State machine crate and rust impl of executor (#17)

* Executor.

* Rust contracts implementation.

* Add documentation and fix transfer data.

* Fix auth contract interface.

* Add some executor tests.

* Validator set contract.

substrate/state_machine/src/lib.rs

@@ -0,0 +1,61 @@
+// Copyright 2017 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot 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.
+
+// Polkadot 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 Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Polkadot state machine
+
+#![warn(missing_docs)]
+
+extern crate polkadot_primitives as primitives;
+
+use std::fmt;
+
+use primitives::contract::{CallData, OutData};
+
+/// State Machine Error bound.
+///
+/// This should reflect WASM error type bound for future compatibility.
+pub trait Error: 'static + fmt::Debug + fmt::Display + Send {}
+
+/// Externalities
+pub trait Externalities<Executor> {
+	/// Externalities error type.
+	type Error: Error;
+}
+
+/// Contract code executor.
+pub trait Executor: Sized {
+	/// Error type for contract execution.
+	type Error: Error;
+
+	/// Execute a contract in read-only mode.
+	/// The execution is not allowed to modify the state.
+	fn static_call<E: Externalities<Self>>(
+		&self,
+		ext: &E,
+		code: &[u8],
+		method: &str,
+		data: &CallData,
+	) -> Result<OutData, Self::Error>;
+
+	/// Execute a contract.
+	fn call<E: Externalities<Self>>(
+		&self,
+		ext: &mut E,
+		code: &[u8],
+		method: &str,
+		data: &CallData,
+	) -> Result<OutData, Self::Error>;
+}