impl partial ord/ord for PublicKey

src/util/key.rs

@@ -17,7 +17,7 @@
 //!
 
 use std::fmt::{self, Write};
-use std::{io, ops, error};
+use std::{cmp, io, ops, error};
 use std::str::FromStr;
 
 use secp256k1::{self, Secp256k1};
@@ -69,14 +69,36 @@ impl From<secp256k1::Error> for Error {
 }
 
 /// A Bitcoin ECDSA public key
-#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub struct PublicKey {
     /// Whether this public key should be serialized as compressed
     pub compressed: bool,
     /// The actual ECDSA key
     pub key: secp256k1::PublicKey,
 }
 
+impl Ord for PublicKey{
+
+    // implement lexical partial ord for PublicKey as per BIP 67 if both keys are
+    // compressed/uncompressed. Since, compressed Pk's start with 0x02 and 0x03
+    // they are always less than the 0x04 uncompressed keys
+    fn cmp(&self, other: &PublicKey) -> cmp::Ordering {
+        match (self.compressed, other.compressed){
+            (true, false) => cmp::Ordering::Less,
+            (false, true) => cmp::Ordering::Greater,
+            (true, true) => self.key.serialize().cmp(&other.key.serialize()),
+            (false, false) => self.key.serialize_uncompressed().cmp(&other.key.serialize_uncompressed()),
+        }
+    }
+}
+
+impl PartialOrd for PublicKey{
+
+    fn partial_cmp(&self, other: &PublicKey) -> Option<cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
 impl PublicKey {
     /// Returns bitcoin 160-bit hash of the public key
     pub fn pubkey_hash(&self) -> PubkeyHash {