Re: problem in c++ Translation
Farsad wrote:
I have this code in c++ :
[snipped horrible and partially broken C++ code]
and need to translate this in vb.net 2005. I do this but have some
problem. my translation is:
[...]
Declare Auto Function prGetDeviceList Lib "PRSDK.dll" Alias
"PR_GetDeviceList" (ByRef pBufferSize As System.UInt32, ByRef pDeviceList
As prDeviceList) As Integer
This might be a problem already if C++ name mangling is used.
Dim pBufferSize As System.UInt32
Dim pSourceInfo As New PSReCWrap.prDeviceInfoTable
Dim pDeviceList As PSReCWrap.prDeviceList
pDeviceList = Nothing
pBufferSize = Marshal.SizeOf(pDeviceList) +
(Marshal.SizeOf(pSourceInfo) * 10)
(Line1:) pGetDevList = (prDeviceList*)new prUInt8[BufferSize];
(Line2:) PSReCWrap.prGetDeviceList(pBufferSize, pDeviceList)
I have problem in Line1. are you know what is translated code of this
line.
It would be best to delete and forget about this line, it manages to break
two C++ coding guidelines and further invoke undefined behaviour. You
should never use C style casts in C++ and this particular case is even more
broken. However, let's stop the ranting here...
Now, what the code does is to create an structure who's last member is an
array of unspecified length. C++ normally doesn't allow this, so this code
relies on nonportable, platform-specific behaviour. Anyhow, in order to do
the equivalent in VB, you will either have to resort to low-level decoding
of the binary layout or you write a sensible wrapper in C or C++ and then
use that from VB. I'm pretty sure that simply declaring an equivalent
structure in VB will not create one with the exact same binary layout which
would be required for interaction.
Suggestion for the C[++] interface:
// create array and fill it
open()
// number of entries in the array
integer count()
// read a single entry from the array
// pass arguments by reference with types like prDeviceInfoTable
get( integer index, string& internal_name, string& model_name, ...)
// discard array
close()
This shouldn't be too difficult to implement in C++ and presents an
interface that is also easy to use from VB. It isn't that beautiful because
it will need static data but it can do the job.
Uli