Implement runtime api client side directly in the runtime (#1094)

* Move `initialise_block` into `Core` trait as it is crucial calling the API functions * Switch to first version of new runtime API implementation * Fixes bug in tests * Reenable asserts * Directly use the `TestAPI` in the tests * Start improving the api traits :100644 100644 898aadc7 49217199 M Cargo.lock :100644 100644 61570436 465ed664 M core/client/src/backend.rs :100644 100644 5d0c886b 64d710fd M core/client/src/block_builder.rs :100644 100644 c447855e 5ecbe474 M core/client/src/client.rs :100644 100644 139cef13 f90dbf3d M core/client/src/error.rs :100644 100644 2800c503 3298e66a M core/client/src/runtime_api.rs :100644 100644 affa1c5c 809b08bc M core/primitives/src/lib.rs :100644 100644 2877dfa9 d5547413 M core/sr-api/Cargo.toml :100644 100644 9a49784d 6a625a03 M core/sr-api/src/lib.rs :100644 100644 7c28e1c7 a1a444a9 M core/sr-primitives/src/traits.rs :100644 100644 2e113ab6 dcc01a6d M srml/metadata/Cargo.toml :100644 100644 ea722a70 0809531a M srml/metadata/src/lib.rs * Refactoring * Move `sr-api` into client and more refactoring * Fixes tests * Some documentation and cleanup * Fixes compilation after rebase * More refactoring and more documentation * Makes `substrate-client` compilable on `wasm` On `wasm` it basically just exports the runtime api stuff. * Fixes grumbles * Updates wasm files after rebasing the master * Remove TODO comment * Remove whitespaces * Fixes after rebasing master * Another rebase, another fix commit
2026-06-12 07:41:08 +00:00 · 2018-11-13 13:33:28 +01:00
parent 6e3c56c135
commit 9063d1acae
51 changed files with 2993 additions and 777 deletions
@@ -47,8 +47,7 @@ impl NewBlockState {
 }

 /// Block insertion operation. Keeps hold if the inserted block state and data.
-pub trait BlockImportOperation<Block, H>
-where
+pub trait BlockImportOperation<Block, H> where
 	Block: BlockT,
 	H: Hasher<Out=Block::Hash>,
 {
@@ -85,11 +84,9 @@ where
 ///
 /// The same applies for live `BlockImportOperation`s: while an import operation building on a parent `P`
 /// is alive, the state for `P` should not be pruned.
-pub trait Backend<Block, H>: Send + Sync
-where
+pub trait Backend<Block, H>: Send + Sync where
 	Block: BlockT,
 	H: Hasher<Out=Block::Hash>,
-
 {
 	/// Associated block insertion operation type.
 	type BlockImportOperation: BlockImportOperation<Block, H>;
@@ -0,0 +1,40 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! The runtime api for building blocks.
+
+use runtime_primitives::{traits::Block as BlockT, ApplyResult};
+use rstd::vec::Vec;
+
+decl_runtime_apis! {
+	/// The `BlockBuilder` api trait that provides required functions for building a block for a runtime.
+	pub trait BlockBuilder<Block: BlockT> {
+		/// The runtime api for building blocks./// Apply the given extrinsics.
+		fn apply_extrinsic(extrinsic: <Block as BlockT>::Extrinsic) -> ApplyResult;
+		/// Finish the current block.
+		fn finalise_block() -> <Block as BlockT>::Header;
+		/// Generate inherent extrinsics.
+		fn inherent_extrinsics<InherentExtrinsic, UncheckedExtrinsic>(
+			inherent: InherentExtrinsic
+		) -> Vec<UncheckedExtrinsic>;
+		/// Check that the inherents are valid.
+		fn check_inherents<InherentData, Error>(
+			block: Block, data: InherentData
+		) -> Result<(), Error>;
+		/// Generate a random seed.
+		fn random_seed() -> <Block as BlockT>::Hash;
+	}
+}
@@ -14,60 +14,48 @@
 // You should have received a copy of the GNU General Public License
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.

-//! Utility struct to build a block.
-
+use super::api::BlockBuilder as BlockBuilderApi;
 use std::vec::Vec;
-use std::marker::PhantomData;
 use codec::Encode;
-use state_machine;
-use runtime_primitives::traits::{Header as HeaderT, Hash, Block as BlockT, One, HashFor};
+use blockchain::HeaderBackend;
+use runtime_primitives::traits::{
+	Header as HeaderT, Hash, Block as BlockT, One, HashFor, ProvideRuntimeApi, ApiRef
+};
+use primitives::H256;
 use runtime_primitives::generic::BlockId;
-use runtime_api::BlockBuilder as BlockBuilderAPI;
-use {backend, error, Client, CallExecutor};
+use runtime_api::Core;
+use error;
 use runtime_primitives::ApplyOutcome;
-use primitives::{Blake2Hasher, H256};
-use hash_db::Hasher;

 /// Utility for building new (valid) blocks from a stream of extrinsics.
-pub struct BlockBuilder<'a, B, E, Block, H>
-where
-	B: backend::Backend<Block, H> + 'a,
-	E: CallExecutor<Block, H> + Clone + 'a,
-	Block: BlockT,
-	H: Hasher<Out=Block::Hash>,
-	H::Out: Ord,
-
-{
+pub struct BlockBuilder<'a, Block, A: ProvideRuntimeApi> where Block: BlockT {
 	header: <Block as BlockT>::Header,
 	extrinsics: Vec<<Block as BlockT>::Extrinsic>,
-	client: &'a Client<B, E, Block>,
+	api: ApiRef<'a, A::Api>,
 	block_id: BlockId<Block>,
-	changes: state_machine::OverlayedChanges,
-	_marker: PhantomData<H>,
 }

-impl<'a, B, E, Block> BlockBuilder<'a, B, E, Block, Blake2Hasher>
+impl<'a, Block, A> BlockBuilder<'a, Block, A>
 where
-	B: backend::Backend<Block, Blake2Hasher> + 'a,
-	E: CallExecutor<Block, Blake2Hasher> + Clone + 'a,
 	Block: BlockT<Hash=H256>,
+	A: ProvideRuntimeApi + HeaderBackend<Block> + 'a,
+	A::Api: BlockBuilderApi<Block>,
 {
 	/// Create a new instance of builder from the given client, building on the latest block.
-	pub fn new(client: &'a Client<B, E, Block>) -> error::Result<Self> {
-		client.info().and_then(|i| Self::at_block(&BlockId::Hash(i.chain.best_hash), client))
+	pub fn new(api: &'a A) -> error::Result<Self> {
+		api.info().and_then(|i| Self::at_block(&BlockId::Hash(i.best_hash), api))
 	}

 	/// Create a new instance of builder from the given client using a particular block's ID to
 	/// build upon.
-	pub fn at_block(block_id: &BlockId<Block>, client: &'a Client<B, E, Block>) -> error::Result<Self> {
-		let number = client.block_number_from_id(block_id)?
+	pub fn at_block(block_id: &BlockId<Block>, api: &'a A) -> error::Result<Self> {
+		let number = api.block_number_from_id(block_id)?
 			.ok_or_else(|| error::ErrorKind::UnknownBlock(format!("{}", block_id)))?
 			+ One::one();

-		let parent_hash = client.block_hash_from_id(block_id)?
+		let parent_hash = api.block_hash_from_id(block_id)?
 			.ok_or_else(|| error::ErrorKind::UnknownBlock(format!("{}", block_id)))?;

-		let mut changes = Default::default();
 		let header = <<Block as BlockT>::Header as HeaderT>::new(
 			number,
 			Default::default(),
@@ -76,16 +64,14 @@ where
 			Default::default()
 		);

-		client.initialise_block(block_id, &mut changes, &header)?;
-		changes.commit_prospective();
+		let api = api.runtime_api();
+		api.initialise_block(block_id, &header)?;

 		Ok(BlockBuilder {
 			header,
 			extrinsics: Vec::new(),
-			client,
+			api,
 			block_id: *block_id,
-			changes,
-			_marker: Default::default(),
 		})
 	}

@@ -93,30 +79,32 @@ where
 	/// can be validly executed (by executing it); if it is invalid, it'll be returned along with
 	/// the error. Otherwise, it will return a mutable reference to self (in order to chain).
 	pub fn push(&mut self, xt: <Block as BlockT>::Extrinsic) -> error::Result<()> {
-		match self.client.apply_extrinsic(&self.block_id, &mut self.changes, &xt) {
-			Ok(result) => {
-				match result {
+		fn impl_push<'a, T, Block: BlockT>(
+			api: &mut ApiRef<'a, T>,
+			block_id: &BlockId<Block>,
+			xt: Block::Extrinsic,
+			extrinsics: &mut Vec<Block::Extrinsic>
+		) -> error::Result<()> where T: BlockBuilderApi<Block> {
+			api.map_api_result(|api| {
+				match api.apply_extrinsic(block_id, &xt)? {
 					Ok(ApplyOutcome::Success) | Ok(ApplyOutcome::Fail) => {
-						self.extrinsics.push(xt);
-						self.changes.commit_prospective();
+						extrinsics.push(xt);
 						Ok(())
 					}
 					Err(e) => {
-						self.changes.discard_prospective();
 						Err(error::ErrorKind::ApplyExtrinsicFailed(e).into())
 					}
 				}
-			}
-			Err(e) => {
-				self.changes.discard_prospective();
-				Err(e)
-			}
+			})
 		}
+
+		//FIXME: Please NLL, help me!
+		impl_push(&mut self.api, &self.block_id, xt, &mut self.extrinsics)
 	}

 	/// Consume the builder to return a valid `Block` containing all pushed extrinsics.
 	pub fn bake(mut self) -> error::Result<Block> {
-		self.header = self.client.finalise_block(&self.block_id, &mut self.changes)?;
+		self.header = self.api.finalise_block(&self.block_id)?;

 		debug_assert_eq!(
 			self.header.extrinsics_root().clone(),
@@ -0,0 +1,23 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Utility struct to build a block.
+
+#[cfg(feature = "std")]
+mod block_builder;
+#[cfg(feature = "std")]
+pub use self::block_builder::*;
+pub mod api;
@@ -40,6 +40,22 @@ pub trait HeaderBackend<Block: BlockT>: Send + Sync {
 	fn expect_header(&self, id: BlockId<Block>) -> Result<Block::Header> {
 		self.header(id)?.ok_or_else(|| ErrorKind::UnknownBlock(format!("{}", id)).into())
 	}
+
+	/// Convert an arbitrary block ID into a block hash.
+	fn block_hash_from_id(&self, id: &BlockId<Block>) -> Result<Option<Block::Hash>> {
+		match *id {
+			BlockId::Hash(h) => Ok(Some(h)),
+			BlockId::Number(n) => self.hash(n),
+		}
+	}
+
+	/// Convert an arbitrary block ID into a block hash.
+	fn block_number_from_id(&self, id: &BlockId<Block>) -> Result<Option<NumberFor<Block>>> {
+		match *id {
+			BlockId::Hash(_) => Ok(self.header(*id)?.map(|h| h.number().clone())),
+			BlockId::Number(n) => Ok(Some(n)),
+		}
+	}
 }

 /// Blockchain database backend. Does not perform any validation.
@@ -16,8 +16,8 @@

 //! Substrate Client

-use std::sync::Arc;
-use error::{Error, ErrorKind};
+use std::{marker::PhantomData, sync::Arc};
+use error::Error;
 use futures::sync::mpsc;
 use parking_lot::{Mutex, RwLock};
 use primitives::AuthorityId;
@@ -27,25 +27,29 @@ use runtime_primitives::{
 	transaction_validity::{TransactionValidity, TransactionTag},
 };
 use consensus::{ImportBlock, ImportResult, BlockOrigin};
-use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, Zero, As, NumberFor, CurrentHeight, BlockNumberToHash};
-use runtime_primitives::{ApplyResult, BuildStorage};
-use runtime_api as api;
+use runtime_primitives::traits::{
+	Block as BlockT, Header as HeaderT, Zero, As, NumberFor, CurrentHeight, BlockNumberToHash,
+	ApiRef, ProvideRuntimeApi
+};
+use runtime_primitives::BuildStorage;
+use runtime_api::{Core as CoreAPI, CallApiAt, TaggedTransactionQueue, ConstructRuntimeApi};
 use primitives::{Blake2Hasher, H256, ChangesTrieConfiguration, convert_hash};
 use primitives::storage::{StorageKey, StorageData};
 use primitives::storage::well_known_keys;
-use codec::{Encode, Decode};
+use codec::Decode;
 use state_machine::{
-	Backend as StateBackend, CodeExecutor,
-	ExecutionStrategy, ExecutionManager, ChangesTrieAnchorBlockId,
-	prove_read, key_changes, key_changes_proof, OverlayedChanges
+	Backend as StateBackend, CodeExecutor, ChangesTrieAnchorBlockId,
+	ExecutionStrategy, ExecutionManager, prove_read,
+	key_changes, key_changes_proof, OverlayedChanges
 };
+use codec::Encode;

 use backend::{self, BlockImportOperation};
 use blockchain::{self, Info as ChainInfo, Backend as ChainBackend, HeaderBackend as ChainHeaderBackend};
 use call_executor::{CallExecutor, LocalCallExecutor};
 use executor::{RuntimeVersion, RuntimeInfo};
 use notifications::{StorageNotifications, StorageEventStream};
-use {cht, error, in_mem, block_builder, genesis, consensus};
+use {cht, error, in_mem, block_builder::{self, api::BlockBuilder as BlockBuilderAPI}, genesis, consensus};

 /// Type that implements `futures::Stream` of block import events.
 pub type ImportNotifications<Block> = mpsc::UnboundedReceiver<BlockImportNotification<Block>>;
@@ -54,7 +58,7 @@ pub type ImportNotifications<Block> = mpsc::UnboundedReceiver<BlockImportNotific
 pub type FinalityNotifications<Block> = mpsc::UnboundedReceiver<FinalityNotification<Block>>;

 /// Substrate Client
-pub struct Client<B, E, Block> where Block: BlockT {
+pub struct Client<B, E, Block, RA> where Block: BlockT {
 	backend: Arc<B>,
 	executor: E,
 	storage_notifications: Mutex<StorageNotifications<Block>>,
@@ -65,6 +69,7 @@ pub struct Client<B, E, Block> where Block: BlockT {
 	block_execution_strategy: ExecutionStrategy,
 	api_execution_strategy: ExecutionStrategy,
 	changes_trie_config: Option<ChangesTrieConfiguration>,
+	_phantom: PhantomData<RA>,
 }

 /// A source of blockchain events.
@@ -180,36 +185,36 @@ impl<H> PrePostHeader<H> {
 }

 /// Create an instance of in-memory client.
-pub fn new_in_mem<E, Block, S>(
+pub fn new_in_mem<E, Block, S, RA>(
 	executor: E,
 	genesis_storage: S,
-) -> error::Result<Client<in_mem::Backend<Block, Blake2Hasher>, LocalCallExecutor<in_mem::Backend<Block, Blake2Hasher>, E>, Block>>
-where
-	E: CodeExecutor<Blake2Hasher> + RuntimeInfo,
-	S: BuildStorage,
-	Block: BlockT<Hash=H256>,
+) -> error::Result<Client<in_mem::Backend<Block, Blake2Hasher>, LocalCallExecutor<in_mem::Backend<Block, Blake2Hasher>, E>, Block, RA>>
+	where
+		E: CodeExecutor<Blake2Hasher> + RuntimeInfo,
+		S: BuildStorage,
+		Block: BlockT<Hash=H256>,
 {
 	new_with_backend(Arc::new(in_mem::Backend::new()), executor, genesis_storage)
 }

 /// Create a client with the explicitely provided backend.
 /// This is useful for testing backend implementations.
-pub fn new_with_backend<B, E, Block, S>(
+pub fn new_with_backend<B, E, Block, S, RA>(
 	backend: Arc<B>,
 	executor: E,
 	build_genesis_storage: S,
-) -> error::Result<Client<B, LocalCallExecutor<B, E>, Block>>
-where
-	E: CodeExecutor<Blake2Hasher> + RuntimeInfo,
-	S: BuildStorage,
-	Block: BlockT<Hash=H256>,
-	B: backend::LocalBackend<Block, Blake2Hasher>
+) -> error::Result<Client<B, LocalCallExecutor<B, E>, Block, RA>>
+	where
+		E: CodeExecutor<Blake2Hasher> + RuntimeInfo,
+		S: BuildStorage,
+		Block: BlockT<Hash=H256>,
+		B: backend::LocalBackend<Block, Blake2Hasher>
 {
 	let call_executor = LocalCallExecutor::new(backend.clone(), executor);
 	Client::new(backend, call_executor, build_genesis_storage, ExecutionStrategy::NativeWhenPossible, ExecutionStrategy::NativeWhenPossible)
 }

-impl<B, E, Block> Client<B, E, Block> where
+impl<B, E, Block, RA> Client<B, E, Block, RA> where
 	B: backend::Backend<Block, Blake2Hasher>,
 	E: CallExecutor<Block, Blake2Hasher>,
 	Block: BlockT<Hash=H256>,
@@ -255,6 +260,7 @@ impl<B, E, Block> Client<B, E, Block> where
 			block_execution_strategy,
 			api_execution_strategy,
 			changes_trie_config,
+			_phantom: Default::default(),
 		})
 	}

@@ -323,6 +329,36 @@ impl<B, E, Block> Client<B, E, Block> where
 		self.header_proof_with_cht_size(id, cht::SIZE)
 	}

+	pub(crate) fn call_at_state(
+		&self,
+		at: &BlockId<Block>,
+		function: &'static str,
+		args: Vec<u8>,
+		changes: &mut OverlayedChanges
+	) -> error::Result<Vec<u8>> {
+		let state = self.state_at(at)?;
+
+		let execution_manager = || match self.api_execution_strategy {
+			ExecutionStrategy::NativeWhenPossible => ExecutionManager::NativeWhenPossible,
+			ExecutionStrategy::AlwaysWasm => ExecutionManager::AlwaysWasm,
+			ExecutionStrategy::Both => ExecutionManager::Both(|wasm_result, native_result| {
+				warn!("Consensus error between wasm and native runtime execution at block {:?}", at);
+				warn!("   Function {:?}", function);
+				warn!("   Native result {:?}", native_result);
+				warn!("   Wasm result {:?}", wasm_result);
+				wasm_result
+			}),
+		};
+
+		self.executor.call_at_state(&state, changes, function, &args, execution_manager())
+			.map(|res| res.0)
+	}
+
+	/// Get block hash by number.
+	pub fn block_hash(&self, block_number: <<Block as BlockT>::Header as HeaderT>::Number) -> error::Result<Option<Block::Hash>> {
+		self.backend.blockchain().hash(block_number)
+	}
+
 	/// Reads given header and generates CHT-based header proof for CHT of given size.
 	pub fn header_proof_with_cht_size(&self, id: &BlockId<Block>, cht_size: u64) -> error::Result<(Block::Header, Vec<Vec<u8>>)> {
 		let proof_error = || error::ErrorKind::Backend(format!("Failed to generate header proof for {:?}", id));
@@ -402,88 +438,41 @@ impl<B, E, Block> Client<B, E, Block> where
 	}

 	/// Create a new block, built on the head of the chain.
-	pub fn new_block(&self) -> error::Result<block_builder::BlockBuilder<B, E, Block, Blake2Hasher>>
-	where E: Clone
+	pub fn new_block(
+		&self
+	) -> error::Result<block_builder::BlockBuilder<Block, Self>> where
+		E: Clone + Send + Sync,
+		RA: BlockBuilderAPI<Block>
 	{
 		block_builder::BlockBuilder::new(self)
 	}

 	/// Create a new block, built on top of `parent`.
-	pub fn new_block_at(&self, parent: &BlockId<Block>) -> error::Result<block_builder::BlockBuilder<B, E, Block, Blake2Hasher>>
-	where E: Clone
+	pub fn new_block_at(
+		&self, parent: &BlockId<Block>
+	) -> error::Result<block_builder::BlockBuilder<Block, Self>> where
+		E: Clone + Send + Sync,
+		RA: BlockBuilderAPI<Block>
 	{
 		block_builder::BlockBuilder::at_block(parent, &self)
 	}

-	/// Set up the native execution environment to call into a native runtime code.
-	pub fn call_api<A, R>(&self, function: &'static str, args: &A) -> error::Result<R>
-		where A: Encode, R: Decode
-	{
-		self.call_api_at(&BlockId::Number(self.info()?.chain.best_number), function, args)
-	}
-
-	/// Call a runtime function at given block.
-	pub fn call_api_at<A, R>(&self, at: &BlockId<Block>, function: &'static str, args: &A) -> error::Result<R>
-		where A: Encode, R: Decode
-	{
-		let parent = at;
-		let header = <<Block as BlockT>::Header as HeaderT>::new(
-			self.block_number_from_id(&parent)?
-				.ok_or_else(|| error::ErrorKind::UnknownBlock(format!("{:?}", parent)))? + As::sa(1),
-			Default::default(),
-			Default::default(),
-			self.block_hash_from_id(&parent)?
-				.ok_or_else(|| error::ErrorKind::UnknownBlock(format!("{:?}", parent)))?,
-			Default::default()
-		);
-		let mut overlay = Default::default();
-
-		self.call_at_state(at, "initialise_block", &header, &mut overlay)?;
-		self.call_at_state(at, function, args, &mut overlay)
-	}
-
-	fn call_at_state<A: Encode, R: Decode>(
-		&self,
-		at: &BlockId<Block>,
-		function: &'static str,
-		args: &A,
-		changes: &mut OverlayedChanges
-	) -> error::Result<R> {
-		let state = self.state_at(at)?;
-
-		let execution_manager = || match self.api_execution_strategy {
-			ExecutionStrategy::NativeWhenPossible => ExecutionManager::NativeWhenPossible,
-			ExecutionStrategy::AlwaysWasm => ExecutionManager::AlwaysWasm,
-			ExecutionStrategy::Both => ExecutionManager::Both(|wasm_result, native_result| {
-				warn!("Consensus error between wasm and native runtime execution at block {:?}", at);
-				warn!("   Function {:?}", function);
-				warn!("   Native result {:?}", native_result);
-				warn!("   Wasm result {:?}", wasm_result);
-				wasm_result
-			}),
-		};
-
-		self.executor.call_at_state(
-			&state,
-			changes,
-			function,
-			&args.encode(),
-			execution_manager()
-		).and_then(|res|
-			R::decode(&mut &res.0[..])
-				.ok_or_else(|| Error::from(ErrorKind::CallResultDecode(function)))
-		)
-	}
-
 	// TODO [ToDr] Optimize and re-use tags from the pool.
-	fn transaction_tags(&self, at: Block::Hash, body: &Option<Vec<Block::Extrinsic>>) -> error::Result<Vec<TransactionTag>> {
+	fn transaction_tags(
+		&self,
+		at: Block::Hash,
+		body: &Option<Vec<Block::Extrinsic>>
+	) -> error::Result<Vec<TransactionTag>> where
+		RA: TaggedTransactionQueue<Block>,
+		E: CallExecutor<Block, Blake2Hasher> + Send + Sync + Clone,
+	{
 		let id = BlockId::Hash(at);
 		Ok(match body {
 			None => vec![],
 			Some(ref extrinsics) => {
 				let mut tags = vec![];
 				for tx in extrinsics {
-					let tx = api::TaggedTransactionQueue::validate_transaction(self, &id, &tx)?;
+					let tx = self.runtime_api().validate_transaction(&id, &tx)?;
 					match tx {
 						TransactionValidity::Valid { mut provides, .. } => {
 							tags.append(&mut provides);
@@ -508,7 +497,10 @@ impl<B, E, Block> Client<B, E, Block> where
 		body: Option<Vec<Block::Extrinsic>>,
 		authorities: Option<Vec<AuthorityId>>,
 		finalized: bool,
-	) -> error::Result<ImportResult> {
+	) -> error::Result<ImportResult> where
+		RA: TaggedTransactionQueue<Block>,
+		E: CallExecutor<Block, Blake2Hasher> + Send + Sync + Clone,
+	{
 		let parent_hash = import_headers.post().parent_hash().clone();
 		match self.backend.blockchain().status(BlockId::Hash(hash))? {
 			blockchain::BlockStatus::InChain => return Ok(ImportResult::AlreadyInChain),
@@ -737,30 +729,9 @@ impl<B, E, Block> Client<B, E, Block> where
 		}
 	}

-	/// Get block hash by number.
-	pub fn block_hash(&self, block_number: <<Block as BlockT>::Header as HeaderT>::Number) -> error::Result<Option<Block::Hash>> {
-		self.backend.blockchain().hash(block_number)
-	}
-
-	/// Convert an arbitrary block ID into a block hash.
-	pub fn block_hash_from_id(&self, id: &BlockId<Block>) -> error::Result<Option<Block::Hash>> {
-		match *id {
-			BlockId::Hash(h) => Ok(Some(h)),
-			BlockId::Number(n) => self.block_hash(n),
-		}
-	}
-
-	/// Convert an arbitrary block ID into a block hash.
-	pub fn block_number_from_id(&self, id: &BlockId<Block>) -> error::Result<Option<NumberFor<Block>>> {
-		match *id {
-			BlockId::Hash(_) => Ok(self.header(id)?.map(|h| h.number().clone())),
-			BlockId::Number(n) => Ok(Some(n)),
-		}
-	}
-
 	/// Convert an arbitrary block ID into a block hash, returning error if the block is unknown.
 	fn require_block_number_from_id(&self, id: &BlockId<Block>) -> error::Result<NumberFor<Block>> {
-		self.block_number_from_id(id)
+		self.backend.blockchain().block_number_from_id(id)
 			.and_then(|n| n.ok_or_else(|| error::ErrorKind::UnknownBlock(format!("{}", id)).into()))
 	}

@@ -896,11 +867,87 @@ impl<B, E, Block> Client<B, E, Block> where
 	}
 }

-
-impl<B, E, Block> consensus::BlockImport<Block> for Client<B, E, Block> where
+impl<B, E, Block, RA> ChainHeaderBackend<Block> for Client<B, E, Block, RA> where
 	B: backend::Backend<Block, Blake2Hasher>,
-	E: CallExecutor<Block, Blake2Hasher> + Clone,
+	E: CallExecutor<Block, Blake2Hasher> + Send + Sync,
 	Block: BlockT<Hash=H256>,
+	RA: Send + Sync
+{
+	fn header(&self, id: BlockId<Block>) -> error::Result<Option<Block::Header>> {
+		self.backend.blockchain().header(id)
+	}
+
+	fn info(&self) -> error::Result<blockchain::Info<Block>> {
+		self.backend.blockchain().info()
+	}
+
+	fn status(&self, id: BlockId<Block>) -> error::Result<blockchain::BlockStatus> {
+		self.backend.blockchain().status(id)
+	}
+
+	fn number(&self, hash: Block::Hash) -> error::Result<Option<<<Block as BlockT>::Header as HeaderT>::Number>> {
+		self.backend.blockchain().number(hash)
+	}
+
+	fn hash(&self, number: NumberFor<Block>) -> error::Result<Option<Block::Hash>> {
+		self.backend.blockchain().hash(number)
+	}
+}
+
+impl<B, E, Block, RA> ProvideRuntimeApi for Client<B, E, Block, RA> where
+	B: backend::Backend<Block, Blake2Hasher>,
+	E: CallExecutor<Block, Blake2Hasher> + Clone + Send + Sync,
+	Block: BlockT<Hash=H256>,
+	RA: CoreAPI<Block>
+{
+	type Api = RA;
+
+	fn runtime_api<'a>(&'a self) -> ApiRef<'a, Self::Api> {
+		Self::Api::construct_runtime_api(self)
+	}
+}
+
+impl<B, E, Block, RA> CallApiAt<Block> for Client<B, E, Block, RA> where
+	B: backend::Backend<Block, Blake2Hasher>,
+	E: CallExecutor<Block, Blake2Hasher> + Clone + Send + Sync,
+	Block: BlockT<Hash=H256>,
+	RA: CoreAPI<Block>
+{
+	fn call_api_at(
+		&self,
+		at: &BlockId<Block>,
+		function: &'static str,
+		args: Vec<u8>,
+		changes: &mut OverlayedChanges,
+		initialised_block: &mut Option<BlockId<Block>>,
+	) -> error::Result<Vec<u8>> {
+		//TODO: Find a better way to prevent double block initialization
+		if function != "initialise_block" && initialised_block.map(|id| id != *at).unwrap_or(true) {
+			let parent = at;
+			let header = <<Block as BlockT>::Header as HeaderT>::new(
+				self.block_number_from_id(parent)?
+					.ok_or_else(|| error::ErrorKind::UnknownBlock(format!("{:?}", parent)))?
+				+ As::sa(1),
+				Default::default(),
+				Default::default(),
+				self.block_hash_from_id(&parent)?
+					.ok_or_else(|| error::ErrorKind::UnknownBlock(format!("{:?}", parent)))?,
+				Default::default()
+			);
+			self.call_at_state(at, "initialise_block", header.encode(), changes)?;
+			*initialised_block = Some(*at);
+		}
+
+		self.call_at_state(at, function, args, changes)
+	}
+}
+
+
+impl<B, E, Block, RA> consensus::BlockImport<Block> for Client<B, E, Block, RA> where
+	B: backend::Backend<Block, Blake2Hasher>,
+	E: CallExecutor<Block, Blake2Hasher> + Clone + Send + Sync,
+	Block: BlockT<Hash=H256>,
+	RA: TaggedTransactionQueue<Block>
 {
 	type Error = Error;

@@ -963,7 +1010,7 @@ impl<B, E, Block> consensus::BlockImport<Block> for Client<B, E, Block> where
 	}
 }

-impl<B, E, Block> consensus::Authorities<Block> for Client<B, E, Block> where
+impl<B, E, Block, RA> consensus::Authorities<Block> for Client<B, E, Block, RA> where
 	B: backend::Backend<Block, Blake2Hasher>,
 	E: CallExecutor<Block, Blake2Hasher> + Clone,
 	Block: BlockT<Hash=H256>,
@@ -974,7 +1021,7 @@ impl<B, E, Block> consensus::Authorities<Block> for Client<B, E, Block> where
 	}
 }

-impl<B, E, Block> CurrentHeight for Client<B, E, Block> where
+impl<B, E, Block, RA> CurrentHeight for Client<B, E, Block, RA> where
 	B: backend::Backend<Block, Blake2Hasher>,
 	E: CallExecutor<Block, Blake2Hasher> + Clone,
 	Block: BlockT<Hash=H256>,
@@ -985,7 +1032,7 @@ impl<B, E, Block> CurrentHeight for Client<B, E, Block> where
 	}
 }

-impl<B, E, Block> BlockNumberToHash for Client<B, E, Block> where
+impl<B, E, Block, RA> BlockNumberToHash for Client<B, E, Block, RA> where
 	B: backend::Backend<Block, Blake2Hasher>,
 	E: CallExecutor<Block, Blake2Hasher> + Clone,
 	Block: BlockT<Hash=H256>,
@@ -998,7 +1045,7 @@ impl<B, E, Block> BlockNumberToHash for Client<B, E, Block> where
 }


-impl<B, E, Block> BlockchainEvents<Block> for Client<B, E, Block>
+impl<B, E, Block, RA> BlockchainEvents<Block> for Client<B, E, Block, RA>
 where
 	E: CallExecutor<Block, Blake2Hasher>,
 	Block: BlockT<Hash=H256>,
@@ -1022,7 +1069,7 @@ where
 	}
 }

-impl<B, E, Block> ChainHead<Block> for Client<B, E, Block>
+impl<B, E, Block, RA> ChainHead<Block> for Client<B, E, Block, RA>
 where
 	B: backend::Backend<Block, Blake2Hasher>,
 	E: CallExecutor<Block, Blake2Hasher>,
@@ -1033,116 +1080,17 @@ where
 	}
 }

-impl<B, E, Block> BlockBody<Block> for Client<B, E, Block> where
-	B: backend::Backend<Block, Blake2Hasher>,
-	E: CallExecutor<Block, Blake2Hasher>,
-	Block: BlockT<Hash=H256>,
+impl<B, E, Block, RA> BlockBody<Block> for Client<B, E, Block, RA>
+	where
+		B: backend::Backend<Block, Blake2Hasher>,
+		E: CallExecutor<Block, Blake2Hasher>,
+		Block: BlockT<Hash=H256>,
 {
 	fn block_body(&self, id: &BlockId<Block>) -> error::Result<Option<Vec<<Block as BlockT>::Extrinsic>>> {
 		self.body(id)
 	}
 }

-impl<B, E, Block> api::Core<Block, AuthorityId> for Client<B, E, Block> where
-	B: backend::Backend<Block, Blake2Hasher>,
-	E: CallExecutor<Block, Blake2Hasher>,
-	Block: BlockT<Hash=H256>,
-{
-	type Error = Error;
-
-	fn version(&self, at: &BlockId<Block>) -> Result<RuntimeVersion, Self::Error> {
-		self.call_api_at(at, "version", &())
-	}
-
-	fn authorities(&self, at: &BlockId<Block>) -> Result<Vec<AuthorityId>, Self::Error> {
-		self.authorities_at(at)
-	}
-
-	fn execute_block(&self, at: &BlockId<Block>, block: &Block) -> Result<(), Self::Error> {
-		self.call_api_at(at, "execute_block", &(block))
-	}
-}
-
-impl<B, E, Block> api::Metadata<Block, Vec<u8>> for Client<B, E, Block> where
-	B: backend::Backend<Block, Blake2Hasher>,
-	E: CallExecutor<Block, Blake2Hasher>,
-	Block: BlockT<Hash=H256>,
-{
-	type Error = Error;
-
-	fn metadata(&self, at: &BlockId<Block>) -> Result<Vec<u8>, Self::Error> {
-		self.executor.call(at, "metadata",&[]).map(|v| v.return_data)
-	}
-}
-
-impl<B, E, Block> api::BlockBuilder<Block> for Client<B, E, Block> where
-	B: backend::Backend<Block, Blake2Hasher>,
-	E: CallExecutor<Block, Blake2Hasher>,
-	Block: BlockT<Hash=H256>,
-{
-	type Error = Error;
-	type OverlayedChanges = OverlayedChanges;
-
-	fn initialise_block(
-		&self,
-		at: &BlockId<Block>,
-		changes: &mut OverlayedChanges,
-		header: &<Block as BlockT>::Header
-	) -> Result<(), Self::Error> {
-		self.call_at_state(at, "initialise_block", header, changes)
-	}
-
-	fn apply_extrinsic(
-		&self,
-		at: &BlockId<Block>,
-		changes: &mut OverlayedChanges,
-		extrinsic: &<Block as BlockT>::Extrinsic
-	) -> Result<ApplyResult, Self::Error> {
-		self.call_at_state(at, "apply_extrinsic", extrinsic, changes)
-	}
-
-	fn finalise_block(
-		&self,
-		at: &BlockId<Block>,
-		changes: &mut OverlayedChanges
-	) -> Result<<Block as BlockT>::Header, Self::Error> {
-		self.call_at_state(at, "finalise_block", &(), changes)
-	}
-
-	fn inherent_extrinsics<InherentExtrinsic: Encode + Decode, UncheckedExtrinsic: Encode + Decode>(
-		&self, at: &BlockId<Block>, inherent: &InherentExtrinsic
-	) -> Result<Vec<UncheckedExtrinsic>, Self::Error> {
-		self.call_api_at(at, "inherent_extrinsics", &(inherent))
-	}
-
-	fn check_inherents<InherentData: Encode + Decode, InherentError: Encode + Decode>(
-		&self,
-		at: &BlockId<Block>,
-		block: &Block,
-		data: &InherentData
-	) -> Result<Result<(), InherentError>, Self::Error> {
-		self.call_api_at(at, "check_inherents", &(block, data))
-	}
-
-	fn random_seed(&self, at: &BlockId<Block>) -> Result<<Block as BlockT>::Hash, Self::Error> {
-		self.call_api_at(at, "random_seed", &())
-	}
-}
-
-impl<B, E, Block> api::TaggedTransactionQueue<Block> for Client<B, E, Block> where
-	B: backend::Backend<Block, Blake2Hasher>,
-	E: CallExecutor<Block, Blake2Hasher>,
-	Block: BlockT<Hash=H256>,
-{
-	type Error = Error;
-
-	fn validate_transaction<TransactionValidity: Encode + Decode>(
-		&self, at: &BlockId<Block>, tx: &<Block as BlockT>::Extrinsic
-	) -> Result<TransactionValidity, Self::Error> {
-		self.call_api_at(at, "validate_transaction", &(tx))
-	}
-}
-
 #[cfg(test)]
 pub(crate) mod tests {
 	use std::collections::HashMap;
@@ -1155,14 +1103,14 @@ pub(crate) mod tests {
 	use consensus::BlockOrigin;
 	use test_client::client::backend::Backend as TestBackend;
 	use test_client::BlockBuilderExt;
-	use test_client::runtime::{self, Block, Transfer};
+	use test_client::runtime::{self, Block, Transfer, ClientWithApi, test_api::TestAPI};

 	/// Returns tuple, consisting of:
 	/// 1) test client pre-filled with blocks changing balances;
 	/// 2) roots of changes tries for these blocks
 	/// 3) test cases in form (begin, end, key, vec![(block, extrinsic)]) that are required to pass
 	pub fn prepare_client_with_key_changes() -> (
-		test_client::client::Client<test_client::Backend, test_client::Executor, Block>,
+		test_client::client::Client<test_client::Backend, test_client::Executor, Block, ClientWithApi>,
 		Vec<H256>,
 		Vec<(u64, u64, Vec<u8>, Vec<(u64, u32)>)>,
 	) {
@@ -1234,8 +1182,20 @@ pub(crate) mod tests {
 	fn client_initialises_from_genesis_ok() {
 		let client = test_client::new();

-		assert_eq!(client.call_api::<_, u64>("balance_of", &Keyring::Alice.to_raw_public()).unwrap(), 1000);
-		assert_eq!(client.call_api::<_, u64>("balance_of", &Keyring::Ferdie.to_raw_public()).unwrap(), 0);
+		assert_eq!(
+			client.runtime_api().balance_of(
+				&BlockId::Number(client.info().unwrap().chain.best_number),
+				&Keyring::Alice.to_raw_public()
+			).unwrap(),
+			1000
+		);
+		assert_eq!(
+			client.runtime_api().balance_of(
+				&BlockId::Number(client.info().unwrap().chain.best_number),
+				&Keyring::Ferdie.to_raw_public()
+			).unwrap(),
+			0
+		);
 	}

 	#[test]
@@ -1278,8 +1238,20 @@ pub(crate) mod tests {

 		assert_eq!(client.info().unwrap().chain.best_number, 1);
 		assert!(client.state_at(&BlockId::Number(1)).unwrap() != client.state_at(&BlockId::Number(0)).unwrap());
-		assert_eq!(client.call_api::<_, u64>("balance_of", &Keyring::Alice.to_raw_public()).unwrap(), 958);
-		assert_eq!(client.call_api::<_, u64>("balance_of", &Keyring::Ferdie.to_raw_public()).unwrap(), 42);
+		assert_eq!(
+			client.runtime_api().balance_of(
+				&BlockId::Number(client.info().unwrap().chain.best_number),
+				&Keyring::Alice.to_raw_public()
+			).unwrap(),
+			958
+		);
+		assert_eq!(
+			client.runtime_api().balance_of(
+				&BlockId::Number(client.info().unwrap().chain.best_number),
+				&Keyring::Ferdie.to_raw_public()
+			).unwrap(),
+			42
+		);
 	}

 	#[test]
@@ -16,60 +16,101 @@

 //! Substrate Client and associated logic.

+#![cfg_attr(not(feature = "std"), no_std)]
 #![warn(missing_docs)]
 #![recursion_limit="128"]

+#[cfg(feature = "std")]
 extern crate substrate_trie as trie;
 extern crate parity_codec as codec;
 extern crate substrate_primitives as primitives;
 extern crate sr_primitives as runtime_primitives;
+#[cfg(feature = "std")]
 extern crate substrate_state_machine as state_machine;
+#[cfg(feature = "std")]
 extern crate substrate_consensus_common as consensus;
-#[cfg(test)] extern crate substrate_keyring as keyring;
-#[cfg(test)] extern crate substrate_test_client as test_client;
-#[macro_use] extern crate substrate_telemetry;
-#[macro_use] extern crate slog;	// needed until we can reexport `slog_info` from `substrate_telemetry`
+extern crate sr_version as runtime_version;
+extern crate sr_std as rstd;
+#[cfg(test)]
+extern crate substrate_keyring as keyring;
+#[cfg(test)]
+extern crate substrate_test_client as test_client;
+#[cfg(feature = "std")]
+#[macro_use]
+extern crate substrate_telemetry;
+#[cfg(feature = "std")]
+#[macro_use]
+extern crate slog;	// needed until we can reexport `slog_info` from `substrate_telemetry`

+#[cfg(feature = "std")]
 extern crate fnv;
+#[cfg(feature = "std")]
 extern crate futures;
+#[cfg(feature = "std")]
 extern crate parking_lot;
+#[cfg(feature = "std")]
 extern crate hash_db;
+#[cfg(feature = "std")]
 extern crate heapsize;
+#[cfg(feature = "std")]
 extern crate kvdb;
-extern crate sr_api;

-#[macro_use] extern crate error_chain;
-#[macro_use] extern crate log;
-#[cfg_attr(test, macro_use)] extern crate substrate_executor as executor;
-#[cfg(test)] #[macro_use] extern crate hex_literal;
-#[cfg(test)] extern crate kvdb_memorydb;
+#[cfg(feature = "std")]
+#[macro_use]
+extern crate error_chain;
+#[cfg(feature = "std")]
+#[macro_use]
+extern crate log;
+#[cfg(feature = "std")]
+#[cfg_attr(test, macro_use)]
+extern crate substrate_executor as executor;
+#[cfg(test)]
+#[macro_use]
+extern crate hex_literal;
+#[cfg(feature = "std")]
+#[cfg(test)]
+extern crate kvdb_memorydb;

+#[macro_use]
+pub mod runtime_api;
+#[cfg(feature = "std")]
 pub mod error;
+#[cfg(feature = "std")]
 pub mod blockchain;
+#[cfg(feature = "std")]
 pub mod backend;
+#[cfg(feature = "std")]
 pub mod cht;
+#[cfg(feature = "std")]
 pub mod in_mem;
+#[cfg(feature = "std")]
 pub mod genesis;
 pub mod block_builder;
+#[cfg(feature = "std")]
 pub mod light;
+#[cfg(feature = "std")]
 mod leaves;
+#[cfg(feature = "std")]
 mod call_executor;
+#[cfg(feature = "std")]
 mod client;
+#[cfg(feature = "std")]
 mod notifications;

+#[cfg(feature = "std")]
 pub use blockchain::Info as ChainInfo;
+#[cfg(feature = "std")]
 pub use call_executor::{CallResult, CallExecutor, LocalCallExecutor};
+#[cfg(feature = "std")]
 pub use client::{
 	new_with_backend,
 	new_in_mem,
 	BlockBody, BlockStatus, ImportNotifications, FinalityNotifications, BlockchainEvents,
 	Client, ClientInfo, ChainHead,
 };
+#[cfg(feature = "std")]
 pub use notifications::{StorageEventStream, StorageChangeSet};
+#[cfg(feature = "std")]
 pub use state_machine::ExecutionStrategy;
+#[cfg(feature = "std")]
 pub use leaves::LeafSet;
-
-/// Traits for interfacing with the runtime from the client.
-pub mod runtime_api {
-	pub use sr_api::*;
-}
@@ -48,11 +48,11 @@ pub fn new_light_backend<B: BlockT, S: BlockchainStorage<B>, F: Fetcher<B>>(bloc
 }

 /// Create an instance of light client.
-pub fn new_light<B, S, F, GS>(
+pub fn new_light<B, S, F, GS, RA>(
 	backend: Arc<Backend<S, F>>,
 	fetcher: Arc<F>,
 	genesis_storage: GS,
-) -> ClientResult<Client<Backend<S, F>, RemoteCallExecutor<Blockchain<S, F>, F, Blake2Hasher>, B>>
+) -> ClientResult<Client<Backend<S, F>, RemoteCallExecutor<Blockchain<S, F>, F, Blake2Hasher>, B, RA>>
 where
 	B: BlockT<Hash=H256>,
 	S: BlockchainStorage<B>,
@@ -0,0 +1,62 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+#[cfg(feature = "std")]
+use super::{ConstructRuntimeApi, ApiExt};
+use runtime_version::RuntimeVersion;
+use runtime_primitives::traits::Block as BlockT;
+#[cfg(feature = "std")]
+use runtime_primitives::generic::BlockId;
+use primitives::AuthorityId;
+#[cfg(feature = "std")]
+use error::Result;
+use rstd::vec::Vec;
+
+/// The `Core` api trait that is mandantory for each runtime.
+/// This is the side that should be implemented for the `RuntimeApi` that is used by the `Client`.
+/// Any modifications at one of these two traits, needs to be done on the other one as well.
+#[cfg(feature = "std")]
+pub trait Core<Block: BlockT>: 'static + Send + Sync + ConstructRuntimeApi<Block> + ApiExt {
+	/// Returns the version of the runtime.
+	fn version(&self, at: &BlockId<Block>) -> Result<RuntimeVersion>;
+	/// Returns the authorities.
+	fn authorities(&self, at: &BlockId<Block>) -> Result<Vec<AuthorityId>>;
+	/// Execute the given block.
+	fn execute_block(&self, at: &BlockId<Block>, block: &Block) -> Result<()>;
+	/// Initialise a block with the given header.
+	fn initialise_block(
+		&self,
+		at: &BlockId<Block>,
+		header: &<Block as BlockT>::Header
+	) -> Result<()>;
+}
+
+pub mod runtime {
+	use super::*;
+
+	/// The `Core` api trait that is mandantory for each runtime.
+	/// This is the side that should be implemented for the `Runtime`.
+	pub trait Core<Block: BlockT> {
+		/// Returns the version of the runtime.
+		fn version() -> RuntimeVersion;
+		/// Returns the authorities.
+		fn authorities() -> Vec<AuthorityId>;
+		/// Execute the given block.
+		fn execute_block(block: Block);
+		/// Initialise a block with the given header.
+		fn initialise_block(header: <Block as BlockT>::Header);
+	}
+}
@@ -0,0 +1,579 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Macros for declaring and implementing the runtime APIs.
+
+/// Declare the given API traits.
+///
+/// # Example:
+///
+/// ```nocompile
+/// decl_runtime_apis!{
+///     pub trait Test<Event> ExtraClientSide<ClientArg> {
+///         fn test<AccountId>(event: Event) -> AccountId;
+///
+///         /// A function that will have the extra parameter `param` on the client side,
+///         /// the runtime does not have any parameter.
+///         fn testWithExtraParams() ExtraClientSide(param: &Self::ClientArg);
+///     }
+/// }
+/// ```
+///
+/// Will result in the following declaration:
+///
+/// ```nocompile
+/// mod runtime {
+///     pub trait Test<Event, AccountId> {
+///         fn test(event: Event) -> AccountId;
+///     }
+/// }
+///
+/// pub trait Test<Block: BlockT, Event> {
+///     type Error;
+///     type ClientArg;
+///     fn test<AccountId: Encode + Decode>(&self, at: &BlockId<Block>, event: Event) -> Result<Event, Self::Error>;
+///     fn testWithExtraParams(&self, at: &BlockId<Block>, param: &Client) -> Result<Event, Self::Error>;
+/// }
+/// ```
+///
+/// The declarations generated in the `runtime` module will be used by `impl_runtime_apis!` for implementing
+/// the traits for a runtime. The other declarations should be used for implementing the interface
+/// in the client.
+#[macro_export]
+macro_rules! decl_runtime_apis {
+	(
+		$(
+			$( #[$attr:meta] )*
+			pub trait $name:ident $(< $( $generic_param:ident $( : $generic_bound:ident )* ),* >)*
+				$( ExtraClientSide < $( $client_generic_param:ident $( : $client_generic_bound:ident )* ),+ > )*
+			{
+				$(
+					$( #[$fn_attr:meta] )*
+					fn $fn_name:ident $( < $( $fn_generic:ident ),* > )* (
+						$( $param_name:ident : $param_type:ty ),*
+					)
+					$( ExtraClientSide ( $( $client_param_name:ident : $client_param_type:ty ),+ ) )*
+					$( -> $return_ty:ty)*;
+				)*
+			}
+		)*
+	) => {
+		$(
+			decl_runtime_apis!(
+				@ADD_BLOCK_GENERIC
+				$( #[$attr] )*
+				pub trait $name $(< $( $generic_param $( : $generic_bound )* ),* >)* {
+					$( $( type $client_generic_param $( : $client_generic_bound )*; )* )*
+					$(
+						$( #[$fn_attr] )*
+						fn $fn_name $( < $( $fn_generic ),* > )* (
+							$( $( $client_param_name: $client_param_type, )* )*
+							$( $param_name : &$param_type, )*
+						) $( -> $return_ty )*;
+					)*
+				};
+				;
+				;
+				$( $( $generic_param $( : $generic_bound )* ),* )*
+			);
+		)*
+		decl_runtime_apis! {
+			@GENERATE_RUNTIME_TRAITS
+			$(
+				$( #[$attr] )*
+				pub trait $name $(< $( $generic_param $( : $generic_bound )* ),* >)* {
+					$(
+						$( #[$fn_attr] )*
+						fn $fn_name $( < $( $fn_generic ),* > )* ($( $param_name : $param_type )* ) $( -> $return_ty )*;
+					)*
+				};
+			)*
+		}
+	};
+	(@ADD_BLOCK_GENERIC
+		$( #[$attr:meta] )*
+		pub trait $name:ident $(< $( $generic_param_orig:ident $( : $generic_bound_orig:ident )* ),* >)* {
+			$( type $client_generic_param:ident $( : $client_generic_bound:ident )*; )*
+			$(
+				$( #[$fn_attr:meta] )*
+				fn $fn_name:ident $( < $( $fn_generic:ident ),* > )* (
+					$( $param_name:ident : $param_type:ty, )*
+				) $( -> $return_ty:ty)*;
+			)*
+		};
+		;
+		$( $generic_param_parsed:ident $( : $generic_bound_parsed:ident )* ),*;
+		Block: BlockT
+		$(, $generic_param_rest:ident $( : $generic_bound_rest:ident )* )*
+	) => {
+		decl_runtime_apis!(
+			@ADD_BLOCK_GENERIC
+			$( #[$attr] )*
+			pub trait $name $(< $( $generic_param_orig $( : $generic_bound_orig )* ),* >)* {
+				$( type $client_generic_param $( : $client_generic_bound )*; )*
+				$(
+					$( #[$fn_attr] )*
+					fn $fn_name $( < $( $fn_generic ),* > )* (
+						$( $param_name : $param_type, )*
+					) $( -> $return_ty )*;
+				)*
+			};
+			Found;
+			$( $generic_param_parsed $( : $generic_bound_parsed )* , )* Block: $crate::runtime_api::BlockT;
+			$( $generic_param_rest $( : $generic_bound_rest )* ),*
+		);
+	};
+	(@ADD_BLOCK_GENERIC
+		$( #[$attr:meta] )*
+		pub trait $name:ident $(< $( $generic_param_orig:ident $( : $generic_bound_orig:ident )* ),* >)* {
+			$( type $client_generic_param:ident $( : $client_generic_bound:ident )*; )*
+	 		$(
+				$( #[$fn_attr:meta] )*
+				fn $fn_name:ident $( < $( $fn_generic:ident ),* > )* (
+					$( $param_name:ident : $param_type:ty, )*
+				) $( -> $return_ty:ty )*;
+			)*
+		};
+		$( $block_found:ident )*;
+		$( $generic_param_parsed:ident $( : $generic_bound_parsed:path )* ),*;
+		$generic_param:ident $( : $generic_bound:ident )*
+		$(, $generic_param_rest:ident $( : $generic_bound_rest:ident )* )*
+	) => {
+		decl_runtime_apis!(
+			@ADD_BLOCK_GENERIC
+			$( #[$attr] )*
+			pub trait $name $(< $( $generic_param_orig $( : $generic_bound_orig )* ),* >)* {
+				$( type $client_generic_param $( : $client_generic_bound )*; )*
+				$(
+					$( #[$fn_attr] )*
+					fn $fn_name $( < $( $fn_generic ),* > )* (
+						$( $param_name : $param_type, )*
+					) $( -> $return_ty )*;
+				)*
+			};
+			$( $block_found )*;
+			$( $generic_param_parsed $( : $generic_bound_parsed )* , )* $generic_param $( : $generic_bound )*;
+			$( $generic_param_rest $( : $generic_bound_rest )* ),*
+		);
+	};
+	(@ADD_BLOCK_GENERIC
+		$( #[$attr:meta] )*
+		pub trait $name:ident $(< $( $generic_param_orig:ident $( : $generic_bound_orig:ident )* ),* >)* {
+			$( type $client_generic_param:ident $( : $client_generic_bound:ident )*; )*
+			$(
+				$( #[$fn_attr:meta] )*
+				fn $fn_name:ident $( < $( $fn_generic:ident ),* > )* (
+					$( $param_name:ident : $param_type:ty, )*
+				) $( -> $return_ty:ty )*;
+			)*
+		};
+		Found;
+	 	$( $generic_param_parsed:ident $( : $generic_bound_parsed:path )* ),*;
+	) => {
+		decl_runtime_apis!(
+			@GENERATE_RETURN_TYPES
+			$( #[$attr] )*
+			pub trait $name $(< $( $generic_param_orig $( : $generic_bound_orig )* ),* >)* {
+				$( type $client_generic_param $( : $client_generic_bound )*; )*
+				$(
+					$( #[$fn_attr] )*
+					fn $fn_name $( < $( $fn_generic ),* > )* (
+						$( $param_name : $param_type, )*
+					) $( -> $return_ty )*;
+				)*
+			};
+			$( $generic_param_parsed $( : $generic_bound_parsed )* ),*;
+			{};
+			$( $( $return_ty )*; )*
+		);
+	};
+	(@ADD_BLOCK_GENERIC
+		$( #[$attr:meta] )*
+		pub trait $name:ident $(< $( $generic_param_orig:ident $( : $generic_bound_orig:ident )* ),* >)* {
+			$( type $client_generic_param:ident $( : $client_generic_bound:ident )*; )*
+			$(
+				$( #[$fn_attr:meta] )*
+				fn $fn_name:ident $( < $( $fn_generic:ident ),* > )* (
+					$( $param_name:ident : $param_type:ty, )*
+				) $( -> $return_ty:ty )*;
+			)*
+		};
+		;
+		$( $generic_param_parsed:ident $( : $generic_bound_parsed:ident )* ),*;
+	) => {
+		decl_runtime_apis!(
+			@GENERATE_RETURN_TYPES
+			$( #[$attr] )*
+			pub trait $name $(< $( $generic_param_orig $( : $generic_bound_orig )* ),* >)* {
+				$( type $client_generic_param $( : $client_generic_bound )*; )*
+				$(
+					$( #[$fn_attr] )*
+					fn $fn_name $( < $( $fn_generic ),* > )* (
+						$( $param_name : $param_type, )*
+					) $( -> $return_ty )*;
+				)*
+			};
+			// We need to add the required generic Block parameter
+			Block: $crate::runtime_api::BlockT $(, $generic_param_parsed $( : $generic_bound_parsed )* )*;
+			{};
+			$( $( $return_ty )*; )*
+		);
+	};
+	(@GENERATE_RETURN_TYPES
+        $( #[$attr:meta] )*
+        pub trait $name:ident $(< $( $generic_param_orig:ident $( : $generic_bound_orig:ident )* ),* >)* {
+			$( type $client_generic_param:ident $( : $client_generic_bound:ident )*; )*
+			$(
+				$( #[$fn_attr:meta] )*
+				fn $fn_name:ident $( < $( $fn_generic:ident ),* > )* (
+					$( $param_name:ident : $param_type:ty, )*
+				) $( -> $return_ty:ty)*;
+			)*
+        };
+        $( $generic_param_parsed:ident $( : $generic_bound_parsed:path )* ),*;
+		{ $( $result_return_ty:ty; )* };
+		$return_ty_current:ty;
+		$( $( $return_ty_rest:ty )*; )*
+	) => {
+		decl_runtime_apis!(
+			@GENERATE_RETURN_TYPES
+			$( #[$attr] )*
+			pub trait $name $(< $( $generic_param_orig $( : $generic_bound_orig )* ),* >)* {
+				$( type $client_generic_param $( : $client_generic_bound )*; )*
+				$(
+					$( #[$fn_attr] )*
+					fn $fn_name $( < $( $fn_generic ),* > )* (
+						$( $param_name : $param_type, )*
+					) $( -> $return_ty )*;
+				)*
+			};
+			$( $generic_param_parsed $( : $generic_bound_parsed )* ),*;
+			{ $( $result_return_ty; )* $crate::error::Result<$return_ty_current>; };
+			$( $( $return_ty_rest )*; )*
+		);
+	};
+	(@GENERATE_RETURN_TYPES
+        $( #[$attr:meta] )*
+        pub trait $name:ident $(< $( $generic_param_orig:ident $( : $generic_bound_orig:ident )* ),* >)* {
+			$( type $client_generic_param:ident $( : $client_generic_bound:ident )*; )*
+			$(
+				$( #[$fn_attr:meta] )*
+				fn $fn_name:ident $( < $( $fn_generic:ident ),* > )* (
+					$( $param_name:ident : $param_type:ty, )*
+				) $( -> $return_ty:ty)*;
+			)*
+        };
+        $( $generic_param_parsed:ident $( : $generic_bound_parsed:path )* ),*;
+		{ $( $result_return_ty:ty; )* };
+		;
+		$( $( $return_ty_rest:ty )*; )*
+	) => {
+		decl_runtime_apis!(
+			@GENERATE_RETURN_TYPES
+			$( #[$attr] )*
+			pub trait $name $(< $( $generic_param_orig $( : $generic_bound_orig )* ),* >)* {
+				$( type $client_generic_param $( : $client_generic_bound )*; )*
+				$(
+					$( #[$fn_attr] )*
+					fn $fn_name $( < $( $fn_generic ),* > )* (
+						$( $param_name : $param_type, )*
+					) $( -> $return_ty )*;
+				)*
+			};
+			$( $generic_param_parsed $( : $generic_bound_parsed )* ),*;
+			{ $( $result_return_ty; )* $crate::error::Result<()>; };
+			$( $( $return_ty_rest )*; )*
+		);
+	};
+	(@GENERATE_RETURN_TYPES
+        $( #[$attr:meta] )*
+        pub trait $name:ident $(< $( $generic_param_orig:ident $( : $generic_bound_orig:ident )* ),* >)* {
+			$( type $client_generic_param:ident $( : $client_generic_bound:ident )*; )*
+			$(
+				$( #[$fn_attr:meta] )*
+				fn $fn_name:ident $( < $( $fn_generic:ident ),* > )* (
+					$( $param_name:ident : $param_type:ty, )*
+				) $( -> $return_ty:ty)*;
+			)*
+        };
+        $( $generic_param_parsed:ident $( : $generic_bound_parsed:path )* ),*;
+		{ $( $result_return_ty:ty; )* };
+	) => {
+		decl_runtime_apis!(
+			@GENERATE_CLIENT_TRAITS
+			$( #[$attr] )*
+			pub trait $name $(< $( $generic_param_orig $( : $generic_bound_orig )* ),* >)* {
+				$( type $client_generic_param $( : $client_generic_bound )*; )*
+				$(
+					$( #[$fn_attr] )*
+					fn $fn_name $( < $( $fn_generic ),* > )* (
+						$( $param_name : $param_type, )*
+					) $( -> $return_ty )*;
+				)*
+			};
+			$( $generic_param_parsed $( : $generic_bound_parsed )* ),*;
+			{ $( $result_return_ty; )* };
+		);
+	};
+	(@GENERATE_CLIENT_TRAITS
+		$( #[$attr:meta] )*
+		pub trait $name:ident $(< $( $generic_param_orig:ident $( : $generic_bound_orig:ident )* ),* >)* {
+			$( type $client_generic_param:ident $( : $client_generic_bound:ident )*; )*
+			$(
+				$( #[$fn_attr:meta] )*
+				fn $fn_name:ident $( < $( $fn_generic:ident ),* > )* (
+					$( $param_name:ident : $param_type:ty, )*
+				) $( -> $return_ty:ty)*;
+			)*
+		};
+		$( $generic_param_parsed:ident $( : $generic_bound_parsed:path )* ),*;
+		{ $( $result_return_ty:ty; )* };
+	) => {
+		$( #[$attr] )*
+		#[cfg(feature = "std")]
+		pub trait $name < $( $generic_param_parsed $( : $generic_bound_parsed )* ),* > : $crate::runtime_api::Core<Block> {
+			$( type $client_generic_param $( : $client_generic_bound )*; )*
+
+			$(
+				$( #[$fn_attr] )*
+				fn $fn_name $( < $( $fn_generic: $crate::runtime_api::Encode + $crate::runtime_api::Decode ),* > )* (
+					&self, at: &$crate::runtime_api::BlockId<Block> $(, $param_name: $param_type )*
+				) -> $result_return_ty;
+			)*
+		}
+	};
+	(@GENERATE_RUNTIME_TRAITS
+		$(
+			$( #[$attr:meta] )*
+			pub trait $name:ident $(< $( $generic_param:ident $( : $generic_bound:ident )* ),* >)* {
+				$(
+					$( #[$fn_attr:meta] )*
+					fn $fn_name:ident $( < $( $fn_generic:ident ),* > )* (
+						$( $param_name:ident : $param_type:ty )*
+					) $( -> $return_ty:ty)*;
+				)*
+			};
+		)*
+	) => {
+		decl_runtime_apis! {
+			@GENERATE_RUNTIME_TRAITS_WITH_JOINED_GENERICS
+			$(
+				$( #[$attr] )*
+				pub trait $name < $( $( $generic_param $( : $generic_bound )*, )* )* $( $( $( $fn_generic, )* )* )* > {
+					$(
+						$( #[$fn_attr] )*
+						fn $fn_name ($( $param_name: $param_type ),*) $( -> $return_ty )*;
+					)*
+				}
+			)*
+		}
+	};
+	(@GENERATE_RUNTIME_TRAITS_WITH_JOINED_GENERICS
+		$(
+			$( #[$attr:meta] )*
+			pub trait $name:ident < $( $generic_param:ident $( : $generic_bound:ident )*, )* > {
+				$(
+					$( #[$fn_attr:meta] )*
+					fn $fn_name:ident($( $param_name:ident : $param_type:ty ),*) $( -> $return_ty:ty)*;
+				)*
+			}
+		)*
+	) => {
+		/// The API traits to implement on the runtime side.
+		pub mod runtime {
+			use super::*;
+
+			$(
+				$( #[$attr] )*
+				pub trait $name < $( $generic_param $( : $generic_bound )* ),* > {
+					$(
+						$( #[$fn_attr] )*
+						fn $fn_name ($( $param_name: $param_type ),*) $( -> $return_ty )*;
+					)*
+				}
+			)*
+		}
+	};
+}
+
+/// Implement the given API's for the given runtime.
+/// All desired API's need to be implemented in one `impl_runtime_apis!` call.
+/// Besides generating the implementation for the runtime, there will be also generated an
+/// auxiliary module named `api` that contains function for inferring with the API in native/wasm.
+/// It is important to use the traits from the `runtime` module with this macro.
+///
+/// # Example:
+///
+/// ```nocompile
+/// #[macro_use]
+/// extern crate substrate_client as client;
+///
+/// use client::runtime_api::runtime::{Core, TaggedTransactionQueue};
+///
+/// impl_runtime_apis! {
+///     impl Core<Block> for Runtime {
+///         fn version() -> RuntimeVersion { unimplemented!() }
+///         fn authorities() -> Vec<AuthorityId> { unimplemented!() }
+///         fn execute_block(block: Block) {
+///             //comment
+///             unimplemented!()
+///         }
+///     }
+///
+///     impl TaggedTransactionQueue<Block> for Runtime {
+///			fn validate_transaction(tx: <Block as BlockT>::Extrinsic) -> TransactionValidity {
+///				unimplemented!()
+///			}
+///     }
+/// }
+///
+/// fn main() {}
+/// ```
+#[macro_export]
+macro_rules! impl_runtime_apis {
+	(
+		impl $trait_name:ident $( < $( $generic:ident ),* > )* for $runtime:ident {
+			$(
+				fn $fn_name:ident ( $( $arg_name:ident : $arg_ty:ty ),* ) $( -> $return_ty:ty )* {
+					$( $impl:tt )*
+				}
+			)*
+		}
+		$( $rest:tt )*
+	) => {
+		impl $trait_name $( < $( $generic ),* > )* for $runtime {
+			$(
+				fn $fn_name ( $( $arg_name : $arg_ty ),* ) $( -> $return_ty )* {
+					$( $impl )*
+				}
+			)*
+		}
+		impl_runtime_apis! {
+			$runtime;
+			$( $fn_name ( $( $arg_name: $arg_ty ),* ); )*;
+			$( $rest )*
+		}
+	};
+	(
+		$runtime:ident;
+		$( $fn_name_parsed:ident ( $( $arg_name_parsed:ident : $arg_ty_parsed:ty ),* ); )*;
+		impl $trait_name:ident $( < $( $generic:ident ),* > )* for $runtime_ignore:ident {
+			$(
+				fn $fn_name:ident ( $( $arg_name:ident : $arg_ty:ty ),* ) $( -> $return_ty:ty )* {
+					$( $impl:tt )*
+				}
+			)*
+		}
+		$( $rest:tt )*
+	) => {
+		impl $trait_name $( < $( $generic ),* > )* for $runtime {
+			$(
+				fn $fn_name ( $( $arg_name : $arg_ty ),* ) $( -> $return_ty )* {
+					$( $impl )*
+				}
+			)*
+		}
+		impl_runtime_apis! {
+			$runtime;
+			$( $fn_name_parsed ( $( $arg_name_parsed: $arg_ty_parsed ),* ); )*
+			$( $fn_name ( $( $arg_name: $arg_ty ),* ); )*;
+			$( $rest )*
+		}
+	};
+	(
+		$runtime:ident;
+		$( $fn_name:ident ( $( $arg_name:ident : $arg_ty:ty ),* ); )*;
+	) => {
+		pub mod api {
+			use super::*;
+
+			#[cfg(feature = "std")]
+			pub fn dispatch(method: &str, mut data: &[u8]) -> Option<Vec<u8>> {
+				match method {
+					$(
+						stringify!($fn_name) => {
+							Some({impl_runtime_apis! {
+								@GENERATE_IMPL_CALL
+								$runtime;
+								$fn_name;
+								$( $arg_name : $arg_ty ),*;
+								data;
+							}})
+						}
+					)*
+						_ => None,
+				}
+			}
+
+			$(
+				#[cfg(not(feature = "std"))]
+				#[no_mangle]
+				pub fn $fn_name(input_data: *mut u8, input_len: usize) -> u64 {
+					let mut input = if input_len == 0 {
+						&[0u8; 0]
+					} else {
+						unsafe {
+							$crate::runtime_api::slice::from_raw_parts(input_data, input_len)
+						}
+					};
+
+					let output = { impl_runtime_apis! {
+						@GENERATE_IMPL_CALL
+						$runtime;
+						$fn_name;
+						$( $arg_name : $arg_ty ),*;
+						input;
+					} };
+					let res = output.as_ptr() as u64 + ((output.len() as u64) << 32);
+
+					// Leak the output vector to avoid it being freed.
+					// This is fine in a WASM context since the heap
+					// will be discarded after the call.
+					::core::mem::forget(output);
+					res
+				}
+			)*
+		}
+	};
+	(@GENERATE_IMPL_CALL
+		$runtime:ident;
+		$fn_name:ident;
+		$arg_name:ident : $arg_ty:ty;
+		$input:ident;
+	) => {
+		let $arg_name : $arg_ty = match $crate::runtime_api::Decode::decode(&mut $input) {
+			Some(input) => input,
+			None => panic!("Bad input data provided to {}", stringify!($fn_name)),
+		};
+
+		let output = $runtime::$fn_name($arg_name);
+		$crate::runtime_api::Encode::encode(&output)
+	};
+	(@GENERATE_IMPL_CALL
+		$runtime:ident;
+		$fn_name:ident;
+		$( $arg_name:ident : $arg_ty:ty ),*;
+		$input:ident;
+	) => {
+		let ( $( $arg_name ),* ) : ($( $arg_ty ),*) = match $crate::runtime_api::Decode::decode(&mut $input) {
+			Some(input) => input,
+			None => panic!("Bad input data provided to {}", stringify!($fn_name)),
+		};
+
+		let output = $runtime::$fn_name($( $arg_name ),*);
+		$crate::runtime_api::Encode::encode(&output)
+	};
+}
@@ -0,0 +1,99 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! All the functionality required for declaring and implementing runtime api's.
+//! Core api's are also declared here.
+
+#[doc(hidden)]
+#[cfg(feature = "std")]
+pub use state_machine::OverlayedChanges;
+#[doc(hidden)]
+pub use runtime_primitives::{traits::Block as BlockT, generic::BlockId};
+#[cfg(feature = "std")]
+use runtime_primitives::traits::ApiRef;
+use runtime_version::ApiId;
+#[doc(hidden)]
+pub use rstd::slice;
+#[cfg(feature = "std")]
+use rstd::result;
+#[doc(hidden)]
+pub use codec::{Encode, Decode};
+#[cfg(feature = "std")]
+use error;
+
+mod core;
+#[macro_use]
+mod macros;
+mod traits;
+
+/// Something that can be constructed to a runtime api.
+#[cfg(feature = "std")]
+pub trait ConstructRuntimeApi<Block: BlockT>: Sized {
+	/// Construct an instance of the runtime api.
+	fn construct_runtime_api<'a, T: CallApiAt<Block>>(call: &'a T) -> ApiRef<'a, Self>;
+}
+
+/// An extension for the `RuntimeApi`.
+#[cfg(feature = "std")]
+pub trait ApiExt {
+	/// The given closure will be called with api instance. Inside the closure any api call is
+	/// allowed. After doing the api call, the closure is allowed to map the `Result` to a
+	/// different `Result` type. This can be important, as the internal data structure that keeps
+	/// track of modifications to the storage, discards changes when the `Result` is an `Err`.
+	/// On `Ok`, the structure commits the changes to an internal buffer.
+	fn map_api_result<F: FnOnce(&Self) -> result::Result<R, E>, R, E>(
+		&self,
+		map_call: F
+	) -> result::Result<R, E>;
+}
+
+/// Something that can call the runtime api at a given block.
+#[cfg(feature = "std")]
+pub trait CallApiAt<Block: BlockT> {
+	/// Calls the given api function with the given encoded arguments at the given block
+	/// and returns the encoded result.
+	fn call_api_at(
+		&self,
+		at: &BlockId<Block>,
+		function: &'static str,
+		args: Vec<u8>,
+		changes: &mut OverlayedChanges,
+		initialised_block: &mut Option<BlockId<Block>>,
+	) -> error::Result<Vec<u8>>;
+}
+
+/// The ApiIds for the various standard runtime APIs.
+pub mod id {
+	use super::ApiId;
+
+	/// ApiId for the BlockBuilder trait.
+	pub const BLOCK_BUILDER: ApiId = *b"blkbuild";
+
+	/// ApiId for the TaggedTransactionQueue trait.
+	pub const TAGGED_TRANSACTION_QUEUE: ApiId = *b"validatx";
+
+	/// ApiId for the Metadata trait.
+	pub const METADATA: ApiId = *b"metadata";
+}
+
+pub use self::core::*;
+pub use self::traits::*;
+
+/// The runtime apis that should be implemented for the `Runtime`.
+pub mod runtime {
+	pub use super::core::runtime::Core;
+	pub use super::traits::runtime::*;
+}
@@ -0,0 +1,35 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+use primitives::OpaqueMetadata;
+use runtime_primitives::{
+	traits::{Block as BlockT},
+	transaction_validity::TransactionValidity
+};
+
+decl_runtime_apis! {
+	/// The `Metadata` api trait that returns metadata for the runtime.
+	pub trait Metadata {
+		/// Returns the metadata of a runtime.
+		fn metadata() -> OpaqueMetadata;
+	}
+
+	/// The `TaggedTransactionQueue` api trait for interfering with the new transaction queue.
+	pub trait TaggedTransactionQueue<Block: BlockT> {
+		/// Validate the given transaction.
+		fn validate_transaction(tx: <Block as BlockT>::Extrinsic) -> TransactionValidity;
+	}
+}