remove dependency on DispatchWallTime (fix #384)

Author: sebsto

Sources/AWSLambdaRuntime/FoundationSupport/Context+Foundation.swift

@@ -21,7 +21,7 @@ import struct Foundation.Date
 
 extension LambdaContext {
     var deadlineDate: Date {
-        let secondsSinceEpoch = Double(Int64(bitPattern: self.deadline.rawValue)) / -1_000_000_000
+        let secondsSinceEpoch = Double(self.deadline.milliseconds()) / -1_000_000_000
         return Date(timeIntervalSince1970: secondsSinceEpoch)
     }
 }

Sources/AWSLambdaRuntime/Lambda+LocalServer.swift

@@ -650,7 +650,7 @@ internal struct LambdaHTTPServer {
                     "arn:aws:lambda:us-east-1:\(Int16.random(in: Int16.min ... Int16.max)):function:custom-runtime"
                 ),
                 (AmazonHeaders.traceID, "Root=\(AmazonHeaders.generateXRayTraceID());Sampled=1"),
-                (AmazonHeaders.deadline, "\(DispatchWallTime.distantFuture.millisSinceEpoch)"),
+                (AmazonHeaders.deadline, "\(Duration.distantFuture.milliseconds())"),
             ])
 
             return LocalServerResponse(

Sources/AWSLambdaRuntime/Lambda.swift

@@ -70,9 +70,7 @@ public enum Lambda {
                             requestID: invocation.metadata.requestID,
                             traceID: invocation.metadata.traceID,
                             invokedFunctionARN: invocation.metadata.invokedFunctionARN,
-                            deadline: DispatchWallTime(
-                                millisSinceEpoch: invocation.metadata.deadlineInMillisSinceEpoch
-                            ),
+                            deadline: Duration(millisSinceEpoch: invocation.metadata.deadlineInMillisSinceEpoch),
                             logger: logger
                         )
                     )

Sources/AWSLambdaRuntime/LambdaContext.swift

@@ -25,7 +25,7 @@ public struct LambdaContext: CustomDebugStringConvertible, Sendable {
         let requestID: String
         let traceID: String
         let invokedFunctionARN: String
-        let deadline: DispatchWallTime
+        let deadline: Duration
         let cognitoIdentity: String?
         let clientContext: String?
         let logger: Logger
@@ -34,7 +34,7 @@ public struct LambdaContext: CustomDebugStringConvertible, Sendable {
             requestID: String,
             traceID: String,
             invokedFunctionARN: String,
-            deadline: DispatchWallTime,
+            deadline: Duration,
             cognitoIdentity: String?,
             clientContext: String?,
             logger: Logger
@@ -67,7 +67,7 @@ public struct LambdaContext: CustomDebugStringConvertible, Sendable {
     }
 
     /// The timestamp that the function times out.
-    public var deadline: DispatchWallTime {
+    public var deadline: Duration {
         self.storage.deadline
     }
 
@@ -92,7 +92,7 @@ public struct LambdaContext: CustomDebugStringConvertible, Sendable {
         requestID: String,
         traceID: String,
         invokedFunctionARN: String,
-        deadline: DispatchWallTime,
+        deadline: Duration,
         cognitoIdentity: String? = nil,
         clientContext: String? = nil,
         logger: Logger
@@ -109,30 +109,30 @@ public struct LambdaContext: CustomDebugStringConvertible, Sendable {
     }
 
     public func getRemainingTime() -> Duration {
-        let deadline = self.deadline.millisSinceEpoch
-        let now = DispatchWallTime.now().millisSinceEpoch
+        let deadline = self.deadline
+        let now = Duration.millisSinceEpoch
 
-        let remaining = deadline - now
-        return .milliseconds(remaining)
+        return deadline - now
     }
 
     public var debugDescription: String {
         "\(Self.self)(requestID: \(self.requestID), traceID: \(self.traceID), invokedFunctionARN: \(self.invokedFunctionARN), cognitoIdentity: \(self.cognitoIdentity ?? "nil"), clientContext: \(self.clientContext ?? "nil"), deadline: \(self.deadline))"
     }
 
     /// This interface is not part of the public API and must not be used by adopters. This API is not part of semver versioning.
+    /// The timeout is expressed relative to now
     package static func __forTestsOnly(
         requestID: String,
         traceID: String,
         invokedFunctionARN: String,
-        timeout: DispatchTimeInterval,
+        timeout: Duration,
         logger: Logger
     ) -> LambdaContext {
         LambdaContext(
             requestID: requestID,
             traceID: traceID,
             invokedFunctionARN: invokedFunctionARN,
-            deadline: .now() + timeout,
+            deadline: Duration.millisSinceEpoch + timeout,
             logger: logger
         )
     }

Sources/AWSLambdaRuntime/Utils.swift

@@ -39,17 +39,36 @@ enum AmazonHeaders {
     static let invokedFunctionARN = "Lambda-Runtime-Invoked-Function-Arn"
 }
 
-extension DispatchWallTime {
+/// A simple set of additions to Duration helping to work with Unix epoch that does not require Foundation.
+/// It provides a distant future value and a way to get the current time in milliseconds since the epoch.
+/// The Lambda execution environment uses UTC as a timezone, this struct must not manage timezones.
+/// see: TZ in https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html
+extension Duration {
+    /// Returns the time in milliseconds since the Unix epoch.
     @usableFromInline
-    init(millisSinceEpoch: Int64) {
-        let nanoSinceEpoch = UInt64(millisSinceEpoch) * 1_000_000
-        let seconds = UInt64(nanoSinceEpoch / 1_000_000_000)
-        let nanoseconds = nanoSinceEpoch - (seconds * 1_000_000_000)
-        self.init(timespec: timespec(tv_sec: Int(seconds), tv_nsec: Int(nanoseconds)))
+    static var millisSinceEpoch: Duration {
+        var ts = timespec()
+        clock_gettime(CLOCK_REALTIME, &ts)
+        return .milliseconds(Int64(ts.tv_sec) * 1000 + Int64(ts.tv_nsec) / 1_000_000)
     }
 
-    var millisSinceEpoch: Int64 {
-        Int64(bitPattern: self.rawValue) / -1_000_000
+    /// Returns a Duration between Unix epoch and the distant future
+    @usableFromInline
+    static var distantFuture: Duration {
+        // Use a very large value to represent the distant future
+        millisSinceEpoch + Duration.seconds(.greatestFiniteMagnitude)
+    }
+
+    /// Returns the Duration in milliseconds
+    @usableFromInline
+    func milliseconds() -> Int64 {
+        Int64(self / .milliseconds(1))
+    }
+
+    /// Create a Duration from milliseconds since Unix Epoch
+    @usableFromInline
+    init(millisSinceEpoch: Int64) {
+        self = .milliseconds(millisSinceEpoch)
     }
 }
 
@@ -103,7 +122,7 @@ extension AmazonHeaders {
         // The version number, that is, 1.
         let version: UInt = 1
         // The time of the original request, in Unix epoch time, in 8 hexadecimal digits.
-        let now = UInt32(DispatchWallTime.now().millisSinceEpoch / 1000)
+        let now = UInt32(Duration.millisSinceEpoch.milliseconds() / 1000)
         let dateValue = String(now, radix: 16, uppercase: false)
         let datePadding = String(repeating: "0", count: max(0, 8 - dateValue.count))
         // A 96-bit identifier for the trace, globally unique, in 24 hexadecimal digits.