From 4181f2175c23ffa1525d7e64db84dd65195641d7 Mon Sep 17 00:00:00 2001
From: George Barnett <gbarnett@apple.com>
Date: Wed, 5 Aug 2026 10:23:33 +0100
Subject: [PATCH] Reduce size of Frame

Frame is large: 161 bytes with a stride of 168 bytes. A reasonably large
part of this is just padding which is easily removed by reordering
stored properties.

This patch moves properties around to reduce the size and stride down
to 136 bytes.
---
 Sources/SwiftNetwork/Protocols/Frame.swift    | 25 ++++++++++---------
 .../SwiftNetworkFrameTests.swift              | 24 ++++++++++++++++++
 2 files changed, 37 insertions(+), 12 deletions(-)
 create mode 100644 Tests/SwiftNetworkTests/SwiftNetworkFrameTests.swift

diff --git a/Sources/SwiftNetwork/Protocols/Frame.swift b/Sources/SwiftNetwork/Protocols/Frame.swift
index f4b8500..b36bb07 100644
--- a/Sources/SwiftNetwork/Protocols/Frame.swift
+++ b/Sources/SwiftNetwork/Protocols/Frame.swift
@@ -37,26 +37,34 @@ public struct Frame: ~Copyable {
         case customFinalizer(buffer: UnsafeMutableRawBufferPointer, finalizer: (UnsafeMutableRawBufferPointer) -> Void)
     }
 
-    public var buffer: Buffer
-
     var _bytes: NetworkUniqueArray<UInt8> = .init()
+    var protocolMetadatas: NetworkUniqueDeque<FrameProtocolMetadata> = .init(minimumCapacity: 0)
+    var ipPacketValues: IPPacketValues? = nil
+    public var buffer: Buffer
+    var appMetadata: AppMetadata? = nil
 
     private var _startOffset: UInt32 = 0
+
+    var timestamp: FrameTimestamp? = nil
+    var flags: Flags = Flags()
+    var _metadataComplete: Bool = false
+    public var connectionComplete: Bool = false
+    private var _endOffset: UInt32 = 0
+    private var _effectiveBufferLength: UInt32 = 0
+    private var _aggregateBufferLength: UInt32 = 0
+
     @usableFromInline var startOffset: Int {
         get { Int(_startOffset) }
         set { _startOffset = UInt32(newValue) }
     }
-    private var _endOffset: UInt32 = 0
     @usableFromInline var endOffset: Int {
         get { Int(_endOffset) }
         set { _endOffset = UInt32(newValue) }
     }
-    private var _effectiveBufferLength: UInt32 = 0
     var effectiveBufferLength: Int {
         get { Int(_effectiveBufferLength) }
         set { _effectiveBufferLength = UInt32(newValue) }
     }
-    private var _aggregateBufferLength: UInt32 = 0
     var aggregateBufferLength: Int {
         get { Int(_aggregateBufferLength) }
         set { _aggregateBufferLength = UInt32(newValue) }
@@ -464,7 +472,6 @@ public struct Frame: ~Copyable {
         static let isBackground = Frame.Flags(rawValue: 1 << 5)
         static let isRealtime = Frame.Flags(rawValue: 1 << 6)
     }
-    var flags: Flags = Flags()
 
     struct IPPacketValues {
         struct Flags: OptionSet {
@@ -507,13 +514,11 @@ public struct Frame: ~Copyable {
             }
         }
     }
-    var ipPacketValues: IPPacketValues? = nil
 
     struct AppMetadata: ~Copyable {
         let appType: UInt8
         let appMetadata: UInt8
     }
-    var appMetadata: AppMetadata? = nil
 
     var isSingleIPAggregate: Bool {
         get { flags.contains(.isSingleIPAggregate) }
@@ -671,7 +676,6 @@ public struct Frame: ~Copyable {
         var metadata: AbstractProtocolMetadata
         var metadataComplete: Bool = false
     }
-    var protocolMetadatas: NetworkUniqueDeque<FrameProtocolMetadata> = .init(minimumCapacity: 0)
 
     public var firstMetadata: AbstractProtocolMetadata? {
         guard protocolMetadatas.count > 0 else {
@@ -679,7 +683,6 @@ public struct Frame: ~Copyable {
         }
         return protocolMetadatas[0].metadata
     }
-    var _metadataComplete: Bool = false
     var metadataComplete: Bool {
         get {
             if protocolMetadatas.count > 0 {
@@ -689,13 +692,11 @@ public struct Frame: ~Copyable {
         }
         set { _metadataComplete = newValue }
     }
-    public var connectionComplete: Bool = false
 
     enum FrameTimestamp {
         case receiveTime(_ timestamp: NetworkClock.Instant)
         case expireTime(_ timestamp: NetworkClock.Instant)
     }
-    var timestamp: FrameTimestamp? = nil
 
     mutating func reduceAggregateBufferLength(by length: Int) {
         if isSingleIPAggregate {
diff --git a/Tests/SwiftNetworkTests/SwiftNetworkFrameTests.swift b/Tests/SwiftNetworkTests/SwiftNetworkFrameTests.swift
new file mode 100644
index 0000000..6d4f283
--- /dev/null
+++ b/Tests/SwiftNetworkTests/SwiftNetworkFrameTests.swift
@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2026 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+@_spi(Essentials) @_spi(ProtocolProvider) import SwiftNetwork
+import XCTest
+
+@available(anyAppleOS 27, *)
+final class SwiftNetworkFrameTests: XCTestCase {
+    func testFrameLayout() {
+        XCTAssertEqual(MemoryLayout<Frame>.size, 136)
+        XCTAssertEqual(MemoryLayout<Frame>.stride, 136)
+    }
+}