Use expect for concensus_encode on engines

Calls to `unwrap` outside of tests are typically unfavourable.

Hash engines do not error when calling `consensus_encode`. Instead of
the current usage of `unwrap` we can use `expect` with a descriptive
string as is done in other parts of the codebase.

src/blockdata/block.rs

@@ -215,7 +215,7 @@ impl Block {
     /// compute witness commitment for the transaction list
     pub fn compute_witness_commitment (witness_root: &WitnessMerkleNode, witness_reserved_value: &[u8]) -> WitnessCommitment {
         let mut encoder = WitnessCommitment::engine();
-        witness_root.consensus_encode(&mut encoder).unwrap();
+        witness_root.consensus_encode(&mut encoder).expect("engines don't error");
         encoder.input(witness_reserved_value);
         WitnessCommitment::from_engine(encoder)
     }

src/blockdata/transaction.rs

@@ -292,10 +292,10 @@ impl Transaction {
     /// will also hash witnesses.
     pub fn txid(&self) -> Txid {
         let mut enc = Txid::engine();
-        self.version.consensus_encode(&mut enc).unwrap();
-        self.input.consensus_encode(&mut enc).unwrap();
-        self.output.consensus_encode(&mut enc).unwrap();
-        self.lock_time.consensus_encode(&mut enc).unwrap();
+        self.version.consensus_encode(&mut enc).expect("engines don't error");
+        self.input.consensus_encode(&mut enc).expect("engines don't error");
+        self.output.consensus_encode(&mut enc).expect("engines don't error");
+        self.lock_time.consensus_encode(&mut enc).expect("engines don't error");
         Txid::from_engine(enc)
     }
 
@@ -304,7 +304,7 @@ impl Transaction {
     /// value returned by txid() function.
     pub fn wtxid(&self) -> Wtxid {
         let mut enc = Wtxid::engine();
-        self.consensus_encode(&mut enc).unwrap();
+        self.consensus_encode(&mut enc).expect("engines don't error");
         Wtxid::from_engine(enc)
     }
 

src/util/bip143.rs

@@ -56,7 +56,7 @@ impl SighashComponents {
         let hash_prevouts = {
             let mut enc = SigHash::engine();
             for txin in &tx.input {
-                txin.previous_output.consensus_encode(&mut enc).unwrap();
+                txin.previous_output.consensus_encode(&mut enc).expect("engines don't error");
             }
             SigHash::from_engine(enc)
         };
@@ -64,7 +64,7 @@ impl SighashComponents {
         let hash_sequence = {
             let mut enc = SigHash::engine();
             for txin in &tx.input {
-                txin.sequence.consensus_encode(&mut enc).unwrap();
+                txin.sequence.consensus_encode(&mut enc).expect("engines don't error");
             }
             SigHash::from_engine(enc)
         };
@@ -72,7 +72,7 @@ impl SighashComponents {
         let hash_outputs = {
             let mut enc = SigHash::engine();
             for txout in &tx.output {
-                txout.consensus_encode(&mut enc).unwrap();
+                txout.consensus_encode(&mut enc).expect("engines don't error");
             }
             SigHash::from_engine(enc)
         };
@@ -90,19 +90,19 @@ impl SighashComponents {
     /// input.
     pub fn sighash_all(&self, txin: &TxIn, script_code: &Script, value: u64) -> SigHash {
         let mut enc = SigHash::engine();
-        self.tx_version.consensus_encode(&mut enc).unwrap();
-        self.hash_prevouts.consensus_encode(&mut enc).unwrap();
-        self.hash_sequence.consensus_encode(&mut enc).unwrap();
+        self.tx_version.consensus_encode(&mut enc).expect("engines don't error");
+        self.hash_prevouts.consensus_encode(&mut enc).expect("engines don't error");
+        self.hash_sequence.consensus_encode(&mut enc).expect("engines don't error");
         txin
             .previous_output
             .consensus_encode(&mut enc)
-            .unwrap();
-        script_code.consensus_encode(&mut enc).unwrap();
-        value.consensus_encode(&mut enc).unwrap();
-        txin.sequence.consensus_encode(&mut enc).unwrap();
-        self.hash_outputs.consensus_encode(&mut enc).unwrap();
-        self.tx_locktime.consensus_encode(&mut enc).unwrap();
-        1u32.consensus_encode(&mut enc).unwrap(); // hashtype
+            .expect("engines don't error");
+        script_code.consensus_encode(&mut enc).expect("engines don't error");
+        value.consensus_encode(&mut enc).expect("engines don't error");
+        txin.sequence.consensus_encode(&mut enc).expect("engines don't error");
+        self.hash_outputs.consensus_encode(&mut enc).expect("engines don't error");
+        self.tx_locktime.consensus_encode(&mut enc).expect("engines don't error");
+        1u32.consensus_encode(&mut enc).expect("engines don't error"); // hashtype
         SigHash::from_engine(enc)
     }
 }

src/util/merkleblock.rs

@@ -341,8 +341,8 @@ impl PartialMerkleTree {
     /// Helper method to produce SHA256D(left + right)
     fn parent_hash(left: TxMerkleNode, right: TxMerkleNode) -> TxMerkleNode {
         let mut encoder = TxMerkleNode::engine();
-        left.consensus_encode(&mut encoder).unwrap();
-        right.consensus_encode(&mut encoder).unwrap();
+        left.consensus_encode(&mut encoder).expect("engines don't error");
+        right.consensus_encode(&mut encoder).expect("engines don't error");
         TxMerkleNode::from_engine(encoder)
     }
 }

src/util/misc.rs

@@ -252,7 +252,7 @@ pub fn signed_msg_hash(msg: &str) -> sha256d::Hash {
     let mut engine = sha256d::Hash::engine();
     engine.input(BITCOIN_SIGNED_MSG_PREFIX);
     let msg_len = encode::VarInt(msg.len() as u64);
-    msg_len.consensus_encode(&mut engine).unwrap();
+    msg_len.consensus_encode(&mut engine).expect("engines don't error");
     engine.input(msg.as_bytes());
     sha256d::Hash::from_engine(engine)
 }