data conversion from a "C" struct

[Dale Gillilan]

I'm interfacing to a SDK that uses "C" structs and DLL's. Everything is going well, except I'm having trouble with one data element in a struct. It is:

char time[3]

I've tried converting this to

time asciiz *3

but, it gives me garbage. I've tried other formats, too, such as byte. All to no avail. Can someone tell me the proper conversion for this piece of data?

Thanks,
Dale

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[Neil Bertz]

Have you tried time as string * 3?


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Neil Bertz
[email protected]
PowerBASIC Staff

[Dale Gillilan]

Thanks, Neil, but it didn't work.

I did find out that each char holds a different time unit: hours, minutes, seconds.

So, I did a lot of experimenting. I am able to get good data if I use bytes, instead of asciiz or string, integer, etc.

However, I can only get the minutes and seconds. Hours are no where to be found.... Any ideas why, or what to do about it?

Thanks,
dale

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[Lance Edmonds]

What did your UDT look like, then?

I would image it must look like this:

TYPE udttypename
  ...
  hms AS BYTE(1 TO 3) ' or may be smh (reverse order)
  ...

or maybe:

  ...
  h AS BYTE
  m AS BYTE
  s AS BYTE
  ...

If this does not help, please post some of the C code that uses these member items.

Thanks!

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Torsten Rienow]

char time[3] and some logic.

If you get s and m but not h from a char time[3] then it seems,
that the c++ source defaults "char = single byte" to
"wchar = double byte".

that means, you should try to pass a buffer of 6 bytes.
this buffer might look

Type TimeType WORD 'word means align to 2 bytes
    h as byte
    m as byte
    s as byte
End Type
 
'or
 
'Dim m_Time(0 to 5) as WORD ' error due coffee underrun
Dim m_Time(0 to 5) as BYTE ' would match correct
Function ProcessTimeStruct(timeStruct as WORD PTR, Byref h as WORD, Byref m as WORD, Byref s as Word) as LONG
    
    h = timeStruct[0]
    m = timeStruct[1]
    s = timeStruct[2]
    
End Function

Function MAIN
    Dim h as Word, m as Word, s as Word
    Call YourCPPFunction(m_Time_By_Ref_OR_Ptr_To_m_Time_Byal)
    Call ProcessTimeStruct(m_Time, h,  m, s)
End Function

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[This message has been edited by Torsten Rienow (edited December 07, 2001).]

[Lance Edmonds]

Good thinking Torsten! I think you may have nailed it.

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Tom Hanlin]

I've never seen "char" mutate away from byte-size. "CHAR", maybe, but
"CHAR" is not "char". It may be that the problem is due to an alignment
error. Perhaps you could post the original struct?


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Tom Hanlin
PowerBASIC Staff

[Dale Gillilan]

I suspect it is an alignment issue, but I haven't been able to trace it down. When I use the bytes as I mentioned the following data is valid, ONLY if I use just 2 bytes (minutes and seconds).

Here are the original structs in c. As you can see, it is multi-layered:

	typedef struct {					// intraday update - sale message
		char	time[3];
		char	format;
		long	seq;					// unique seq # of this trade
		long	value;
		long	volume;
		char	saleCode;				// a code defining the type of sale
	} SALE_UPDATE;
	
	typedef struct {					// intraday update - quote message					
		char	time[3];
		char	format;
		long	seq;					// unique seq # of this quote
		long	bid;
		long	ask;
		USHORT	bidSize;
		USHORT	askSize;
	} QUOTE_UPDATE;
	
	typedef	struct {					
		UCHAR	error;					
		UCHAR	recordType;
		char	flag;					// see below
		char	msgType;				// 0=trade  1=quote
		union	{							
			SALE_UPDATE		sale;
			QUOTE_UPDATE	quote;
		} m;
	} INTRADAY_UPDATE;


/*		the flag will denote the type of data.  there are 3 possibilities:
		0 is for a regular msg, 1 is for a cancellation of a previous msg.
		the msg to be cancelled is the one with the same sequence # that is in
		this msg.  2 is for a correction - replace the msg with the seq #
		that is sent with this msg with the data in this msg (new volume & last)

		not all fields are defined for each record type:
		the following are the valid fields per type of record

		for Sale (a trade):

		type		time	format	seq		value	volume	saleCode
		----		-----	------	-----	-----	----	--------

  0		stock		Yes		Yes		Yes		Yes		Yes		Yes		
  1		index		Yes		Yes		Yes		Yes		No		No	
  2		option		Yes		Yes		Yes		Yes		Yes		No	
  3		reg stock	Yes		Yes		Yes		Yes		Yes		Yes	
  4		mkt stat	Yes		Yes		Yes		Yes		No		No	
  5		future		Yes		Yes		Yes		Yes		Yes		No
  

	time = <hour> <minute> <second>
	saleCode = trade code - usually a blank  - see file stockCodes.stcd
	
//		now define the overall myTrack msg that will come back from the server


	typedef struct {
		short	messageCode;			// defines what type of message this is
		short	spare;
		int		rqn;					// the turn around data 
		union	{
			ERROR_REPORT		errorReport;
			LOGON_RESPONSE		logonResponse;
			LOGOFF_RESPONSE		logoffResponse;
			     <snip -- there are many more structs to this union>
			INTRADAY_UPDATE		tick;
  			     <snip>
			BROKER_ACCT_ORDER       brokerOrder;
                        BROKER_ACCT_CASH_TRANSACTION brokerCashTransaction; // MSG_BROKER_CASH_TRANSACTION 
			BROKER_ERROR_MESSAGE	errorMessage;	// MSG_BROKER_ERROR_MESSAGE
		} u;
	} MYTRACK_MSG;

I converted this into the following PB code:

TYPE SALE_UPDATE
   time(2) AS BYTE             ' can only use 2 bytes, or following
                               ' fields are out of sequence (min & sec)
   format AS BYTE   
   seq AS LONG
   value AS LONG           ' should be byte? Works this way
   volume AS LONG          ' should be byte? Works this way
   saleCode AS ASCIIZ *1
END TYPE

TYPE QUOTE_UPDATE
   time AS ASCIIZ *3
   format AS ASCIIZ *1
   seq AS LONG
   bid AS LONG
   ask AS LONG
   bidSize AS WORD      ' should be dword?
   askSize AS WORD      ' should be dword?
END TYPE

UNION update
   sale AS SALE_UPDATE
   quote AS QUOTE_UPDATE
END UNION

TYPE INTRADAY_UPDATE
   terror AS BYTE
   recordType AS BYTE
   flag AS BYTE 
   msgType AS BYTE               ' 0 = trade; 1 = quote
   m AS update
END TYPE ' INTRADAY_UPDATE


UNION response
   errorReport AS ERROR_REPORT
   logonResponse AS LOGON_RESPONSE
       <snip>
   tick AS INTRADAY_UPDATE
       <snip>
   errorMessage AS BROKER_ERROR_MESSAGE
END UNION   ' response

   '       now define the overall myTrack msg that will come back from the server
TYPE MYTRACK_MSG
   messageCode AS INTEGER
   spare AS INTEGER
   rqn AS LONG
   resp AS response
END TYPE ' MYTRACK_MSG

I included all the struct/type layers in case I made a translation error somewhere earlier in the heirarchy. When I look at data in the higher levels, it seems to check out.

Thanks for your help.
Dale

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[Lance Edmonds]

Originally posted by Dale Gillilan:
Here are the original structs in c. As you can see, it is multi-layered:

typedef struct {					// intraday update - sale message
	char	time[3];
	char	format;
	long	seq;					// unique seq # of this trade
	long	value;
	long	volume;
	char	saleCode;				// a code defining the type of sale
} SALE_UPDATE;
	
<snip>
TYPE SALE_UPDATE
   time(2) AS BYTE             ' can only use 2 bytes, or following
                               ' fields are out of sequence (min & sec)
   format AS BYTE   
   seq AS LONG
   value AS LONG           ' should be byte? Works this way
   volume AS LONG          ' should be byte? Works this way
   saleCode AS ASCIIZ *1
END TYPE

I note that in the C code, the 1st 2 elements add up to 4 bytes, so I think your original declaration is the best approximation:

TYPE SALE_UPDATE BYTE
   btime(1 TO 3) AS BYTE        
   format AS BYTE   
   seq AS LONG
   value AS LONG           
   volume AS LONG          
   saleCode AS ASCIIZ *1
END TYPE

If this does not work, exactly how are the members following "btime" becoming de-synchronized?

Note that the member btime(1 TO 3) AS BYTE creates a member array of btime(1), btime(2), and btime(3).

However, in your declaration btime(2) AS BYTE there are still 3 subscripts in that member array: btime(0), btime(1) and btime(2).

IOW, maybe your translation is ok, but you are missing the 1st subscript whose index is zero?

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Tom Hanlin]

   saleCode AS BYTE

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Tom Hanlin
PowerBASIC Staff

[Dale Gillilan]

Well, I am embarrassed!

It seems that bugs are always in the simple things.... For some reason beyond explanation I had failed to look at byte 0 of the array (time)! I looked there and, lo and behold, there was the hour! And, I know that arrays normally start at 0, too..... oops!

Tom, I haven't looked at the salecode yet. I'll check into that.

Thanks, again, guys! Another pair of eyes helps us see through our blind spots.

Dale

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