Add Timeout

README.md

@@ -26,6 +26,6 @@ To integrate the package:
 
 ```swift
 dependencies: [
-    .package(url: "https://github.com/stairtree/async-helpers.git", from: "0.2.0"),
+    .package(url: "https://github.com/stairtree/async-helpers.git", from: "0.3.0"),
 ]
 ```

Sources/AsyncHelpers/Timeout.swift

@@ -0,0 +1,42 @@
+// Courtesy of Rob Napier and Alexander Cyon
+// See https://gist.github.com/rnapier/af027808dcfca84686f063963e2a29f5
+
+import Dispatch
+#if os(Linux)
+import let CDispatch.NSEC_PER_SEC
+#endif
+
+func firstResult<R>(from tasks: [@Sendable () async throws -> R]) async throws -> R? where R: Sendable {
+    return try await withThrowingTaskGroup(of: R.self) { group in
+        for task in tasks {
+            group.addTask { try await task() }
+        }
+        // First finished child task wins, cancel the other task.
+        let result = try await group.next()
+        group.cancelAll()
+        return result
+    }
+}
+
+public struct TimedOutError: Error, Equatable {}
+func timeout<R>(seconds: Double) -> @Sendable () async throws -> R {
+    return {
+        try await Task.sleep(nanoseconds: UInt64(seconds * Double(NSEC_PER_SEC)))
+        throw TimedOutError()
+    }
+}
+
+/// Runs an async task with a timeout.
+///
+/// - Parameters:
+///   - maxDuration: The duration in seconds `work` is allowed to run before timing out.
+///   - work: The async operation to perform.
+/// - Returns: Returns the result of `work` if it completed in time.
+/// - Throws: Throws ``TimedOutError`` if the timeout expires before `work` completes.
+///   If `work` throws an error before the timeout expires, that error is propagated to the caller.
+public func withTimeout<R>(
+    _ maxDuration: Double,
+    do work: @escaping @Sendable () async throws -> R
+) async throws -> R where R: Sendable {
+    try await firstResult(from: [work, timeout(seconds: maxDuration)])!
+}