PInvoke and Unmanaged DLL calls

[Joe Martin]

Has anyone made use of PKWare's PKCDL.DLL for the Implode and Explode
functions?

I have been able to successfully define everything correctly and even
get the invoked function (Explode) to run properly. This means data is
being exploded properly, confirmed with CRC values and reviewing the
actual data.

However just before the unmanaged function exits, I get a null exception
error. I am using:

ReadHandler rh = new ReadHandler(thi s.ReadData);
WriteHandler wh = new WriteHandler(th is.WriteData);

IntPtr buffer = Marshal.AllocHG lobal(bufferSiz e)
try {
object data = this;

// Invoke DLL here...
PkCdl.Explode(r h, wh, buffer, ref data);

} finally {
Marshal.FreeHGl obal(buffer);
}

to allocate the needed buffer for the DLL. In the corresponding
ReadData/WriteData callback methods, I use the Marshal.Copy() methods to
move data in/out of managed memory.

Now somewhere along the way an the exception happens inside the
try..finally (shown above).

If this rings a bell with anyone, I will gladly supply complete sample
code and would be more than interested in hearing your thoughts.
Thanks,
Joe Martin

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[Ravichandran J.V.]

Is intptr buffer= statement getting any reference ?

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[Willy Denoyette [MVP]]

We are getting closer....
How are PKCALLBACK and PKCALL defined (typedef PKCALL ....), these are
defining the calling convention used.
And the "void* param" is still a mistery to me, you pass it a ref to managed
instance of a class, but this is something that the function is not
expecting for sure.
Worse, it's a reference pointer so the caller can change the reference at
will brrrr....
I suggest you to look at a C sample using that function, and see what get's
passed as param here
Willy.

"Joe Martin" <an*******@devd ex.com> wrote in message
news:uD******** ******@TK2MSFTN GP11.phx.gbl...

Sure, here you go:
typedef unsigned int(PKCALLBACK * PKReadBuf)(void * buf, unsigned int
size, void* param)

Read buffer call back function definition.
Parameters:
buf Pointer the buffer to fill with data
size The amount of data to read
param User specified call back pointer.

Returns:
The actual amount of data read, must be less than or equal to size.

typedef void(PKCALLBACK * PKWriteBuf)(con st void* buf, unsigned int
size, void* param)

Write buffer call back function definition.
Parameters:
buf Pointer to the buffer containing the data to write
size The size of the buffer
param User specified call back pointer.


//----------------------------------

PKCDL_DECL unsigned int PKCALL pkexplode (
PKReadBuf read_buf,
PKWriteBuf write_buf,
void * work_buf,
void * param
)

Function to decompress data using the DCL implode algorithm.
Parameters:
read_buf Pointer to read buffer function.
write_buf Pointer to the write buffer function.
work_buf Pointer to the working buffer.

Returns:
Returns the error code for the function.
See also:
ERROR_CODES for possible return values

//----------------------------
Hope this helps...
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