clean up workspaces a little

substrate/state-machine/src/ext.rs

@@ -0,0 +1,78 @@
+// 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/>.
+
+//! Conrete externalities implementation.
+
+use std::{error, fmt};
+
+use backend::Backend;
+use {Externalities, ExternalitiesError, OverlayedChanges};
+
+/// Errors that can occur when interacting with the externalities.
+#[derive(Debug, Copy, Clone)]
+pub enum Error<B, E> {
+	/// Failure to load state data from the backend.
+	#[allow(unused)]
+	Backend(B),
+	/// Failure to execute a function.
+	#[allow(unused)]
+	Executor(E),
+}
+
+impl<B: fmt::Display, E: fmt::Display> fmt::Display for Error<B, E> {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			Error::Backend(ref e) => write!(f, "Storage backend error: {}", e),
+			Error::Executor(ref e) => write!(f, "Sub-call execution error: {}", e),
+		}
+	}
+}
+
+impl<B: error::Error, E: error::Error> error::Error for Error<B, E> {
+	fn description(&self) -> &str {
+		match *self {
+			Error::Backend(..) => "backend error",
+			Error::Executor(..) => "executor error",
+		}
+	}
+}
+
+/// Wraps a read-only backend, call executor, and current overlayed changes.
+pub struct Ext<'a, B: 'a> {
+	/// The overlayed changes to write to.
+	pub overlay: &'a mut OverlayedChanges,
+	/// The storage backend to read from.
+	pub backend: &'a B,
+}
+
+impl<'a, B: 'a> Externalities for Ext<'a, B>
+	where B: Backend
+{
+	fn storage(&self, key: &[u8]) -> Result<&[u8], ExternalitiesError> {
+		match self.overlay.storage(key) {
+			Some(x) => Ok(x),
+			None => self.backend.storage(key).map_err(|_| ExternalitiesError),
+		}
+	}
+
+	fn set_storage(&mut self, key: Vec<u8>, value: Vec<u8>) {
+		self.overlay.set_storage(key, value);
+	}
+
+	fn chain_id(&self) -> u64 {
+		42
+	}
+}