Adopt Swift structured concurrency (#7)

* Adopt Swift structured concurrency

- Change public API to async/await
- Additional c-ares options and errors
- Fix bug in A and AAAA queries

* Remove usage of Duration

* Address feedback comment

Author: yim-lee

Package.swift

@@ -21,6 +21,9 @@ do {
 
 let package = Package(
     name: "swift-async-dns-resolver",
+    platforms: [
+        .macOS("13.0"),
+    ],
     products: [
         .library(name: "AsyncDNSResolver", targets: ["AsyncDNSResolver"]),
     ],

Sources/AsyncDNSResolver/AsyncDNSResolver.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the SwiftAsyncDNSResolver open source project
 //
-// Copyright (c) 2020 Apple Inc. and the SwiftAsyncDNSResolver project authors
+// Copyright (c) 2020-2023 Apple Inc. and the SwiftAsyncDNSResolver project authors
 // Licensed under Apache License v2.0
 //
 // See LICENSE.txt for license information
@@ -13,22 +13,22 @@
 //===----------------------------------------------------------------------===//
 
 import CAsyncDNSResolver
-import Dispatch
 
 // MARK: - ares_channel
 
-class AresChannel {
-    let pointer: UnsafeMutablePointer<ares_channel?>?
+actor AresChannel {
+    let pointer: UnsafeMutablePointer<ares_channel?>
 
-    private var _ares_channel: ares_channel? {
-        self.pointer?.pointee
+    private var underlying: ares_channel? {
+        self.pointer.pointee
     }
 
-    private let semaphore = DispatchSemaphore(value: 1)
-
     deinit {
-        ares_destroy(self._ares_channel)
-        ares_library_cleanup()
+        Task { [pointer] in
+            ares_destroy(pointer.pointee)
+            pointer.deallocate()
+            ares_library_cleanup()
+        }
     }
 
     init(options: AresOptions) throws {
@@ -52,20 +52,16 @@ class AresChannel {
     }
 
     func withChannel(_ body: (ares_channel) -> Void) {
-        self.semaphore.wait()
-        defer { self.semaphore.signal() }
-
-        guard let _ares_channel = self._ares_channel else {
+        guard let underlying = self.underlying else {
             fatalError("ares_channel not initialized")
         }
-
-        body(_ares_channel)
+        body(underlying)
     }
 }
 
 private func checkAresResult(body: () -> Int32) throws {
     let result = body()
     guard result == ARES_SUCCESS else {
-        throw AsyncDNSResolver.Error(code: result, "Failed to initialize channel")
+        throw AsyncDNSResolver.Error(code: result, "failed to initialize channel")
     }
 }

Sources/AsyncDNSResolver/Channel.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the SwiftAsyncDNSResolver open source project
 //
-// Copyright (c) 2020 Apple Inc. and the SwiftAsyncDNSResolver project authors
+// Copyright (c) 2020-2023 Apple Inc. and the SwiftAsyncDNSResolver project authors
 // Licensed under Apache License v2.0
 //
 // See LICENSE.txt for license information
@@ -39,61 +39,64 @@ extension AsyncDNSResolver {
             case badFlags(String?)
             case noName(String?)
             case badHints(String?)
-            case service(String?)
             case notInitialized(String?)
+            case initError(String?)
             case cancelled(String?)
+            case service(String?)
             case other(code: Int32, String?)
 
             var description: String {
                 switch self {
                 case .noData(let description):
-                    return "No data: \(description ?? "")"
+                    return "no data: \(description ?? "")"
                 case .invalidQuery(let description):
-                    return "Invalid query: \(description ?? "")"
+                    return "invalid query: \(description ?? "")"
                 case .serverFailure(let description):
-                    return "Server failure: \(description ?? "")"
+                    return "server failure: \(description ?? "")"
                 case .notFound(let description):
-                    return "Not found: \(description ?? "")"
+                    return "not found: \(description ?? "")"
                 case .notImplemented(let description):
-                    return "Not implemented: \(description ?? "")"
+                    return "not implemented: \(description ?? "")"
                 case .serverRefused(let description):
-                    return "Server refused: \(description ?? "")"
+                    return "server refused: \(description ?? "")"
                 case .badQuery(let description):
-                    return "Bad query: \(description ?? "")"
+                    return "bad query: \(description ?? "")"
                 case .badName(let description):
-                    return "Bad name: \(description ?? "")"
+                    return "bad name: \(description ?? "")"
                 case .badFamily(let description):
-                    return "Bad family: \(description ?? "")"
+                    return "bad family: \(description ?? "")"
                 case .badResponse(let description):
-                    return "Bad response: \(description ?? "")"
+                    return "bad response: \(description ?? "")"
                 case .connectionRefused(let description):
-                    return "Connection refused: \(description ?? "")"
+                    return "connection refused: \(description ?? "")"
                 case .timeout(let description):
-                    return "Timeout: \(description ?? "")"
+                    return "timeout: \(description ?? "")"
                 case .eof(let description):
                     return "EOF: \(description ?? "")"
                 case .fileIO(let description):
-                    return "File IO: \(description ?? "")"
+                    return "file IO: \(description ?? "")"
                 case .noMemory(let description):
-                    return "No memory: \(description ?? "")"
+                    return "no memory: \(description ?? "")"
                 case .destruction(let description):
-                    return "Destruction: \(description ?? "")"
+                    return "destruction: \(description ?? "")"
                 case .badString(let description):
-                    return "Bad string: \(description ?? "")"
+                    return "bad string: \(description ?? "")"
                 case .badFlags(let description):
-                    return "Bad flags: \(description ?? "")"
+                    return "bad flags: \(description ?? "")"
                 case .noName(let description):
-                    return "No name: \(description ?? "")"
+                    return "no name: \(description ?? "")"
                 case .badHints(let description):
-                    return "Bad hints: \(description ?? "")"
-                case .service(let description):
-                    return "Service: \(description ?? "")"
+                    return "bad hints: \(description ?? "")"
                 case .notInitialized(let description):
-                    return "Not initialized: \(description ?? "")"
+                    return "not initialized: \(description ?? "")"
+                case .initError(let description):
+                    return "initialization error: \(description ?? "")"
                 case .cancelled(let description):
-                    return "Cancelled: \(description ?? "")"
+                    return "cancelled: \(description ?? "")"
+                case .service(let description):
+                    return "service: \(description ?? "")"
                 case .other(let code, let description):
-                    return "Other code [\(code)]: \(description ?? "")"
+                    return "other [\(code)]: \(description ?? "")"
                 }
             }
         }
@@ -146,12 +149,14 @@ extension AsyncDNSResolver {
                 self = .noName(description)
             case ARES_EBADHINTS:
                 self = .badHints(description)
-            case ARES_ESERVICE:
-                self = .service(description)
             case ARES_ENOTINITIALIZED:
                 self = .notInitialized(description)
+            case ARES_ELOADIPHLPAPI, ARES_EADDRGETNETWORKPARAMS:
+                self = .initError(description)
             case ARES_ECANCELLED:
                 self = .cancelled(description)
+            case ARES_ESERVICE:
+                self = .service(description)
             default:
                 self = .other(code: code, description)
             }
@@ -241,18 +246,22 @@ extension AsyncDNSResolver {
             .init(code: .badHints(description))
         }
 
-        public static func service(_ description: String? = nil) -> Error {
-            .init(code: .service(description))
-        }
-
         public static func notInitialized(_ description: String? = nil) -> Error {
             .init(code: .notInitialized(description))
         }
 
+        public static func initError(_ description: String? = nil) -> Error {
+            .init(code: .initError(description))
+        }
+
         public static func cancelled(_ description: String? = nil) -> Error {
             .init(code: .cancelled(description))
         }
 
+        public static func service(_ description: String? = nil) -> Error {
+            .init(code: .service(description))
+        }
+
         public static func other(code: Int32, _ description: String? = nil) -> Error {
             .init(code: .other(code: code, description))
         }