Implement sessions.

substrate/wasm-runtime/polkadot/src/support/mod.rs

@@ -2,6 +2,7 @@ pub mod primitives;
 pub mod function;
 pub mod environment;
 pub mod storage;
+pub mod storagevec;
 
 #[cfg(test)]
 pub mod statichex;

substrate/wasm-runtime/polkadot/src/support/storage.rs

@@ -3,14 +3,14 @@ use endiansensitive::EndianSensitive;
 use runtime_support;
 
 pub trait Storage {
-	fn into(_key: &[u8]) -> Self where Self: Sized { unimplemented!() }
+	fn into(key: &[u8]) -> Self where Self: Sized + Default { Self::try_into(key).unwrap_or_else(Default::default) }
+	fn try_into(_key: &[u8]) -> Option<Self> where Self: Sized { unimplemented!() }
 	fn store(&self, key: &[u8]);
 }
 
 impl<T: Default + Sized + EndianSensitive> Storage for T {
-	fn into(key: &[u8]) -> Self {
+	fn try_into(key: &[u8]) -> Option<Self> {
 		Slicable::set_as_slice(|out| runtime_support::read_storage(key, out) == out.len())
-			.unwrap_or_else(Default::default)
 	}
 	fn store(&self, key: &[u8]) {
 		self.as_slice_then(|slice| runtime_support::set_storage(key, slice));

substrate/wasm-runtime/polkadot/src/support/storagevec.rs

@@ -0,0 +1,38 @@
+use runtime_support::Vec;
+use keyedvec::KeyedVec;
+use storage::Storage;
+
+/// A trait to conveniently store a vector of storable data.
+// TODO: add iterator support
+pub trait StorageVec {
+	type Item: Default + Sized + Storage;
+	const PREFIX: &'static [u8];
+
+	/// Get the current set of items.
+	fn items() -> Vec<Self::Item> {
+		(0..Self::count()).into_iter().map(Self::item).collect()
+	}
+
+	/// Set the current set of items.
+	fn set_items(items: &[Self::Item]) {
+		Self::set_count(items.len() as u32);
+		items.iter().enumerate().for_each(|(v, ref i)| Self::set_item(v as u32, i));
+	}
+
+	fn set_item(index: u32, item: &Self::Item) {
+		item.store(&index.to_keyed_vec(Self::PREFIX));
+	}
+
+	fn item(index: u32) -> Self::Item {
+		Storage::into(&index.to_keyed_vec(Self::PREFIX))
+	}
+
+	fn set_count(count: u32) {
+		(count..Self::count()).for_each(|i| Self::set_item(i, &Self::Item::default()));
+		count.store(&b"len".to_keyed_vec(Self::PREFIX));
+	}
+
+	fn count() -> u32 {
+		Storage::into(&b"len".to_keyed_vec(Self::PREFIX))
+	}
+}