implement display trait for archive error and err code

libraries/libarchive/src/error.rs

@@ -1,3 +1,5 @@
+use std::error;
+use std::fmt;
 use archive;
 
 pub type ArchiveResult<T> = Result<T, ArchiveError>;
@@ -5,13 +7,39 @@ pub type ArchiveResult<T> = Result<T, ArchiveError>;
 #[derive(Debug)]
 pub struct ErrCode(i32);
 
+impl fmt::Display for ErrCode {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(fmt, "{}", self.0)
+    }
+}
+
 #[derive(Debug)]
 pub enum ArchiveError {
     Consumed,
-    Sys(ErrCode, String),
-    ReadFailure,
-    WriteFailure,
     HeaderPosition,
+    Sys(ErrCode, String),
+}
+
+impl error::Error for ArchiveError {
+    fn description(&self) -> &str {
+        match self {
+            &ArchiveError::Consumed => "Builder already consumed",
+            &ArchiveError::HeaderPosition => "Header position expected to be 0",
+            &ArchiveError::Sys(_, _) => "libarchive system error",
+        }
+    }
+}
+
+impl fmt::Display for ArchiveError {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            &ArchiveError::Consumed => write!(fmt, "Builder already consumed"),
+            &ArchiveError::HeaderPosition => write!(fmt, "Header position expected to be 0"),
+            &ArchiveError::Sys(ref code, ref msg) => {
+                write!(fmt, "{} (libarchive err_code={})", msg, code)
+            }
+        }
+    }
 }
 
 impl<'a> From<&'a archive::Handle> for ArchiveError {