occured",
+            CommandError::InvalidString => "You passed a string containing a null byte",
+            CommandError::InvalidSlot => "The given slot is invalid",
+            CommandError::RngError => "An error occured during random number generation",
+        };
+        write!(f, "{}", msg)
+    }
+}
+
 impl From<c_int> for CommandError {
     fn from(value: c_int) -> Self {
         match value {
-- 
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