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Reduce size of Frame #69

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25 changes: 13 additions & 12 deletions Sources/SwiftNetwork/Protocols/Frame.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -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

@agnosticdev agnosticdev Aug 5, 2026

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So because of the out of order arrangement of these properties extra padding was being added, is that what was happening?

@glbrntt glbrntt Aug 5, 2026

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It was the order the properties were in: Swift lays out types in the order they're declared in.

As an example the Buffer enum was stored first and is 33 bytes in size with an 8 byte alignment. It was followed by a NetworkUniqueArray<UInt8> which is 24 bytes (also 8 byte alignment). Because of the alignment there's 7 bytes of padding between the two, instead you can move smaller types (e.g. 7 booleans) into that space that would otherwise be padding.


@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) }
Expand Down Expand Up @@ -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 {
Expand Down Expand Up @@ -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) }
Expand Down Expand Up @@ -671,15 +676,13 @@ 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 {
return nil
}
return protocolMetadatas[0].metadata
}
var _metadataComplete: Bool = false
var metadataComplete: Bool {
get {
if protocolMetadatas.count > 0 {
Expand All @@ -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 {
Expand Down
24 changes: 24 additions & 0 deletions Tests/SwiftNetworkTests/SwiftNetworkFrameTests.swift
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Original file line number Diff line number Diff line change
@@ -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)
}
}
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