/
PerMessageDeflateExtension.swift
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/
PerMessageDeflateExtension.swift
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//===----------------------------------------------------------------------===//
//
// This source file is part of the Hummingbird server framework project
//
// Copyright (c) 2023 the Hummingbird authors
// Licensed under Apache License v2.0
//
// See LICENSE.txt for license information
// See hummingbird/CONTRIBUTORS.txt for the list of Hummingbird authors
//
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//
import CompressNIO
import HummingbirdWebSocket
import NIOCore
import NIOWebSocket
/// PerMessageDeflate Websocket extension builder
struct PerMessageDeflateExtensionBuilder: WebSocketExtensionBuilder {
static var name = "permessage-deflate"
let clientMaxWindow: Int?
let clientNoContextTakeover: Bool
let serverMaxWindow: Int?
let serverNoContextTakeover: Bool
let compressionLevel: Int?
let memoryLevel: Int?
let maxDecompressedFrameSize: Int
init(
clientMaxWindow: Int? = nil,
clientNoContextTakeover: Bool = false,
serverMaxWindow: Int? = nil,
serverNoContextTakeover: Bool = false,
compressionLevel: Int? = nil,
memoryLevel: Int? = nil,
maxDecompressedFrameSize: Int = (1 << 14)
) {
self.clientMaxWindow = clientMaxWindow
self.clientNoContextTakeover = clientNoContextTakeover
self.serverMaxWindow = serverMaxWindow
self.serverNoContextTakeover = serverNoContextTakeover
self.compressionLevel = compressionLevel
self.memoryLevel = memoryLevel
self.maxDecompressedFrameSize = maxDecompressedFrameSize
}
/// Return client request header
func clientRequestHeader() -> String {
var header = "permessage-deflate"
if let maxWindow = self.clientMaxWindow {
header += ";client_max_window_bits=\(maxWindow)"
}
if self.clientNoContextTakeover {
header += ";client_no_context_takeover"
}
if let maxWindow = self.serverMaxWindow {
header += ";server_max_window_bits=\(maxWindow)"
}
if self.serverNoContextTakeover {
header += ";server_no_context_takeover"
}
return header
}
/// Return server response header, given a client request
/// - Parameter request: Client request header parameters
/// - Returns: Server response parameters
func serverReponseHeader(to request: WebSocketExtensionHTTPParameters) -> String? {
let configuration = self.responseConfiguration(to: request)
var header = "permessage-deflate"
if let maxWindow = configuration.receiveMaxWindow {
header += ";client_max_window_bits=\(maxWindow)"
}
if configuration.receiveNoContextTakeover {
header += ";client_no_context_takeover"
}
if let maxWindow = configuration.sendMaxWindow {
header += ";server_max_window_bits=\(maxWindow)"
}
if configuration.sendNoContextTakeover {
header += ";server_no_context_takeover"
}
return header
}
/// Create server PerMessageDeflateExtension based off request headers
/// - Parameters:
/// - request: Client request
func serverExtension(from request: WebSocketExtensionHTTPParameters) throws -> (WebSocketExtension)? {
let configuration = self.responseConfiguration(to: request)
return try PerMessageDeflateExtension(configuration: configuration)
}
/// Create client PerMessageDeflateExtension based off response headers
/// - Parameters:
/// - response: Server response
func clientExtension(from response: WebSocketExtensionHTTPParameters) throws -> WebSocketExtension? {
let clientMaxWindowParam = response.parameters["client_max_window_bits"]?.integer
let clientNoContextTakeoverParam = response.parameters["client_no_context_takeover"] != nil
let serverMaxWindowParam = response.parameters["server_max_window_bits"]?.integer
let serverNoContextTakeoverParam = response.parameters["server_no_context_takeover"] != nil
return try PerMessageDeflateExtension(configuration: .init(
receiveMaxWindow: serverMaxWindowParam,
receiveNoContextTakeover: serverNoContextTakeoverParam,
sendMaxWindow: clientMaxWindowParam,
sendNoContextTakeover: clientNoContextTakeoverParam,
compressionLevel: self.compressionLevel,
memoryLevel: self.memoryLevel,
maxDecompressedFrameSize: self.maxDecompressedFrameSize
))
}
private func responseConfiguration(to request: WebSocketExtensionHTTPParameters) -> PerMessageDeflateExtension.Configuration {
let requestServerMaxWindow = request.parameters["server_max_window_bits"]
let requestServerNoContextTakeover = request.parameters["server_no_context_takeover"] != nil
let requestClientMaxWindow = request.parameters["client_max_window_bits"]
let requestClientNoContextTakeover = request.parameters["client_no_context_takeover"] != nil
let receiveMaxWindow: Int?
// calculate client max window. If parameter doesn't exist then server cannot set it, if it does
// exist then the value should be set to minimum of both values, or the value of the other if
// one is nil
= if let requestClientMaxWindow
{
optionalMin(requestClientMaxWindow.integer, self.clientMaxWindow)
} else {
nil
}
return PerMessageDeflateExtension.Configuration(
receiveMaxWindow: receiveMaxWindow,
receiveNoContextTakeover: requestClientNoContextTakeover || self.clientNoContextTakeover,
sendMaxWindow: optionalMin(requestServerMaxWindow?.integer, self.serverMaxWindow),
sendNoContextTakeover: requestServerNoContextTakeover || self.serverNoContextTakeover,
compressionLevel: self.compressionLevel,
memoryLevel: self.memoryLevel,
maxDecompressedFrameSize: self.maxDecompressedFrameSize
)
}
}
/// PerMessageDeflate websocket extension
///
/// Uses deflate to compress messages sent across a WebSocket
/// See RFC 7692 for more details https://www.rfc-editor.org/rfc/rfc7692
struct PerMessageDeflateExtension: WebSocketExtension {
struct Configuration: Sendable {
let receiveMaxWindow: Int?
let receiveNoContextTakeover: Bool
let sendMaxWindow: Int?
let sendNoContextTakeover: Bool
let compressionLevel: Int?
let memoryLevel: Int?
let maxDecompressedFrameSize: Int
}
actor Decompressor {
fileprivate let decompressor: any NIODecompressor
init(_ decompressor: any NIODecompressor) throws {
self.decompressor = decompressor
try self.decompressor.startStream()
}
func decompress(_ frame: WebSocketFrame, maxSize: Int, resetStream: Bool, context: some WebSocketContextProtocol) throws -> WebSocketFrame {
var frame = frame
precondition(frame.fin, "Only concatenated frames with fin set can be processed by the permessage-deflate extension")
// Reinstate last four bytes 0x00 0x00 0xff 0xff that were removed in the frame
// send (see https://datatracker.ietf.org/doc/html/rfc7692#section-7.2.2).
frame.data.writeBytes([0, 0, 255, 255])
frame.data = try frame.data.decompressStream(with: self.decompressor, maxSize: maxSize, allocator: context.allocator)
if resetStream {
try self.decompressor.resetStream()
}
return frame
}
func shutdown() throws {
try self.decompressor.finishStream()
}
}
actor Compressor {
enum SendState: Sendable {
case idle
case sendingMessage
}
fileprivate let compressor: any NIOCompressor
var sendState: SendState
init(_ compressor: any NIOCompressor) throws {
self.compressor = compressor
self.sendState = .idle
try self.compressor.startStream()
}
func compress(_ frame: WebSocketFrame, resetStream: Bool, context: some WebSocketContextProtocol) throws -> WebSocketFrame {
// if the frame is larger than 16 bytes, we haven't received a final frame or we are in the process of sending a message
// compress the data
let shouldWeCompress = frame.data.readableBytes > 16 || !frame.fin || self.sendState != .idle
if shouldWeCompress {
var newFrame = frame
if self.sendState == .idle {
newFrame.rsv1 = true
self.sendState = .sendingMessage
}
newFrame.data = try newFrame.data.compressStream(with: self.compressor, flush: .sync, allocator: context.allocator)
// if final frame then remove last four bytes 0x00 0x00 0xff 0xff
// (see https://datatracker.ietf.org/doc/html/rfc7692#section-7.2.1)
if newFrame.fin {
newFrame.data = newFrame.data.getSlice(at: newFrame.data.readerIndex, length: newFrame.data.readableBytes - 4) ?? newFrame.data
self.sendState = .idle
if resetStream {
try self.compressor.resetStream()
}
}
return newFrame
}
return frame
}
func shutdown() throws {
try self.compressor.finishStream()
}
}
let name = "permessage-deflate"
let configuration: Configuration
let decompressor: Decompressor
let compressor: Compressor
init(configuration: Configuration) throws {
self.configuration = configuration
self.decompressor = try .init(
CompressionAlgorithm.deflate(
configuration: .init(
windowSize: numericCast(configuration.receiveMaxWindow ?? 15)
)
).decompressor
)
self.compressor = try .init(
CompressionAlgorithm.deflate(
configuration: .init(
windowSize: numericCast(configuration.sendMaxWindow ?? 15),
compressionLevel: configuration.compressionLevel.map { numericCast($0) } ?? -1,
memoryLevel: configuration.memoryLevel.map { numericCast($0) } ?? 8
)
).compressor
)
}
func shutdown() async {
try? await self.decompressor.shutdown()
try? await self.compressor.shutdown()
}
func processReceivedFrame(_ frame: WebSocketFrame, context: some WebSocketContextProtocol) async throws -> WebSocketFrame {
if frame.rsv1 {
return try await self.decompressor.decompress(
frame,
maxSize: self.configuration.maxDecompressedFrameSize,
resetStream: self.configuration.receiveNoContextTakeover,
context: context
)
}
return frame
}
func processFrameToSend(_ frame: WebSocketFrame, context: some WebSocketContextProtocol) async throws -> WebSocketFrame {
let isCorrectType = frame.opcode == .text || frame.opcode == .binary
if isCorrectType {
return try await self.compressor.compress(frame, resetStream: self.configuration.sendNoContextTakeover, context: context)
}
return frame
}
}
extension WebSocketExtensionFactory {
/// permessage-deflate websocket extension
/// - Parameters:
/// - maxWindow: Max window to be used for decompression and compression
/// - noContextTakeover: Should we reset window on every message
public static func perMessageDeflate(
maxWindow: Int? = nil,
noContextTakeover: Bool = false,
maxDecompressedFrameSize: Int = 1 << 14
) -> WebSocketExtensionFactory {
return .init {
PerMessageDeflateExtensionBuilder(
clientMaxWindow: maxWindow,
clientNoContextTakeover: noContextTakeover,
serverMaxWindow: maxWindow,
serverNoContextTakeover: noContextTakeover,
compressionLevel: nil,
memoryLevel: nil,
maxDecompressedFrameSize: maxDecompressedFrameSize
)
}
}
/// permessage-deflate websocket extension
/// - Parameters:
/// - clientMaxWindow: Max window to be used for client compression
/// - clientNoContextTakeover: Should client reset window on every message
/// - serverMaxWindow: Max window to be used for server compression
/// - serverNoContextTakeover: Should server reset window on every message
/// - compressionLevel: Zlib compression level. Value between 0 and 9 where 1 gives best speed, 9 gives
/// give best compression and 0 gives no compression.
/// - memoryLevel: Defines how much memory should be given to compression. Value between 1 and 9 where 1
/// uses least memory and 9 give best compression and optimal speed.
public static func perMessageDeflate(
clientMaxWindow: Int? = nil,
clientNoContextTakeover: Bool = false,
serverMaxWindow: Int? = nil,
serverNoContextTakeover: Bool = false,
compressionLevel: Int? = nil,
memoryLevel: Int? = nil,
maxDecompressedFrameSize: Int = 1 << 14
) -> WebSocketExtensionFactory {
return .init {
PerMessageDeflateExtensionBuilder(
clientMaxWindow: clientMaxWindow,
clientNoContextTakeover: clientNoContextTakeover,
serverMaxWindow: serverMaxWindow,
serverNoContextTakeover: serverNoContextTakeover,
compressionLevel: compressionLevel,
memoryLevel: memoryLevel,
maxDecompressedFrameSize: maxDecompressedFrameSize
)
}
}
}
/// Minimum of two optional integers.
///
/// Returns the other is one of them is nil
private func optionalMin(_ a: Int?, _ b: Int?) -> Int? {
switch (a, b) {
case (.some(let a), .some(let b)):
return min(a, b)
case (.some(a), .none):
return a
case (.none, .some(b)):
return b
default:
return nil
}
}