From 694649543d0c376c0cb1d8d5ff2d34808cb6d0db Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=BCdiger=20Klaehn?= <rklaehn@gmail.com>
Date: Thu, 20 Feb 2020 09:21:07 +0100
Subject: [PATCH 1/3] Add ordering for Multihash and MultihashRef

This is just lexicographical byte ordering, which should be very fast
in case of multihashes since they usually differ within the first 8 byte
word.

Ordering is useful to have if you e.g. want to output a set of multihashes
in a deterministic way for debugging/testing purposes.

Also, many possible storage engines work using lexicographical byte ordering.
---
 src/lib.rs | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 9b2fc43c..e683ef6d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -22,7 +22,7 @@ use unsigned_varint::{decode, encode};
 
 pub use errors::{DecodeError, DecodeOwnedError, EncodeError};
 pub use hashes::Hash;
-use std::fmt;
+use std::{cmp, fmt};
 use storage::Storage;
 
 // Helper macro for encoding input into output using sha1, sha2, tiny_keccak, or blake2
@@ -246,8 +246,14 @@ impl TryFrom<Vec<u8>> for Multihash {
     }
 }
 
+impl PartialOrd for Multihash {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        Some(self.as_ref().cmp(&other.as_ref()))
+    }
+}
+
 /// Represents a valid multihash.
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Ord, Hash)]
 pub struct MultihashRef<'a> {
     bytes: &'a [u8],
 }
@@ -325,6 +331,12 @@ impl<'a> PartialEq<Multihash> for MultihashRef<'a> {
     }
 }
 
+impl<'a> PartialOrd for MultihashRef<'a> {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        Some(self.as_bytes().cmp(other.as_bytes()))
+    }
+}
+
 #[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
 fn as_u64(a: usize) -> u64 {
     a as u64

From 3016ac142676e9e0a0df1e405afebf1eeb7e4e7d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=BCdiger=20Klaehn?= <rklaehn@gmail.com>
Date: Fri, 21 Feb 2020 13:34:59 +0100
Subject: [PATCH 2/3] Derive the PartialOrd

no need for an explicit instance
---
 src/lib.rs | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index e683ef6d..616e2ac5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -253,7 +253,7 @@ impl PartialOrd for Multihash {
 }
 
 /// Represents a valid multihash.
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Ord, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct MultihashRef<'a> {
     bytes: &'a [u8],
 }
@@ -331,12 +331,6 @@ impl<'a> PartialEq<Multihash> for MultihashRef<'a> {
     }
 }
 
-impl<'a> PartialOrd for MultihashRef<'a> {
-    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
-        Some(self.as_bytes().cmp(other.as_bytes()))
-    }
-}
-
 #[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
 fn as_u64(a: usize) -> u64 {
     a as u64

From a61db7963b6603d2ee50ed699243a99a33c5036b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=BCdiger=20Klaehn?= <rklaehn@gmail.com>
Date: Fri, 21 Feb 2020 13:44:53 +0100
Subject: [PATCH 3/3] Actually add Ord for Multihash...

---
 src/lib.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index 616e2ac5..2a6e7289 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -248,7 +248,13 @@ impl TryFrom<Vec<u8>> for Multihash {
 
 impl PartialOrd for Multihash {
     fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
-        Some(self.as_ref().cmp(&other.as_ref()))
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for Multihash {
+    fn cmp(&self, other: &Self) -> cmp::Ordering {
+        self.as_ref().cmp(&other.as_ref())
     }
 }