Use swift-atomics instead of NIOAtomics (#117)

`NIOAtomics` was deprecated in apple/swift-nio#2204 in favor of `swift-atomics` https://github.com/apple/swift-atomics
In addition, the `@preconcrrency` imports of `NIOCore` are not required and do not produce warnings/errors even with the currently latest released version of swift-nio (2.40.0), changes from `main` are not required.

Author: dnadoba

Package.swift

@@ -29,6 +29,7 @@ let package = Package(
     dependencies: [
         .package(url: "https://github.com/apple/swift-nio.git", from: "2.32.0"),
         .package(url: "https://github.com/apple/swift-crypto.git", "1.0.0" ..< "3.0.0"),
+        .package(url: "https://github.com/apple/swift-atomics.git", from: "1.0.2"),
     ],
     targets: [
         .target(
@@ -38,6 +39,7 @@ let package = Package(
                 .product(name: "NIOConcurrencyHelpers", package: "swift-nio"),
                 .product(name: "NIOFoundationCompat", package: "swift-nio"),
                 .product(name: "Crypto", package: "swift-crypto"),
+                .product(name: "Atomics", package: "swift-atomics"),
             ]
         ),
         .executableTarget(

Sources/NIOSSH/Child Channels/SSHChannelType.swift

@@ -11,11 +11,8 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
-#if swift(>=5.6)
-@preconcurrency import NIOCore
-#else
+
 import NIOCore
-#endif // swift(>=5.6)
 
 /// `SSHChannelType` represents the type of a single SSH channel.
 ///

Sources/NIOSSH/Child Channels/SSHChildChannel.swift

@@ -12,12 +12,9 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=5.6)
-@preconcurrency import NIOCore
-#else
-import NIOCore
-#endif
+import Atomics
 import NIOConcurrencyHelpers
+import NIOCore
 
 /// A NIO `Channel` that encapsulates a single SSH `Channel`.
 ///
@@ -90,9 +87,9 @@ final class SSHChildChannel {
 
     public let eventLoop: EventLoop
 
-    private let _isWritable: NIOAtomic<Bool>
+    private let _isWritable: ManagedAtomic<Bool>
 
-    private let _isActive: NIOAtomic<Bool>
+    private let _isActive: ManagedAtomic<Bool>
 
     typealias Initializer = (Channel, SSHChannelType) -> EventLoopFuture<Void>
 
@@ -135,8 +132,8 @@ final class SSHChildChannel {
         self.multiplexer = multiplexer
         self.initializer = initializer
         self.windowManager = ChildChannelWindowManager(targetWindowSize: UInt32(targetWindowSize))
-        self._isWritable = .makeAtomic(value: true)
-        self._isActive = .makeAtomic(value: false)
+        self._isWritable = .init(true)
+        self._isActive = .init(false)
         self.state = initialState
         self.writabilityManager = ChildChannelWritabilityManager(initialWindowSize: initialOutboundWindowSize,
                                                                  parentIsWritable: parent.isWritable)
@@ -240,11 +237,11 @@ extension SSHChildChannel: Channel, ChannelCore {
     }
 
     public var isWritable: Bool {
-        self._isWritable.load()
+        self._isWritable.load(ordering: .relaxed)
     }
 
     public var isActive: Bool {
-        self._isActive.load()
+        self._isActive.load(ordering: .relaxed)
     }
 
     public var _channelCore: ChannelCore {
@@ -618,7 +615,7 @@ extension SSHChildChannel: Channel, ChannelCore {
     }
 
     private func changeWritability(to newWritability: Bool) {
-        self._isWritable.store(newWritability)
+        self._isWritable.store(newWritability, ordering: .relaxed)
         self.pipeline.fireChannelWritabilityChanged()
     }
 
@@ -1030,14 +1027,14 @@ extension SSHChildChannel {
         switch self.activationState {
         case .neverActivated:
             self.activationState = .activated
-            self._isActive.store(true)
+            self._isActive.store(true, ordering: .relaxed)
             self.pipeline.fireChannelActive()
 
         case .activated:
-            assert(self._isActive.load() == true)
+            assert(self._isActive.load(ordering: .relaxed) == true)
 
         case .deactivated:
-            assert(self._isActive.load() == false)
+            assert(self._isActive.load(ordering: .relaxed) == false)
         }
     }
 
@@ -1046,15 +1043,15 @@ extension SSHChildChannel {
         case .neverActivated:
             // Do nothing, transition to inactive.
             self.activationState = .deactivated
-            assert(self._isActive.load() == false)
+            assert(self._isActive.load(ordering: .relaxed) == false)
 
         case .activated:
             self.activationState = .deactivated
-            self._isActive.store(false)
+            self._isActive.store(false, ordering: .relaxed)
             self.pipeline.fireChannelInactive()
 
         case .deactivated:
-            assert(self._isActive.load() == false)
+            assert(self._isActive.load(ordering: .relaxed) == false)
         }
     }
 }