Migrate OnchainEvent serialization to be MaybeReadable.
[rust-lightning] / lightning / src / util / ser_macros.rs
index 48e87b3bc2108a35b97282981b8738b5b87a93fb..af1bebe680b3db9324be291c257f293f8d6f90a8 100644 (file)
+// 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.
+
+macro_rules! encode_tlv {
+       ($stream: expr, $type: expr, $field: expr, (default_value, $default: expr)) => {
+               encode_tlv!($stream, $type, $field, required)
+       };
+       ($stream: expr, $type: expr, $field: expr, required) => {
+               BigSize($type).write($stream)?;
+               BigSize($field.serialized_length() as u64).write($stream)?;
+               $field.write($stream)?;
+       };
+       ($stream: expr, $type: expr, $field: expr, vec_type) => {
+               encode_tlv!($stream, $type, ::util::ser::VecWriteWrapper(&$field), required);
+       };
+       ($stream: expr, $optional_type: expr, $optional_field: expr, option) => {
+               if let Some(ref field) = $optional_field {
+                       BigSize($optional_type).write($stream)?;
+                       BigSize(field.serialized_length() as u64).write($stream)?;
+                       field.write($stream)?;
+               }
+       };
+}
+
+macro_rules! encode_tlv_stream {
+       ($stream: expr, {$(($type: expr, $field: expr, $fieldty: tt)),* $(,)*}) => { {
+               #[allow(unused_imports)]
+               use {
+                       ln::msgs::DecodeError,
+                       util::ser,
+                       util::ser::BigSize,
+               };
+
+               $(
+                       encode_tlv!($stream, $type, $field, $fieldty);
+               )*
+
+               #[allow(unused_mut, unused_variables, unused_assignments)]
+               #[cfg(debug_assertions)]
+               {
+                       let mut last_seen: Option<u64> = None;
+                       $(
+                               if let Some(t) = last_seen {
+                                       debug_assert!(t <= $type);
+                               }
+                               last_seen = Some($type);
+                       )*
+               }
+       } }
+}
+
+macro_rules! get_varint_length_prefixed_tlv_length {
+       ($len: expr, $type: expr, $field: expr, (default_value, $default: expr)) => {
+               get_varint_length_prefixed_tlv_length!($len, $type, $field, required)
+       };
+       ($len: expr, $type: expr, $field: expr, required) => {
+               BigSize($type).write(&mut $len).expect("No in-memory data may fail to serialize");
+               let field_len = $field.serialized_length();
+               BigSize(field_len as u64).write(&mut $len).expect("No in-memory data may fail to serialize");
+               $len.0 += field_len;
+       };
+       ($len: expr, $type: expr, $field: expr, vec_type) => {
+               get_varint_length_prefixed_tlv_length!($len, $type, ::util::ser::VecWriteWrapper(&$field), required);
+       };
+       ($len: expr, $optional_type: expr, $optional_field: expr, option) => {
+               if let Some(ref field) = $optional_field {
+                       BigSize($optional_type).write(&mut $len).expect("No in-memory data may fail to serialize");
+                       let field_len = field.serialized_length();
+                       BigSize(field_len as u64).write(&mut $len).expect("No in-memory data may fail to serialize");
+                       $len.0 += field_len;
+               }
+       };
+}
+
+macro_rules! encode_varint_length_prefixed_tlv {
+       ($stream: expr, {$(($type: expr, $field: expr, $fieldty: tt)),*}) => { {
+               use util::ser::BigSize;
+               let len = {
+                       #[allow(unused_mut)]
+                       let mut len = ::util::ser::LengthCalculatingWriter(0);
+                       $(
+                               get_varint_length_prefixed_tlv_length!(len, $type, $field, $fieldty);
+                       )*
+                       len.0
+               };
+               BigSize(len as u64).write($stream)?;
+               encode_tlv_stream!($stream, { $(($type, $field, $fieldty)),* });
+       } }
+}
+
+macro_rules! check_tlv_order {
+       ($last_seen_type: expr, $typ: expr, $type: expr, $field: ident, (default_value, $default: expr)) => {{
+               #[allow(unused_comparisons)] // Note that $type may be 0 making the second comparison always true
+               let invalid_order = ($last_seen_type.is_none() || $last_seen_type.unwrap() < $type) && $typ.0 > $type;
+               if invalid_order {
+                       $field = $default;
+               }
+       }};
+       ($last_seen_type: expr, $typ: expr, $type: expr, $field: ident, required) => {{
+               #[allow(unused_comparisons)] // Note that $type may be 0 making the second comparison always true
+               let invalid_order = ($last_seen_type.is_none() || $last_seen_type.unwrap() < $type) && $typ.0 > $type;
+               if invalid_order {
+                       return Err(DecodeError::InvalidValue);
+               }
+       }};
+       ($last_seen_type: expr, $typ: expr, $type: expr, $field: ident, option) => {{
+               // no-op
+       }};
+       ($last_seen_type: expr, $typ: expr, $type: expr, $field: ident, vec_type) => {{
+               // no-op
+       }};
+       ($last_seen_type: expr, $typ: expr, $type: expr, $field: ident, ignorable) => {{
+               // no-op
+       }};
+}
+
+macro_rules! check_missing_tlv {
+       ($last_seen_type: expr, $type: expr, $field: ident, (default_value, $default: expr)) => {{
+               #[allow(unused_comparisons)] // Note that $type may be 0 making the second comparison always true
+               let missing_req_type = $last_seen_type.is_none() || $last_seen_type.unwrap() < $type;
+               if missing_req_type {
+                       $field = $default;
+               }
+       }};
+       ($last_seen_type: expr, $type: expr, $field: ident, required) => {{
+               #[allow(unused_comparisons)] // Note that $type may be 0 making the second comparison always true
+               let missing_req_type = $last_seen_type.is_none() || $last_seen_type.unwrap() < $type;
+               if missing_req_type {
+                       return Err(DecodeError::InvalidValue);
+               }
+       }};
+       ($last_seen_type: expr, $type: expr, $field: ident, vec_type) => {{
+               // no-op
+       }};
+       ($last_seen_type: expr, $type: expr, $field: ident, option) => {{
+               // no-op
+       }};
+       ($last_seen_type: expr, $type: expr, $field: ident, ignorable) => {{
+               // no-op
+       }};
+}
+
+macro_rules! decode_tlv {
+       ($reader: expr, $field: ident, (default_value, $default: expr)) => {{
+               decode_tlv!($reader, $field, required)
+       }};
+       ($reader: expr, $field: ident, required) => {{
+               $field = ser::Readable::read(&mut $reader)?;
+       }};
+       ($reader: expr, $field: ident, vec_type) => {{
+               $field = Some(ser::Readable::read(&mut $reader)?);
+       }};
+       ($reader: expr, $field: ident, option) => {{
+               $field = Some(ser::Readable::read(&mut $reader)?);
+       }};
+       ($reader: expr, $field: ident, ignorable) => {{
+               $field = ser::MaybeReadable::read(&mut $reader)?;
+       }};
+}
+
+macro_rules! decode_tlv_stream {
+       ($stream: expr, {$(($type: expr, $field: ident, $fieldty: tt)),* $(,)*}) => { {
+               use ln::msgs::DecodeError;
+               let mut last_seen_type: Option<u64> = None;
+               'tlv_read: loop {
+                       use util::ser;
+
+                       // First decode the type of this TLV:
+                       let typ: ser::BigSize = {
+                               // We track whether any bytes were read during the consensus_decode call to
+                               // determine whether we should break or return ShortRead if we get an
+                               // UnexpectedEof. This should in every case be largely cosmetic, but its nice to
+                               // pass the TLV test vectors exactly, which requre this distinction.
+                               let mut tracking_reader = ser::ReadTrackingReader::new($stream);
+                               match ser::Readable::read(&mut tracking_reader) {
+                                       Err(DecodeError::ShortRead) => {
+                                               if !tracking_reader.have_read {
+                                                       break 'tlv_read;
+                                               } else {
+                                                       return Err(DecodeError::ShortRead);
+                                               }
+                                       },
+                                       Err(e) => return Err(e),
+                                       Ok(t) => t,
+                               }
+                       };
+
+                       // Types must be unique and monotonically increasing:
+                       match last_seen_type {
+                               Some(t) if typ.0 <= t => {
+                                       return Err(DecodeError::InvalidValue);
+                               },
+                               _ => {},
+                       }
+                       // As we read types, make sure we hit every required type:
+                       $({
+                               check_tlv_order!(last_seen_type, typ, $type, $field, $fieldty);
+                       })*
+                       last_seen_type = Some(typ.0);
+
+                       // Finally, read the length and value itself:
+                       let length: ser::BigSize = ser::Readable::read($stream)?;
+                       let mut s = ser::FixedLengthReader::new($stream, length.0);
+                       match typ.0 {
+                               $($type => {
+                                       decode_tlv!(s, $field, $fieldty);
+                                       if s.bytes_remain() {
+                                               s.eat_remaining()?; // Return ShortRead if there's actually not enough bytes
+                                               return Err(DecodeError::InvalidValue);
+                                       }
+                               },)*
+                               x if x % 2 == 0 => {
+                                       return Err(DecodeError::UnknownRequiredFeature);
+                               },
+                               _ => {},
+                       }
+                       s.eat_remaining()?;
+               }
+               // Make sure we got to each required type after we've read every TLV:
+               $({
+                       check_missing_tlv!(last_seen_type, $type, $field, $fieldty);
+               })*
+       } }
+}
+
 macro_rules! impl_writeable {
        ($st:ident, $len: expr, {$($field:ident),*}) => {
                impl ::util::ser::Writeable for $st {
-                       fn write<W: ::util::ser::Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
+                       fn write<W: ::util::ser::Writer>(&self, w: &mut W) -> Result<(), $crate::io::Error> {
                                if $len != 0 {
                                        w.size_hint($len);
                                }
+                               #[cfg(any(test, feature = "fuzztarget"))]
+                               {
+                                       // In tests, assert that the hard-coded length matches the actual one
+                                       if $len != 0 {
+                                               let mut len_calc = ::util::ser::LengthCalculatingWriter(0);
+                                               $( self.$field.write(&mut len_calc).expect("No in-memory data may fail to serialize"); )*
+                                               assert_eq!(len_calc.0, $len);
+                                               assert_eq!(self.serialized_length(), $len);
+                                       }
+                               }
                                $( self.$field.write(w)?; )*
                                Ok(())
                        }
+
+                       #[inline]
+                       fn serialized_length(&self) -> usize {
+                               if $len == 0 || cfg!(any(test, feature = "fuzztarget")) {
+                                       let mut len_calc = 0;
+                                       $( len_calc += self.$field.serialized_length(); )*
+                                       if $len != 0 {
+                                               // In tests, assert that the hard-coded length matches the actual one
+                                               assert_eq!(len_calc, $len);
+                                       } else {
+                                               return len_calc;
+                                       }
+                               }
+                               $len
+                       }
                }
 
-               impl<R: ::std::io::Read> ::util::ser::Readable<R> for $st {
-                       fn read(r: &mut R) -> Result<Self, ::ln::msgs::DecodeError> {
+               impl ::util::ser::Readable for $st {
+                       fn read<R: $crate::io::Read>(r: &mut R) -> Result<Self, ::ln::msgs::DecodeError> {
                                Ok(Self {
                                        $($field: ::util::ser::Readable::read(r)?),*
                                })
@@ -20,23 +276,541 @@ macro_rules! impl_writeable {
        }
 }
 macro_rules! impl_writeable_len_match {
-       ($st:ident, {$({$m: pat, $l: expr}),*}, {$($field:ident),*}) => {
-               impl Writeable for $st {
-                       fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
-                               w.size_hint(match *self {
-                                       $($m => $l,)*
-                               });
+       ($struct: ident, $cmp: tt, ($calc_len: expr), {$({$match: pat, $length: expr}),*}, {$($field:ident),*}) => {
+               impl Writeable for $struct {
+                       fn write<W: Writer>(&self, w: &mut W) -> Result<(), $crate::io::Error> {
+                               let len = match *self {
+                                       $($match => $length,)*
+                               };
+                               w.size_hint(len);
+                               #[cfg(any(test, feature = "fuzztarget"))]
+                               {
+                                       // In tests, assert that the hard-coded length matches the actual one
+                                       let mut len_calc = ::util::ser::LengthCalculatingWriter(0);
+                                       $( self.$field.write(&mut len_calc).expect("No in-memory data may fail to serialize"); )*
+                                       assert!(len_calc.0 $cmp len);
+                                       assert_eq!(len_calc.0, self.serialized_length());
+                               }
                                $( self.$field.write(w)?; )*
                                Ok(())
                        }
+
+                       #[inline]
+                       fn serialized_length(&self) -> usize {
+                               if $calc_len || cfg!(any(test, feature = "fuzztarget")) {
+                                       let mut len_calc = 0;
+                                       $( len_calc += self.$field.serialized_length(); )*
+                                       if !$calc_len {
+                                               assert_eq!(len_calc, match *self {
+                                                       $($match => $length,)*
+                                               });
+                                       }
+                                       return len_calc
+                               }
+                               match *self {
+                                       $($match => $length,)*
+                               }
+                       }
                }
 
-               impl<R: ::std::io::Read> Readable<R> for $st {
-                       fn read(r: &mut R) -> Result<Self, DecodeError> {
+               impl ::util::ser::Readable for $struct {
+                       fn read<R: $crate::io::Read>(r: &mut R) -> Result<Self, DecodeError> {
                                Ok(Self {
                                        $($field: Readable::read(r)?),*
                                })
                        }
                }
+       };
+       ($struct: ident, $cmp: tt, {$({$match: pat, $length: expr}),*}, {$($field:ident),*}) => {
+               impl_writeable_len_match!($struct, $cmp, (true), { $({ $match, $length }),* }, { $($field),* });
+       };
+       ($struct: ident, {$({$match: pat, $length: expr}),*}, {$($field:ident),*}) => {
+               impl_writeable_len_match!($struct, ==, (false), { $({ $match, $length }),* }, { $($field),* });
+       }
+}
+
+/// Write out two bytes to indicate the version of an object.
+/// $this_version represents a unique version of a type. Incremented whenever the type's
+///               serialization format has changed or has a new interpretation. Used by a type's
+///               reader to determine how to interpret fields or if it can understand a serialized
+///               object.
+/// $min_version_that_can_read_this is the minimum reader version which can understand this
+///                                 serialized object. Previous versions will simply err with a
+///                                 DecodeError::UnknownVersion.
+///
+/// Updates to either $this_version or $min_version_that_can_read_this should be included in
+/// release notes.
+///
+/// Both version fields can be specific to this type of object.
+macro_rules! write_ver_prefix {
+       ($stream: expr, $this_version: expr, $min_version_that_can_read_this: expr) => {
+               $stream.write_all(&[$this_version; 1])?;
+               $stream.write_all(&[$min_version_that_can_read_this; 1])?;
+       }
+}
+
+/// Writes out a suffix to an object which contains potentially backwards-compatible, optional
+/// fields which old nodes can happily ignore.
+///
+/// It is written out in TLV format and, as with all TLV fields, unknown even fields cause a
+/// DecodeError::UnknownRequiredFeature error, with unknown odd fields ignored.
+///
+/// This is the preferred method of adding new fields that old nodes can ignore and still function
+/// correctly.
+macro_rules! write_tlv_fields {
+       ($stream: expr, {$(($type: expr, $field: expr, $fieldty: tt)),* $(,)*}) => {
+               encode_varint_length_prefixed_tlv!($stream, {$(($type, $field, $fieldty)),*});
+       }
+}
+
+/// Reads a prefix added by write_ver_prefix!(), above. Takes the current version of the
+/// serialization logic for this object. This is compared against the
+/// $min_version_that_can_read_this added by write_ver_prefix!().
+macro_rules! read_ver_prefix {
+       ($stream: expr, $this_version: expr) => { {
+               let ver: u8 = Readable::read($stream)?;
+               let min_ver: u8 = Readable::read($stream)?;
+               if min_ver > $this_version {
+                       return Err(DecodeError::UnknownVersion);
+               }
+               ver
+       } }
+}
+
+/// Reads a suffix added by write_tlv_fields.
+macro_rules! read_tlv_fields {
+       ($stream: expr, {$(($type: expr, $field: ident, $fieldty: tt)),* $(,)*}) => { {
+               let tlv_len: ::util::ser::BigSize = ::util::ser::Readable::read($stream)?;
+               let mut rd = ::util::ser::FixedLengthReader::new($stream, tlv_len.0);
+               decode_tlv_stream!(&mut rd, {$(($type, $field, $fieldty)),*});
+               rd.eat_remaining().map_err(|_| ::ln::msgs::DecodeError::ShortRead)?;
+       } }
+}
+
+macro_rules! init_tlv_based_struct_field {
+       ($field: ident, (default_value, $default: expr)) => {
+               $field
+       };
+       ($field: ident, option) => {
+               $field
+       };
+       ($field: ident, required) => {
+               $field.0.unwrap()
+       };
+       ($field: ident, vec_type) => {
+               $field.unwrap().0
+       };
+}
+
+macro_rules! init_tlv_field_var {
+       ($field: ident, (default_value, $default: expr)) => {
+               let mut $field = $default;
+       };
+       ($field: ident, required) => {
+               let mut $field = ::util::ser::OptionDeserWrapper(None);
+       };
+       ($field: ident, vec_type) => {
+               let mut $field = Some(::util::ser::VecReadWrapper(Vec::new()));
+       };
+       ($field: ident, option) => {
+               let mut $field = None;
+       };
+}
+
+/// Implements Readable/Writeable for a struct storing it as a set of TLVs
+/// If $fieldty is `required`, then $field is a required field that is not an Option nor a Vec.
+/// If $fieldty is `option`, then $field is optional field.
+/// if $fieldty is `vec_type`, then $field is a Vec, which needs to have its individual elements
+/// serialized.
+macro_rules! impl_writeable_tlv_based {
+       ($st: ident, {$(($type: expr, $field: ident, $fieldty: tt)),* $(,)*}) => {
+               impl ::util::ser::Writeable for $st {
+                       fn write<W: ::util::ser::Writer>(&self, writer: &mut W) -> Result<(), $crate::io::Error> {
+                               write_tlv_fields!(writer, {
+                                       $(($type, self.$field, $fieldty)),*
+                               });
+                               Ok(())
+                       }
+
+                       #[inline]
+                       fn serialized_length(&self) -> usize {
+                               use util::ser::BigSize;
+                               let len = {
+                                       #[allow(unused_mut)]
+                                       let mut len = ::util::ser::LengthCalculatingWriter(0);
+                                       $(
+                                               get_varint_length_prefixed_tlv_length!(len, $type, self.$field, $fieldty);
+                                       )*
+                                       len.0
+                               };
+                               let mut len_calc = ::util::ser::LengthCalculatingWriter(0);
+                               BigSize(len as u64).write(&mut len_calc).expect("No in-memory data may fail to serialize");
+                               len + len_calc.0
+                       }
+               }
+
+               impl ::util::ser::Readable for $st {
+                       fn read<R: $crate::io::Read>(reader: &mut R) -> Result<Self, ::ln::msgs::DecodeError> {
+                               $(
+                                       init_tlv_field_var!($field, $fieldty);
+                               )*
+                               read_tlv_fields!(reader, {
+                                       $(($type, $field, $fieldty)),*
+                               });
+                               Ok(Self {
+                                       $(
+                                               $field: init_tlv_based_struct_field!($field, $fieldty)
+                                       ),*
+                               })
+                       }
+               }
+       }
+}
+
+macro_rules! _impl_writeable_tlv_based_enum_common {
+       ($st: ident, $(($variant_id: expr, $variant_name: ident) =>
+               {$(($type: expr, $field: ident, $fieldty: tt)),* $(,)*}
+       ),* $(,)*;
+       $(($tuple_variant_id: expr, $tuple_variant_name: ident)),*  $(,)*) => {
+               impl ::util::ser::Writeable for $st {
+                       fn write<W: ::util::ser::Writer>(&self, writer: &mut W) -> Result<(), $crate::io::Error> {
+                               match self {
+                                       $($st::$variant_name { $(ref $field),* } => {
+                                               let id: u8 = $variant_id;
+                                               id.write(writer)?;
+                                               write_tlv_fields!(writer, {
+                                                       $(($type, $field, $fieldty)),*
+                                               });
+                                       }),*
+                                       $($st::$tuple_variant_name (ref field) => {
+                                               let id: u8 = $tuple_variant_id;
+                                               id.write(writer)?;
+                                               field.write(writer)?;
+                                       }),*
+                               }
+                               Ok(())
+                       }
+               }
+       }
+}
+
+/// Implement MaybeReadable and Writeable for an enum, with struct variants stored as TLVs and
+/// tuple variants stored directly.
+///
+/// This is largely identical to `impl_writeable_tlv_based_enum`, except that odd variants will
+/// return `Ok(None)` instead of `Err(UnknownRequiredFeature)`. It should generally be preferred
+/// when `MaybeReadable` is practical instead of just `Readable` as it provides an upgrade path for
+/// new variants to be added which are simply ignored by existing clients.
+macro_rules! impl_writeable_tlv_based_enum_upgradable {
+       ($st: ident, $(($variant_id: expr, $variant_name: ident) =>
+               {$(($type: expr, $field: ident, $fieldty: tt)),* $(,)*}
+       ),* $(,)*) => {
+               _impl_writeable_tlv_based_enum_common!($st,
+                       $(($variant_id, $variant_name) => {$(($type, $field, $fieldty)),*}),*; );
+
+               impl ::util::ser::MaybeReadable for $st {
+                       fn read<R: $crate::io::Read>(reader: &mut R) -> Result<Option<Self>, ::ln::msgs::DecodeError> {
+                               let id: u8 = ::util::ser::Readable::read(reader)?;
+                               match id {
+                                       $($variant_id => {
+                                               // Because read_tlv_fields creates a labeled loop, we cannot call it twice
+                                               // in the same function body. Instead, we define a closure and call it.
+                                               let f = || {
+                                                       $(
+                                                               init_tlv_field_var!($field, $fieldty);
+                                                       )*
+                                                       read_tlv_fields!(reader, {
+                                                               $(($type, $field, $fieldty)),*
+                                                       });
+                                                       Ok(Some($st::$variant_name {
+                                                               $(
+                                                                       $field: init_tlv_based_struct_field!($field, $fieldty)
+                                                               ),*
+                                                       }))
+                                               };
+                                               f()
+                                       }),*
+                                       _ if id % 2 == 1 => Ok(None),
+                                       _ => Err(DecodeError::UnknownRequiredFeature),
+                               }
+                       }
+               }
+
+       }
+}
+
+/// Implement Readable and Writeable for an enum, with struct variants stored as TLVs and tuple
+/// variants stored directly.
+/// The format is, for example
+/// impl_writeable_tlv_based_enum!(EnumName,
+///   (0, StructVariantA) => {(0, required_variant_field, required), (1, optional_variant_field, option)},
+///   (1, StructVariantB) => {(0, variant_field_a, required), (1, variant_field_b, required), (2, variant_vec_field, vec_type)};
+///   (2, TupleVariantA), (3, TupleVariantB),
+/// );
+/// The type is written as a single byte, followed by any variant data.
+/// Attempts to read an unknown type byte result in DecodeError::UnknownRequiredFeature.
+macro_rules! impl_writeable_tlv_based_enum {
+       ($st: ident, $(($variant_id: expr, $variant_name: ident) =>
+               {$(($type: expr, $field: ident, $fieldty: tt)),* $(,)*}
+       ),* $(,)*;
+       $(($tuple_variant_id: expr, $tuple_variant_name: ident)),*  $(,)*) => {
+               _impl_writeable_tlv_based_enum_common!($st,
+                       $(($variant_id, $variant_name) => {$(($type, $field, $fieldty)),*}),*;
+                       $(($tuple_variant_id, $tuple_variant_name)),*);
+
+               impl ::util::ser::Readable for $st {
+                       fn read<R: $crate::io::Read>(reader: &mut R) -> Result<Self, ::ln::msgs::DecodeError> {
+                               let id: u8 = ::util::ser::Readable::read(reader)?;
+                               match id {
+                                       $($variant_id => {
+                                               // Because read_tlv_fields creates a labeled loop, we cannot call it twice
+                                               // in the same function body. Instead, we define a closure and call it.
+                                               let f = || {
+                                                       $(
+                                                               init_tlv_field_var!($field, $fieldty);
+                                                       )*
+                                                       read_tlv_fields!(reader, {
+                                                               $(($type, $field, $fieldty)),*
+                                                       });
+                                                       Ok($st::$variant_name {
+                                                               $(
+                                                                       $field: init_tlv_based_struct_field!($field, $fieldty)
+                                                               ),*
+                                                       })
+                                               };
+                                               f()
+                                       }),*
+                                       $($tuple_variant_id => {
+                                               Ok($st::$tuple_variant_name(Readable::read(reader)?))
+                                       }),*
+                                       _ => {
+                                               Err(DecodeError::UnknownRequiredFeature)
+                                       },
+                               }
+                       }
+               }
+       }
+}
+
+#[cfg(test)]
+mod tests {
+       use io::{self, Cursor};
+       use prelude::*;
+       use ln::msgs::DecodeError;
+       use util::ser::{Writeable, HighZeroBytesDroppedVarInt, VecWriter};
+       use bitcoin::secp256k1::PublicKey;
+
+       // The BOLT TLV test cases don't include any tests which use our "required-value" logic since
+       // the encoding layer in the BOLTs has no such concept, though it makes our macros easier to
+       // work with so they're baked into the decoder. Thus, we have a few additional tests below
+       fn tlv_reader(s: &[u8]) -> Result<(u64, u32, Option<u32>), DecodeError> {
+               let mut s = Cursor::new(s);
+               let mut a: u64 = 0;
+               let mut b: u32 = 0;
+               let mut c: Option<u32> = None;
+               decode_tlv_stream!(&mut s, {(2, a, required), (3, b, required), (4, c, option)});
+               Ok((a, b, c))
+       }
+
+       #[test]
+       fn tlv_v_short_read() {
+               // We only expect a u32 for type 3 (which we are given), but the L says its 8 bytes.
+               if let Err(DecodeError::ShortRead) = tlv_reader(&::hex::decode(
+                               concat!("0100", "0208deadbeef1badbeef", "0308deadbeef")
+                               ).unwrap()[..]) {
+               } else { panic!(); }
+       }
+
+       #[test]
+       fn tlv_types_out_of_order() {
+               if let Err(DecodeError::InvalidValue) = tlv_reader(&::hex::decode(
+                               concat!("0100", "0304deadbeef", "0208deadbeef1badbeef")
+                               ).unwrap()[..]) {
+               } else { panic!(); }
+               // ...even if its some field we don't understand
+               if let Err(DecodeError::InvalidValue) = tlv_reader(&::hex::decode(
+                               concat!("0208deadbeef1badbeef", "0100", "0304deadbeef")
+                               ).unwrap()[..]) {
+               } else { panic!(); }
+       }
+
+       #[test]
+       fn tlv_req_type_missing_or_extra() {
+               // It's also bad if they included even fields we don't understand
+               if let Err(DecodeError::UnknownRequiredFeature) = tlv_reader(&::hex::decode(
+                               concat!("0100", "0208deadbeef1badbeef", "0304deadbeef", "0600")
+                               ).unwrap()[..]) {
+               } else { panic!(); }
+               // ... or if they're missing fields we need
+               if let Err(DecodeError::InvalidValue) = tlv_reader(&::hex::decode(
+                               concat!("0100", "0208deadbeef1badbeef")
+                               ).unwrap()[..]) {
+               } else { panic!(); }
+               // ... even if that field is even
+               if let Err(DecodeError::InvalidValue) = tlv_reader(&::hex::decode(
+                               concat!("0304deadbeef", "0500")
+                               ).unwrap()[..]) {
+               } else { panic!(); }
+       }
+
+       #[test]
+       fn tlv_simple_good_cases() {
+               assert_eq!(tlv_reader(&::hex::decode(
+                               concat!("0208deadbeef1badbeef", "03041bad1dea")
+                               ).unwrap()[..]).unwrap(),
+                       (0xdeadbeef1badbeef, 0x1bad1dea, None));
+               assert_eq!(tlv_reader(&::hex::decode(
+                               concat!("0208deadbeef1badbeef", "03041bad1dea", "040401020304")
+                               ).unwrap()[..]).unwrap(),
+                       (0xdeadbeef1badbeef, 0x1bad1dea, Some(0x01020304)));
+       }
+
+       // BOLT TLV test cases
+       fn tlv_reader_n1(s: &[u8]) -> Result<(Option<HighZeroBytesDroppedVarInt<u64>>, Option<u64>, Option<(PublicKey, u64, u64)>, Option<u16>), DecodeError> {
+               let mut s = Cursor::new(s);
+               let mut tlv1: Option<HighZeroBytesDroppedVarInt<u64>> = None;
+               let mut tlv2: Option<u64> = None;
+               let mut tlv3: Option<(PublicKey, u64, u64)> = None;
+               let mut tlv4: Option<u16> = None;
+               decode_tlv_stream!(&mut s, {(1, tlv1, option), (2, tlv2, option), (3, tlv3, option), (254, tlv4, option)});
+               Ok((tlv1, tlv2, tlv3, tlv4))
+       }
+
+       #[test]
+       fn bolt_tlv_bogus_stream() {
+               macro_rules! do_test {
+                       ($stream: expr, $reason: ident) => {
+                               if let Err(DecodeError::$reason) = tlv_reader_n1(&::hex::decode($stream).unwrap()[..]) {
+                               } else { panic!(); }
+                       }
+               }
+
+               // TLVs from the BOLT test cases which should not decode as either n1 or n2
+               do_test!(concat!("fd01"), ShortRead);
+               do_test!(concat!("fd0001", "00"), InvalidValue);
+               do_test!(concat!("fd0101"), ShortRead);
+               do_test!(concat!("0f", "fd"), ShortRead);
+               do_test!(concat!("0f", "fd26"), ShortRead);
+               do_test!(concat!("0f", "fd2602"), ShortRead);
+               do_test!(concat!("0f", "fd0001", "00"), InvalidValue);
+               do_test!(concat!("0f", "fd0201", "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"), ShortRead);
+
+               do_test!(concat!("12", "00"), UnknownRequiredFeature);
+               do_test!(concat!("fd0102", "00"), UnknownRequiredFeature);
+               do_test!(concat!("fe01000002", "00"), UnknownRequiredFeature);
+               do_test!(concat!("ff0100000000000002", "00"), UnknownRequiredFeature);
+       }
+
+       #[test]
+       fn bolt_tlv_bogus_n1_stream() {
+               macro_rules! do_test {
+                       ($stream: expr, $reason: ident) => {
+                               if let Err(DecodeError::$reason) = tlv_reader_n1(&::hex::decode($stream).unwrap()[..]) {
+                               } else { panic!(); }
+                       }
+               }
+
+               // TLVs from the BOLT test cases which should not decode as n1
+               do_test!(concat!("01", "09", "ffffffffffffffffff"), InvalidValue);
+               do_test!(concat!("01", "01", "00"), InvalidValue);
+               do_test!(concat!("01", "02", "0001"), InvalidValue);
+               do_test!(concat!("01", "03", "000100"), InvalidValue);
+               do_test!(concat!("01", "04", "00010000"), InvalidValue);
+               do_test!(concat!("01", "05", "0001000000"), InvalidValue);
+               do_test!(concat!("01", "06", "000100000000"), InvalidValue);
+               do_test!(concat!("01", "07", "00010000000000"), InvalidValue);
+               do_test!(concat!("01", "08", "0001000000000000"), InvalidValue);
+               do_test!(concat!("02", "07", "01010101010101"), ShortRead);
+               do_test!(concat!("02", "09", "010101010101010101"), InvalidValue);
+               do_test!(concat!("03", "21", "023da092f6980e58d2c037173180e9a465476026ee50f96695963e8efe436f54eb"), ShortRead);
+               do_test!(concat!("03", "29", "023da092f6980e58d2c037173180e9a465476026ee50f96695963e8efe436f54eb0000000000000001"), ShortRead);
+               do_test!(concat!("03", "30", "023da092f6980e58d2c037173180e9a465476026ee50f96695963e8efe436f54eb000000000000000100000000000001"), ShortRead);
+               do_test!(concat!("03", "31", "043da092f6980e58d2c037173180e9a465476026ee50f96695963e8efe436f54eb00000000000000010000000000000002"), InvalidValue);
+               do_test!(concat!("03", "32", "023da092f6980e58d2c037173180e9a465476026ee50f96695963e8efe436f54eb0000000000000001000000000000000001"), InvalidValue);
+               do_test!(concat!("fd00fe", "00"), ShortRead);
+               do_test!(concat!("fd00fe", "01", "01"), ShortRead);
+               do_test!(concat!("fd00fe", "03", "010101"), InvalidValue);
+               do_test!(concat!("00", "00"), UnknownRequiredFeature);
+
+               do_test!(concat!("02", "08", "0000000000000226", "01", "01", "2a"), InvalidValue);
+               do_test!(concat!("02", "08", "0000000000000231", "02", "08", "0000000000000451"), InvalidValue);
+               do_test!(concat!("1f", "00", "0f", "01", "2a"), InvalidValue);
+               do_test!(concat!("1f", "00", "1f", "01", "2a"), InvalidValue);
+
+               // The last BOLT test modified to not require creating a new decoder for one trivial test.
+               do_test!(concat!("ffffffffffffffffff", "00", "01", "00"), InvalidValue);
+       }
+
+       #[test]
+       fn bolt_tlv_valid_n1_stream() {
+               macro_rules! do_test {
+                       ($stream: expr, $tlv1: expr, $tlv2: expr, $tlv3: expr, $tlv4: expr) => {
+                               if let Ok((tlv1, tlv2, tlv3, tlv4)) = tlv_reader_n1(&::hex::decode($stream).unwrap()[..]) {
+                                       assert_eq!(tlv1.map(|v| v.0), $tlv1);
+                                       assert_eq!(tlv2, $tlv2);
+                                       assert_eq!(tlv3, $tlv3);
+                                       assert_eq!(tlv4, $tlv4);
+                               } else { panic!(); }
+                       }
+               }
+
+               do_test!(concat!(""), None, None, None, None);
+               do_test!(concat!("21", "00"), None, None, None, None);
+               do_test!(concat!("fd0201", "00"), None, None, None, None);
+               do_test!(concat!("fd00fd", "00"), None, None, None, None);
+               do_test!(concat!("fd00ff", "00"), None, None, None, None);
+               do_test!(concat!("fe02000001", "00"), None, None, None, None);
+               do_test!(concat!("ff0200000000000001", "00"), None, None, None, None);
+
+               do_test!(concat!("01", "00"), Some(0), None, None, None);
+               do_test!(concat!("01", "01", "01"), Some(1), None, None, None);
+               do_test!(concat!("01", "02", "0100"), Some(256), None, None, None);
+               do_test!(concat!("01", "03", "010000"), Some(65536), None, None, None);
+               do_test!(concat!("01", "04", "01000000"), Some(16777216), None, None, None);
+               do_test!(concat!("01", "05", "0100000000"), Some(4294967296), None, None, None);
+               do_test!(concat!("01", "06", "010000000000"), Some(1099511627776), None, None, None);
+               do_test!(concat!("01", "07", "01000000000000"), Some(281474976710656), None, None, None);
+               do_test!(concat!("01", "08", "0100000000000000"), Some(72057594037927936), None, None, None);
+               do_test!(concat!("02", "08", "0000000000000226"), None, Some((0 << 30) | (0 << 5) | (550 << 0)), None, None);
+               do_test!(concat!("03", "31", "023da092f6980e58d2c037173180e9a465476026ee50f96695963e8efe436f54eb00000000000000010000000000000002"),
+                       None, None, Some((
+                               PublicKey::from_slice(&::hex::decode("023da092f6980e58d2c037173180e9a465476026ee50f96695963e8efe436f54eb").unwrap()[..]).unwrap(), 1, 2)),
+                       None);
+               do_test!(concat!("fd00fe", "02", "0226"), None, None, None, Some(550));
+       }
+
+       fn do_simple_test_tlv_write() -> Result<(), io::Error> {
+               let mut stream = VecWriter(Vec::new());
+
+               stream.0.clear();
+               encode_varint_length_prefixed_tlv!(&mut stream, {(1, 1u8, required), (42, None::<u64>, option)});
+               assert_eq!(stream.0, ::hex::decode("03010101").unwrap());
+
+               stream.0.clear();
+               encode_varint_length_prefixed_tlv!(&mut stream, {(1, Some(1u8), option)});
+               assert_eq!(stream.0, ::hex::decode("03010101").unwrap());
+
+               stream.0.clear();
+               encode_varint_length_prefixed_tlv!(&mut stream, {(4, 0xabcdu16, required), (42, None::<u64>, option)});
+               assert_eq!(stream.0, ::hex::decode("040402abcd").unwrap());
+
+               stream.0.clear();
+               encode_varint_length_prefixed_tlv!(&mut stream, {(42, None::<u64>, option), (0xff, 0xabcdu16, required)});
+               assert_eq!(stream.0, ::hex::decode("06fd00ff02abcd").unwrap());
+
+               stream.0.clear();
+               encode_varint_length_prefixed_tlv!(&mut stream, {(0, 1u64, required), (42, None::<u64>, option), (0xff, HighZeroBytesDroppedVarInt(0u64), required)});
+               assert_eq!(stream.0, ::hex::decode("0e00080000000000000001fd00ff00").unwrap());
+
+               stream.0.clear();
+               encode_varint_length_prefixed_tlv!(&mut stream, {(0, Some(1u64), option), (0xff, HighZeroBytesDroppedVarInt(0u64), required)});
+               assert_eq!(stream.0, ::hex::decode("0e00080000000000000001fd00ff00").unwrap());
+
+               Ok(())
+       }
+
+       #[test]
+       fn simple_test_tlv_write() {
+               do_simple_test_tlv_write().unwrap();
        }
 }