Receiving TBytes

[EugeneK 19]

Hi

 

We now have method to sending TBytes in socket, can we have the same for receiving?

[aehimself 396]

var
  buffer: TBytes;
  read: Integer;
Begin
  [...]
  read := Self.Receive(@buffer[0], Length(buffer));

 

[Fr0sT.Brutal 900]

Any example when it could be useful?

[Angus Robertson 574]

From the notes for ICS V8.70 TWSocket:

 

Added ReceiveTB(var Data : TBytes; MaxLen : Integer = -1) : Integer; where MaxLen is optional, to receive TCP data into a TBytes dynamic array of bytes. Also ReceiveFromTB and ReceiveFrom6TB for UDP datagrams.

 

Receiving into a fixed size buffer is more slightly more efficient, but TBytes has more RTL support for converting to strings, etc.  ReceiveTB will resize the variable up to MaxLen. 

 

The new functions are used in the OverbyteIcsIpStreamLog unit which how they were tested.

 

Angus

 

 

 

 

[Fr0sT.Brutal 900]

@TC

Just remember the streamed data could be broken into different TCP packets at literally any place. So even converting a chunk to a string is not reliable unless you use 1-byte encodings (no, UTF-8 is not one of them). Otherwise you must use some kind of concatenating buffer/stream which makes TBytes application useless

Edited February 1, 2023 by Fr0sT.Brutal

[aehimself 396]

9 minutes ago, Fr0sT.Brutal said:

Otherwise you must use some kind of concatenating buffer/stream

I wrote my helper class for this purpose, it can be used and abused as one feels like it:

Maybe it worth to revisit that code, I don't remember what lurks within it's lines.

[Angus Robertson 574]

Indeed, the OverbyteIcsIpStreamLog unit builds text lines by parsing a TByte buffer one character at a time.  But many quick and dirty programs accept that TCP sends full packets, like my new WebSocket sample. 

 

The other advantage of TByte is avoidance of pointer handling, all those @ and ^ symbols that really have no place in modern applications since they can be abused so easily.  Ditto the Move function.  ICS simply offers alternatives, choose the easiest to use.

 

Angus 

[EugeneK 19]

Hi

 

Can we also have function that returns TBytes? It is more convenient in many cases

[Angus Robertson 574]

Quote

Can we also have function that returns TBytes? It is more convenient in many cases

This will be in SVN next week, seems simpler but needs an extra line of code to check the TBytes length.

 

Angus

[EugeneK 19]

Hi

 

I wonder what is the need for MaxLen parameter? There is no such logic in ReceiveStr functions, if there is more data than MaxLen is it discarded or you can receive it in next call?

[Angus Robertson 574]

While ReceiveStr may not have MaxLen, other similar functions do, so it's backward compatible.  Since it is defaulted, you can ignore it.

 

Angus