chore: import upstream snapshot with attribution

Sources/Services/ContainerAPIService/Client/ClientProcess.swift

@@ -0,0 +1,109 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the container project authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import ContainerXPC
+import Containerization
+import ContainerizationError
+import ContainerizationOCI
+import ContainerizationOS
+import Foundation
+import NIOCore
+import NIOPosix
+import TerminalProgress
+
+/// A protocol that defines the methods and data members available to a process
+/// started inside of a container.
+public protocol ClientProcess: Sendable {
+    /// Identifier for the process.
+    var id: String { get }
+
+    /// Start the underlying process inside of the container.
+    func start() async throws
+    /// Send a terminal resize request to the process `id`.
+    func resize(_ size: Terminal.Size) async throws
+    /// Send a signal to the process `id`.
+    /// Kill does not wait for the process to exit, it only delivers the signal.
+    func kill(_ signal: Int32) async throws
+    ///  Wait for the process `id` to complete and return its exit code.
+    /// This method blocks until the process exits and the code is obtained.
+    func wait() async throws -> Int32
+}
+
+struct ClientProcessImpl: ClientProcess, Sendable {
+    static let serviceIdentifier = "com.apple.container.apiserver"
+
+    /// ID of the process.
+    public var id: String {
+        processId ?? containerId
+    }
+
+    /// Identifier of the container.
+    public let containerId: String
+
+    /// Identifier of a process. That is running inside of a container.
+    /// This field is nil if the process this objects refers to is the
+    /// init process of the container.
+    public let processId: String?
+
+    private let xpcClient: XPCClient
+
+    init(containerId: String, processId: String? = nil, xpcClient: XPCClient) {
+        self.containerId = containerId
+        self.processId = processId
+        self.xpcClient = xpcClient
+    }
+
+    /// Start the process.
+    public func start() async throws {
+        let request = XPCMessage(route: .containerStartProcess)
+        request.set(key: .id, value: containerId)
+        request.set(key: .processIdentifier, value: id)
+
+        try await xpcClient.send(request)
+    }
+
+    /// Send a signal to the process.
+    public func kill(_ signal: Int32) async throws {
+        let request = XPCMessage(route: .containerKill)
+        request.set(key: .id, value: containerId)
+        request.set(key: .processIdentifier, value: id)
+        request.set(key: .signal, value: Int64(signal))
+
+        try await xpcClient.send(request)
+    }
+
+    /// Resize the processes PTY if it has one.
+    public func resize(_ size: Terminal.Size) async throws {
+        let request = XPCMessage(route: .containerResize)
+        request.set(key: .id, value: containerId)
+        request.set(key: .processIdentifier, value: id)
+        request.set(key: .width, value: UInt64(size.width))
+        request.set(key: .height, value: UInt64(size.height))
+
+        try await xpcClient.send(request)
+    }
+
+    /// Wait for the process to exit.
+    public func wait() async throws -> Int32 {
+        let request = XPCMessage(route: .containerWait)
+        request.set(key: .id, value: containerId)
+        request.set(key: .processIdentifier, value: id)
+
+        let response = try await xpcClient.send(request)
+        let code = response.int64(key: .exitCode)
+        return Int32(code)
+    }
+}