Add BoundedSortedVec and SortedVec (#532)

* Add BoundedSortedVec and SortedVec

* fail on unsorted decodes

frame/composable-support/Cargo.toml

@@ -11,6 +11,7 @@ targets = ["x86_64-unknown-linux-gnu"]
 
 [dev-dependencies]
 proptest = { version = "1.0" }
+serde_json = "1.*"
 
 [dependencies]
 frame-support = { default-features = false, git = "https://github.com/paritytech/substrate", branch = "polkadot-v0.9.13"  }
@@ -19,6 +20,10 @@ sp-arithmetic = { default-features = false, git = "https://github.com/paritytech
 sp-runtime = { default-features = false, git = "https://github.com/paritytech/substrate", branch = "polkadot-v0.9.13" }
 sp-std = { default-features = false,  git = "https://github.com/paritytech/substrate", branch = "polkadot-v0.9.13" }
 scale-info = { version = "1.0", default-features = false, features = ["derive"] }
+sorted-vec = "0.7.0"
+serde = { version = "1.*", features = [ "derive" ], optional = true }
+is_sorted = "0.1.1"
+
 
 [dependencies.codec]
 default-features = false
@@ -35,4 +40,4 @@ std = [
     "sp-runtime/std",
     "sp-std/std",
     "scale-info/std",
-]
+]

frame/composable-support/src/collections/mod.rs

@@ -0,0 +1,3 @@
+pub mod vec;
+
+// pub use vec::BoundedSortedVec;

frame/composable-support/src/collections/vec/bounded/mod.rs

@@ -0,0 +1,3 @@
+pub mod sorted_vec;
+
+pub use self::sorted_vec::BoundedSortedVec;

frame/composable-support/src/collections/vec/bounded/sorted_vec.rs

@@ -0,0 +1,360 @@
+use crate::collections::vec::sorted::SortedVec;
+use codec::{Decode, Encode, EncodeLike, MaxEncodedLen};
+use core::{
+	ops::{Deref, Index},
+	slice::SliceIndex,
+};
+use frame_support::{traits::Get, BoundedVec};
+use sp_std::{convert::TryFrom, fmt, marker::PhantomData, prelude::*};
+
+/// A bounded, sorted vector.
+///
+/// It has implementations for efficient append and length decoding, as with a normal `Vec<_>`, once
+/// put into storage as a raw value, map or double-map.
+///
+/// As the name suggests, the length of the queue is always bounded and sorted. All internal
+/// operations ensure this bound is respected and order is maintained.
+#[derive(Encode)]
+pub struct BoundedSortedVec<T: Ord, S>(SortedVec<T>, PhantomData<S>);
+
+impl<T: Decode + Ord, S: Get<u32>> Decode for BoundedSortedVec<T, S> {
+	#[inline]
+	fn decode<I: codec::Input>(input: &mut I) -> Result<Self, codec::Error> {
+		use is_sorted::IsSorted;
+
+		let inner = Vec::<T>::decode(input)?;
+		if inner.len() > S::get() as usize {
+			return Err("BoundedSortedVec exceeds its limit".into())
+		}
+
+		if !IsSorted::is_sorted(&mut inner.iter()) {
+			return Err("input is not sorted".into())
+		}
+		// checked above
+		Ok(Self(SortedVec::unchecked_from(inner), PhantomData))
+	}
+
+	#[inline]
+	fn skip<I: codec::Input>(input: &mut I) -> Result<(), codec::Error> {
+		Vec::<T>::skip(input)
+	}
+}
+
+// `BoundedSortedVec`s encode to something which will always decode as a `Vec`.
+impl<T: Encode + Decode + Ord, S: Get<u32>> EncodeLike<Vec<T>> for BoundedSortedVec<T, S> {}
+
+impl<T: Ord, S> BoundedSortedVec<T, S> {
+	/// Create `Self` from `t` without any checks.
+	fn unchecked_from(t: Vec<T>) -> Self {
+		Self(SortedVec::unchecked_from(t), Default::default())
+	}
+
+	/// Consume self, and return the inner `Vec`. Henceforth, the `Vec<_>` can be altered in an
+	/// arbitrary way. At some point, if the reverse conversion is required, `TryFrom<Vec<_>>` can
+	/// be used.
+	///
+	/// This is useful for cases if you need access to an internal API of the inner `Vec<_>` which
+	/// is not provided by the wrapper `BoundedVec`.
+	#[inline]
+	pub fn into_inner(self) -> SortedVec<T> {
+		self.0
+	}
+
+	/// Exactly the same semantics as [`Vec::remove`].
+	///
+	/// # Panics
+	///
+	/// Panics if `index` is out of bounds.
+	#[inline]
+	pub fn remove(&mut self, index: usize) -> T {
+		self.0.remove(index)
+	}
+
+	/// Exactly the same semantics as [`Vec::retain`].
+	#[inline]
+	pub fn retain<F: FnMut(&T) -> bool>(&mut self, f: F) {
+		self.0.retain(f)
+	}
+}
+
+impl<T: Ord, S: Get<u32>> From<BoundedSortedVec<T, S>> for Vec<T> {
+	#[inline]
+	fn from(x: BoundedSortedVec<T, S>) -> Vec<T> {
+		x.0.into_inner()
+	}
+}
+
+impl<T: Ord, S: Get<u32>> TryFrom<BoundedSortedVec<T, S>> for BoundedVec<T, S> {
+	type Error = ();
+
+	#[inline]
+	fn try_from(x: BoundedSortedVec<T, S>) -> Result<Self, Self::Error> {
+		BoundedVec::try_from(x.0.into_inner())
+	}
+}
+
+impl<T: Ord, S: Get<u32>> BoundedSortedVec<T, S> {
+	/// Get the bound of the type in `usize`.
+	#[inline]
+	pub fn bound() -> usize {
+		S::get() as usize
+	}
+
+	/// Exactly the same semantics as [`Vec::insert`], but returns an `Err` (and is a noop) if the
+	/// new length of the vector exceeds `S`.
+	#[inline]
+	pub fn try_insert(&mut self, element: T) -> Result<(), T> {
+		if self.len() < Self::bound() {
+			self.0.insert(element);
+			Ok(())
+		} else {
+			Err(element)
+		}
+	}
+
+	/// Exactly the same semantics as [`Vec::push`], but returns an `Err` (and is a noop) if the
+	/// new length of the vector exceeds `S`.
+	///
+	/// # Panics
+	///
+	/// Panics if the new capacity exceeds isize::MAX bytes.
+	#[inline]
+	pub fn try_push(&mut self, element: T) -> Result<(), T> {
+		if self.len() < Self::bound() {
+			self.0.insert(element);
+			Ok(())
+		} else {
+			Err(element)
+		}
+	}
+}
+
+impl<T: Ord, S> Default for BoundedSortedVec<T, S> {
+	fn default() -> Self {
+		// the bound cannot be below 0, which is satisfied by an empty vector
+		Self::unchecked_from(Vec::default())
+	}
+}
+
+#[cfg(feature = "std")]
+impl<T: Ord, S> fmt::Debug for BoundedSortedVec<T, S>
+where
+	T: fmt::Debug,
+	S: Get<u32>,
+{
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		f.debug_tuple("BoundedVec").field(&self.0).field(&Self::bound()).finish()
+	}
+}
+
+impl<T: Ord, S> Clone for BoundedSortedVec<T, S>
+where
+	T: Clone,
+{
+	#[inline]
+	fn clone(&self) -> Self {
+		// bound is retained
+		Self::unchecked_from(self.0.as_inner().to_vec())
+	}
+}
+
+impl<T: Ord, S: Get<u32>> TryFrom<Vec<T>> for BoundedSortedVec<T, S> {
+	type Error = ();
+
+	#[inline]
+	fn try_from(t: Vec<T>) -> Result<Self, Self::Error> {
+		if t.len() <= Self::bound() {
+			// explicit check just above
+			Ok(Self::unchecked_from(t))
+		} else {
+			Err(())
+		}
+	}
+}
+
+// It is okay to give a non-mutable reference of the inner vec to anyone.
+impl<T: Ord, S> AsRef<Vec<T>> for BoundedSortedVec<T, S> {
+	#[inline]
+	fn as_ref(&self) -> &Vec<T> {
+		&self.0
+	}
+}
+
+impl<T: Ord, S> AsRef<[T]> for BoundedSortedVec<T, S> {
+	#[inline]
+	fn as_ref(&self) -> &[T] {
+		&self.0
+	}
+}
+
+// will allow for immutable all operations of `Vec<T>` on `BoundedVec<T>`.
+impl<T: Ord, S> Deref for BoundedSortedVec<T, S> {
+	type Target = Vec<T>;
+
+	#[inline]
+	fn deref(&self) -> &Self::Target {
+		&self.0
+	}
+}
+
+// Allows for indexing similar to a normal `Vec`. Can panic if out of bound.
+impl<T: Ord, S, I> Index<I> for BoundedSortedVec<T, S>
+where
+	I: SliceIndex<[T]>,
+{
+	type Output = I::Output;
+
+	#[inline]
+	fn index(&self, index: I) -> &Self::Output {
+		self.0.index(index)
+	}
+}
+
+impl<T: Ord, S> sp_std::iter::IntoIterator for BoundedSortedVec<T, S> {
+	type Item = T;
+	type IntoIter = sp_std::vec::IntoIter<T>;
+
+	#[inline]
+	fn into_iter(self) -> Self::IntoIter {
+		self.0.into_inner().into_iter()
+	}
+}
+
+impl<T: Ord, S> codec::DecodeLength for BoundedSortedVec<T, S> {
+	#[inline]
+	fn len(self_encoded: &[u8]) -> Result<usize, codec::Error> {
+		// `BoundedSortedVec<T, _>` stored just a `Vec<T>`, thus the length is at the beginning in
+		// `Compact` form, and same implementation as `Vec<T>` can be used.
+		<Vec<T> as codec::DecodeLength>::len(self_encoded)
+	}
+}
+
+/// Allows for comparing vectors with different bounds.
+impl<T, S1: Get<u32>, S2: Get<u32>> PartialEq<BoundedSortedVec<T, S2>> for BoundedSortedVec<T, S1>
+where
+	T: PartialEq + Ord,
+{
+	#[inline]
+	fn eq(&self, rhs: &BoundedSortedVec<T, S2>) -> bool {
+		self.0 == rhs.0
+	}
+}
+
+impl<T: PartialEq + Ord, S: Get<u32>> PartialEq<Vec<T>> for BoundedSortedVec<T, S> {
+	#[inline]
+	fn eq(&self, other: &Vec<T>) -> bool {
+		self.0.as_inner() == other
+	}
+}
+
+impl<T: PartialEq + Ord, S: Get<u32>> Eq for BoundedSortedVec<T, S> where T: Eq {}
+
+impl<T: Ord, S> MaxEncodedLen for BoundedSortedVec<T, S>
+where
+	T: MaxEncodedLen,
+	S: Get<u32>,
+	BoundedSortedVec<T, S>: Encode,
+{
+	#[inline]
+	fn max_encoded_len() -> usize {
+		// BoundedSortedVec<T, S> encodes like Vec<T> which encodes like [T], which is a compact u32
+		// plus each item in the slice:
+		// https://substrate.dev/rustdocs/v3.0.0/src/parity_scale_codec/codec.rs.html#798-808
+		codec::Compact(S::get())
+			.encoded_size()
+			.saturating_add(Self::bound().saturating_mul(T::max_encoded_len()))
+	}
+}
+
+#[cfg(test)]
+pub mod test {
+	use super::*;
+	use frame_support::sp_io::TestExternalities;
+	use sp_std::convert::TryInto;
+
+	frame_support::parameter_types! {
+		pub const Seven: u32 = 7;
+		pub const Four: u32 = 4;
+	}
+
+	frame_support::generate_storage_alias! { Prefix, Foo => Value<BoundedSortedVec<u32, Seven>> }
+
+	#[test]
+	fn store_works() {
+		TestExternalities::default().execute_with(|| {
+			let bounded: BoundedSortedVec<u32, Seven> = vec![1, 2, 3].try_into().unwrap();
+			Foo::put(bounded.clone());
+			assert_eq!(Foo::get().unwrap(), bounded);
+		});
+	}
+
+	#[test]
+	fn try_append_is_correct() {
+		assert_eq!(BoundedSortedVec::<u32, Seven>::bound(), 7);
+	}
+
+	#[test]
+	fn try_insert_works() {
+		let mut bounded: BoundedSortedVec<u32, Four> = vec![1, 2, 3].try_into().unwrap();
+		bounded.try_insert(1).unwrap();
+		assert_eq!(*bounded, vec![1, 1, 2, 3]);
+
+		assert!(bounded.try_insert(0).is_err());
+		assert_eq!(*bounded, vec![1, 1, 2, 3]);
+	}
+
+	#[test]
+	#[should_panic]
+	fn try_insert_panics_if_oob() {
+		let mut bounded: BoundedSortedVec<u32, Four> = vec![1, 2, 3, 4].try_into().unwrap();
+		bounded.try_insert(9).unwrap();
+	}
+
+	#[test]
+	fn try_push_works() {
+		let mut bounded: BoundedSortedVec<u32, Four> = vec![1, 2, 3].try_into().unwrap();
+		bounded.try_push(0).unwrap();
+		assert_eq!(*bounded, vec![0, 1, 2, 3]);
+
+		assert!(bounded.try_push(9).is_err());
+	}
+
+	#[test]
+	fn deref_coercion_works() {
+		let bounded: BoundedSortedVec<u32, Seven> = vec![1, 2, 3].try_into().unwrap();
+		// these methods come from deref-ed vec.
+		assert_eq!(bounded.len(), 3);
+		assert!(bounded.iter().next().is_some());
+		assert!(!bounded.is_empty());
+	}
+
+	#[test]
+	fn slice_indexing_works() {
+		let bounded: BoundedSortedVec<u32, Seven> = vec![1, 2, 3, 4, 5, 6].try_into().unwrap();
+		assert_eq!(&bounded[0..=2], &[1, 2, 3]);
+	}
+
+	#[test]
+	fn vec_eq_works() {
+		let bounded: BoundedSortedVec<u32, Seven> = vec![1, 2, 3, 4, 5, 6].try_into().unwrap();
+		assert_eq!(bounded, vec![1, 2, 3, 4, 5, 6]);
+	}
+
+	#[test]
+	fn too_big_vec_fail_to_decode() {
+		let v: Vec<u32> = vec![1, 2, 3, 4, 5];
+		assert_eq!(
+			BoundedSortedVec::<u32, Four>::decode(&mut &v.encode()[..]),
+			Err("BoundedSortedVec exceeds its limit".into()),
+		);
+	}
+
+	#[test]
+	fn unsorted_fail_to_decode() {
+		let v: Vec<u32> = vec![1, 2, 5, 4];
+		assert_eq!(
+			BoundedSortedVec::<u32, Four>::decode(&mut &v.encode()[..]),
+			Err("input is not sorted".into()),
+		);
+	}
+}