我有一张PCB印刷电路板,其中有一个ATMEL微控制器通过Lantronix Xport进行TCP通信。它以ASCII字符串格式发送一些继电器和传感器的状态报告,长度为30个字节,格式如下:
400000000000000000414243303031303030303030303030303030303339
| | | |
| byte[0] = $40 | | |
| | |- byte[11] = $43 // 'C' Always
| |--- byte[10] = $42 // 'B' Always
|----- byte[9] = $41 // 'A' Always
byte[1..8] = boolean values := Bool(byte[x]);
byte[12..29] = 6 different numbers as string, 3 chars long each, range 0..999
我已经对数据包的加载状态进行了简单的验证:
procedure Load(iData: TBytes);
const vsp = 9; //Validation String Postition
buflen = 30;
begin
If (Length(iData) = buflen) And (iData[0] = $40) And (iData[vsp] = $41) And (iData[vsp + 1] = $42) And (iData[vsp + 2] = $43) Then
SetStatus(iData) //Function for loading validated packet
Else Begin
DoError(1, 'Invalid packet. Length = ' + IntToStr(Length(iData)) + #13#10 +
'iData[0] = ' + String(ByteToHex(iData[0])) + #13#10 +
'iData[vsp] = ' + String(ByteToHex(iData[vsp])) + #13#10 +
'iData[vsp + 1] = ' + String(ByteToHex(iData[vsp + 1])) + #13#10 +
'iData[vsp + 2] = ' + String(ByteToHex(iData[vsp + 2]))
);
End;
End;
问题在于有时候 ASCII 字符串会被分成多个数据包或者拼接成一个数据包(第一个数字是时间戳):
4239483 4000 // Could be missing in case of disconnect-reconnect.
4239514 00000000000000414243303030303030303030303030303030303338400000000000000000414243
4239545 303031303030303030303030303030303339
4239576 400000000000000000414243303031303030303030303030303030303339400000000000000000414243303031303030303030303030303030303338
4239670 40000000000000000041424330303130
4239701 3030303030303030303030303339
在断开重新连接的情况下,状态信息的部分内容将丢失。
我该如何利用TMemoryStream或Move来读取每个接收到的数据包而不丢失任何信息?
编辑: SetStatus看起来像这样,所以我想避免将状态报告移植到字符串中:
Procedure TTractor.SetStatus(AData: TBytes);
begin
StatusStream := AData;
pStatus.HighSpeed := Bool(AData[1]);
pStatus.RevDir := Bool(AData[2]);
pStatus.FwdDir := Bool(AData[3]);
pStatus.FrontExpanded := Bool(AData[4]);
pStatus.RearExpanded := Bool(AData[5]);
pStatus.AntiSpin := Bool(AData[6]);
pStatus.Unknown1 := DecodePCBNumber(AData[12], AData[13], AData[14]);
pStatus.PumpPressureVoltage := DecodePCBNumber(AData[15], AData[16], AData[17]);
pStatus.Unknown2 := DecodePCBNumber(AData[18], AData[19], AData[20]);
pStatus.WheelPressureVoltage := DecodePCBNumber(AData[21], AData[22], AData[23]);
pStatus.OilTemperatureVoltage := DecodePCBNumber(AData[24], AData[25], AData[26]);
pStatus.PCBTemperatureVoltage := DecodePCBNumber(AData[27], AData[28], AData[29]);
End;
阅读代码:
procedure TForm1.FormCreate(Sender: TObject);
begin
If Traktor = nil Then Traktor := TTractor.Create(500);
//...
End;
// TidConnectionIntercept
procedure TForm1.trCItcReceive(ASender: TIdConnectionIntercept; var ABuffer: TArray<System.Byte>);
Var
tmpList: TList;
i: Integer;
Begin
If Traktor <> nil Then Traktor.StatusTBytes := ABuffer;
AppendConLog(TraktorReceive, False, False, BytesToHexStr(ABuffer) );
End;
procedure TForm1.AppendConLog(LogTyp: TLogType; ShowInConsole, PlainText: Boolean; Text: String);
begin
If ShowInConsole Or (PlainText And DebugMode) Then Begin
MemoConsole.Lines.Add(FormatDateTime('[hh:nn:ss] ', Now) + Text);
Text := String2Hex(AnsiString(Text));
End;
LogFile.Add(IntToHex(DateTimeToUNIXTimeFAST(Now()), 8) + ' ' + IntToHex(GetTickCount, 8) + ' ' +
IntToHex(Word(ShowInConsole), 1) + IntToHex(Word(PlainText), 1) + ' ' +
IntToHex( Ord(LogTyp), 2) + ' ' + Text);
end;
Type TTractor = class
constructor Create(LoadInterval: Cardinal; SyncInterval: Cardinal = 25);
//....
public
property StatusTBytes: TBytes read StatusStream write Load;
//...
End;
ReadBytes(30)
,并让它处理数据包的拆分/合并。 - Remy LebeauByte
代替Char
和TBytes
代替string
进行操作。 - Sir RufoIntercept
的作用是用于处理数据(压缩、加密等),而不是用于检测何时读取数据。相反,应该使用IOHandler
方法,如ReadBytes()
。TIdIOHandler
有自己的内部缓冲区来处理拆分/合并的数据包。这样,您就可以专注于更高级别的逻辑(读取 30 字节消息),而 Indy 处理低级别的细节(在循环中读取直到有 30 字节可用,缓存未使用的数据以供后续读取等)。如果您展示您当前的读取代码,我可以帮您重写以正确使用 Indy 的IOHandler
。 - Remy Lebeau