123 lines
3.2 KiB
Swift
123 lines
3.2 KiB
Swift
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import Foundation
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import NIOCore
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/**
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An authenticated message to or from the device.
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*/
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struct Message: Equatable, Hashable {
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/**
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The message content without authentication.
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*/
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struct Content: Equatable, Hashable {
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/// The time of message creation, in UNIX time (seconds since 1970)
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let time: UInt32
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/// The counter of the message (for freshness)
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let id: UInt32
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/**
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Create new message content.
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- Parameter time: The time of message creation,
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- Parameter id: The counter of the message
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*/
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init(time: UInt32, id: UInt32) {
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self.time = time
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self.id = id
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}
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/**
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Decode message content from data.
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The data consists of two `UInt32` encoded in big endian format (MSB at index 0)
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- Warning: The sequence must contain at least 8 bytes, or the function will crash.
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- Parameter data: The sequence containing the bytes.
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*/
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init<T: Sequence>(decodeFrom data: T) where T.Element == UInt8 {
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self.time = UInt32(data: data.prefix(MemoryLayout<UInt32>.size))
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self.id = UInt32(data: data.dropFirst(MemoryLayout<UInt32>.size))
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}
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/// The byte length of an encoded message content
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static var length: Int {
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MemoryLayout<UInt32>.size * 2
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}
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/// The message content encoded to data
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var encoded: Data {
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time.encoded + id.encoded
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}
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/// The message content encoded to bytes
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var bytes: [UInt8] {
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time.bytes + id.bytes
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}
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}
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/// The message authentication code for the message (32 bytes)
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let mac: Data
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/// The message content
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let content: Content
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/**
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Create an authenticated message
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- Parameter mac: The message authentication code
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- Parameter content: The message content
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*/
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init(mac: Data, content: Content) {
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self.mac = mac
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self.content = content
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}
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/**
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Decode a message from a byte buffer.
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The buffer must contain at least `Message.length` bytes, or it will return `nil`.
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- Parameter buffer: The buffer containing the bytes.
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*/
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init?(decodeFrom buffer: ByteBuffer) {
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guard let data = buffer.getBytes(at: 0, length: Message.length) else {
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return nil
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}
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self.init(decodeFrom: data)
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}
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/// The message encoded to data
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var encoded: Data {
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mac + content.encoded
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}
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/// The message encoded to bytes
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var bytes: [UInt8] {
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Array(mac) + content.bytes
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}
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}
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extension UInt32 {
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/**
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Create a value from a big-endian data representation (MSB first)
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- Note: The data must contain exactly four bytes.
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*/
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init<T: Sequence>(data: T) where T.Element == UInt8 {
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self = data
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.reversed()
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.enumerated()
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.map { UInt32($0.element) << ($0.offset * 8) }
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.reduce(0, +)
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}
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/// The value encoded to a big-endian representation
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var encoded: Data {
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.init(bytes)
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}
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/// The value encoded to a big-endian byte array
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var bytes: [UInt8] {
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(0..<4).reversed().map {
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UInt8((self >> ($0*8)) & 0xFF)
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}
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}
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}
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