"Nick Schultz" <>
Thu, 3 Jul 2008 11:44:34 -0700
Thanks joe, is this called serialization?

also, while I still understand your example, memcpy is defined as:

    void * memcpy ( void * destination, const void * source, size_t num );

"Joseph M. Newcomer" <> wrote in message

See below...
On Thu, 3 Jul 2008 09:50:06 -0700, "Nick Schultz" <>

so i have classes A and B with the following definitions:

class A{
   unsigned char m_priority;
   std::vector<char> m_data;
   std::vector<B> m_rawPackets;

Absolutely not. std::vector puts the actual contents somewhere else, so
what the
receiving process would get is
[P] [yyyy] [zzzz]

where [P] is m_priority, [yyyy] is a pointer to the vector contents, and
[zzzz] is a
pointer to the vector contents. I would do this as I described earlier:

class A {
    DWORD m_len; // total length of this structure
    BYTE m_priority;
    DWORD m_data;
    DWORD m_packets;
    BYTE info[1];

where m_data is the offset into the data array where the assembled data is
(typically 0) and m_packets is the offset into the data array where the
raw packets are
found. THus, what I would send is

where LLLL is the total length of the structure, which is
sizeof(A) + data.size + rawPackets.size * sizeof(B);

Assuming you have std::vector<BYTE>m_data and std::vector<B> rawpackets,
you would do

(using char instead of BYTE is often an error; for raw data use BYTE
unless the values are
8-bit signed values; you will have fewer errors)

A * ptr = (A*)new BYTE[sizeof(A) + data.size + rawPackets.size *

then you would do

memcpy(A->info, data.size, data.whatever());

(I forget the method of std::vector that gives you the address of the
elements, you;ll
have to see what is used for 'whatever')

A->m_data = 0;
A->m_packets = data.size;
memcpy(&A->info[A-m_packets], sizeof(B)*rawPackets.size,

Now THIS you can send with WM_COPYDATA!

class B{
   long m_id;
   unsigned int m_flags;
   unsigned char m_data[8];
   unsigned long m_time;

Would I be able to send an instance of class A from process 1 to process 2
using WM_COPYDATA, by simply filling the COPYDATASTRUCT in process 1, copy
the struct to local memory in process 2, and cast COPYDATASTRUCT.lpData as
class A?

Is that how I would do it? or would having a vector complicate things?


"Joseph M. Newcomer" <> wrote in message

Certainly NOT the clipboard. It doesn't really matter. But a copy is
made, temporarily
mapped into the recipient's address space, and deleted when you return
from handling the
CopyData call.

On Thu, 3 Jul 2008 10:26:48 +0200, Kerem G?mr?kc?

Hi Doug,

Yes, a copy will be made to memory the target process can read. If you
to avoid this, use memory mapped files.

thanks for your answer. One more Question: Where is the copy
holdet, in Clipboard or some other locked memory?



Joseph M. Newcomer [MVP]
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Joseph M. Newcomer [MVP]
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