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// Copyright 2018-2022 Parity Technologies (UK) Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use super::KeyPtr;
/// This constant is used by some types to make sure that cleaning up
/// behind them won't become way too expensive. Since we are missing
/// Substrate's storage bulk removal feature we cannot do better than
/// this at the moment.
/// The number is arbitrarily chosen. Might need adjustments later.
pub const FOOTPRINT_CLEANUP_THRESHOLD: u64 = 32;
/// Types that can be default initialized to some area of the contract storage.
pub trait SpreadAllocate: SpreadLayout {
/// Default initializes the implementing type using spread layout.
///
/// # Note
///
/// - The key pointer denotes the position in contract storage where
/// the instance is being allocated at.
/// - Fields of `Self` are allocated in order and construct `Self` upon
/// completion.
fn allocate_spread(ptr: &mut KeyPtr) -> Self;
}
/// Types that can be stored to and loaded from the contract storage.
pub trait SpreadLayout {
/// The footprint of the type.
///
/// This is the number of adjunctive cells the type requires in order to
/// be stored in the contract storage with spread layout.
///
/// # Examples
///
/// An instance of type `i32` requires one storage cell, so its footprint is 1.
/// An instance of type `(i32, i32)` requires 2 storage cells since a
/// tuple or any other combined data structure always associates disjunctive
/// cells for its sub types. The same applies to arrays, e.g. `[i32; 5]`
/// has a footprint of 5.
const FOOTPRINT: u64;
/// Indicates whether a type requires deep clean-up of its state meaning that
/// a clean-up routine has to decode an entity into an instance in order to
/// eventually recurse upon its tear-down.
/// This is not required for the majority of primitive data types such as `i32`,
/// however types such as `storage::Box` that might want to forward the clean-up
/// procedure to their inner `T` require a deep clean-up.
///
/// # Note
///
/// The default is set to `true` in order to have correctness by default since
/// no type invariants break if a deep clean-up is performed on a type that does
/// not need it but performing a shallow clean-up for a type that requires a
/// deep clean-up would break invariants.
/// This is solely a setting to improve performance upon clean-up for some types.
const REQUIRES_DEEP_CLEAN_UP: bool = true;
/// Pulls an instance of `Self` from the contract storage.
///
/// The key pointer denotes the position where the instance is being pulled
/// from within the contract storage
///
/// # Note
///
/// This method of pulling is depth-first: Sub-types are pulled first and
/// construct the super-type through this procedure.
fn pull_spread(ptr: &mut KeyPtr) -> Self;
/// Pushes an instance of `Self` to the contract storage.
///
/// - Tries to spread `Self` to as many storage cells as possible.
/// - The key pointer denotes the position where the instance is being pushed
/// to the contract storage.
///
/// # Note
///
/// This method of pushing is depth-first: Sub-types are pushed before
/// their parent or super type.
fn push_spread(&self, ptr: &mut KeyPtr);
/// Clears an instance of `Self` from the contract storage.
///
/// - Tries to clean `Self` from contract storage as if `self` was stored
/// in it using spread layout.
/// - The key pointer denotes the position where the instance is being cleared
/// from the contract storage.
///
/// # Note
///
/// This method of clearing is depth-first: Sub-types are cleared before
/// their parent or super type.
fn clear_spread(&self, ptr: &mut KeyPtr);
}