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83 lines
2.8 KiB
Swift
83 lines
2.8 KiB
Swift
//===--- CocoaArray.swift - A subset of the NSArray interface -------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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//
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// To implement bridging, the core standard library needs to interact
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// a little bit with Cocoa. Because we want to keep the core
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// decoupled from the Foundation module, we can't use NSArray
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// directly. We _can_, however, use an @objc protocol with a
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// compatible API. That's _NSArrayCore.
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//
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//===----------------------------------------------------------------------===//
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#if _runtime(_ObjC)
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import SwiftShims
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/// A wrapper around any `_NSArrayCore` that gives it
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/// `Collection` conformance. Why not make
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/// `_NSArrayCore` conform directly? It's a class, and I
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/// don't want to pay for the dynamic dispatch overhead.
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internal struct _CocoaArrayWrapper : RandomAccessCollection {
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typealias Indices = CountableRange<Int>
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var startIndex: Int {
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return 0
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}
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var endIndex: Int {
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return buffer.count
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}
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subscript(i: Int) -> AnyObject {
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return buffer.objectAt(i)
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}
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/// Returns a pointer to the first element in the given non-empty `subRange`
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/// if the subRange is stored contiguously. Otherwise, return `nil`.
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///
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/// The "non-empty" condition saves a branch within this method that can
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/// likely be better handled in a caller.
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///
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/// - Note: This method should only be used as an optimization; it
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/// is sometimes conservative and may return `nil` even when
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/// contiguous storage exists, e.g., if array doesn't have a smart
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/// implementation of countByEnumerating.
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func contiguousStorage(
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_ subRange: Range<Int>
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) -> UnsafeMutablePointer<AnyObject>?
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{
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_sanityCheck(!subRange.isEmpty)
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var enumerationState = _makeSwiftNSFastEnumerationState()
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// This function currently returns nil unless the first
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// subRange.upperBound items are stored contiguously. This is an
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// acceptable conservative behavior, but could potentially be
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// optimized for other cases.
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let contiguousCount = withUnsafeMutablePointer(to: &enumerationState) {
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self.buffer.countByEnumerating(with: $0, objects: nil, count: 0)
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}
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return contiguousCount >= subRange.upperBound
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? UnsafeMutableRawPointer(enumerationState.itemsPtr!)
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.assumingMemoryBound(to: AnyObject.self)
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+ subRange.lowerBound
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: nil
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}
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@_transparent
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init(_ buffer: _NSArrayCore) {
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self.buffer = buffer
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}
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var buffer: _NSArrayCore
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}
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#endif
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