CTYPES problems: Need a way to pass through multiple structure

[Marc]

Hi:

Needless to say I have tried this several different ways and can't
find a working solution. Exasperated, I now look for help. This may be
wordy, but I want to make sure I cover all the bases.

I am using CTYPES to integrate with a test box that included C type
DLL's as the interface. This has worked very well for me until this
impass. The interface expects the following format:

Declare Function HTGetStructure Lib "ETSMBW32" (ByVal iType1 As Long,
ByVal   iType2 As Long, ByVal iType3 As Long, ByVal iType4 As Long,
pData As Any, ByVal uiLen As Long, ByVal iHub As Long, ByVal iSlot As
Long, ByVal iPort As Long) As Long

Or more plainly as:

HTGetStructure( STRUCTURE_TYPE, 0, 0, 0, *pointer to Structure Object,
sizeof(Structure), a, b, c);


An example:


class HTCountStructure(Structure):
	_fields_ = [("uiMainLength", "h"),
		    ("ucPreambleByteLength", "B"),
		    ("ucFramesPerCarrier", "B"),
		    ("ulGap", "L")]
count = HTCountStructure()
windll.etsmbw32.HTGetStructure(20505,0,0,0,byref(count),sizeof(count),0,9,0)


The function sizeof() is taken from mxTools. As long as I have
standard variable types it works fine. However, the DLL later defines
a structure as having a special variable length - U64, which uses two
32-bit longs:

typedef struct tagU64 {
	unsigned long	high;
	unsigned long	low;
	} U64;

It then uses the structure in the following way:

typedef struct tagETHExtendedCounterInfo {
	U64				u64RxVLANFrames;
	U64				u64RxIPFrames;		
        U64				u64RxIPChecksumErrors;		
	unsigned long	                ulTxARPReplies;				
	unsigned long	                ulRxARPReplies;		
ETHExtendedCounterInfo;


CTYPES has a signed and unsigned 64 bit variable built in, but neither
one of them worked. It's possible to nest a structure within a
structure in CTYPES, and I performed this in the following way:

class U64(Structure):
	_fields_ = [("high", "L"),
		    ("low", "L")]

class ETHExtCounter(Structure):
	_fields_ = [("u64RxVLANFrames", "U64"),
		    ("u64RxIPFrames", "U64"),
		    ("u64RxIPChecksumErrors", "U64"),
		    ("ulTxARPReplies", "L"),
		    ("ulRxARPReplies", "L")]

count = ETHExtCounter()
windll.etsmbw32.HTGetStructure(20505,0,0,0,byref(count),sizeof(count),0,9,0)
print count.u64RxIPFrames.high
print count.u64RxIPFrames.low


However, I still could not get the values to be returned from the test
box to show up. Am I missing something?

If someone can spot my error I would greatly appreciate it. If not,
then I am open to all theories on ways to go about this another way.
This is something I really need to get working quickly.

Thanks ahead of time,
Marc