openpgp: Add a function to compare the public bits of two Keys

  - This is made available as Key::public_cmp and not as an
    implementation of Ord::cmp, because Ord::cmp, should it be
    implemented, should also compare the private bits.

1 files changed, 29 insertions, 0 deletions

diff --git a/openpgp/src/packet/key.rs b/openpgp/src/packet/key.rs
index c5a9e663..f31d58aa 100644
--- a/openpgp/src/packet/key.rs
+++ b/openpgp/src/packet/key.rs
@@ -1,6 +1,8 @@
 //! Public key, public subkey, private key and private subkey packets.
 
 use std::fmt;
+use std::mem;
+use std::cmp::Ordering;
 use time;
 
 use Error;
@@ -57,6 +59,33 @@ impl fmt::Display for Key {
 }
 
 impl Key {
+    /// Compares the public bits of two keys.
+    ///
+    /// This returns Ordering::Equal if the public MPIs, version,
+    /// creation time and algorithm of the two `Key`s match.  This
+    /// does not consider the packet's encoding, packet's tag or the
+    /// secret key material.
+    pub fn public_cmp(a: &Self, b: &Self) -> Ordering {
+        match a.mpis.cmp(&b.mpis) {
+            Ordering::Equal => (),
+            o => return o,
+        }
+
+        match a.version.cmp(&b.version) {
+            Ordering::Equal => (),
+            o => return o,
+        }
+
+        match a.creation_time.cmp(&b.creation_time) {
+            Ordering::Equal => (),
+            o => return o,
+        }
+
+        a.pk_algo.cmp(&b.pk_algo)
+    }
+}
+
+impl Key {
     pub(crate) fn new_(creation_time: time::Tm,pk_algo: PublicKeyAlgorithm,
                        mpis: mpis::PublicKey, secret: Option<SecretKey>)
                        -> Result<Key>