maintain switch_commit_hashes in the output pmmr (not used yet) (#583)

chain/src/sumtree.rs

@@ -100,7 +100,9 @@ impl SumTrees {
 				);
 				if let Some(hs) = output_pmmr.get(pos) {
 					let hashsum = HashSum::from_summable(
-						pos, &SumCommit{commit: commit.clone()});
+						pos,
+						&SumCommit::from_commit(&commit),
+					);
 					Ok(hs.hash == hashsum.hash)
 				} else {
 					Ok(false)
@@ -264,6 +266,12 @@ impl<'a> Extension<'a> {
 
 		for out in &b.outputs {
 			let commit = out.commitment();
+			let switch_commit_hash = out.switch_commit_hash();
+			let sum_commit = SumCommit {
+				commit,
+				switch_commit_hash,
+			};
+
 			if let Ok(pos) = self.get_output_pos(&commit) {
 				// we need to check whether the commitment is in the current MMR view
 				// as well as the index doesn't support rewind and is non-authoritative
@@ -271,7 +279,8 @@ impl<'a> Extension<'a> {
 				// note that this doesn't show the commitment *never* existed, just
 				// that this is not an existing unspent commitment right now
 				if let Some(c) = self.output_pmmr.get(pos) {
-					let hashsum = HashSum::from_summable(pos, &SumCommit{commit});
+					let hashsum = HashSum::from_summable(pos, &sum_commit);
+
 					// processing a new fork so we may get a position on the old
 					// fork that exists but matches a different node
 					// filtering that case out
@@ -282,11 +291,7 @@ impl<'a> Extension<'a> {
 			}
 			// push new outputs commitments in their MMR and save them in the index
 			let pos = self.output_pmmr
-				.push(
-					SumCommit {
-						commit: out.commitment(),
-					},
-				)
+				.push(sum_commit)
 				.map_err(&Error::SumTreeErr)?;
 
 			self.new_output_commits.insert(out.commitment(), pos);

core/src/core/transaction.rs

@@ -467,6 +467,11 @@ impl SwitchCommitHash {
 		}
 		SwitchCommitHash { hash: h }
 	}
+
+	/// Build an "zero" switch commitment hash
+	pub fn zero() -> SwitchCommitHash {
+		SwitchCommitHash { hash: [0; SWITCH_COMMIT_HASH_SIZE] }
+	}
 }
 
 /// Output for a transaction, defining the new ownership of coins that are being
@@ -571,6 +576,19 @@ impl Output {
 pub struct SumCommit {
 	/// Output commitment
 	pub commit: Commitment,
+	/// The corresponding "switch commit hash"
+	pub switch_commit_hash: SwitchCommitHash,
+}
+
+impl SumCommit {
+	/// For when we do not care about the switch_commit_hash
+	/// for example when comparing sum_commit hashes
+	pub fn from_commit(commit: &Commitment) -> SumCommit {
+		SumCommit {
+			commit: commit.clone(),
+			switch_commit_hash: SwitchCommitHash::zero(),
+		}
+	}
 }
 
 /// Outputs get summed through their commitments.
@@ -578,17 +596,23 @@ impl Summable for SumCommit {
 	type Sum = SumCommit;
 
 	fn sum(&self) -> SumCommit {
-		SumCommit { commit: self.commit.clone() }
+		SumCommit {
+			commit: self.commit.clone(),
+			switch_commit_hash: self.switch_commit_hash.clone(),
+		}
 	}
 
 	fn sum_len() -> usize {
-		secp::constants::PEDERSEN_COMMITMENT_SIZE
+		secp::constants::PEDERSEN_COMMITMENT_SIZE + SWITCH_COMMIT_HASH_SIZE
 	}
 }
 
 impl Writeable for SumCommit {
 	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ser::Error> {
 		self.commit.write(writer)?;
+		if writer.serialization_mode() == ser::SerializationMode::Full {
+			self.switch_commit_hash.write(writer)?;
+		}
 		Ok(())
 	}
 }
@@ -596,8 +620,12 @@ impl Writeable for SumCommit {
 impl Readable for SumCommit {
 	fn read(reader: &mut Reader) -> Result<SumCommit, ser::Error> {
 		let commit = Commitment::read(reader)?;
+		let switch_commit_hash = SwitchCommitHash::read(reader)?;
 
-		Ok(SumCommit { commit: commit })
+		Ok(SumCommit {
+			commit: commit,
+			switch_commit_hash: switch_commit_hash,
+		})
 	}
 }
 
@@ -616,7 +644,7 @@ impl ops::Add for SumCommit {
 			Ok(s) => s,
 			Err(_) => Commitment::from_vec(vec![1; 33]),
 		};
-		SumCommit { commit: sum }
+		SumCommit::from_commit(&sum)
 	}
 }