87 lines
2.7 KiB
Swift
87 lines
2.7 KiB
Swift
// Copyright 2022 Tokamak contributors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// Created by Carson Katri on 2/11/22.
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//
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@_spi(TokamakCore)
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public enum WalkWorkResult<Success> {
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case `continue`
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case `break`(with: Success)
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case pause
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}
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@_spi(TokamakCore)
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public enum WalkResult<Renderer: FiberRenderer, Success> {
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case success(Success)
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case finished
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case paused(at: FiberReconciler<Renderer>.Fiber)
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}
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/// Walk a fiber tree from `root` until the `work` predicate returns `false`.
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@_spi(TokamakCore)
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@discardableResult
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public func walk<Renderer: FiberRenderer>(
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_ root: FiberReconciler<Renderer>.Fiber,
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_ work: @escaping (FiberReconciler<Renderer>.Fiber) throws -> Bool
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) rethrows -> WalkResult<Renderer, ()> {
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try walk(root) {
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try work($0) ? .continue : .pause
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}
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}
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/// Parent-first depth-first traversal of a `Fiber` tree.
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/// `work` is called with each `Fiber` in the tree as they are entered.
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///
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/// Traversal uses the following process:
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/// 1. Perform work on the current `Fiber`.
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/// 2. If the `Fiber` has a child, repeat from (1) with the child.
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/// 3. If the `Fiber` does not have a sibling, walk up until we find a `Fiber` that does have one.
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/// 4. Walk across to the sibling.
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///
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/// When the `root` is reached, the loop exits.
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@_spi(TokamakCore)
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public func walk<Renderer: FiberRenderer, Success>(
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_ root: FiberReconciler<Renderer>.Fiber,
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_ work: @escaping (FiberReconciler<Renderer>.Fiber) throws -> WalkWorkResult<Success>
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) rethrows -> WalkResult<Renderer, Success> {
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var current = root
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while true {
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// Perform work on the node
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switch try work(current) {
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case .continue: break
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case let .break(success): return .success(success)
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case .pause: return .paused(at: current)
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}
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// Walk into the child
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if let child = current.child {
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current = child
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continue
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}
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// When we walk back to the root, exit
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if current === root {
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return .finished
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}
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// Walk back up until we find a sibling
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while current.sibling == nil {
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// When we walk back to the root, exit
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guard let parent = current.parent,
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parent !== root else { return .finished }
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current = parent
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}
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// Walk the sibling
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current = current.sibling!
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}
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}
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