1
這是一個相當長的問題，所以請和我一起裸照。你會如何解決這個數據解析問題？
我們正在爲一塊硬件實現一個模擬器，該硬件同時正在開發中。這個想法是給第三方 一個軟件解決方案來測試他們的客戶端軟件，並給開發人員一個參考點來實現他們的固件。
編寫硬件協議的人員使用名爲INCA_XDR的定製的SUN XDR的 版本。這是一個序列化和反序列化消息的工具。它用C語言編寫，我們希望避免任何 本地代碼，因此我們正在手動解析協議數據。
該協議是由性質相當複雜和數據分組 可以具有許多不同的結構，但它總是具有相同的全局結構：
[HEAD] [INTRO] [DATA] [TAIL]
[HEAD] =
byte sync 0x03
byte length X [MSB] X = length of [HEADER] + [INTRO] + [DATA]
byte length X [LSB] X = length of [HEADER] + [INTRO] + [DATA]
byte check X [MSB] X = crc of [INTRO] [DATA]
byte check X [LSB] X = crc of [INTRO] [DATA]
byte headercheck X X = XOR over [SYNC] [LENGTH] [CHECK]
[INTRO]
byte version 0x03
byte address X X = 0 for point-to-point, 1-254 for specific controller, 255 = broadcast
byte sequence X X = sequence number
byte group X [MSB] X = The category of the message
byte group X [LSB] X = The category of the message
byte type X [MSB] X = The id of the message
byte type X [LSB] X = The id of the message
[DATA] =
The actuall data for the specified message,
this format really differs a lot.
It always starts with a DRCode which is one byte.
It more or less specifies the general structure of
the data, but even within the same structure the data
can mean many different things and have different lenghts.
(I think this is an artifact of the INCA_XDR tool)
[TAIL] =
byte 0x0D
正如你可以看到有大量的開銷數據，但這是因爲 協議需要與兩個RS232（點對點，點對多點）和TCP/IP（P2P）的工作。
name size value
drcode 1 1
name 8 contains a name that can be used as a file name (only alphanumeric characters allowed)
timestamp 14 yyyymmddhhmmss contains timestamp of bitmap library
size 4 size of bitmap library to be loaded
options 1 currently no options
或者，它可能有一個完全不同的結構：
name size value
drcode 1 2
lastblock 1 0 - 1 1 indicates last block. Firmware can be stored
blocknumber 2 Indicates block of firmware
blocksize 2 N size of block to load
blockdata N data of block of firmware
有時，它只是一個DRCode並沒有額外的數據。
基於組和類型字段，模擬器 需要執行某些操作。所以首先我們看看這兩個字段，並基於此我們知道對數據 有什麼期望，並且必須正確解析它。
然後需要生成響應數據，其中還有許多不同的數據結構。一些消息簡單地生成ACK或NACK消息，而另一些則生成數據的真實答覆。
我們決定把東西分成小塊。
首先是IDataProcessor。
實現此接口的類負責 驗證原始數據並生成Message類的實例。 他們不負責通信，他們只是通過一個字節[]
原始數據驗證意味着檢查標題的校驗和，crc和長度錯誤。
生成的消息被傳遞給實現IMessageProcessor的類。 即使原始數據被認爲是無效的，因爲IDataProcessor沒有 迴應消息的概念或其他任何東西，它所做的只是驗證原始數據。
，告知錯誤IMessageProcessor，一些額外的屬性已添加 到Message類：
bool nakError = false;
bool tailError = false;
bool crcError = false;
bool headerError = false;
bool lengthError = false;
他們沒有相關的協議，只存在了IMessageProcessor
的IMessageProcessor是真正的工作在哪裏完成。 因爲所有不同的消息組和類型的我決定 使用F＃實現IMessageProcessor接口，因爲模式匹配 似乎是一個很好的方式，以避免大量的嵌套if/else和種姓語句。我之前沒有使用過F＃或LINQ和SQL以外的函數式語言的經驗）
IMessageProcessor分析數據並決定在IHardwareController上應該調用哪些方法 。這似乎是多餘的有IHardwareController， 但我們希望能夠有不同的實現 掉出來，而不是將被迫使用F＃。目前的實現是一個WPF窗口，但它可能是一個Cocoa＃窗口或簡單的控制檯。
IHardwareController還負責管理狀態，因爲 開發人員應該能夠通過用戶界面操縱硬件參數和錯誤。
因此，一旦IMessageProcessor在IHardwareController上調用了正確的方法， 就必須生成響應消息。再次...這些響應消息 中的數據可以有許多不同的結構。
最終IDataFactory用於將消息轉換爲原始協議數據 準備發送到任何負責通信的類。 （數據的附加封裝可能需要例如）
這是什麼「硬」關於編寫這些代碼，但所有的不同 命令和數據結構需要很多很多的代碼，並有少數 事情我們可以重用。 （至少據我現在可以看到的，希望有人能證明我錯了）
這是我第一次使用F＃，所以我其實學習，我去。下面的代碼遠沒有完成 ，可能看起來像一個巨大的混亂。它只有實現了所有消息的漢福的協議 ，我可以告訴你有很多很多的人。所以這個文件會變得很大！
重要的是知道：字節順序顛倒通過線路（歷史原因）
module Arendee.Hardware.MessageProcessors
open System;
open System.Collections
open Arendee.Hardware.Extenders
open Arendee.Hardware.Interfaces
open System.ComponentModel.Composition
open System.Threading
open System.Text
let VPL_NOERROR = (uint16)0
let VPL_CHECKSUM = (uint16)1
let VPL_FRAMELENGTH = (uint16)2
let VPL_OUTOFSEQUENCE = (uint16)3
let VPL_GROUPNOTSUPPORTED = (uint16)4
let VPL_REQUESTNOTSUPPORTED = (uint16)5
let VPL_EXISTS = (uint16)6
let VPL_INVALID = (uint16)7
let VPL_TYPERROR = (uint16)8
let VPL_NOTLOADING = (uint16)9
let VPL_NOTFOUND = (uint16)10
let VPL_OUTOFMEM = (uint16)11
let VPL_INUSE = (uint16)12
let VPL_SIZE = (uint16)13
let VPL_BUSY = (uint16)14
let SYNC_BYTE = (byte)0xE3
let TAIL_BYTE = (byte)0x0D
let MESSAGE_GROUP_VERSION = 3uy
let MESSAGE_GROUP = 701us
[<Export(typeof<IMessageProcessor>)>]
type public StandardMessageProcessor() = class
let mutable controller : IHardwareController = null
interface IMessageProcessor with
member this.ProcessMessage m : Message =
printfn "%A" controller.Status
controller.Status <- ControllerStatusExtender.DisableBit(controller.Status,ControllerStatus.Nak)
match m with
| m when m.LengthError -> this.nakResponse(m,VPL_FRAMELENGTH)
| m when m.CrcError -> this.nakResponse(m,VPL_CHECKSUM)
| m when m.HeaderError -> this.nakResponse(m,VPL_CHECKSUM)
| m -> this.processValidMessage m
| _ -> null
member public x.HardwareController
with get() = controller
and set y = controller <- y
end
member private this.processValidMessage (m : Message) =
match m.Intro.MessageGroup with
| 701us -> this.processDefaultGroupMessage(m);
| _ -> this.nakResponse(m, VPL_GROUPNOTSUPPORTED);
member private this.processDefaultGroupMessage(m : Message) =
match m.Intro.MessageType with
| (1us) -> this.firmwareVersionListResponse(m) //ListFirmwareVersions 0
| (2us) -> this.StartLoadingFirmwareVersion(m) //StartLoadingFirmwareVersion 1
| (3us) -> this.LoadFirmwareVersionBlock(m) //LoadFirmwareVersionBlock 2
| (4us) -> this.nakResponse(m, VPL_FRAMELENGTH) //RemoveFirmwareVersion 3
| (5us) -> this.nakResponse(m, VPL_FRAMELENGTH) //ActivateFirmwareVersion 3
| (12us) -> this.nakResponse(m,VPL_FRAMELENGTH) //StartLoadingBitmapLibrary 2
| (13us) -> this.nakResponse(m,VPL_FRAMELENGTH) //LoadBitmapLibraryBlock 2
| (21us) -> this.nakResponse(m, VPL_FRAMELENGTH) //ListFonts 0
| (22us) -> this.nakResponse(m, VPL_FRAMELENGTH) //LoadFont 4
| (23us) -> this.nakResponse(m, VPL_FRAMELENGTH) //RemoveFont 3
| (24us) -> this.nakResponse(m, VPL_FRAMELENGTH) //SetDefaultFont 3
| (31us) -> this.nakResponse(m, VPL_FRAMELENGTH) //ListParameterSets 0
| (32us) -> this.nakResponse(m, VPL_FRAMELENGTH) //LoadParameterSets 4
| (33us) -> this.nakResponse(m, VPL_FRAMELENGTH) //RemoveParameterSet 3
| (34us) -> this.nakResponse(m, VPL_FRAMELENGTH) //ActivateParameterSet 3
| (35us) -> this.nakResponse(m, VPL_FRAMELENGTH) //GetParameterSet 3
| (41us) -> this.nakResponse(m, VPL_FRAMELENGTH) //StartSelfTest 0
| (42us) -> this.returnStatus(m) //GetStatus 0
| (43us) -> this.nakResponse(m, VPL_FRAMELENGTH) //GetStatusDetail 0
| (44us) -> this.ResetStatus(m) //ResetStatus 5
| (45us) -> this.nakResponse(m, VPL_FRAMELENGTH) //SetDateTime 6
| (46us) -> this.nakResponse(m, VPL_FRAMELENGTH) //GetDateTime 0
| _ -> this.nakResponse(m, VPL_REQUESTNOTSUPPORTED)
(* The various responses follow *)
//Generate a NAK response
member private this.nakResponse (message : Message , error) =
controller.Status <- controller.Status ||| ControllerStatus.Nak
let intro = new MessageIntro()
intro.MessageGroupVersion <- MESSAGE_GROUP_VERSION
intro.Address <- message.Intro.Address
intro.SequenceNumber <- this.setHigh(message.Intro.SequenceNumber)
intro.MessageGroup <- MESSAGE_GROUP
intro.MessageType <- 130us
let errorBytes = UShortExtender.ToIntelOrderedByteArray(error)
let data = Array.zero_create(5)
let x = this.getStatusBytes
let y = this.getStatusBytes
data.[0] <- 7uy
data.[1..2] <- this.getStatusBytes
data.[3..4] <- errorBytes
let header = this.buildHeader intro data
let message = new Message()
message.Header <- header
message.Intro <- intro
message.Tail <- TAIL_BYTE
message.Data <- data
message
//Generate an ACK response
member private this.ackResponse (message : Message) =
let intro = new MessageIntro()
intro.MessageGroupVersion <- MESSAGE_GROUP_VERSION
intro.Address <- message.Intro.Address
intro.SequenceNumber <- this.setHigh(message.Intro.SequenceNumber)
intro.MessageGroup <- MESSAGE_GROUP
intro.MessageType <- 129us
let data = Array.zero_create(3);
data.[0] <- 0x05uy
data.[1..2] <- this.getStatusBytes
let header = this.buildHeader intro data
message.Header <- header
message.Intro <- intro
message.Tail <- TAIL_BYTE
message.Data <- data
message
//Generate a ReturnFirmwareVersionList
member private this.firmwareVersionListResponse (message : Message) =
//Validation
if message.Data.[0] <> 0x00uy then
this.nakResponse(message,VPL_INVALID)
else
let intro = new MessageIntro()
intro.MessageGroupVersion <- MESSAGE_GROUP_VERSION
intro.Address <- message.Intro.Address
intro.SequenceNumber <- this.setHigh(message.Intro.SequenceNumber)
intro.MessageGroup <- MESSAGE_GROUP
intro.MessageType <- 132us
let firmwareVersions = controller.ReturnFirmwareVersionList();
let firmwareVersionBytes = BitConverter.GetBytes((uint16)firmwareVersions.Count) |> Array.rev
//Create the data
let data = Array.zero_create(3 + (int)firmwareVersions.Count * 27)
data.[0] <- 0x09uy //drcode
data.[1..2] <- firmwareVersionBytes //Number of firmware versions
let mutable index = 0
let loops = firmwareVersions.Count - 1
for i = 0 to loops do
let nameBytes = ASCIIEncoding.ASCII.GetBytes(firmwareVersions.[i].Name) |> Array.rev
let timestampBytes = this.getTimeStampBytes firmwareVersions.[i].Timestamp |> Array.rev
let sizeBytes = BitConverter.GetBytes(firmwareVersions.[i].Size) |> Array.rev
data.[index + 3 .. index + 10] <- nameBytes
data.[index + 11 .. index + 24] <- timestampBytes
data.[index + 25 .. index + 28] <- sizeBytes
data.[index + 29] <- firmwareVersions.[i].Status
index <- index + 27
let header = this.buildHeader intro data
message.Header <- header
message.Intro <- intro
message.Data <- data
message.Tail <- TAIL_BYTE
message
//Generate ReturnStatus
member private this.returnStatus (message : Message) =
//Validation
if message.Data.[0] <> 0x00uy then
this.nakResponse(message,VPL_INVALID)
else
let intro = new MessageIntro()
intro.MessageGroupVersion <- MESSAGE_GROUP_VERSION
intro.Address <- message.Intro.Address
intro.SequenceNumber <- this.setHigh(message.Intro.SequenceNumber)
intro.MessageGroup <- MESSAGE_GROUP
intro.MessageType <- 131us
let statusDetails = controller.ReturnStatus();
let sizeBytes = BitConverter.GetBytes((uint16)statusDetails.Length) |> Array.rev
let detailBytes = ASCIIEncoding.ASCII.GetBytes(statusDetails) |> Array.rev
let data = Array.zero_create(statusDetails.Length + 5)
data.[0] <- 0x08uy
data.[1..2] <- this.getStatusBytes
data.[3..4] <- sizeBytes //Details size
data.[5..5 + statusDetails.Length - 1] <- detailBytes
let header = this.buildHeader intro data
message.Header <- header
message.Intro <- intro
message.Data <- data
message.Tail <- TAIL_BYTE
message
//Reset some status bytes
member private this.ResetStatus (message : Message) =
if message.Data.[0] <> 0x05uy then
this.nakResponse(message, VPL_INVALID)
else
let flagBytes = message.Data.[1..2] |> Array.rev
let flags = Enum.ToObject(typeof<ControllerStatus>,BitConverter.ToInt16(flagBytes,0)) :?> ControllerStatus
let retVal = controller.ResetStatus flags
if retVal <> 0x00us then
this.nakResponse(message,retVal)
else
this.ackResponse(message)
//StartLoadingFirmwareVersion (Ack/Nak)
member private this.StartLoadingFirmwareVersion (message : Message) =
if (message.Data.[0] <> 0x01uy) then
this.nakResponse(message, VPL_INVALID)
else
//Analyze the data
let name = message.Data.[1..8] |> Array.rev |> ASCIIEncoding.ASCII.GetString
let text = message.Data.[9..22] |> Array.rev |> Seq.map(fun x -> ASCIIEncoding.ASCII.GetBytes(x.ToString()).[0]) |> Seq.to_array |> ASCIIEncoding.ASCII.GetString
let timestamp = DateTime.ParseExact(text,"yyyyMMddHHmmss",Thread.CurrentThread.CurrentCulture)
let size = BitConverter.ToUInt32(message.Data.[23..26] |> Array.rev,0)
let overwrite =
match message.Data.[27] with
| 0x00uy -> false
| _ -> true
//Create a FirmwareVersion instance
let firmware = new FirmwareVersion();
firmware.Name <- name
firmware.Timestamp <- timestamp
firmware.Size <- size
let retVal = controller.StartLoadingFirmwareVersion(firmware,overwrite)
if retVal <> 0x00us then
this.nakResponse(message, retVal) //The controller denied the request
else
this.ackResponse(message);
//LoadFirmwareVersionBlock (ACK/NAK)
member private this.LoadFirmwareVersionBlock (message : Message) =
if message.Data.[0] <> 0x02uy then
this.nakResponse(message, VPL_INVALID)
else
//Analyze the data
let lastBlock =
match message.Data.[1] with
| 0x00uy -> false
| _true -> true
let blockNumber = BitConverter.ToUInt16(message.Data.[2..3] |> Array.rev,0)
let blockSize = BitConverter.ToUInt16(message.Data.[4..5] |> Array.rev,0)
let blockData = message.Data.[6..6 + (int)blockSize - 1] |> Array.rev
let retVal = controller.LoadFirmwareVersionBlock(lastBlock, blockNumber, blockSize, blockData)
if retVal <> 0x00us then
this.nakResponse(message, retVal)
else
this.ackResponse(message)
(* Helper methods *)
//We need to convert the DateTime instance to a byte[] understood by the device "yyyymmddhhmmss"
member private this.getTimeStampBytes (date : DateTime) =
let stringNumberToByte s = Byte.Parse(s.ToString()) //Casting to (byte) would give different results
let yearString = date.Year.ToString("0000")
let monthString = date.Month.ToString("00")
let dayString = date.Day.ToString("00")
let hourString = date.Hour.ToString("00")
let minuteString = date.Minute.ToString("00")
let secondsString = date.Second.ToString("00")
let y1 = stringNumberToByte yearString.[0]
let y2 = stringNumberToByte yearString.[1]
let y3 = stringNumberToByte yearString.[2]
let y4 = stringNumberToByte yearString.[3]
let m1 = stringNumberToByte monthString.[0]
let m2 = stringNumberToByte monthString.[1]
let d1 = stringNumberToByte dayString.[0]
let d2 = stringNumberToByte dayString.[1]
let h1 = stringNumberToByte hourString.[0]
let h2 = stringNumberToByte hourString.[1]
let min1 = stringNumberToByte minuteString.[0]
let min2 = stringNumberToByte minuteString.[1]
let s1 = stringNumberToByte secondsString.[0]
let s2 = stringNumberToByte secondsString.[1]
[| y1 ; y2 ; y3 ; y4 ; m1 ; m2 ; d1 ; d2 ; h1 ; h2 ; min1 ; min2 ; s1; s2 |]
//Sets the high bit of a byte to 1
member private this.setHigh (b : byte) : byte =
let array = new BitArray([| b |])
array.[7] <- true
let mutable converted = [| 0 |]
array.CopyTo(converted, 0);
(byte)converted.[0]
//Build the header of a Message based on Intro + Data
member private this.buildHeader (intro : MessageIntro) (data : byte[]) =
let headerLength = 7;
let introLength = 7;
let length = (uint16)(headerLength + introLength + data.Length)
let crcData = ByteArrayExtender.Concat(intro.GetRawData(),data)
let crcValue = ByteArrayExtender.CalculateCRC16(crcData)
let lengthBytes = UShortExtender.ToIntelOrderedByteArray(length);
let crcValueBytes = UShortExtender.ToIntelOrderedByteArray(crcValue);
let headerChecksum = (byte)(SYNC_BYTE ^^^ lengthBytes.[0] ^^^ lengthBytes.[1] ^^^ crcValueBytes.[0] ^^^ crcValueBytes.[1])
let header = new MessageHeader();
header.Sync <- SYNC_BYTE
header.Length <- length
header.HeaderChecksum <- headerChecksum
header.DataChecksum <- crcValue
header
member private this.getStatusBytes =
let l = controller.Status
let status = (uint16)controller.Status
let statusBytes = BitConverter.GetBytes(status);
statusBytes |> Array.rev
end
（請注意，真正的源頭，這些類有不同的名稱，而不是「硬件」更具體）
我希望的建議，如何改善代碼，甚至不同的方式來處理這個問題。 例如，將使用動態語言 - 如IronPython使事情更容易， 我是在錯誤的方式去一起。你有什麼經驗，像這樣的問題， 你會改變什麼，避免，等等......
更新：
基於由Brian答案，我寫下了以下內容：
type DrCode9Item = {Name : string ; Timestamp : DateTime ; Size : uint32; Status : byte}
type DrCode11Item = {Id : byte ; X : uint16 ; Y : uint16 ; SizeX : uint16 ; SizeY : uint16
Font : string ; Alignment : byte ; Scroll : byte ; Flash : byte}
type DrCode12Item = {Id : byte ; X : uint16 ; Y : uint16 ; SizeX : uint16 ; SizeY : uint16}
type DrCode14Item = {X : byte ; Y : byte}
type DRType =
| DrCode0 of byte
| DrCode1 of byte * string * DateTime * uint32 * byte
| DrCode2 of byte * byte * uint16 * uint16 * array<byte>
| DrCode3 of byte * string
| DrCode4 of byte * string * DateTime * byte * uint16 * array<byte>
| DrCode5 of byte * uint16
| DrCode6 of byte * DateTime
| DrCode7 of byte * uint16 * uint16
| DrCode8 of byte * uint16 * uint16 * uint16 * array<byte>
| DrCode9 of byte * uint16 * array<DrCode9Item>
| DrCode10 of byte * string * DateTime * uint32 * byte * array<byte>
| DrCode11 of byte * array<DrCode11Item>
| DrCode12 of byte * array<DrCode12Item>
| DrCode13 of byte * uint16 * byte * uint16 * uint16 * string * byte * byte
| DrCode14 of byte * array<DrCode14Item>
我可以繼續做這一切的DR類型（相當多的）， 但我仍然不明白這對我有什麼幫助。我已經在Wikibooks和F＃的基礎上閱讀了關於它的 ，但是還沒有點擊我的頭像。
更新2
所以，我知道我能做到以下幾點：
let execute dr =
match dr with
| DrCode0(drCode) -> printfn "Do something"
| DrCode1(drCode, name, timestamp, size, options) -> printfn "Show the size %A" size
| _ ->()
let date = DateTime.Now
let x = DrCode1(1uy,"blabla", date, 100ul, 0uy)
但是當消息進入的IMessageProcessor， 的的choise由右邊有什麼樣的信息呢是 然後調用正確的功能。以上只是 是額外的代碼，至少這是如何理解它， 所以我必須真的在這裏忽略了點...但我沒有看到它。
execute x
關於約束條件： 我們希望模擬器的核心是跨平臺的。 我們從不使用本機代碼，特別是不使用C代碼。 我已經看到C硬件開發人員編寫代碼的方式，這太可怕了！無處不在的縮略詞 第三方使用他們想要與模擬器通信的任何內容（通過tcp/ip或rs232）。 – TimothyP 2009-05-04 07:58:33