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glbrnttjosephnoir
glbrntt
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josephnoir
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Index the QPACK static table by name (#10)
Motivation: StaticHeaderTable.find does a linear scan of all 99 static table entries. It's called once per header by both the static and dynamic encoders. The scan relies on string comparisons for (potentially) every header name in the table which is where a lot of the cost lies. Modifications: - Add a static field name to index map. This is used by `find` to get all indexes for a given header in constant time. - Add benchmarks Result: Faster header encoding - static encoding benchmark: 2.8x faster - dynamic encoding benchmark: 1.3x faster --------- Co-authored-by: Raphael Hiesgen <github@hiesgen.dev>
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‎Benchmarks/Package.swift‎

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// swift-tools-version:6.3
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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the SwiftNIO open source project
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//
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// Copyright (c) 2026 Apple Inc. and the SwiftNIO project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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import PackageDescription
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let package = Package(
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name: "swift-nio-http3-benchmarks",
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platforms: [
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.macOS(.v13)
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],
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dependencies: [
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.package(path: "../"),
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.package(url: "https://github.com/apple/swift-http-types.git", from: "1.3.0"),
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.package(url: "https://github.com/apple/swift-nio-quic-helpers.git", branch: "main"),
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.package(url: "https://github.com/ordo-one/benchmark.git", from: "1.35.0"),
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],
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targets: [
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.executableTarget(
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name: "QPACKBenchmarks",
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dependencies: [
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.product(name: "NIOHTTP3", package: "swift-nio-http3"),
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.product(name: "HTTPTypes", package: "swift-http-types"),
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.product(name: "NIOQUICHelpers", package: "swift-nio-quic-helpers"),
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.product(name: "Benchmark", package: "benchmark"),
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],
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path: "QPACKBenchmarks",
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plugins: [
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.plugin(name: "BenchmarkPlugin", package: "benchmark")
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]
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)
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]
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)

‎Benchmarks/QPACKBenchmarks/QPACKBenchmarks.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the SwiftNIO open source project
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//
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// Copyright (c) 2026 Apple Inc. and the SwiftNIO project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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import Benchmark
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import HTTPTypes
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@_spi(Benchmarks) import NIOHTTP3
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import NIOQUICHelpers
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/// A realistic request header set for a browser GET, exercising a mix of exact
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/// static-table matches (`:method GET`), name-only matches (`:authority`) and
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/// headers absent from the table (`x-custom-header`).
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private let requestHeaders: [HTTPField] = [
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HTTPField(name: .init(parsed: ":method")!, value: "GET"),
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HTTPField(name: .init(parsed: ":scheme")!, value: "https"),
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HTTPField(name: .init(parsed: ":authority")!, value: "www.example.com"),
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HTTPField(name: .init(parsed: ":path")!, value: "/index.html"),
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HTTPField(name: .init(parsed: "user-agent")!, value: "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7)"),
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HTTPField(name: .init(parsed: "accept")!, value: "*/*"),
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HTTPField(name: .init(parsed: "accept-encoding")!, value: "gzip, deflate, br"),
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HTTPField(name: .init(parsed: "accept-language")!, value: "en-US,en;q=0.9"),
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HTTPField(name: .init(parsed: "cache-control")!, value: "no-cache"),
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HTTPField(name: .init(parsed: "cookie")!, value: "session=abc123def456; theme=dark"),
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HTTPField(name: .init(parsed: "referer")!, value: "https://www.example.com/"),
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HTTPField(name: .init(parsed: "x-custom-header")!, value: "some-custom-value"),
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]
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let benchmarks: @Sendable () -> Void = {
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// Exercises StaticHeaderTable.find on every header, with no dynamic table.
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Benchmark(
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"QPACKStaticEncode_BrowserGET",
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configuration: .init(
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metrics: [.mallocCountTotal, .instructions, .wallClock],
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scalingFactor: .kilo
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)
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) { benchmark in
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for _ in benchmark.scaledIterations {
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blackHole(QPACKBenchmarks.staticEncode(headers: requestHeaders))
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}
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}
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// Exercises the static-table lookup plus the dynamic table on every header.
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Benchmark(
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"QPACKDynamicEncode_BrowserGET",
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configuration: .init(
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metrics: [.mallocCountTotal, .instructions, .wallClock],
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scalingFactor: .kilo
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)
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) { benchmark in
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for _ in benchmark.scaledIterations {
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blackHole(
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QPACKBenchmarks.dynamicEncode(
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headers: requestHeaders,
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streamID: QUICStreamID(rawValue: 0),
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dynamicTableMaxCapacity: 4096,
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dynamicTableInitialCapacity: 4096,
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maxBlockedStreams: 100,
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targetEvictableFraction: 0.5
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)
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)
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}
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}
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}

‎Sources/NIOHTTP3/QPACK+SPI.swift‎

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//===----------------------------------------------------------------------===//
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//
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// This source file is part of the SwiftNIO open source project
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//
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// Copyright (c) 2026 Apple Inc. and the SwiftNIO project authors
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// Licensed under Apache License v2.0
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//
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// See LICENSE.txt for license information
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// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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//===----------------------------------------------------------------------===//
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public import HTTPTypes
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public import NIOQUICHelpers
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private import QPACK
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// QPACK isn't a library product, so add entry points for benchmarks here under SPI.
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@_spi(Benchmarks)
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public enum QPACKBenchmarks {
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/// Encode `headers` with the static-only encoder. Returns the number of field lines
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/// produced.
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///
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/// The return value doesn't matter, but needs to be there so the calling benchmark
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/// can stop the function call from being optimised away.
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@_spi(Benchmarks)
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public static func staticEncode(headers: [HTTPField]) -> Int {
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let encoder = StaticQPACKEncoder()
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return encoder.encode(headers: headers).lines.count
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}
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/// Create a dynamic encoder and encode `headers` on `streamID`. Returns the number
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/// of field lines produced.
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///
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/// The return value doesn't matter, but needs to be there so the calling benchmark
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/// can stop the function call from being optimised away.
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@_spi(Benchmarks)
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public static func dynamicEncode(
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headers: [HTTPField],
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streamID: QUICStreamID,
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dynamicTableMaxCapacity: Int,
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dynamicTableInitialCapacity: Int,
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maxBlockedStreams: Int,
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targetEvictableFraction: Double
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) -> Int {
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var (encoder, _) = DynamicQPACKEncoder.create(
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dynamicTableMaxCapacity: dynamicTableMaxCapacity,
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dynamicTableInitialCapacity: dynamicTableInitialCapacity,
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maxBlockedStreams: maxBlockedStreams,
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targetEvictableFraction: targetEvictableFraction
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)
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return encoder.encode(headers: headers, forStream: streamID).fieldSection.lines.count
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}
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}

‎Sources/QPACK/Headers/StaticHeaderTable.swift‎

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(.init(parsed: "x-frame-options")!, "sameorigin"), // 98
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]
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/// A mapping of header name to the array of static table indices carrying that name.
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/// Arrays are guaranteed to be non-empty, and their values are in ascending index order.
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private static let indicesByName: [HTTPField.Name: [Int]] = {
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var result = [HTTPField.Name: [Int]](minimumCapacity: Self.shared.count)
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for index in Self.shared.indices {
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result[Self.shared[index].0, default: []].append(index)
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}
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return result
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}()
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/// Get the element of the static table at the specific index if it exists
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package static func get(at index: Int) -> (HTTPField.Name, String)? {
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if self.shared.indices.contains(index) {
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/// parameter, an indication whether that value was also found. Returns `nil`
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/// if no matching header name could be located.
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static func find(name: HTTPField.Name, value: String?) -> (index: Int, containsValue: Bool)? {
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var nameOnlyMatchIndex: Int?
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for index in Self.shared.indices {
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let header = Self.shared[index]
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if header.0 == name {
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if header.1 == value {
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guard let indices = Self.indicesByName[name] else {
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return nil
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}
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if let value = value {
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for index in indices {
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if Self.shared[index].1 == value {
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return (index: index, containsValue: true)
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} else if nameOnlyMatchIndex == nil {
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nameOnlyMatchIndex = index
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}
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}
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}
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if let nameOnlyMatchIndex {
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return (index: nameOnlyMatchIndex, containsValue: false)
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} else {
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return nil
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}
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// No value (or no matching value), return the first index.
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return (index: indices[0], containsValue: false)
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}
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}

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