no_std support for substrate trie (#2146)

* no_std trie compile in test_runtime (require to set nightly feature due
to the way hashbrown currently works).

* No nightly with hashmap_core.

* using crate elastic-array

* switch to publish trie crates

* fix default array decl

* bump impl_version for ci

* set all semver when possible wasm, and remove redundant code.

* Actually test use_trie function

* impl version +1

* Bump impl version

substrate/core/trie/src/error.rs

@@ -6,7 +6,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#[cfg(feature="std")]
 use std::fmt;
+#[cfg(feature="std")]
 use std::error::Error as StdError;
 
 #[derive(Debug, PartialEq, Eq, Clone)]
@@ -16,12 +18,14 @@ pub enum Error {
 	BadFormat,
 }
 
+#[cfg(feature="std")]
 impl StdError for Error {
 	fn description(&self) -> &str {
 		"codec error"
 	}
 }
 
+#[cfg(feature="std")]
 impl fmt::Display for Error {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		fmt::Debug::fmt(&self, f)

substrate/core/trie/src/lib.rs

@@ -16,13 +16,16 @@
 
 //! Utility functions to interact with Substrate's Base-16 Modified Merkle Patricia tree ("trie").
 
-// FIXME: no_std - https://github.com/paritytech/substrate/issues/1574
+#![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(not(feature = "std"), feature(alloc))]
 
 mod error;
 mod node_header;
 mod node_codec;
 mod trie_stream;
 
+use rstd::boxed::Box;
+use rstd::vec::Vec;
 use hash_db::Hasher;
 /// Our `NodeCodec`-specific error.
 pub use error::Error;
@@ -290,7 +293,7 @@ fn take<'a>(input: &mut &'a[u8], count: usize) -> Option<&'a[u8]> {
 fn partial_to_key(partial: &[u8], offset: u8, big: u8) -> Vec<u8> {
 	let nibble_count = (partial.len() - 1) * 2 + if partial[0] & 16 == 16 { 1 } else { 0 };
 	let (first_byte_small, big_threshold) = (offset, (big - offset) as usize);
-	let mut output = vec![first_byte_small + nibble_count.min(big_threshold) as u8];
+	let mut output = [first_byte_small + nibble_count.min(big_threshold) as u8].to_vec();
 	if nibble_count >= big_threshold { output.push((nibble_count - big_threshold) as u8) }
 	if nibble_count % 2 == 1 {
 		output.push(partial[0] & 0x0f);

substrate/core/trie/src/node_codec.rs

@@ -16,7 +16,8 @@
 
 //! `NodeCodec` implementation for Substrate's trie format.
 
-use std::marker::PhantomData;
+use rstd::marker::PhantomData;
+use rstd::vec::Vec;
 use codec::{Encode, Decode, Compact};
 use hash_db::Hasher;
 use trie_db::{self, DBValue, NibbleSlice, node::Node, ChildReference};
@@ -28,10 +29,6 @@ use super::{EMPTY_TRIE, LEAF_NODE_OFFSET, LEAF_NODE_BIG, EXTENSION_NODE_OFFSET,
 #[derive(Default, Clone)]
 pub struct NodeCodec<H: Hasher>(PhantomData<H>);
 
-// NOTE: what we'd really like here is:
-// `impl<H: Hasher> NodeCodec<H> for RlpNodeCodec<H> where H::Out: Decodable`
-// but due to the current limitations of Rust const evaluation we can't
-// do `const HASHED_NULL_NODE: H::Out = H::Out( … … )`. Perhaps one day soon?
 impl<H: Hasher> trie_db::NodeCodec<H> for NodeCodec<H> {
 	type Error = Error;
 
@@ -39,7 +36,7 @@ impl<H: Hasher> trie_db::NodeCodec<H> for NodeCodec<H> {
 		H::hash(&[0u8][..])
 	}
 
-	fn decode(data: &[u8]) -> ::std::result::Result<Node, Self::Error> {
+	fn decode(data: &[u8]) -> ::rstd::result::Result<Node, Self::Error> {
 		use Error::BadFormat;
 		let input = &mut &*data;
 		match NodeHeader::decode(input).ok_or(BadFormat)? {
@@ -92,7 +89,7 @@ impl<H: Hasher> trie_db::NodeCodec<H> for NodeCodec<H> {
 		data == &[EMPTY_TRIE][..]
 	}
 	fn empty_node() -> Vec<u8> {
-		vec![EMPTY_TRIE]
+		[EMPTY_TRIE].to_vec()
 	}
 
 	// FIXME: refactor this so that `partial` isn't already encoded with HPE. Should just be an `impl Iterator<Item=u8>`.
@@ -117,7 +114,7 @@ impl<H: Hasher> trie_db::NodeCodec<H> for NodeCodec<H> {
 	fn branch_node<I>(children: I, maybe_value: Option<DBValue>) -> Vec<u8>
 		where I: IntoIterator<Item=Option<ChildReference<H::Out>>> + Iterator<Item=Option<ChildReference<H::Out>>>
 	{
-		let mut output = vec![0, 0, 0];
+		let mut output = [0, 0, 0].to_vec();
 		let have_value = if let Some(value) = maybe_value {
 			(&*value).encode_to(&mut output);
 			true

substrate/core/trie/src/trie_stream.rs

@@ -16,10 +16,11 @@
 
 //! `TrieStream` implementation for Substrate's trie format. 
 
-use std::iter::once;
+use rstd::iter::once;
 use hash_db::Hasher;
 use trie_root;
 use codec::Encode;
+use rstd::vec::Vec;
 
 use super::{EMPTY_TRIE, LEAF_NODE_OFFSET, LEAF_NODE_BIG, EXTENSION_NODE_OFFSET,
 	EXTENSION_NODE_BIG, branch_node};