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Petr Prokop
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Mar 6, 2021
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,82 @@ | ||
| import Foundation | ||
|
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| /// Thread-safe priority queue wrapper | ||
| /// - Important: Note that this is a `class`, i.e. reference (not value) type | ||
| public final class ConcurrentPriorityQueue<Element> { | ||
|
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| private var container: PriorityQueue<Element> | ||
| private let rwlock = RWLock() | ||
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| public var count: Int { | ||
| rwlock.readLock() | ||
| defer { | ||
| rwlock.unlock() | ||
| } | ||
| return container.count | ||
| } | ||
|
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| public init(capacity: Int, complexComparator: @escaping PriorityQueue<Element>.ComplexComparator) { | ||
| self.container = PriorityQueue(capacity: capacity, complexComparator: complexComparator) | ||
| } | ||
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| public init(capacity: Int, comparator: @escaping PriorityQueue<Element>.Comparator) { | ||
| self.container = PriorityQueue(capacity: capacity, comparator: comparator) | ||
| } | ||
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| /// Creates `ConcurrentPriorityQueue` with default capacity | ||
| /// - Parameter comparator: heap property will hold if `comparator(parent(i), i)` is `true` | ||
| /// e.g. `<` will create a minimum-queue and `>` - maximum-queue | ||
| public init(_ comparator: @escaping PriorityQueue<Element>.Comparator) { | ||
| self.container = PriorityQueue(comparator) | ||
| } | ||
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| public func insert(_ value: Element) { | ||
| rwlock.writeLock() | ||
| container.insert(value) | ||
| rwlock.unlock() | ||
| } | ||
|
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| /// Remove top element from the queue | ||
| public func pop() -> Element { | ||
| rwlock.writeLock() | ||
| defer { | ||
| rwlock.unlock() | ||
| } | ||
|
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| return container.pop() | ||
| } | ||
|
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| /// Get top element from the queue | ||
| public func peek() -> Element { | ||
| rwlock.readLock() | ||
| defer { | ||
| rwlock.unlock() | ||
| } | ||
|
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| return container.peek() | ||
| } | ||
|
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| /// Get top element from the queue, returns `nil`if queue is empty | ||
| public func safePeek() -> Element? { | ||
| rwlock.readLock() | ||
| defer { | ||
| rwlock.unlock() | ||
| } | ||
| return container.count > 0 | ||
| ? container.peek() | ||
| : nil | ||
| } | ||
|
|
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| /// Remove top element from the queue, returns `nil`if queue is empty | ||
| public func safePop() -> Element? { | ||
| rwlock.writeLock() | ||
| defer { | ||
| rwlock.unlock() | ||
| } | ||
|
|
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| return container.count > 0 | ||
| ? container.pop() | ||
| : nil | ||
| } | ||
|
|
||
| } |
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78 changes: 78 additions & 0 deletions
78
SwiftConcurrentCollectionsTests/ConcurrentPriorityQueueTests.swift
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,78 @@ | ||
| import XCTest | ||
| @testable import SwiftConcurrentCollections | ||
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| class ConcurrentPriorityQueueTests: XCTestCase { | ||
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| func testConcurrentReadingAndWriting() { | ||
| let startDate = Date().timeIntervalSince1970 | ||
| let concurrentPriorityQueue = ConcurrentPriorityQueue<Int>(<) | ||
| // Unsafe version: | ||
| // var concurrentPriorityQueue = PriorityQueue<Int>(<) | ||
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| let readingQueue = DispatchQueue( | ||
| label: "ConcurrentArrayTests.readingQueue", | ||
| qos: .userInteractive, | ||
| attributes: .concurrent | ||
| ) | ||
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| let writingQueue = DispatchQueue( | ||
| label: "ConcurrentArrayTests.writingQueue", | ||
| qos: .userInteractive, | ||
| attributes: .concurrent | ||
| ) | ||
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| // 100 seems to be small enough not to cause performance problems | ||
| for i in 0 ..< 100 { | ||
| let writeExpectation = expectation(description: "Write expectation") | ||
| let readExpectation = expectation(description: "Read expectation") | ||
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| writingQueue.async { | ||
| concurrentPriorityQueue.insert(i) | ||
| writeExpectation.fulfill() | ||
| } | ||
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| readingQueue.async { | ||
| let count = concurrentPriorityQueue.count | ||
| guard count > 0 else { | ||
| return | ||
| } | ||
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| let value = concurrentPriorityQueue.peek() | ||
| print(value) | ||
| readExpectation.fulfill() | ||
| } | ||
| } | ||
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| waitForExpectations(timeout: 10, handler: nil) | ||
| print("\(#function) took \(Date().timeIntervalSince1970 - startDate) seconds") | ||
| } | ||
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| func testPop() { | ||
| let concurrentPriorityQueue = ConcurrentPriorityQueue<Int>(<) | ||
|
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| concurrentPriorityQueue.insert(1) | ||
| XCTAssertEqual(concurrentPriorityQueue.count, 1) | ||
| XCTAssertEqual(concurrentPriorityQueue.peek(), 1) | ||
| XCTAssertEqual(concurrentPriorityQueue.pop(), 1) | ||
| XCTAssertEqual(concurrentPriorityQueue.count, 0) | ||
| } | ||
|
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| func testSafePop() { | ||
| let concurrentPriorityQueue = ConcurrentPriorityQueue<Int>(<) | ||
|
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| XCTAssertEqual(concurrentPriorityQueue.safePop(), nil) | ||
| concurrentPriorityQueue.insert(1) | ||
| XCTAssertEqual(concurrentPriorityQueue.safePop(), 1) | ||
| XCTAssertEqual(concurrentPriorityQueue.count, 0) | ||
| } | ||
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| func testSafePeek() { | ||
| let concurrentPriorityQueue = ConcurrentPriorityQueue<Int>(<) | ||
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| XCTAssertEqual(concurrentPriorityQueue.safePeek(), nil) | ||
| concurrentPriorityQueue.insert(1) | ||
| XCTAssertEqual(concurrentPriorityQueue.safePeek(), 1) | ||
| XCTAssertEqual(concurrentPriorityQueue.count, 1) | ||
| } | ||
|
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| } |