What on earth am I doing wrong??

EvilNoodle · Post by **EvilNoodle** » Sat Jun 06, 2009 6:12 pm

Hi,

I am trying to write some network code but to do that I need to be able to construct my packets.

I wrote the code below to push into a message...

The type of the message as a byte
The length of the message content as a long
The message as a string

and read it back out again to make sure I didn't suffer from garbage in garbage out.

Code: Select all

Debug("===> Setting up message data...")
messageType.b = 1
message.s = "Test Message :)"
messageLength.l = Len(message)

Debug("===> Printing source message data...")
Debug("")
Debug("--- Source Message Begins ---")
Debug("Message type : " + Str(messageType))
Debug("Message length : " + Str(messageLength))
Debug("Message : " + message)
Debug("--- Source Message Ends---")
Debug("")

Debug("===> Allocating memory block (size = " + Str((5 + messageLength)) + ")...")

;Allocate 1 byte for the type (byte), 4 for the length (long) and the length of the message string
*packet = AllocateMemory(5 + messageLength)

Debug("===> Writing message to memory block...")
PokeB(*packet, messageType)
PokeL(*packet, messageLength)
PokeS(*packet, message)

Debug("===> Extracting message from memory block...")
msgType.b = PeekB(*packet)
msgLen.l = PeekL(*packet)
msg.s = PeekS(*packet)

Debug("===> Printing extracted message data...")
Debug("")
Debug("--- Extracted Message Begins ---")
Debug("Message type : " + Str(msgType))
Debug("Message length : " + Str(msgLen))
Debug("Message : " + msg)
Debug("--- Extracted Message Ends ---")
Debug("")

Is this code correct or am I being really really really stupid because instead of getting the values I expect out...

Message type : 1
Message length : 15
Message : Test Message :)

What I actually get is

Message type : 84
Message length : 1953719636
Message : Test Message :)

Here is the full output...

Code: Select all

===> Setting up message data...
===> Printing source message data...

--- Source Message Begins ---
Message type : 1
Message length : 15
Message : Test Message :)
--- Source Message Ends---

===> Allocating memory block (size = 20)...
===> Writing message to memory block...
===> Extracting message from memory block...
===> Printing extracted message data...

--- Extracted Message Begins ---
Message type : 84
Message length : 1953719636
Message : Test Message :)
--- Extracted Message Ends ---

This is driving me nuts and my only conclusion can be that I am doing something fundamentally wrong here. Any help would be greatly appreciated.

Noodle

maw · Post by **maw** » Sat Jun 06, 2009 6:23 pm

Oh dear, oh dear.. You're going to hit yourself over the head for this

Your are actually writing, and reading, the byte, long and string at the same memory address! You need to increase the pointer for each read and write!

Code: Select all

PokeB(*packet, messageType)
PokeL(*packet + 1, messageLength)
PokeS(*packet + 5, message)

Code: Select all

msgType.b = PeekB(*packet)
msgLen.l = PeekL(*packet + 1)
msg.s = PeekS(*packet + 5)

EvilNoodle · Post by **EvilNoodle** » Sat Jun 06, 2009 6:26 pm

Thanks a lot for that. I was recently using a different language that maintaines its own read pointer.

Its woking fine now

netmaestro · Post by **netmaestro** » Sat Jun 06, 2009 6:28 pm

Code: Select all

Structure MESSAGE
  type.b
  length.l
  content.b[0]
EndStructure

Debug("===> Setting up message data...") 
messageType.b = 1 
message.s = "Test Message :)" 
messageLength.l = Len(message) 

Debug("===> Printing source message data...") 
Debug("") 
Debug("--- Source Message Begins ---") 
Debug("Message type : " + Str(messageType)) 
Debug("Message length : " + Str(messageLength)) 
Debug("Message : " + message) 
Debug("--- Source Message Ends---") 
Debug("") 

Debug("===> Allocating memory block (size = " + Str((5 + messageLength)) + ")...") 

;Allocate 1 byte for the type (byte), 4 for the length (long) and the length of the message string 
*packet.MESSAGE = AllocateMemory(5 + messageLength) 

Debug("===> Writing message to memory block...") 

With *packet
  \type = messageType
  \length = messageLength
EndWith

PokeS(@*packet\content, message) 


Debug("===> Extracting message from memory block...") 
msgType.b = *packet\type
msgLen.l = *packet\length 
msg.s = PeekS(@*packet\content) 

Debug("===> Printing extracted message data...") 
Debug("") 
Debug("--- Extracted Message Begins ---") 
Debug("Message type : " + Str(msgType)) 
Debug("Message length : " + Str(msgLen)) 
Debug("Message : " + msg) 
Debug("--- Extracted Message Ends ---") 
Debug("")