LARGE_INTEGER value gets changed while marshalling : from LARGE_INTEGER to UINT64 (C) to C#'s uint64

Question

I try to marshal NdisGetCurrentSystemTime result to a C# program via ioctl.

LARGE_INTEGER data;
NdisGetCurrentSystemTime (&data );
marshal_data->time = (UINT64)(data.QuadPart / 10^6);
    DBGPRINT(("Time: %64u", marshal_data->time));

At C# receiver side, the time field is defined as uint64; there's also a couple of other uint64 fields in the marshalled structure. However, when doing

    String.Format(("Time was {0}", recv_data->time)) 

I get unexpectedly large number that differs from the one in DBGPRINT.

C#:

    [StructLayout(LayoutKind.Sequential)]
    ...
    public UInt64 time

C:

    struct _marshalme {
    ... 
    UINT64 time
    ...
    }

Is there anything going weird with a byte order?

Answer 1

LARGE_INTEGER represents a 64-bit signed integer . I expect your problems come from using UInt64 instead of Int64 .

Answer 2

The problem was mainly in improper struct alignment thus different size; but for some reason, it seems to keep damaging data at transfer (eg last DBGPRINT prints saved value correctly) for int32, int64 cases even when size is same; I've been forced to use

  long startTime;
  long padding;

to receive proper value as C#'s long, other ways of marshalling that value failed. Will post more completed sample later, unless that - the question is closed.