From bc380163855cac465bf19c003709c46d048566c1 Mon Sep 17 00:00:00 2001
From: Merope Riddle <merope07@protonmail.com>
Date: Mon, 31 Oct 2016 22:17:53 +0000
Subject: [PATCH 1/6] core/ser: change serialization trait to use Result<(),
 Error> in place of Option<Error>

---
 core/src/core/block.rs       |  18 +++----
 core/src/core/transaction.rs |  30 +++++------
 core/src/macros.rs           |  15 +-----
 core/src/pow/mod.rs          |  20 +++----
 core/src/ser.rs              | 102 ++++++++++++++++++++++++-----------
 5 files changed, 104 insertions(+), 81 deletions(-)

diff --git a/core/src/core/block.rs b/core/src/core/block.rs
index e18013171..5d3ee716e 100644
--- a/core/src/core/block.rs
+++ b/core/src/core/block.rs
@@ -60,7 +60,7 @@ impl Default for BlockHeader {
 // Only Writeable implementation is required for hashing, which is part of
 // core. Readable is in the ser package.
 impl Writeable for BlockHeader {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		ser_multiwrite!(writer,
 		                [write_u64, self.height],
 		                [write_fixed_bytes, &self.previous],
@@ -70,10 +70,10 @@ impl Writeable for BlockHeader {
 		                [write_u64, self.total_fees]);
 		// make sure to not introduce any variable length data before the nonce to
 		// avoid complicating PoW
-		try_o!(writer.write_u64(self.nonce));
+		try!(writer.write_u64(self.nonce));
 		// cuckoo cycle of 42 nodes
 		for n in 0..42 {
-			try_o!(writer.write_u32(self.pow.0[n]));
+			try!(writer.write_u32(self.pow.0[n]));
 		}
 		writer.write_u64(self.td)
 	}
@@ -101,23 +101,23 @@ pub struct Block {
 /// Implementation of Writeable for a block, defines how to write the full
 /// block as binary.
 impl Writeable for Block {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
-		try_o!(self.header.write(writer));
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
+		try!(self.header.write(writer));
 
 		ser_multiwrite!(writer,
 		                [write_u64, self.inputs.len() as u64],
 		                [write_u64, self.outputs.len() as u64],
 		                [write_u64, self.proofs.len() as u64]);
 		for inp in &self.inputs {
-			try_o!(inp.write(writer));
+			try!(inp.write(writer));
 		}
 		for out in &self.outputs {
-			try_o!(out.write(writer));
+			try!(out.write(writer));
 		}
 		for proof in &self.proofs {
-			try_o!(proof.write(writer));
+			try!(proof.write(writer));
 		}
-		None
+		Ok(())
 	}
 }
 
diff --git a/core/src/core/transaction.rs b/core/src/core/transaction.rs
index 98566c83a..a250cb90e 100644
--- a/core/src/core/transaction.rs
+++ b/core/src/core/transaction.rs
@@ -39,8 +39,8 @@ pub struct TxProof {
 }
 
 impl Writeable for TxProof {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
-		try_o!(writer.write_fixed_bytes(&self.remainder));
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
+		try!(writer.write_fixed_bytes(&self.remainder));
 		writer.write_vec(&mut self.sig.clone())
 	}
 }
@@ -68,19 +68,19 @@ pub struct Transaction {
 /// Implementation of Writeable for a fully blinded transaction, defines how to
 /// write the transaction as binary.
 impl Writeable for Transaction {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		ser_multiwrite!(writer,
 		                [write_u64, self.fee],
 		                [write_vec, &mut self.zerosig.clone()],
 		                [write_u64, self.inputs.len() as u64],
 		                [write_u64, self.outputs.len() as u64]);
 		for inp in &self.inputs {
-			try_o!(inp.write(writer));
+			try!(inp.write(writer));
 		}
 		for out in &self.outputs {
-			try_o!(out.write(writer));
+			try!(out.write(writer));
 		}
-		None
+		Ok(())
 	}
 }
 
@@ -235,7 +235,7 @@ pub enum Input {
 /// Implementation of Writeable for a transaction Input, defines how to write
 /// an Input as binary.
 impl Writeable for Input {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		writer.write_fixed_bytes(&self.output_hash())
 	}
 }
@@ -302,8 +302,8 @@ pub enum Output {
 /// Implementation of Writeable for a transaction Output, defines how to write
 /// an Output as binary.
 impl Writeable for Output {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
-		try_o!(writer.write_fixed_bytes(&self.commitment().unwrap()));
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
+		try!(writer.write_fixed_bytes(&self.commitment().unwrap()));
 		writer.write_vec(&mut self.proof().unwrap().bytes().to_vec())
 	}
 }
@@ -407,9 +407,7 @@ mod test {
 		let tx = tx2i1o(secp, &mut rng);
 		let btx = tx.blind(&secp).unwrap();
 		let mut vec = Vec::new();
-		if let Some(e) = serialize(&mut vec, &btx) {
-			panic!(e);
-		}
+		serialize(&mut vec, &btx).expect("serialized failed");
 		assert!(vec.len() > 5320);
 		assert!(vec.len() < 5340);
 	}
@@ -422,9 +420,7 @@ mod test {
 		let tx = tx2i1o(secp, &mut rng);
 		let mut btx = tx.blind(&secp).unwrap();
 		let mut vec = Vec::new();
-		if let Some(e) = serialize(&mut vec, &btx) {
-			panic!(e);
-		}
+		serialize(&mut vec, &btx).expect("serialization failed");
 		// let mut dtx = Transaction::read(&mut BinReader { source: &mut &vec[..]
 		// }).unwrap();
 		let mut dtx: Transaction = deserialize(&mut &vec[..]).unwrap();
@@ -444,11 +440,11 @@ mod test {
 		let mut btx = tx.blind(&secp).unwrap();
 
 		let mut vec = Vec::new();
-		assert!(serialize(&mut vec, &btx).is_none());
+		assert!(serialize(&mut vec, &btx).is_ok());
 		let mut dtx: Transaction = deserialize(&mut &vec[..]).unwrap();
 
 		let mut vec2 = Vec::new();
-		assert!(serialize(&mut vec2, &btx).is_none());
+		assert!(serialize(&mut vec2, &btx).is_ok());
 		let mut dtx2: Transaction = deserialize(&mut &vec2[..]).unwrap();
 
 		assert_eq!(btx.hash(), dtx.hash());
diff --git a/core/src/macros.rs b/core/src/macros.rs
index 59d3017e4..0f13a999e 100644
--- a/core/src/macros.rs
+++ b/core/src/macros.rs
@@ -61,19 +61,6 @@ macro_rules! tee {
   }
 }
 
-/// Simple equivalent of try! but for an Option<Error>. Motivated mostly by the
-/// io package and our serialization as an alternative to silly Result<(),
-/// Error>.
-#[macro_export]
-macro_rules! try_o {
-  ($trying:expr) => {
-		let tried = $trying;
-		if let Some(_) = tried {
-			return tried;
-		}
-  }
-}
-
 #[macro_export]
 macro_rules! try_to_o {
   ($trying:expr) => {{
@@ -109,6 +96,6 @@ macro_rules! ser_multiread {
 #[macro_export]
 macro_rules! ser_multiwrite {
   ($wrtr:ident, $([ $write_call:ident, $val:expr ]),* ) => {
-    $( try_o!($wrtr.$write_call($val)) );*
+    $( try!($wrtr.$write_call($val)) );*
   }
 }
diff --git a/core/src/pow/mod.rs b/core/src/pow/mod.rs
index b06383aea..d17da511b 100644
--- a/core/src/pow/mod.rs
+++ b/core/src/pow/mod.rs
@@ -71,16 +71,16 @@ struct PowHeader {
 /// the data that gets hashed for PoW calculation. The nonce is written first
 /// to make incrementing from the serialized form trivial.
 impl Writeable for PowHeader {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
-		try_o!(writer.write_u64(self.nonce));
-		try_o!(writer.write_u64(self.height));
-		try_o!(writer.write_fixed_bytes(&self.previous));
-		try_o!(writer.write_i64(self.timestamp.to_timespec().sec));
-		try_o!(writer.write_fixed_bytes(&self.utxo_merkle));
-		try_o!(writer.write_fixed_bytes(&self.tx_merkle));
-		try_o!(writer.write_u64(self.total_fees));
-		try_o!(writer.write_u64(self.n_in));
-		try_o!(writer.write_u64(self.n_out));
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
+		try!(writer.write_u64(self.nonce));
+		try!(writer.write_u64(self.height));
+		try!(writer.write_fixed_bytes(&self.previous));
+		try!(writer.write_i64(self.timestamp.to_timespec().sec));
+		try!(writer.write_fixed_bytes(&self.utxo_merkle));
+		try!(writer.write_fixed_bytes(&self.tx_merkle));
+		try!(writer.write_u64(self.total_fees));
+		try!(writer.write_u64(self.n_in));
+		try!(writer.write_u64(self.n_out));
 		writer.write_u64(self.n_proofs)
 	}
 }
diff --git a/core/src/ser.rs b/core/src/ser.rs
index 99680c5f7..e1f5e4e3e 100644
--- a/core/src/ser.rs
+++ b/core/src/ser.rs
@@ -19,8 +19,8 @@
 //! To use it simply implement `Writeable` or `Readable` and then use the
 //! `serialize` or `deserialize` functions on them as appropriate.
 
-use std::io;
-use std::io::{Write, Read};
+use std::{error, fmt};
+use std::io::{self, Write, Read};
 use byteorder::{ReadBytesExt, WriteBytesExt, BigEndian};
 
 /// Possible errors deriving from serializing or deserializing.
@@ -33,12 +33,47 @@ pub enum Error {
 		expected: Vec<u8>,
 		received: Vec<u8>,
 	},
-  /// Data wasn't in a consumable format
-  CorruptedData,
+	/// Data wasn't in a consumable format
+	CorruptedData,
 	/// When asked to read too much data
 	TooLargeReadErr(String),
 }
 
+impl From<io::Error> for Error {
+	fn from(e: io::Error) -> Error {
+		Error::IOErr(e)
+	}
+}
+
+impl fmt::Display for Error {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			Error::IOErr(ref e) => write!(f, "{}", e),
+			Error::UnexpectedData { expected: ref e, received: ref r } => write!(f, "expected {:?}, got {:?}", e, r),
+			Error::CorruptedData => f.write_str("corrupted data"),
+			Error::TooLargeReadErr(ref s) => f.write_str(&s)
+		}
+	}
+}
+
+impl error::Error for Error {
+	fn cause(&self) -> Option<&error::Error> {
+		match *self {
+			Error::IOErr(ref e) => Some(e),
+			_ => None
+		}
+	}
+
+	fn description(&self) -> &str {
+		match *self {
+			Error::IOErr(ref e) => error::Error::description(e),
+			Error::UnexpectedData { expected: _, received: _ } => "unexpected data",
+			Error::CorruptedData => "corrupted data",
+			Error::TooLargeReadErr(ref s) => s
+		}
+	}
+}
+
 /// Useful trait to implement on types that can be translated to byte slices
 /// directly. Allows the use of `write_fixed_bytes` on them.
 pub trait AsFixedBytes {
@@ -50,21 +85,21 @@ pub trait AsFixedBytes {
 /// written to an underlying stream or container (depending on implementation).
 pub trait Writer {
 	/// Writes a u8 as bytes
-	fn write_u8(&mut self, n: u8) -> Option<Error>;
+	fn write_u8(&mut self, n: u8) -> Result<(), Error>;
 	/// Writes a u16 as bytes
-	fn write_u16(&mut self, n: u16) -> Option<Error>;
+	fn write_u16(&mut self, n: u16) -> Result<(), Error>;
 	/// Writes a u32 as bytes
-	fn write_u32(&mut self, n: u32) -> Option<Error>;
+	fn write_u32(&mut self, n: u32) -> Result<(), Error>;
 	/// Writes a u64 as bytes
-	fn write_u64(&mut self, n: u64) -> Option<Error>;
+	fn write_u64(&mut self, n: u64) -> Result<(), Error>;
 	/// Writes a i64 as bytes
-	fn write_i64(&mut self, n: i64) -> Option<Error>;
+	fn write_i64(&mut self, n: i64) -> Result<(), Error>;
 	/// Writes a variable length `Vec`, the length of the `Vec` is encoded as a
 	/// prefix.
-	fn write_vec(&mut self, vec: &mut Vec<u8>) -> Option<Error>;
+	fn write_vec(&mut self, vec: &mut Vec<u8>) -> Result<(), Error>;
 	/// Writes a fixed number of bytes from something that can turn itself into
 	/// a `&[u8]`. The reader is expected to know the actual length on read.
-	fn write_fixed_bytes(&mut self, b32: &AsFixedBytes) -> Option<Error>;
+	fn write_fixed_bytes(&mut self, b32: &AsFixedBytes) -> Result<(), Error>;
 }
 
 /// Implementations defined how different numbers and binary structures are
@@ -98,7 +133,7 @@ pub trait Reader {
 /// underlying Write implementation.
 pub trait Writeable {
 	/// Write the data held by this Writeable to the provided writer
-	fn write(&self, writer: &mut Writer) -> Option<Error>;
+	fn write(&self, writer: &mut Writer) -> Result<(), Error>;
 }
 
 /// Trait that every type that can be deserialized from binary must implement.
@@ -116,7 +151,7 @@ pub fn deserialize<T: Readable<T>>(mut source: &mut Read) -> Result<T, Error> {
 }
 
 /// Serializes a Writeable into any std::io::Write implementation.
-pub fn serialize(mut sink: &mut Write, thing: &Writeable) -> Option<Error> {
+pub fn serialize(mut sink: &mut Write, thing: &Writeable) -> Result<(), Error> {
 	let mut writer = BinWriter { sink: sink };
 	thing.write(&mut writer)
 }
@@ -125,9 +160,7 @@ pub fn serialize(mut sink: &mut Write, thing: &Writeable) -> Option<Error> {
 /// Vec<u8>.
 pub fn ser_vec(thing: &Writeable) -> Result<Vec<u8>, Error> {
 	let mut vec = Vec::new();
-	if let Some(err) = serialize(&mut vec, thing) {
-		return Err(err);
-	}
+	try!(serialize(&mut vec, thing));
 	Ok(vec)
 }
 
@@ -192,33 +225,40 @@ struct BinWriter<'a> {
 }
 
 impl<'a> Writer for BinWriter<'a> {
-	fn write_u8(&mut self, n: u8) -> Option<Error> {
-		self.sink.write_u8(n).err().map(Error::IOErr)
+	fn write_u8(&mut self, n: u8) -> Result<(), Error> {
+		try!(self.sink.write_u8(n));
+		Ok(())
 	}
-	fn write_u16(&mut self, n: u16) -> Option<Error> {
-		self.sink.write_u16::<BigEndian>(n).err().map(Error::IOErr)
+	fn write_u16(&mut self, n: u16) -> Result<(), Error> {
+		try!(self.sink.write_u16::<BigEndian>(n));
+		Ok(())
 	}
-	fn write_u32(&mut self, n: u32) -> Option<Error> {
-		self.sink.write_u32::<BigEndian>(n).err().map(Error::IOErr)
+	fn write_u32(&mut self, n: u32) -> Result<(), Error> {
+		try!(self.sink.write_u32::<BigEndian>(n));
+		Ok(())
 	}
 
-	fn write_u64(&mut self, n: u64) -> Option<Error> {
-		self.sink.write_u64::<BigEndian>(n).err().map(Error::IOErr)
+	fn write_u64(&mut self, n: u64) -> Result<(), Error> {
+		try!(self.sink.write_u64::<BigEndian>(n));
+		Ok(())
 	}
 
-	fn write_i64(&mut self, n: i64) -> Option<Error> {
-		self.sink.write_i64::<BigEndian>(n).err().map(Error::IOErr)
+	fn write_i64(&mut self, n: i64) -> Result<(), Error> {
+		try!(self.sink.write_i64::<BigEndian>(n));
+		Ok(())
 	}
 
 
-	fn write_vec(&mut self, vec: &mut Vec<u8>) -> Option<Error> {
-		try_o!(self.write_u64(vec.len() as u64));
-		self.sink.write_all(vec).err().map(Error::IOErr)
+	fn write_vec(&mut self, vec: &mut Vec<u8>) -> Result<(), Error> {
+		try!(self.write_u64(vec.len() as u64));
+		try!(self.sink.write_all(vec));
+		Ok(())
 	}
 
-	fn write_fixed_bytes(&mut self, b32: &AsFixedBytes) -> Option<Error> {
+	fn write_fixed_bytes(&mut self, b32: &AsFixedBytes) -> Result<(), Error> {
 		let bs = b32.as_fixed_bytes();
-		self.sink.write_all(bs).err().map(Error::IOErr)
+		try!(self.sink.write_all(bs));
+		Ok(())
 	}
 }
 

From 630c4eb6fb7b8d2b04809c2fd5ded06d2e53a87e Mon Sep 17 00:00:00 2001
From: Merope Riddle <merope07@protonmail.com>
Date: Mon, 31 Oct 2016 22:24:43 +0000
Subject: [PATCH 2/6] core/ser: replace `write_vec` with `write_bytes`, drop a
 bunch of clones

---
 core/src/core/transaction.rs | 6 +++---
 core/src/ser.rs              | 8 ++++----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/core/src/core/transaction.rs b/core/src/core/transaction.rs
index a250cb90e..5af9ccd79 100644
--- a/core/src/core/transaction.rs
+++ b/core/src/core/transaction.rs
@@ -41,7 +41,7 @@ pub struct TxProof {
 impl Writeable for TxProof {
 	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		try!(writer.write_fixed_bytes(&self.remainder));
-		writer.write_vec(&mut self.sig.clone())
+		writer.write_bytes(&self.sig)
 	}
 }
 
@@ -71,7 +71,7 @@ impl Writeable for Transaction {
 	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		ser_multiwrite!(writer,
 		                [write_u64, self.fee],
-		                [write_vec, &mut self.zerosig.clone()],
+		                [write_bytes, &self.zerosig],
 		                [write_u64, self.inputs.len() as u64],
 		                [write_u64, self.outputs.len() as u64]);
 		for inp in &self.inputs {
@@ -304,7 +304,7 @@ pub enum Output {
 impl Writeable for Output {
 	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		try!(writer.write_fixed_bytes(&self.commitment().unwrap()));
-		writer.write_vec(&mut self.proof().unwrap().bytes().to_vec())
+		writer.write_bytes(&mut self.proof().unwrap().bytes())
 	}
 }
 
diff --git a/core/src/ser.rs b/core/src/ser.rs
index e1f5e4e3e..a0e09c7a3 100644
--- a/core/src/ser.rs
+++ b/core/src/ser.rs
@@ -96,7 +96,7 @@ pub trait Writer {
 	fn write_i64(&mut self, n: i64) -> Result<(), Error>;
 	/// Writes a variable length `Vec`, the length of the `Vec` is encoded as a
 	/// prefix.
-	fn write_vec(&mut self, vec: &mut Vec<u8>) -> Result<(), Error>;
+	fn write_bytes(&mut self, data: &[u8]) -> Result<(), Error>;
 	/// Writes a fixed number of bytes from something that can turn itself into
 	/// a `&[u8]`. The reader is expected to know the actual length on read.
 	fn write_fixed_bytes(&mut self, b32: &AsFixedBytes) -> Result<(), Error>;
@@ -249,9 +249,9 @@ impl<'a> Writer for BinWriter<'a> {
 	}
 
 
-	fn write_vec(&mut self, vec: &mut Vec<u8>) -> Result<(), Error> {
-		try!(self.write_u64(vec.len() as u64));
-		try!(self.sink.write_all(vec));
+	fn write_bytes(&mut self, data: &[u8]) -> Result<(), Error> {
+		try!(self.write_u64(data.len() as u64));
+		try!(self.sink.write_all(data));
 		Ok(())
 	}
 

From 565374bac7dc4089c2f3d91fb7979e901ad885a6 Mon Sep 17 00:00:00 2001
From: Merope Riddle <merope07@protonmail.com>
Date: Tue, 1 Nov 2016 02:03:12 +0000
Subject: [PATCH 3/6] p2p: fix for changes in core serialization API

---
 p2p/src/handshake.rs | 38 +++++++++++++++-----------------------
 p2p/src/msg.rs       | 32 ++++++++++++++++----------------
 2 files changed, 31 insertions(+), 39 deletions(-)

diff --git a/p2p/src/handshake.rs b/p2p/src/handshake.rs
index 24305c8b4..0534d03e6 100644
--- a/p2p/src/handshake.rs
+++ b/p2p/src/handshake.rs
@@ -51,19 +51,15 @@ impl Handshake {
 		// send the first part of the handshake
 		let sender_addr = conn.local_addr().unwrap();
 		let receiver_addr = conn.peer_addr().unwrap();
-		let opt_err = serialize(&mut conn,
-		                        &Hand {
-			                        version: PROTOCOL_VERSION,
-			                        capabilities: FULL_SYNC,
-			                        nonce: nonce,
-			                        sender_addr: SockAddr(sender_addr),
-			                        receiver_addr: SockAddr(receiver_addr),
-			                        user_agent: USER_AGENT.to_string(),
-		                        });
-		match opt_err {
-			Some(err) => return Err(err),
-			None => {}
-		}
+		try!(serialize(&mut conn,
+		               &Hand {
+			               version: PROTOCOL_VERSION,
+			               capabilities: FULL_SYNC,
+			               nonce: nonce,
+			               sender_addr: SockAddr(sender_addr),
+			               receiver_addr: SockAddr(receiver_addr),
+			               user_agent: USER_AGENT.to_string(),
+		               }));
 
 		// deserialize the handshake response and do version negotiation
 		let shake = try!(deserialize::<Shake>(&mut conn));
@@ -127,16 +123,12 @@ impl Handshake {
 		};
 
 		// send our reply with our info
-		let opt_err = serialize(&mut conn,
-		                        &Shake {
-			                        version: PROTOCOL_VERSION,
-			                        capabilities: FULL_SYNC,
-			                        user_agent: USER_AGENT.to_string(),
-		                        });
-		match opt_err {
-			Some(err) => return Err(err),
-			None => {}
-		}
+		try!(serialize(&mut conn,
+		               &Shake {
+			               version: PROTOCOL_VERSION,
+			               capabilities: FULL_SYNC,
+			               user_agent: USER_AGENT.to_string(),
+		               }));
 
 		info!("Received connection from peer {:?}", peer_info);
 		// when more than one protocol version is supported, choosing should go here
diff --git a/p2p/src/msg.rs b/p2p/src/msg.rs
index f247eddcc..8921d7c0b 100644
--- a/p2p/src/msg.rs
+++ b/p2p/src/msg.rs
@@ -18,7 +18,7 @@ use std::net::*;
 
 use num::FromPrimitive;
 
-use core::ser::{self, Writeable, Readable, Writer, Reader, Error};
+use core::ser::{self, Writeable, Readable, Writer, Reader};
 
 use types::*;
 
@@ -72,12 +72,12 @@ impl MsgHeader {
 }
 
 impl Writeable for MsgHeader {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		ser_multiwrite!(writer,
 		                [write_u8, self.magic[0]],
 		                [write_u8, self.magic[1]],
 		                [write_u8, self.msg_type as u8]);
-		None
+		Ok(())
 	}
 }
 
@@ -111,14 +111,14 @@ pub struct Hand {
 }
 
 impl Writeable for Hand {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		ser_multiwrite!(writer,
 		                [write_u32, self.version],
 		                [write_u32, self.capabilities.bits()],
 		                [write_u64, self.nonce]);
 		self.sender_addr.write(writer);
 		self.receiver_addr.write(writer);
-		writer.write_vec(&mut self.user_agent.clone().into_bytes())
+		writer.write_bytes(self.user_agent.as_bytes())
 	}
 }
 
@@ -153,12 +153,12 @@ pub struct Shake {
 }
 
 impl Writeable for Shake {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		ser_multiwrite!(writer,
 		                [write_u32, self.version],
 		                [write_u32, self.capabilities.bits()],
-		                [write_vec, &mut self.user_agent.as_bytes().to_vec()]);
-		None
+		                [write_bytes, self.user_agent.as_bytes()]);
+		Ok(())
 	}
 }
 
@@ -233,11 +233,11 @@ pub struct PeerError {
 }
 
 impl Writeable for PeerError {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		ser_multiwrite!(writer,
 		                [write_u32, self.code],
-		                [write_vec, &mut self.message.clone().into_bytes()]);
-		None
+		                [write_bytes, self.message.as_bytes()]);
+		Ok(())
 	}
 }
 
@@ -258,7 +258,7 @@ impl Readable<PeerError> for PeerError {
 pub struct SockAddr(pub SocketAddr);
 
 impl Writeable for SockAddr {
-	fn write(&self, writer: &mut Writer) -> Option<ser::Error> {
+	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		match self.0 {
 			SocketAddr::V4(sav4) => {
 				ser_multiwrite!(writer,
@@ -267,14 +267,14 @@ impl Writeable for SockAddr {
 				                [write_u16, sav4.port()]);
 			}
 			SocketAddr::V6(sav6) => {
-				try_o!(writer.write_u8(1));
+				try!(writer.write_u8(1));
 				for seg in &sav6.ip().segments() {
-					try_o!(writer.write_u16(*seg));
+					try!(writer.write_u16(*seg));
 				}
-				try_o!(writer.write_u16(sav6.port()));
+				try!(writer.write_u16(sav6.port()));
 			}
 		}
-		None
+		Ok(())
 	}
 }
 

From 245f0a8b565f3f40c79c550d9cc931506efb9f34 Mon Sep 17 00:00:00 2001
From: Merope Riddle <merope07@protonmail.com>
Date: Tue, 1 Nov 2016 13:14:26 +0000
Subject: [PATCH 4/6] core/ser: add default implementations for most methods of
 `Writer`

---
 core/src/core/transaction.rs |  2 +-
 core/src/ser.rs              | 89 +++++++++++++++++++-----------------
 2 files changed, 49 insertions(+), 42 deletions(-)

diff --git a/core/src/core/transaction.rs b/core/src/core/transaction.rs
index 5af9ccd79..6884cc858 100644
--- a/core/src/core/transaction.rs
+++ b/core/src/core/transaction.rs
@@ -304,7 +304,7 @@ pub enum Output {
 impl Writeable for Output {
 	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
 		try!(writer.write_fixed_bytes(&self.commitment().unwrap()));
-		writer.write_bytes(&mut self.proof().unwrap().bytes())
+		writer.write_bytes(&self.proof().unwrap().bytes())
 	}
 }
 
diff --git a/core/src/ser.rs b/core/src/ser.rs
index a0e09c7a3..4ffd516ed 100644
--- a/core/src/ser.rs
+++ b/core/src/ser.rs
@@ -21,7 +21,7 @@
 
 use std::{error, fmt};
 use std::io::{self, Write, Read};
-use byteorder::{ReadBytesExt, WriteBytesExt, BigEndian};
+use byteorder::{ByteOrder, ReadBytesExt, BigEndian};
 
 /// Possible errors deriving from serializing or deserializing.
 #[derive(Debug)]
@@ -85,21 +85,48 @@ pub trait AsFixedBytes {
 /// written to an underlying stream or container (depending on implementation).
 pub trait Writer {
 	/// Writes a u8 as bytes
-	fn write_u8(&mut self, n: u8) -> Result<(), Error>;
+	fn write_u8(&mut self, n: u8) -> Result<(), Error> {
+		self.write_fixed_bytes(&[n])
+	}
+
 	/// Writes a u16 as bytes
-	fn write_u16(&mut self, n: u16) -> Result<(), Error>;
+	fn write_u16(&mut self, n: u16) -> Result<(), Error> {
+		let mut bytes = [0; 2];
+		BigEndian::write_u16(&mut bytes, n);
+		self.write_fixed_bytes(&bytes)
+	}
+
 	/// Writes a u32 as bytes
-	fn write_u32(&mut self, n: u32) -> Result<(), Error>;
+	fn write_u32(&mut self, n: u32) -> Result<(), Error> {
+		let mut bytes = [0; 4];
+		BigEndian::write_u32(&mut bytes, n);
+		self.write_fixed_bytes(&bytes)
+	}
+
 	/// Writes a u64 as bytes
-	fn write_u64(&mut self, n: u64) -> Result<(), Error>;
+	fn write_u64(&mut self, n: u64) -> Result<(), Error> {
+		let mut bytes = [0; 8];
+		BigEndian::write_u64(&mut bytes, n);
+		self.write_fixed_bytes(&bytes)
+	}
+
 	/// Writes a i64 as bytes
-	fn write_i64(&mut self, n: i64) -> Result<(), Error>;
-	/// Writes a variable length `Vec`, the length of the `Vec` is encoded as a
+	fn write_i64(&mut self, n: i64) -> Result<(), Error> {
+		let mut bytes = [0; 8];
+		BigEndian::write_i64(&mut bytes, n);
+		self.write_fixed_bytes(&bytes)
+	}
+
+	/// Writes a variable number of bytes. The length is encoded as a 64-bit
 	/// prefix.
-	fn write_bytes(&mut self, data: &[u8]) -> Result<(), Error>;
+	fn write_bytes(&mut self, bytes: &AsFixedBytes) -> Result<(), Error> {
+		try!(self.write_u64(bytes.as_fixed_bytes().len() as u64));
+		self.write_fixed_bytes(bytes)
+	}
+
 	/// Writes a fixed number of bytes from something that can turn itself into
 	/// a `&[u8]`. The reader is expected to know the actual length on read.
-	fn write_fixed_bytes(&mut self, b32: &AsFixedBytes) -> Result<(), Error>;
+	fn write_fixed_bytes(&mut self, fixed: &AsFixedBytes) -> Result<(), Error>;
 }
 
 /// Implementations defined how different numbers and binary structures are
@@ -225,38 +252,8 @@ struct BinWriter<'a> {
 }
 
 impl<'a> Writer for BinWriter<'a> {
-	fn write_u8(&mut self, n: u8) -> Result<(), Error> {
-		try!(self.sink.write_u8(n));
-		Ok(())
-	}
-	fn write_u16(&mut self, n: u16) -> Result<(), Error> {
-		try!(self.sink.write_u16::<BigEndian>(n));
-		Ok(())
-	}
-	fn write_u32(&mut self, n: u32) -> Result<(), Error> {
-		try!(self.sink.write_u32::<BigEndian>(n));
-		Ok(())
-	}
-
-	fn write_u64(&mut self, n: u64) -> Result<(), Error> {
-		try!(self.sink.write_u64::<BigEndian>(n));
-		Ok(())
-	}
-
-	fn write_i64(&mut self, n: i64) -> Result<(), Error> {
-		try!(self.sink.write_i64::<BigEndian>(n));
-		Ok(())
-	}
-
-
-	fn write_bytes(&mut self, data: &[u8]) -> Result<(), Error> {
-		try!(self.write_u64(data.len() as u64));
-		try!(self.sink.write_all(data));
-		Ok(())
-	}
-
-	fn write_fixed_bytes(&mut self, b32: &AsFixedBytes) -> Result<(), Error> {
-		let bs = b32.as_fixed_bytes();
+	fn write_fixed_bytes(&mut self, fixed: &AsFixedBytes) -> Result<(), Error> {
+		let bs = fixed.as_fixed_bytes();
 		try!(self.sink.write_all(bs));
 		Ok(())
 	}
@@ -276,6 +273,16 @@ impl_slice_bytes!(::secp::key::SecretKey);
 impl_slice_bytes!(::secp::Signature);
 impl_slice_bytes!(::secp::pedersen::Commitment);
 impl_slice_bytes!(Vec<u8>);
+impl_slice_bytes!([u8; 1]);
+impl_slice_bytes!([u8; 2]);
+impl_slice_bytes!([u8; 4]);
+impl_slice_bytes!([u8; 8]);
+
+impl<'a> AsFixedBytes for &'a [u8] {
+	fn as_fixed_bytes(&self) -> &[u8] {
+		*self
+	}
+}
 
 impl AsFixedBytes for ::core::hash::Hash {
 	fn as_fixed_bytes(&self) -> &[u8] {

From ca89dae7e1206fbb097a563f486818dd513ddf95 Mon Sep 17 00:00:00 2001
From: Merope Riddle <merope07@protonmail.com>
Date: Tue, 1 Nov 2016 01:37:06 +0000
Subject: [PATCH 5/6] core: unify Hashed and Writeable to simplify things and
 remove allocations

---
 core/src/core/block.rs       |  9 +----
 core/src/core/hash.rs        | 69 ++++++++++++++++++++++++++----------
 core/src/core/mod.rs         | 12 +++----
 core/src/core/transaction.rs | 40 +++++++--------------
 core/src/pow/mod.rs          |  7 ----
 core/src/ser.rs              | 19 ++++++++++
 6 files changed, 90 insertions(+), 66 deletions(-)

diff --git a/core/src/core/block.rs b/core/src/core/block.rs
index 5d3ee716e..3985705e0 100644
--- a/core/src/core/block.rs
+++ b/core/src/core/block.rs
@@ -26,7 +26,7 @@ use core::transaction::merkle_inputs_outputs;
 use core::{PROOFSIZE, REWARD};
 use core::hash::{Hash, Hashed, ZERO_HASH};
 use core::transaction::MAX_IN_OUT_LEN;
-use ser::{self, Readable, Reader, Writeable, Writer, ser_vec};
+use ser::{self, Readable, Reader, Writeable, Writer};
 
 /// Block header, fairly standard compared to other blockchains.
 pub struct BlockHeader {
@@ -79,13 +79,6 @@ impl Writeable for BlockHeader {
 	}
 }
 
-impl Hashed for BlockHeader {
-	fn bytes(&self) -> Vec<u8> {
-		// no serialization errors are applicable in this specific case
-		ser_vec(self).unwrap()
-	}
-}
-
 /// A block as expressed in the MimbleWimble protocol. The reward is
 /// non-explicit, assumed to be deductible from block height (similar to
 /// bitcoin's schedule) and expressed as a global transaction fee (added v.H),
diff --git a/core/src/core/hash.rs b/core/src/core/hash.rs
index ad3328ec6..543b6ddfa 100644
--- a/core/src/core/hash.rs
+++ b/core/src/core/hash.rs
@@ -17,10 +17,12 @@
 //! Primary hash function used in the protocol
 //!
 
+use byteorder::{ByteOrder, WriteBytesExt, BigEndian};
 use std::fmt;
-
 use tiny_keccak::Keccak;
 
+use ser::{self, AsFixedBytes};
+
 /// A hash to uniquely (or close enough) identify one of the main blockchain
 /// constructs. Used pervasively for blocks, transactions and ouputs.
 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
@@ -56,27 +58,58 @@ impl Hash {
 
 pub const ZERO_HASH: Hash = Hash([0; 32]);
 
-/// A trait for types that get their hash (double SHA256) from their byte
-/// serialzation.
-pub trait Hashed {
-	fn hash(&self) -> Hash {
-		let data = self.bytes();
-		Hash(sha3(data))
-	}
-
-	fn bytes(&self) -> Vec<u8>;
+/// Serializer that outputs a hash of the serialized object
+pub struct HashWriter {
+	state: Keccak
 }
 
-fn sha3(data: Vec<u8>) -> [u8; 32] {
-	let mut sha3 = Keccak::new_sha3_256();
-	let mut buf = [0; 32];
-	sha3.update(&data);
-	sha3.finalize(&mut buf);
-	buf
+impl HashWriter {
+	fn finalize(self, output: &mut [u8]) {
+		self.state.finalize(output);
+	}
+}
+
+impl Default for HashWriter {
+	fn default() -> HashWriter {
+		HashWriter {
+			state: Keccak::new_sha3_256()
+		}
+	}
+}
+
+impl ser::Writer for HashWriter {
+	fn serialization_mode(&self) -> ser::SerializationMode {
+		ser::SerializationMode::Hash
+	}
+
+	fn write_fixed_bytes(&mut self, b32: &AsFixedBytes) -> Result<(), ser::Error> {
+		self.state.update(b32.as_fixed_bytes());
+		Ok(())
+	}
+}
+
+/// A trait for types that have a canonical hash
+pub trait Hashed {
+       fn hash(&self) -> Hash;
+}
+
+impl<W: ser::Writeable> Hashed for W {
+	fn hash(&self) -> Hash {
+		let mut hasher = HashWriter::default();
+		ser::Writeable::write(self, &mut hasher).unwrap();
+		let mut ret = [0; 32];
+		hasher.finalize(&mut ret);
+		Hash(ret)
+	}
 }
 
 impl Hashed for [u8] {
-	fn bytes(&self) -> Vec<u8> {
-		self.to_owned()
+	fn hash(&self) -> Hash {
+		let mut hasher = HashWriter::default();
+		let mut ret = [0; 32];
+		ser::Writer::write_bytes(&mut hasher, &self).unwrap();
+		hasher.finalize(&mut ret);
+		Hash(ret)
 	}
 }
+
diff --git a/core/src/core/mod.rs b/core/src/core/mod.rs
index 1095c70aa..d1472eed7 100644
--- a/core/src/core/mod.rs
+++ b/core/src/core/mod.rs
@@ -154,12 +154,12 @@ impl Proof {
 /// Two hashes that will get hashed together in a Merkle tree to build the next
 /// level up.
 struct HPair(Hash, Hash);
-impl Hashed for HPair {
-	fn bytes(&self) -> Vec<u8> {
-		let mut data = Vec::with_capacity(64);
-		data.extend_from_slice(self.0.to_slice());
-		data.extend_from_slice(self.1.to_slice());
-		return data;
+
+impl Writeable for HPair {
+	fn write(&self, writer: &mut Writer) -> Result<(), Error> {
+		try!(writer.write_bytes(&self.0.to_slice()));
+		try!(writer.write_bytes(&self.1.to_slice()));
+		Ok(())
 	}
 }
 /// An iterator over hashes in a vector that pairs them to build a row in a
diff --git a/core/src/core/transaction.rs b/core/src/core/transaction.rs
index 6884cc858..d1d6bcc02 100644
--- a/core/src/core/transaction.rs
+++ b/core/src/core/transaction.rs
@@ -16,7 +16,7 @@
 
 use core::Committed;
 use core::MerkleRow;
-use core::hash::{Hashed, Hash};
+use core::hash::{Hash, Hashed};
 use ser::{self, Reader, Writer, Readable, Writeable};
 
 use secp::{self, Secp256k1, Message, Signature};
@@ -283,13 +283,6 @@ impl Input {
 	}
 }
 
-/// The hash of an input is the hash of the output hash it references.
-impl Hashed for Input {
-	fn bytes(&self) -> Vec<u8> {
-		self.output_hash().to_vec()
-	}
-}
-
 #[derive(Debug, Copy, Clone)]
 pub enum Output {
 	BlindOutput {
@@ -303,8 +296,12 @@ pub enum Output {
 /// an Output as binary.
 impl Writeable for Output {
 	fn write(&self, writer: &mut Writer) -> Result<(), ser::Error> {
+		// The hash of an output is only the hash of its commitment.
 		try!(writer.write_fixed_bytes(&self.commitment().unwrap()));
-		writer.write_bytes(&self.proof().unwrap().bytes())
+		if writer.serialization_mode() == ser::SerializationMode::Full {
+			try!(writer.write_bytes(&self.proof().unwrap().bytes()))
+		}
+		Ok(())
 	}
 }
 
@@ -363,17 +360,6 @@ impl Output {
 	}
 }
 
-/// The hash of an output is the hash of its commitment.
-impl Hashed for Output {
-	fn bytes(&self) -> Vec<u8> {
-		if let &Output::BlindOutput { commit, .. } = self {
-			return commit.bytes().to_vec();
-		} else {
-			panic!("cannot hash an overt output");
-		}
-	}
-}
-
 /// Utility function to calculate the Merkle root of vectors of inputs and
 /// outputs.
 pub fn merkle_inputs_outputs(inputs: &Vec<Input>, outputs: &Vec<Output>) -> Hash {
@@ -418,12 +404,12 @@ mod test {
 		let ref secp = new_secp();
 
 		let tx = tx2i1o(secp, &mut rng);
-		let mut btx = tx.blind(&secp).unwrap();
+		let btx = tx.blind(&secp).unwrap();
 		let mut vec = Vec::new();
 		serialize(&mut vec, &btx).expect("serialization failed");
 		// let mut dtx = Transaction::read(&mut BinReader { source: &mut &vec[..]
 		// }).unwrap();
-		let mut dtx: Transaction = deserialize(&mut &vec[..]).unwrap();
+		let dtx: Transaction = deserialize(&mut &vec[..]).unwrap();
 		assert_eq!(dtx.fee, 1);
 		assert_eq!(dtx.inputs.len(), 2);
 		assert_eq!(dtx.outputs.len(), 1);
@@ -437,15 +423,15 @@ mod test {
 		let ref secp = new_secp();
 
 		let tx = tx2i1o(secp, &mut rng);
-		let mut btx = tx.blind(&secp).unwrap();
+		let btx = tx.blind(&secp).unwrap();
 
 		let mut vec = Vec::new();
 		assert!(serialize(&mut vec, &btx).is_ok());
-		let mut dtx: Transaction = deserialize(&mut &vec[..]).unwrap();
+		let dtx: Transaction = deserialize(&mut &vec[..]).unwrap();
 
 		let mut vec2 = Vec::new();
 		assert!(serialize(&mut vec2, &btx).is_ok());
-		let mut dtx2: Transaction = deserialize(&mut &vec2[..]).unwrap();
+		let dtx2: Transaction = deserialize(&mut &vec2[..]).unwrap();
 
 		assert_eq!(btx.hash(), dtx.hash());
 		assert_eq!(dtx.hash(), dtx2.hash());
@@ -532,10 +518,10 @@ mod test {
 		let mut rng = OsRng::new().unwrap();
 
 		let tx1 = tx2i1o(secp, &mut rng);
-		let mut btx1 = tx1.blind(&secp).unwrap();
+		let btx1 = tx1.blind(&secp).unwrap();
 
 		let tx2 = tx1i1o(secp, &mut rng);
-		let mut btx2 = tx2.blind(&secp).unwrap();
+		let btx2 = tx2.blind(&secp).unwrap();
 
 		if btx1.hash() == btx2.hash() {
 			panic!("diff txs have same hash")
diff --git a/core/src/pow/mod.rs b/core/src/pow/mod.rs
index d17da511b..7047c10c6 100644
--- a/core/src/pow/mod.rs
+++ b/core/src/pow/mod.rs
@@ -85,13 +85,6 @@ impl Writeable for PowHeader {
 	}
 }
 
-impl Hashed for PowHeader {
-	fn bytes(&self) -> Vec<u8> {
-		// no serialization errors are applicable in this specific case
-		ser_vec(self).unwrap()
-	}
-}
-
 impl PowHeader {
 	fn from_block(b: &Block) -> PowHeader {
 		let ref h = b.header;
diff --git a/core/src/ser.rs b/core/src/ser.rs
index 4ffd516ed..54ed99255 100644
--- a/core/src/ser.rs
+++ b/core/src/ser.rs
@@ -81,9 +81,24 @@ pub trait AsFixedBytes {
 	fn as_fixed_bytes(&self) -> &[u8];
 }
 
+
+/// Signal to a serializable object how much of its data should be serialized
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum SerializationMode {
+	/// Serialize everything sufficiently to fully reconstruct the object
+	Full,
+	/// Serialize the data that defines the object
+	Hash,
+	/// Serialize everything that a signer of the object should know
+	SigHash
+}
+
 /// Implementations defined how different numbers and binary structures are
 /// written to an underlying stream or container (depending on implementation).
 pub trait Writer {
+	/// The mode this serializer is writing in
+	fn serialization_mode(&self) -> SerializationMode;
+
 	/// Writes a u8 as bytes
 	fn write_u8(&mut self, n: u8) -> Result<(), Error> {
 		self.write_fixed_bytes(&[n])
@@ -252,6 +267,10 @@ struct BinWriter<'a> {
 }
 
 impl<'a> Writer for BinWriter<'a> {
+	fn serialization_mode(&self) -> SerializationMode {
+		SerializationMode::Full
+	}
+
 	fn write_fixed_bytes(&mut self, fixed: &AsFixedBytes) -> Result<(), Error> {
 		let bs = fixed.as_fixed_bytes();
 		try!(self.sink.write_all(bs));

From 33ccfe3b65ef5dc896fd9b8d2167300af7a9d749 Mon Sep 17 00:00:00 2001
From: Merope Riddle <merope07@protonmail.com>
Date: Tue, 1 Nov 2016 01:44:11 +0000
Subject: [PATCH 6/6] core: remove several unused imports

---
 core/src/core/hash.rs        |  2 +-
 core/src/core/mod.rs         | 13 +++----------
 core/src/core/transaction.rs |  1 -
 core/src/pow/cuckoo.rs       |  1 -
 core/src/pow/mod.rs          |  8 +++-----
 5 files changed, 7 insertions(+), 18 deletions(-)

diff --git a/core/src/core/hash.rs b/core/src/core/hash.rs
index 543b6ddfa..770a45ae0 100644
--- a/core/src/core/hash.rs
+++ b/core/src/core/hash.rs
@@ -17,7 +17,7 @@
 //! Primary hash function used in the protocol
 //!
 
-use byteorder::{ByteOrder, WriteBytesExt, BigEndian};
+use byteorder::{ByteOrder, BigEndian};
 use std::fmt;
 use tiny_keccak::Keccak;
 
diff --git a/core/src/core/mod.rs b/core/src/core/mod.rs
index d1472eed7..af5f7368c 100644
--- a/core/src/core/mod.rs
+++ b/core/src/core/mod.rs
@@ -18,25 +18,18 @@ pub mod block;
 pub mod hash;
 pub mod transaction;
 #[allow(dead_code)]
-#[macro_use]
 
 pub use self::block::{Block, BlockHeader};
 pub use self::transaction::{Transaction, Input, Output, TxProof};
 use self::hash::{Hash, Hashed, ZERO_HASH};
-use ser::{Writeable, Writer, Error, ser_vec};
-
-use time;
+use ser::{Writeable, Writer, Error};
 
 use std::fmt;
 use std::cmp::Ordering;
 
-use secp;
-use secp::{Secp256k1, Signature, Message};
-use secp::key::SecretKey;
+use secp::{self, Secp256k1};
 use secp::pedersen::*;
 
-use tiny_keccak::Keccak;
-
 /// The block subsidy amount
 pub const REWARD: u64 = 1_000_000_000;
 
@@ -198,7 +191,7 @@ impl MerkleRow {
 #[cfg(test)]
 mod test {
 	use super::*;
-	use super::hash::{Hash, Hashed, ZERO_HASH};
+	use core::hash::ZERO_HASH;
 	use secp;
 	use secp::Secp256k1;
 	use secp::key::SecretKey;
diff --git a/core/src/core/transaction.rs b/core/src/core/transaction.rs
index d1d6bcc02..33c715dbd 100644
--- a/core/src/core/transaction.rs
+++ b/core/src/core/transaction.rs
@@ -378,7 +378,6 @@ mod test {
 
 	use secp::{self, Secp256k1};
 	use secp::key::SecretKey;
-	use rand::Rng;
 	use rand::os::OsRng;
 
 	fn new_secp() -> Secp256k1 {
diff --git a/core/src/pow/cuckoo.rs b/core/src/pow/cuckoo.rs
index 6d0a4615c..544aef68b 100644
--- a/core/src/pow/cuckoo.rs
+++ b/core/src/pow/cuckoo.rs
@@ -19,7 +19,6 @@
 
 use std::collections::HashSet;
 use std::cmp;
-use std::fmt;
 
 use crypto::digest::Digest;
 use crypto::sha2::Sha256;
diff --git a/core/src/pow/mod.rs b/core/src/pow/mod.rs
index 7047c10c6..d2069721f 100644
--- a/core/src/pow/mod.rs
+++ b/core/src/pow/mod.rs
@@ -27,12 +27,12 @@ mod cuckoo;
 
 use time;
 
-use core::{Block, BlockHeader, Proof, PROOFSIZE};
+use core::{Block, Proof, PROOFSIZE};
 use core::hash::{Hash, Hashed};
 use pow::cuckoo::{Cuckoo, Miner, Error};
 
 use ser;
-use ser::{Writeable, Writer, ser_vec};
+use ser::{Writeable, Writer};
 
 /// Default Cuckoo Cycle size shift used is 28. We may decide to increase it.
 /// when difficuty increases.
@@ -169,9 +169,7 @@ fn pow_size(b: &Block, target: Proof, sizeshift: u32) -> Result<(Proof, u64), Er
 #[cfg(test)]
 mod test {
 	use super::*;
-	use core::{BlockHeader, Proof};
-	use core::hash::Hash;
-	use std::time::Instant;
+	use core::Proof;
 	use genesis;
 
 	#[test]