reference_trie/

substrate.rs

// Copyright (C) Parity Technologies (UK) Ltd.
//
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Codec and layout directly copy-pasted from substrate with minimal modifications.

use core::{borrow::Borrow, iter::once, marker::PhantomData, ops::Range};
use hash_db::Hasher;
use parity_scale_codec as codec;
use parity_scale_codec::{Compact, Decode, Encode, Input, Output};
use trie_db::{
	nibble_ops,
	node::{NibbleSlicePlan, NodeHandlePlan, NodePlan, Value, ValuePlan},
	ChildReference, NodeCodec as NodeCodecT, TrieConfiguration, TrieLayout,
};

/// Constants used into trie simplification codec.
mod trie_constants {
	const FIRST_PREFIX: u8 = 0b_00 << 6;
	pub const LEAF_PREFIX_MASK: u8 = 0b_01 << 6;
	pub const BRANCH_WITHOUT_MASK: u8 = 0b_10 << 6;
	pub const BRANCH_WITH_MASK: u8 = 0b_11 << 6;
	pub const EMPTY_TRIE: u8 = FIRST_PREFIX | (0b_00 << 4);
	pub const ALT_HASHING_LEAF_PREFIX_MASK: u8 = FIRST_PREFIX | (0b_1 << 5);
	pub const ALT_HASHING_BRANCH_WITH_MASK: u8 = FIRST_PREFIX | (0b_01 << 4);
	pub const ESCAPE_COMPACT_HEADER: u8 = EMPTY_TRIE | 0b_00_01;
}

pub const TRIE_VALUE_NODE_THRESHOLD: u32 = 33;

/// Codec-flavored TrieStream.
#[derive(Default, Clone)]
pub struct TrieStream {
	/// Current node buffer.
	buffer: Vec<u8>,
}

fn branch_node_bit_mask(has_children: impl Iterator<Item = bool>) -> (u8, u8) {
	let mut bitmap: u16 = 0;
	let mut cursor: u16 = 1;
	for v in has_children {
		if v {
			bitmap |= cursor
		}
		cursor <<= 1;
	}
	((bitmap % 256) as u8, (bitmap / 256) as u8)
}

/// Create a leaf/branch node, encoding a number of nibbles.
fn fuse_nibbles_node(nibbles: &[u8], kind: NodeKind) -> impl Iterator<Item = u8> + '_ {
	let size = nibbles.len();
	let iter_start = match kind {
		NodeKind::Leaf => size_and_prefix_iterator(size, trie_constants::LEAF_PREFIX_MASK, 2),
		NodeKind::BranchNoValue =>
			size_and_prefix_iterator(size, trie_constants::BRANCH_WITHOUT_MASK, 2),
		NodeKind::BranchWithValue =>
			size_and_prefix_iterator(size, trie_constants::BRANCH_WITH_MASK, 2),
		NodeKind::HashedValueLeaf =>
			size_and_prefix_iterator(size, trie_constants::ALT_HASHING_LEAF_PREFIX_MASK, 3),
		NodeKind::HashedValueBranch =>
			size_and_prefix_iterator(size, trie_constants::ALT_HASHING_BRANCH_WITH_MASK, 4),
	};
	iter_start
		.chain(if nibbles.len() % 2 == 1 { Some(nibbles[0]) } else { None })
		.chain(nibbles[nibbles.len() % 2..].chunks(2).map(|ch| ch[0] << 4 | ch[1]))
}

use trie_root::Value as TrieStreamValue;
impl trie_root::TrieStream for TrieStream {
	fn new() -> Self {
		Self { buffer: Vec::new() }
	}

	fn append_empty_data(&mut self) {
		self.buffer.push(trie_constants::EMPTY_TRIE);
	}

	fn append_leaf(&mut self, key: &[u8], value: TrieStreamValue) {
		let kind = match &value {
			TrieStreamValue::Inline(..) => NodeKind::Leaf,
			TrieStreamValue::Node(..) => NodeKind::HashedValueLeaf,
		};
		self.buffer.extend(fuse_nibbles_node(key, kind));
		match &value {
			TrieStreamValue::Inline(value) => {
				Compact(value.len() as u32).encode_to(&mut self.buffer);
				self.buffer.extend_from_slice(value);
			},
			TrieStreamValue::Node(hash) => {
				self.buffer.extend_from_slice(hash.as_slice());
			},
		};
	}

	fn begin_branch(
		&mut self,
		maybe_partial: Option<&[u8]>,
		maybe_value: Option<TrieStreamValue>,
		has_children: impl Iterator<Item = bool>,
	) {
		if let Some(partial) = maybe_partial {
			let kind = match &maybe_value {
				None => NodeKind::BranchNoValue,
				Some(TrieStreamValue::Inline(..)) => NodeKind::BranchWithValue,
				Some(TrieStreamValue::Node(..)) => NodeKind::HashedValueBranch,
			};

			self.buffer.extend(fuse_nibbles_node(partial, kind));
			let bm = branch_node_bit_mask(has_children);
			self.buffer.extend([bm.0, bm.1].iter());
		} else {
			unreachable!("trie stream codec only for no extension trie");
		}
		match maybe_value {
			None => (),
			Some(TrieStreamValue::Inline(value)) => {
				Compact(value.len() as u32).encode_to(&mut self.buffer);
				self.buffer.extend_from_slice(value);
			},
			Some(TrieStreamValue::Node(hash)) => {
				self.buffer.extend_from_slice(hash.as_slice());
			},
		}
	}

	fn append_extension(&mut self, _key: &[u8]) {
		debug_assert!(false, "trie stream codec only for no extension trie");
	}

	fn append_substream<H: Hasher>(&mut self, other: Self) {
		let data = other.out();
		match data.len() {
			0..=31 => data.encode_to(&mut self.buffer),
			_ => H::hash(&data).as_ref().encode_to(&mut self.buffer),
		}
	}

	fn out(self) -> Vec<u8> {
		self.buffer
	}
}

/// Helper struct for trie node decoder. This implements `codec::Input` on a byte slice, while
/// tracking the absolute position. This is similar to `std::io::Cursor` but does not implement
/// `Read` and `io` is not in `sp-std`.
struct ByteSliceInput<'a> {
	data: &'a [u8],
	offset: usize,
}

impl<'a> ByteSliceInput<'a> {
	fn new(data: &'a [u8]) -> Self {
		ByteSliceInput { data, offset: 0 }
	}

	fn take(&mut self, count: usize) -> Result<Range<usize>, codec::Error> {
		if self.offset + count > self.data.len() {
			return Err("out of data".into())
		}

		let range = self.offset..(self.offset + count);
		self.offset += count;
		Ok(range)
	}
}

impl<'a> Input for ByteSliceInput<'a> {
	fn remaining_len(&mut self) -> Result<Option<usize>, codec::Error> {
		Ok(Some(self.data.len().saturating_sub(self.offset)))
	}

	fn read(&mut self, into: &mut [u8]) -> Result<(), codec::Error> {
		let range = self.take(into.len())?;
		into.copy_from_slice(&self.data[range]);
		Ok(())
	}

	fn read_byte(&mut self) -> Result<u8, codec::Error> {
		if self.offset + 1 > self.data.len() {
			return Err("out of data".into())
		}

		let byte = self.data[self.offset];
		self.offset += 1;
		Ok(byte)
	}
}

/// Concrete implementation of a [`NodeCodecT`] with SCALE encoding.
///
/// It is generic over `H` the [`Hasher`].
#[derive(Default, Clone)]
pub struct NodeCodec<H>(PhantomData<H>);

impl<H> NodeCodecT for NodeCodec<H>
where
	H: Hasher,
{
	const ESCAPE_HEADER: Option<u8> = Some(trie_constants::ESCAPE_COMPACT_HEADER);
	type Error = Error<H::Out>;
	type HashOut = H::Out;

	fn hashed_null_node() -> <H as Hasher>::Out {
		H::hash(<Self as NodeCodecT>::empty_node())
	}

	fn decode_plan(data: &[u8]) -> Result<NodePlan, Self::Error> {
		let mut input = ByteSliceInput::new(data);

		let header = NodeHeader::decode(&mut input)?;
		let contains_hash = header.contains_hash_of_value();

		let branch_has_value = if let NodeHeader::Branch(has_value, _) = &header {
			*has_value
		} else {
			// hashed_value_branch
			true
		};

		match header {
			NodeHeader::Null => Ok(NodePlan::Empty),
			NodeHeader::HashedValueBranch(nibble_count) | NodeHeader::Branch(_, nibble_count) => {
				let padding = nibble_count % nibble_ops::NIBBLE_PER_BYTE != 0;
				// check that the padding is valid (if any)
				if padding && nibble_ops::pad_left(data[input.offset]) != 0 {
					return Err(Error::BadFormat)
				}
				let partial = input.take(
					(nibble_count + (nibble_ops::NIBBLE_PER_BYTE - 1)) /
						nibble_ops::NIBBLE_PER_BYTE,
				)?;
				let partial_padding = nibble_ops::number_padding(nibble_count);
				let bitmap_range = input.take(BITMAP_LENGTH)?;
				let bitmap = Bitmap::decode(&data[bitmap_range])?;
				let value = if branch_has_value {
					Some(if contains_hash {
						ValuePlan::Node(input.take(H::LENGTH)?)
					} else {
						let count = <Compact<u32>>::decode(&mut input)?.0 as usize;
						ValuePlan::Inline(input.take(count)?)
					})
				} else {
					None
				};
				let mut children = [
					None, None, None, None, None, None, None, None, None, None, None, None, None,
					None, None, None,
				];
				for i in 0..nibble_ops::NIBBLE_LENGTH {
					if bitmap.value_at(i) {
						let count = <Compact<u32>>::decode(&mut input)?.0 as usize;
						let range = input.take(count)?;
						children[i] = Some(if count == H::LENGTH {
							NodeHandlePlan::Hash(range)
						} else {
							NodeHandlePlan::Inline(range)
						});
					}
				}
				Ok(NodePlan::NibbledBranch {
					partial: NibbleSlicePlan::new(partial, partial_padding),
					value,
					children,
				})
			},
			NodeHeader::HashedValueLeaf(nibble_count) | NodeHeader::Leaf(nibble_count) => {
				let padding = nibble_count % nibble_ops::NIBBLE_PER_BYTE != 0;
				// check that the padding is valid (if any)
				if padding && nibble_ops::pad_left(data[input.offset]) != 0 {
					return Err(Error::BadFormat)
				}
				let partial = input.take(
					(nibble_count + (nibble_ops::NIBBLE_PER_BYTE - 1)) /
						nibble_ops::NIBBLE_PER_BYTE,
				)?;
				let partial_padding = nibble_ops::number_padding(nibble_count);
				let value = if contains_hash {
					ValuePlan::Node(input.take(H::LENGTH)?)
				} else {
					let count = <Compact<u32>>::decode(&mut input)?.0 as usize;
					ValuePlan::Inline(input.take(count)?)
				};

				Ok(NodePlan::Leaf {
					partial: NibbleSlicePlan::new(partial, partial_padding),
					value,
				})
			},
		}
	}

	fn is_empty_node(data: &[u8]) -> bool {
		data == <Self as NodeCodecT>::empty_node()
	}

	fn empty_node() -> &'static [u8] {
		&[trie_constants::EMPTY_TRIE]
	}

	fn leaf_node(partial: impl Iterator<Item = u8>, number_nibble: usize, value: Value) -> Vec<u8> {
		let contains_hash = matches!(&value, Value::Node(..));
		let mut output = if contains_hash {
			partial_from_iterator_encode(partial, number_nibble, NodeKind::HashedValueLeaf)
		} else {
			partial_from_iterator_encode(partial, number_nibble, NodeKind::Leaf)
		};
		match value {
			Value::Inline(value) => {
				Compact(value.len() as u32).encode_to(&mut output);
				output.extend_from_slice(value);
			},
			Value::Node(hash) => {
				debug_assert!(hash.len() == H::LENGTH);
				output.extend_from_slice(hash);
			},
		}
		output
	}

	fn extension_node(
		_partial: impl Iterator<Item = u8>,
		_nbnibble: usize,
		_child: ChildReference<<H as Hasher>::Out>,
	) -> Vec<u8> {
		unreachable!("No extension codec.")
	}

	fn branch_node(
		_children: impl Iterator<Item = impl Borrow<Option<ChildReference<<H as Hasher>::Out>>>>,
		_maybe_value: Option<Value>,
	) -> Vec<u8> {
		unreachable!("No extension codec.")
	}

	fn branch_node_nibbled(
		partial: impl Iterator<Item = u8>,
		number_nibble: usize,
		children: impl Iterator<Item = impl Borrow<Option<ChildReference<<H as Hasher>::Out>>>>,
		value: Option<Value>,
	) -> Vec<u8> {
		let contains_hash = matches!(&value, Some(Value::Node(..)));
		let mut output = match (&value, contains_hash) {
			(&None, _) =>
				partial_from_iterator_encode(partial, number_nibble, NodeKind::BranchNoValue),
			(_, false) =>
				partial_from_iterator_encode(partial, number_nibble, NodeKind::BranchWithValue),
			(_, true) =>
				partial_from_iterator_encode(partial, number_nibble, NodeKind::HashedValueBranch),
		};

		let bitmap_index = output.len();
		let mut bitmap: [u8; BITMAP_LENGTH] = [0; BITMAP_LENGTH];
		(0..BITMAP_LENGTH).for_each(|_| output.push(0));
		match value {
			Some(Value::Inline(value)) => {
				Compact(value.len() as u32).encode_to(&mut output);
				output.extend_from_slice(value);
			},
			Some(Value::Node(hash)) => {
				debug_assert!(hash.len() == H::LENGTH);
				output.extend_from_slice(hash);
			},
			None => (),
		}
		Bitmap::encode(
			children.map(|maybe_child| match maybe_child.borrow() {
				Some(ChildReference::Hash(h)) => {
					h.as_ref().encode_to(&mut output);
					true
				},
				&Some(ChildReference::Inline(inline_data, len)) => {
					inline_data.as_ref()[..len].encode_to(&mut output);
					true
				},
				None => false,
			}),
			bitmap.as_mut(),
		);
		output[bitmap_index..bitmap_index + BITMAP_LENGTH]
			.copy_from_slice(&bitmap[..BITMAP_LENGTH]);
		output
	}
}

// utils

/// Encode and allocate node type header (type and size), and partial value.
/// It uses an iterator over encoded partial bytes as input.
fn partial_from_iterator_encode<I: Iterator<Item = u8>>(
	partial: I,
	nibble_count: usize,
	node_kind: NodeKind,
) -> Vec<u8> {
	let mut output = Vec::with_capacity(4 + (nibble_count / nibble_ops::NIBBLE_PER_BYTE));
	match node_kind {
		NodeKind::Leaf => NodeHeader::Leaf(nibble_count).encode_to(&mut output),
		NodeKind::BranchWithValue => NodeHeader::Branch(true, nibble_count).encode_to(&mut output),
		NodeKind::BranchNoValue => NodeHeader::Branch(false, nibble_count).encode_to(&mut output),
		NodeKind::HashedValueLeaf =>
			NodeHeader::HashedValueLeaf(nibble_count).encode_to(&mut output),
		NodeKind::HashedValueBranch =>
			NodeHeader::HashedValueBranch(nibble_count).encode_to(&mut output),
	};
	output.extend(partial);
	output
}

const BITMAP_LENGTH: usize = 2;

/// Radix 16 trie, bitmap encoding implementation,
/// it contains children mapping information for a branch
/// (children presence only), it encodes into
/// a compact bitmap encoding representation.
pub(crate) struct Bitmap(u16);

impl Bitmap {
	pub fn decode(data: &[u8]) -> Result<Self, codec::Error> {
		let value = u16::decode(&mut &data[..])?;
		if value == 0 {
			Err("Bitmap without a child.".into())
		} else {
			Ok(Bitmap(value))
		}
	}

	pub fn value_at(&self, i: usize) -> bool {
		self.0 & (1u16 << i) != 0
	}

	pub fn encode<I: Iterator<Item = bool>>(has_children: I, dest: &mut [u8]) {
		let mut bitmap: u16 = 0;
		let mut cursor: u16 = 1;
		for v in has_children {
			if v {
				bitmap |= cursor
			}
			cursor <<= 1;
		}
		dest[0] = (bitmap % 256) as u8;
		dest[1] = (bitmap / 256) as u8;
	}
}

/// substrate trie layout
pub struct LayoutV0<H>(PhantomData<H>);

/// substrate trie layout, with external value nodes.
pub struct LayoutV1<H>(PhantomData<H>);

impl<H> TrieLayout for LayoutV0<H>
where
	H: Hasher + core::fmt::Debug,
{
	const USE_EXTENSION: bool = false;
	const ALLOW_EMPTY: bool = true;
	const MAX_INLINE_VALUE: Option<u32> = None;

	type Hash = H;
	type Codec = NodeCodec<Self::Hash>;
}

impl<H> TrieConfiguration for LayoutV0<H>
where
	H: Hasher + core::fmt::Debug,
{
	fn trie_root<I, A, B>(input: I) -> <Self::Hash as Hasher>::Out
	where
		I: IntoIterator<Item = (A, B)>,
		A: AsRef<[u8]> + Ord,
		B: AsRef<[u8]>,
	{
		trie_root::trie_root_no_extension::<H, TrieStream, _, _, _>(input, Self::MAX_INLINE_VALUE)
	}

	fn trie_root_unhashed<I, A, B>(input: I) -> Vec<u8>
	where
		I: IntoIterator<Item = (A, B)>,
		A: AsRef<[u8]> + Ord,
		B: AsRef<[u8]>,
	{
		trie_root::unhashed_trie_no_extension::<H, TrieStream, _, _, _>(
			input,
			Self::MAX_INLINE_VALUE,
		)
	}

	fn encode_index(input: u32) -> Vec<u8> {
		codec::Encode::encode(&codec::Compact(input))
	}
}

impl<H> TrieLayout for LayoutV1<H>
where
	H: Hasher + core::fmt::Debug,
{
	const USE_EXTENSION: bool = false;
	const ALLOW_EMPTY: bool = true;
	const MAX_INLINE_VALUE: Option<u32> = Some(TRIE_VALUE_NODE_THRESHOLD);

	type Hash = H;
	type Codec = NodeCodec<Self::Hash>;
}

impl<H> TrieConfiguration for LayoutV1<H>
where
	H: Hasher + core::fmt::Debug,
{
	fn trie_root<I, A, B>(input: I) -> <Self::Hash as Hasher>::Out
	where
		I: IntoIterator<Item = (A, B)>,
		A: AsRef<[u8]> + Ord,
		B: AsRef<[u8]>,
	{
		trie_root::trie_root_no_extension::<H, TrieStream, _, _, _>(input, Self::MAX_INLINE_VALUE)
	}

	fn trie_root_unhashed<I, A, B>(input: I) -> Vec<u8>
	where
		I: IntoIterator<Item = (A, B)>,
		A: AsRef<[u8]> + Ord,
		B: AsRef<[u8]>,
	{
		trie_root::unhashed_trie_no_extension::<H, TrieStream, _, _, _>(
			input,
			Self::MAX_INLINE_VALUE,
		)
	}

	fn encode_index(input: u32) -> Vec<u8> {
		codec::Encode::encode(&codec::Compact(input))
	}
}

/// A node header
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub(crate) enum NodeHeader {
	Null,
	// contains wether there is a value and nibble count
	Branch(bool, usize),
	// contains nibble count
	Leaf(usize),
	// contains nibble count.
	HashedValueBranch(usize),
	// contains nibble count.
	HashedValueLeaf(usize),
}

impl NodeHeader {
	pub(crate) fn contains_hash_of_value(&self) -> bool {
		matches!(self, NodeHeader::HashedValueBranch(_) | NodeHeader::HashedValueLeaf(_))
	}
}

/// NodeHeader without content
pub(crate) enum NodeKind {
	Leaf,
	BranchNoValue,
	BranchWithValue,
	HashedValueLeaf,
	HashedValueBranch,
}

impl Encode for NodeHeader {
	fn encode_to<T: Output + ?Sized>(&self, output: &mut T) {
		match self {
			NodeHeader::Null => output.push_byte(trie_constants::EMPTY_TRIE),
			NodeHeader::Branch(true, nibble_count) =>
				encode_size_and_prefix(*nibble_count, trie_constants::BRANCH_WITH_MASK, 2, output),
			NodeHeader::Branch(false, nibble_count) => encode_size_and_prefix(
				*nibble_count,
				trie_constants::BRANCH_WITHOUT_MASK,
				2,
				output,
			),
			NodeHeader::Leaf(nibble_count) =>
				encode_size_and_prefix(*nibble_count, trie_constants::LEAF_PREFIX_MASK, 2, output),
			NodeHeader::HashedValueBranch(nibble_count) => encode_size_and_prefix(
				*nibble_count,
				trie_constants::ALT_HASHING_BRANCH_WITH_MASK,
				4,
				output,
			),
			NodeHeader::HashedValueLeaf(nibble_count) => encode_size_and_prefix(
				*nibble_count,
				trie_constants::ALT_HASHING_LEAF_PREFIX_MASK,
				3,
				output,
			),
		}
	}
}

impl codec::EncodeLike for NodeHeader {}

impl Decode for NodeHeader {
	fn decode<I: Input>(input: &mut I) -> Result<Self, codec::Error> {
		let i = input.read_byte()?;
		if i == trie_constants::EMPTY_TRIE {
			return Ok(NodeHeader::Null)
		}
		match i & (0b11 << 6) {
			trie_constants::LEAF_PREFIX_MASK => Ok(NodeHeader::Leaf(decode_size(i, input, 2)?)),
			trie_constants::BRANCH_WITH_MASK =>
				Ok(NodeHeader::Branch(true, decode_size(i, input, 2)?)),
			trie_constants::BRANCH_WITHOUT_MASK =>
				Ok(NodeHeader::Branch(false, decode_size(i, input, 2)?)),
			trie_constants::EMPTY_TRIE => {
				if i & (0b111 << 5) == trie_constants::ALT_HASHING_LEAF_PREFIX_MASK {
					Ok(NodeHeader::HashedValueLeaf(decode_size(i, input, 3)?))
				} else if i & (0b1111 << 4) == trie_constants::ALT_HASHING_BRANCH_WITH_MASK {
					Ok(NodeHeader::HashedValueBranch(decode_size(i, input, 4)?))
				} else {
					// do not allow any special encoding
					Err("Unallowed encoding".into())
				}
			},
			_ => unreachable!(),
		}
	}
}

/// Returns an iterator over encoded bytes for node header and size.
/// Size encoding allows unlimited, length inefficient, representation, but
/// is bounded to 16 bit maximum value to avoid possible DOS.
pub(crate) fn size_and_prefix_iterator(
	size: usize,
	prefix: u8,
	prefix_mask: usize,
) -> impl Iterator<Item = u8> {
	let max_value = 255u8 >> prefix_mask;
	let l1 = core::cmp::min((max_value as usize).saturating_sub(1), size);
	let (first_byte, mut rem) = if size == l1 {
		(once(prefix + l1 as u8), 0)
	} else {
		(once(prefix + max_value as u8), size - l1)
	};
	let next_bytes = move || {
		if rem > 0 {
			if rem < 256 {
				let result = rem - 1;
				rem = 0;
				Some(result as u8)
			} else {
				rem = rem.saturating_sub(255);
				Some(255)
			}
		} else {
			None
		}
	};
	first_byte.chain(core::iter::from_fn(next_bytes))
}

/// Encodes size and prefix to a stream output.
fn encode_size_and_prefix<W>(size: usize, prefix: u8, prefix_mask: usize, out: &mut W)
where
	W: Output + ?Sized,
{
	for b in size_and_prefix_iterator(size, prefix, prefix_mask) {
		out.push_byte(b)
	}
}

/// Decode size only from stream input and header byte.
fn decode_size(
	first: u8,
	input: &mut impl Input,
	prefix_mask: usize,
) -> Result<usize, codec::Error> {
	let max_value = 255u8 >> prefix_mask;
	let mut result = (first & max_value) as usize;
	if result < max_value as usize {
		return Ok(result)
	}
	result -= 1;
	loop {
		let n = input.read_byte()? as usize;
		if n < 255 {
			return Ok(result + n + 1)
		}
		result += 255;
	}
}

/// Error type used for trie related errors.
#[derive(Debug, PartialEq, Eq, Clone)]
pub enum Error<H> {
	BadFormat,
	Decode(codec::Error),
	InvalidRecording(Vec<u8>, bool),
	TrieError(Box<trie_db::TrieError<H, Self>>),
}

impl<H> core::fmt::Display for Error<H> {
	fn fmt(&self, fmt: &mut core::fmt::Formatter) -> core::fmt::Result {
		fmt.write_str("Error")
	}
}

impl<H> std::error::Error for Error<H> where H: core::fmt::Debug {}

impl<H> From<codec::Error> for Error<H> {
	fn from(x: codec::Error) -> Self {
		Error::Decode(x)
	}
}

impl<H> From<Box<trie_db::TrieError<H, Self>>> for Error<H> {
	fn from(x: Box<trie_db::TrieError<H, Self>>) -> Self {
		Error::TrieError(x)
	}
}