[rust-lightning] / lightning / src / util / ser.rs

// This file is Copyright its original authors, visible in version control
// history.
//
// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
// You may not use this file except in accordance with one or both of these
// licenses.

//! A very simple serialization framework which is used to serialize/deserialize messages as well
//! as ChannelsManagers and ChannelMonitors.

use prelude::*;
use std::io::{Read, Write};
use core::hash::Hash;
use std::sync::Mutex;
use core::cmp;

use bitcoin::secp256k1::Signature;
use bitcoin::secp256k1::key::{PublicKey, SecretKey};
use bitcoin::secp256k1::constants::{PUBLIC_KEY_SIZE, SECRET_KEY_SIZE, COMPACT_SIGNATURE_SIZE};
use bitcoin::blockdata::script::Script;
use bitcoin::blockdata::transaction::{OutPoint, Transaction, TxOut};
use bitcoin::consensus;
use bitcoin::consensus::Encodable;
use bitcoin::hashes::sha256d::Hash as Sha256dHash;
use bitcoin::hash_types::{Txid, BlockHash};
use core::marker::Sized;
use ln::msgs::DecodeError;
use ln::{PaymentPreimage, PaymentHash, PaymentSecret};

use util::byte_utils::{be48_to_array, slice_to_be48};

/// serialization buffer size
pub const MAX_BUF_SIZE: usize = 64 * 1024;

/// A trait that is similar to std::io::Write but has one extra function which can be used to size
/// buffers being written into.
/// An impl is provided for any type that also impls std::io::Write which simply ignores size
/// hints.
///
/// (C-not exported) as we only export serialization to/from byte arrays instead
pub trait Writer {
        /// Writes the given buf out. See std::io::Write::write_all for more
        fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error>;
        /// Hints that data of the given size is about the be written. This may not always be called
        /// prior to data being written and may be safely ignored.
        fn size_hint(&mut self, size: usize);
}

impl<W: Write> Writer for W {
        #[inline]
        fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error> {
                <Self as ::std::io::Write>::write_all(self, buf)
        }
        #[inline]
        fn size_hint(&mut self, _size: usize) { }
}

pub(crate) struct WriterWriteAdaptor<'a, W: Writer + 'a>(pub &'a mut W);
impl<'a, W: Writer + 'a> Write for WriterWriteAdaptor<'a, W> {
        #[inline]
        fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error> {
                self.0.write_all(buf)
        }
        #[inline]
        fn write(&mut self, buf: &[u8]) -> Result<usize, ::std::io::Error> {
                self.0.write_all(buf)?;
                Ok(buf.len())
        }
        #[inline]
        fn flush(&mut self) -> Result<(), ::std::io::Error> {
                Ok(())
        }
}

pub(crate) struct VecWriter(pub Vec<u8>);
impl Writer for VecWriter {
        #[inline]
        fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error> {
                self.0.extend_from_slice(buf);
                Ok(())
        }
        #[inline]
        fn size_hint(&mut self, size: usize) {
                self.0.reserve_exact(size);
        }
}

/// Writer that only tracks the amount of data written - useful if you need to calculate the length
/// of some data when serialized but don't yet need the full data.
pub(crate) struct LengthCalculatingWriter(pub usize);
impl Writer for LengthCalculatingWriter {
        #[inline]
        fn write_all(&mut self, buf: &[u8]) -> Result<(), ::std::io::Error> {
                self.0 += buf.len();
                Ok(())
        }
        #[inline]
        fn size_hint(&mut self, _size: usize) {}
}

/// Essentially std::io::Take but a bit simpler and with a method to walk the underlying stream
/// forward to ensure we always consume exactly the fixed length specified.
pub(crate) struct FixedLengthReader<R: Read> {
        read: R,
        bytes_read: u64,
        total_bytes: u64,
}
impl<R: Read> FixedLengthReader<R> {
        pub fn new(read: R, total_bytes: u64) -> Self {
                Self { read, bytes_read: 0, total_bytes }
        }

        #[inline]
        pub fn bytes_remain(&mut self) -> bool {
                self.bytes_read != self.total_bytes
        }

        #[inline]
        pub fn eat_remaining(&mut self) -> Result<(), DecodeError> {
                ::std::io::copy(self, &mut ::std::io::sink()).unwrap();
                if self.bytes_read != self.total_bytes {
                        Err(DecodeError::ShortRead)
                } else {
                        Ok(())
                }
        }
}
impl<R: Read> Read for FixedLengthReader<R> {
        #[inline]
        fn read(&mut self, dest: &mut [u8]) -> Result<usize, ::std::io::Error> {
                if self.total_bytes == self.bytes_read {
                        Ok(0)
                } else {
                        let read_len = cmp::min(dest.len() as u64, self.total_bytes - self.bytes_read);
                        match self.read.read(&mut dest[0..(read_len as usize)]) {
                                Ok(v) => {
                                        self.bytes_read += v as u64;
                                        Ok(v)
                                },
                                Err(e) => Err(e),
                        }
                }
        }
}

/// A Read which tracks whether any bytes have been read at all. This allows us to distinguish
/// between "EOF reached before we started" and "EOF reached mid-read".
pub(crate) struct ReadTrackingReader<R: Read> {
        read: R,
        pub have_read: bool,
}
impl<R: Read> ReadTrackingReader<R> {
        pub fn new(read: R) -> Self {
                Self { read, have_read: false }
        }
}
impl<R: Read> Read for ReadTrackingReader<R> {
        #[inline]
        fn read(&mut self, dest: &mut [u8]) -> Result<usize, ::std::io::Error> {
                match self.read.read(dest) {
                        Ok(0) => Ok(0),
                        Ok(len) => {
                                self.have_read = true;
                                Ok(len)
                        },
                        Err(e) => Err(e),
                }
        }
}

/// A trait that various rust-lightning types implement allowing them to be written out to a Writer
///
/// (C-not exported) as we only export serialization to/from byte arrays instead
pub trait Writeable {
        /// Writes self out to the given Writer
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error>;

        /// Writes self out to a Vec<u8>
        fn encode(&self) -> Vec<u8> {
                let mut msg = VecWriter(Vec::new());
                self.write(&mut msg).unwrap();
                msg.0
        }

        /// Writes self out to a Vec<u8>
        fn encode_with_len(&self) -> Vec<u8> {
                let mut msg = VecWriter(Vec::new());
                0u16.write(&mut msg).unwrap();
                self.write(&mut msg).unwrap();
                let len = msg.0.len();
                msg.0[..2].copy_from_slice(&(len as u16 - 2).to_be_bytes());
                msg.0
        }

        /// Gets the length of this object after it has been serialized. This can be overridden to
        /// optimize cases where we prepend an object with its length.
        // Note that LLVM optimizes this away in most cases! Check that it isn't before you override!
        #[inline]
        fn serialized_length(&self) -> usize {
                let mut len_calc = LengthCalculatingWriter(0);
                self.write(&mut len_calc).expect("No in-memory data may fail to serialize");
                len_calc.0
        }
}

impl<'a, T: Writeable> Writeable for &'a T {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> { (*self).write(writer) }
}

/// A trait that various rust-lightning types implement allowing them to be read in from a Read
///
/// (C-not exported) as we only export serialization to/from byte arrays instead
pub trait Readable
        where Self: Sized
{
        /// Reads a Self in from the given Read
        fn read<R: Read>(reader: &mut R) -> Result<Self, DecodeError>;
}

/// A trait that various higher-level rust-lightning types implement allowing them to be read in
/// from a Read given some additional set of arguments which is required to deserialize.
///
/// (C-not exported) as we only export serialization to/from byte arrays instead
pub trait ReadableArgs<P>
        where Self: Sized
{
        /// Reads a Self in from the given Read
        fn read<R: Read>(reader: &mut R, params: P) -> Result<Self, DecodeError>;
}

/// A trait that various rust-lightning types implement allowing them to (maybe) be read in from a Read
///
/// (C-not exported) as we only export serialization to/from byte arrays instead
pub trait MaybeReadable
        where Self: Sized
{
        /// Reads a Self in from the given Read
        fn read<R: Read>(reader: &mut R) -> Result<Option<Self>, DecodeError>;
}

pub(crate) struct OptionDeserWrapper<T: Readable>(pub Option<T>);
impl<T: Readable> Readable for OptionDeserWrapper<T> {
        #[inline]
        fn read<R: Read>(reader: &mut R) -> Result<Self, DecodeError> {
                Ok(Self(Some(Readable::read(reader)?)))
        }
}

/// Wrapper to write each element of a Vec with no length prefix
pub(crate) struct VecWriteWrapper<'a, T: Writeable>(pub &'a Vec<T>);
impl<'a, T: Writeable> Writeable for VecWriteWrapper<'a, T> {
        #[inline]
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                for ref v in self.0.iter() {
                        v.write(writer)?;
                }
                Ok(())
        }
}

/// Wrapper to read elements from a given stream until it reaches the end of the stream.
pub(crate) struct VecReadWrapper<T: Readable>(pub Vec<T>);
impl<T: Readable> Readable for VecReadWrapper<T> {
        #[inline]
        fn read<R: Read>(mut reader: &mut R) -> Result<Self, DecodeError> {
                let mut values = Vec::new();
                loop {
                        let mut track_read = ReadTrackingReader::new(&mut reader);
                        match Readable::read(&mut track_read) {
                                Ok(v) => { values.push(v); },
                                // If we failed to read any bytes at all, we reached the end of our TLV
                                // stream and have simply exhausted all entries.
                                Err(ref e) if e == &DecodeError::ShortRead && !track_read.have_read => break,
                                Err(e) => return Err(e),
                        }
                }
                Ok(Self(values))
        }
}

pub(crate) struct U48(pub u64);
impl Writeable for U48 {
        #[inline]
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                writer.write_all(&be48_to_array(self.0))
        }
}
impl Readable for U48 {
        #[inline]
        fn read<R: Read>(reader: &mut R) -> Result<U48, DecodeError> {
                let mut buf = [0; 6];
                reader.read_exact(&mut buf)?;
                Ok(U48(slice_to_be48(&buf)))
        }
}

/// Lightning TLV uses a custom variable-length integer called BigSize. It is similar to Bitcoin's
/// variable-length integers except that it is serialized in big-endian instead of little-endian.
///
/// Like Bitcoin's variable-length integer, it exhibits ambiguity in that certain values can be
/// encoded in several different ways, which we must check for at deserialization-time. Thus, if
/// you're looking for an example of a variable-length integer to use for your own project, move
/// along, this is a rather poor design.
pub(crate) struct BigSize(pub u64);
impl Writeable for BigSize {
        #[inline]
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                match self.0 {
                        0...0xFC => {
                                (self.0 as u8).write(writer)
                        },
                        0xFD...0xFFFF => {
                                0xFDu8.write(writer)?;
                                (self.0 as u16).write(writer)
                        },
                        0x10000...0xFFFFFFFF => {
                                0xFEu8.write(writer)?;
                                (self.0 as u32).write(writer)
                        },
                        _ => {
                                0xFFu8.write(writer)?;
                                (self.0 as u64).write(writer)
                        },
                }
        }
}
impl Readable for BigSize {
        #[inline]
        fn read<R: Read>(reader: &mut R) -> Result<BigSize, DecodeError> {
                let n: u8 = Readable::read(reader)?;
                match n {
                        0xFF => {
                                let x: u64 = Readable::read(reader)?;
                                if x < 0x100000000 {
                                        Err(DecodeError::InvalidValue)
                                } else {
                                        Ok(BigSize(x))
                                }
                        }
                        0xFE => {
                                let x: u32 = Readable::read(reader)?;
                                if x < 0x10000 {
                                        Err(DecodeError::InvalidValue)
                                } else {
                                        Ok(BigSize(x as u64))
                                }
                        }
                        0xFD => {
                                let x: u16 = Readable::read(reader)?;
                                if x < 0xFD {
                                        Err(DecodeError::InvalidValue)
                                } else {
                                        Ok(BigSize(x as u64))
                                }
                        }
                        n => Ok(BigSize(n as u64))
                }
        }
}

/// In TLV we occasionally send fields which only consist of, or potentially end with, a
/// variable-length integer which is simply truncated by skipping high zero bytes. This type
/// encapsulates such integers implementing Readable/Writeable for them.
#[cfg_attr(test, derive(PartialEq, Debug))]
pub(crate) struct HighZeroBytesDroppedVarInt<T>(pub T);

macro_rules! impl_writeable_primitive {
        ($val_type:ty, $len: expr) => {
                impl Writeable for $val_type {
                        #[inline]
                        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                                writer.write_all(&self.to_be_bytes())
                        }
                }
                impl Writeable for HighZeroBytesDroppedVarInt<$val_type> {
                        #[inline]
                        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                                // Skip any full leading 0 bytes when writing (in BE):
                                writer.write_all(&self.0.to_be_bytes()[(self.0.leading_zeros()/8) as usize..$len])
                        }
                }
                impl Readable for $val_type {
                        #[inline]
                        fn read<R: Read>(reader: &mut R) -> Result<$val_type, DecodeError> {
                                let mut buf = [0; $len];
                                reader.read_exact(&mut buf)?;
                                Ok(<$val_type>::from_be_bytes(buf))
                        }
                }
                impl Readable for HighZeroBytesDroppedVarInt<$val_type> {
                        #[inline]
                        fn read<R: Read>(reader: &mut R) -> Result<HighZeroBytesDroppedVarInt<$val_type>, DecodeError> {
                                // We need to accept short reads (read_len == 0) as "EOF" and handle them as simply
                                // the high bytes being dropped. To do so, we start reading into the middle of buf
                                // and then convert the appropriate number of bytes with extra high bytes out of
                                // buf.
                                let mut buf = [0; $len*2];
                                let mut read_len = reader.read(&mut buf[$len..])?;
                                let mut total_read_len = read_len;
                                while read_len != 0 && total_read_len != $len {
                                        read_len = reader.read(&mut buf[($len + total_read_len)..])?;
                                        total_read_len += read_len;
                                }
                                if total_read_len == 0 || buf[$len] != 0 {
                                        let first_byte = $len - ($len - total_read_len);
                                        let mut bytes = [0; $len];
                                        bytes.copy_from_slice(&buf[first_byte..first_byte + $len]);
                                        Ok(HighZeroBytesDroppedVarInt(<$val_type>::from_be_bytes(bytes)))
                                } else {
                                        // If the encoding had extra zero bytes, return a failure even though we know
                                        // what they meant (as the TLV test vectors require this)
                                        Err(DecodeError::InvalidValue)
                                }
                        }
                }
        }
}

impl_writeable_primitive!(u64, 8);
impl_writeable_primitive!(u32, 4);
impl_writeable_primitive!(u16, 2);

impl Writeable for u8 {
        #[inline]
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                writer.write_all(&[*self])
        }
}
impl Readable for u8 {
        #[inline]
        fn read<R: Read>(reader: &mut R) -> Result<u8, DecodeError> {
                let mut buf = [0; 1];
                reader.read_exact(&mut buf)?;
                Ok(buf[0])
        }
}

impl Writeable for bool {
        #[inline]
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                writer.write_all(&[if *self {1} else {0}])
        }
}
impl Readable for bool {
        #[inline]
        fn read<R: Read>(reader: &mut R) -> Result<bool, DecodeError> {
                let mut buf = [0; 1];
                reader.read_exact(&mut buf)?;
                if buf[0] != 0 && buf[0] != 1 {
                        return Err(DecodeError::InvalidValue);
                }
                Ok(buf[0] == 1)
        }
}

// u8 arrays
macro_rules! impl_array {
        ( $size:expr ) => (
                impl Writeable for [u8; $size]
                {
                        #[inline]
                        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                                w.write_all(self)
                        }
                }

                impl Readable for [u8; $size]
                {
                        #[inline]
                        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                                let mut buf = [0u8; $size];
                                r.read_exact(&mut buf)?;
                                Ok(buf)
                        }
                }
        );
}

//TODO: performance issue with [u8; size] with impl_array!()
impl_array!(3); // for rgb
impl_array!(4); // for IPv4
impl_array!(10); // for OnionV2
impl_array!(16); // for IPv6
impl_array!(32); // for channel id & hmac
impl_array!(PUBLIC_KEY_SIZE); // for PublicKey
impl_array!(COMPACT_SIGNATURE_SIZE); // for Signature
impl_array!(1300); // for OnionPacket.hop_data

// HashMap
impl<K, V> Writeable for HashMap<K, V>
        where K: Writeable + Eq + Hash,
              V: Writeable
{
        #[inline]
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
        (self.len() as u16).write(w)?;
                for (key, value) in self.iter() {
                        key.write(w)?;
                        value.write(w)?;
                }
                Ok(())
        }
}

impl<K, V> Readable for HashMap<K, V>
        where K: Readable + Eq + Hash,
              V: Readable
{
        #[inline]
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let len: u16 = Readable::read(r)?;
                let mut ret = HashMap::with_capacity(len as usize);
                for _ in 0..len {
                        ret.insert(K::read(r)?, V::read(r)?);
                }
                Ok(ret)
        }
}

// Vectors
impl Writeable for Vec<u8> {
        #[inline]
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                (self.len() as u16).write(w)?;
                w.write_all(&self)
        }
}

impl Readable for Vec<u8> {
        #[inline]
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let len: u16 = Readable::read(r)?;
                let mut ret = Vec::with_capacity(len as usize);
                ret.resize(len as usize, 0);
                r.read_exact(&mut ret)?;
                Ok(ret)
        }
}
impl Writeable for Vec<Signature> {
        #[inline]
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                (self.len() as u16).write(w)?;
                for e in self.iter() {
                        e.write(w)?;
                }
                Ok(())
        }
}

impl Readable for Vec<Signature> {
        #[inline]
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let len: u16 = Readable::read(r)?;
                let byte_size = (len as usize)
                                .checked_mul(COMPACT_SIGNATURE_SIZE)
                                .ok_or(DecodeError::BadLengthDescriptor)?;
                if byte_size > MAX_BUF_SIZE {
                        return Err(DecodeError::BadLengthDescriptor);
                }
                let mut ret = Vec::with_capacity(len as usize);
                for _ in 0..len { ret.push(Signature::read(r)?); }
                Ok(ret)
        }
}

impl Writeable for Script {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                (self.len() as u16).write(w)?;
                w.write_all(self.as_bytes())
        }
}

impl Readable for Script {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let len = <u16 as Readable>::read(r)? as usize;
                let mut buf = vec![0; len];
                r.read_exact(&mut buf)?;
                Ok(Script::from(buf))
        }
}

impl Writeable for PublicKey {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.serialize().write(w)
        }
        #[inline]
        fn serialized_length(&self) -> usize {
                PUBLIC_KEY_SIZE
        }
}

impl Readable for PublicKey {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let buf: [u8; PUBLIC_KEY_SIZE] = Readable::read(r)?;
                match PublicKey::from_slice(&buf) {
                        Ok(key) => Ok(key),
                        Err(_) => return Err(DecodeError::InvalidValue),
                }
        }
}

impl Writeable for SecretKey {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                let mut ser = [0; SECRET_KEY_SIZE];
                ser.copy_from_slice(&self[..]);
                ser.write(w)
        }
        #[inline]
        fn serialized_length(&self) -> usize {
                SECRET_KEY_SIZE
        }
}

impl Readable for SecretKey {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let buf: [u8; SECRET_KEY_SIZE] = Readable::read(r)?;
                match SecretKey::from_slice(&buf) {
                        Ok(key) => Ok(key),
                        Err(_) => return Err(DecodeError::InvalidValue),
                }
        }
}

impl Writeable for Sha256dHash {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                w.write_all(&self[..])
        }
}

impl Readable for Sha256dHash {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                use bitcoin::hashes::Hash;

                let buf: [u8; 32] = Readable::read(r)?;
                Ok(Sha256dHash::from_slice(&buf[..]).unwrap())
        }
}

impl Writeable for Signature {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.serialize_compact().write(w)
        }
        #[inline]
        fn serialized_length(&self) -> usize {
                COMPACT_SIGNATURE_SIZE
        }
}

impl Readable for Signature {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let buf: [u8; COMPACT_SIGNATURE_SIZE] = Readable::read(r)?;
                match Signature::from_compact(&buf) {
                        Ok(sig) => Ok(sig),
                        Err(_) => return Err(DecodeError::InvalidValue),
                }
        }
}

impl Writeable for PaymentPreimage {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.0.write(w)
        }
}

impl Readable for PaymentPreimage {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let buf: [u8; 32] = Readable::read(r)?;
                Ok(PaymentPreimage(buf))
        }
}

impl Writeable for PaymentHash {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.0.write(w)
        }
}

impl Readable for PaymentHash {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let buf: [u8; 32] = Readable::read(r)?;
                Ok(PaymentHash(buf))
        }
}

impl Writeable for PaymentSecret {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.0.write(w)
        }
}

impl Readable for PaymentSecret {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let buf: [u8; 32] = Readable::read(r)?;
                Ok(PaymentSecret(buf))
        }
}

impl<T: Writeable> Writeable for Box<T> {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                T::write(&**self, w)
        }
}

impl<T: Readable> Readable for Box<T> {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                Ok(Box::new(Readable::read(r)?))
        }
}

impl<T: Writeable> Writeable for Option<T> {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                match *self {
                        None => 0u8.write(w)?,
                        Some(ref data) => {
                                BigSize(data.serialized_length() as u64 + 1).write(w)?;
                                data.write(w)?;
                        }
                }
                Ok(())
        }
}

impl<T: Readable> Readable for Option<T>
{
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                match BigSize::read(r)?.0 {
                        0 => Ok(None),
                        len => {
                                let mut reader = FixedLengthReader::new(r, len - 1);
                                Ok(Some(Readable::read(&mut reader)?))
                        }
                }
        }
}

impl Writeable for Txid {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                w.write_all(&self[..])
        }
}

impl Readable for Txid {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                use bitcoin::hashes::Hash;

                let buf: [u8; 32] = Readable::read(r)?;
                Ok(Txid::from_slice(&buf[..]).unwrap())
        }
}

impl Writeable for BlockHash {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                w.write_all(&self[..])
        }
}

impl Readable for BlockHash {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                use bitcoin::hashes::Hash;

                let buf: [u8; 32] = Readable::read(r)?;
                Ok(BlockHash::from_slice(&buf[..]).unwrap())
        }
}

impl Writeable for OutPoint {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.txid.write(w)?;
                self.vout.write(w)?;
                Ok(())
        }
}

impl Readable for OutPoint {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let txid = Readable::read(r)?;
                let vout = Readable::read(r)?;
                Ok(OutPoint {
                        txid,
                        vout,
                })
        }
}

macro_rules! impl_consensus_ser {
        ($bitcoin_type: ty) => {
                impl Writeable for $bitcoin_type {
                        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                                match self.consensus_encode(WriterWriteAdaptor(writer)) {
                                        Ok(_) => Ok(()),
                                        Err(e) => Err(e),
                                }
                        }
                }

                impl Readable for $bitcoin_type {
                        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                                match consensus::encode::Decodable::consensus_decode(r) {
                                        Ok(t) => Ok(t),
                                        Err(consensus::encode::Error::Io(ref e)) if e.kind() == ::std::io::ErrorKind::UnexpectedEof => Err(DecodeError::ShortRead),
                                        Err(consensus::encode::Error::Io(e)) => Err(DecodeError::Io(e.kind())),
                                        Err(_) => Err(DecodeError::InvalidValue),
                                }
                        }
                }
        }
}
impl_consensus_ser!(Transaction);
impl_consensus_ser!(TxOut);

impl<T: Readable> Readable for Mutex<T> {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let t: T = Readable::read(r)?;
                Ok(Mutex::new(t))
        }
}
impl<T: Writeable> Writeable for Mutex<T> {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.lock().unwrap().write(w)
        }
}

impl<A: Readable, B: Readable> Readable for (A, B) {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let a: A = Readable::read(r)?;
                let b: B = Readable::read(r)?;
                Ok((a, b))
        }
}
impl<A: Writeable, B: Writeable> Writeable for (A, B) {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.0.write(w)?;
                self.1.write(w)
        }
}

impl<A: Readable, B: Readable, C: Readable> Readable for (A, B, C) {
        fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
                let a: A = Readable::read(r)?;
                let b: B = Readable::read(r)?;
                let c: C = Readable::read(r)?;
                Ok((a, b, c))
        }
}
impl<A: Writeable, B: Writeable, C: Writeable> Writeable for (A, B, C) {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.0.write(w)?;
                self.1.write(w)?;
                self.2.write(w)
        }
}