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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Collections open source project
//
// Copyright (c) 2023 - 2024 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
/// An internal protocol describing a summarizable entity that isn't a full `RopeElement`.
///
/// Used as an implementation detail to increase code reuse across internal nodes and leaf nodes.
/// (Ideally `Rope._Node` would just conform to the full `RopeElement` protocol on its own, but
/// while that's an obvious refactoring idea, it hasn't happened yet.)
@usableFromInline
internal protocol _RopeItem<Summary> {
associatedtype Summary: RopeSummary
var summary: Summary { get }
}
extension Sequence where Element: _RopeItem {
@inlinable
internal func _sum() -> Element.Summary {
self.reduce(into: .zero) { $0.add($1.summary) }
}
}
extension Rope: _RopeItem {
public typealias Summary = Element.Summary
@inlinable
public var summary: Summary {
guard _root != nil else { return .zero }
return root.summary
}
}
extension Rope {
/// A trivial wrapper around a rope's Element type, giving it `_RopeItem` conformance without
/// having to make the protocol public.
@usableFromInline
@frozen // Not really! This module isn't ABI stable.
internal struct _Item {
@usableFromInline internal var value: Element
@inlinable
internal init(_ value: Element) { self.value = value }
}
}
extension Rope._Item: _RopeItem {
@usableFromInline internal typealias Summary = Rope.Summary
@inlinable
internal var summary: Summary { value.summary }
}
extension Rope._Item: CustomStringConvertible {
@usableFromInline
internal var description: String {
"\(value)"
}
}
extension Rope._Item {
@inlinable
internal var isEmpty: Bool { value.isEmpty }
@inlinable
internal var isUndersized: Bool { value.isUndersized }
@inlinable
internal mutating func rebalance(nextNeighbor right: inout Self) -> Bool {
value.rebalance(nextNeighbor: &right.value)
}
@inlinable
internal mutating func rebalance(prevNeighbor left: inout Self) -> Bool {
value.rebalance(prevNeighbor: &left.value)
}
@usableFromInline internal typealias Index = Element.Index
@inlinable
internal mutating func split(at index: Index) -> Self {
Self(self.value.split(at: index))
}
}
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