Pointer to memory blocks

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3 total messages Started by Ray Thu, 18 Jan 2007 18:04

#113

Author: Ray
Date: Thu, 18 Jan 2007 18:04

31 lines
1763 bytes

Hi

I am trying to transfer data from one application to another by sending a
pointer to a memory block. To test this out I have two applications, a
sender and a receiver. The sender fills an integer buffer and sets a pointer
to its address. Then I send a message via the interop SendMessage();.

I get the message in the Receiver ok and the pointer value received is the
same as the one sent. But when I try to get the data all I get is garbage.

To simplify things both applications are set as an unsafe class;

Send code is

fixed(int* p1=outbuff)
{
    SendMessage(recHandle, msg, (IntPtr)(p1),(IntPtr)(p1));
}

Receive code is

protected override void WndProc(ref Message m)
{
    if(m.Msg==msg)
    {
       int* pptr=(int*)m.WParam.ToPointer();
       for(int i=0;i<100;i++) richTextBox1.AppendText(i+";
"+(*pptr++).ToString()+"\n");
    }
   base.WndProc(ref m);
}

Re: Pointer to memory blocks

#114

Author: Marc Rohloff TeamB
Date: Thu, 18 Jan 2007 19:45

25 lines
1980 bytes

On Thu, 18 Jan 2007 18:04:02 -0000, Ray wrote:

> I am trying to transfer data from one application to another by sending a
> pointer to a memory block. To test this out I have two applications, a
> sender and a receiver. The sender fills an integer buffer and sets a pointer
> to its address. Then I send a message via the interop SendMessage();.
> 
> I get the message in the Receiver ok and the pointer value received is the
> same as the one sent. But when I try to get the data all I get is garbage.

You cannot send memory between applications by just sending a pointer.
Each application addresses its own unique memory space and contents.

You need to use one of:
1) TCP/IP
2) Webservices, remoting, etc.
3) Shared memory, Memory Mapped Files, etc
4) The WM_COPYDATA windows message
5) Real files
6) etc

-- 
Marc Rohloff [TeamB]
marc rohloff -at- myrealbox -dot- com

Re: Pointer to memory blocks

#115

Author: Ray
Date: Fri, 19 Jan 2007 18:45

37 lines
2135 bytes

Thanks Marc

Can you point me in the direction of some info on 3) Shared memory, Memory 
Mapped Files, etc


Ray
"Marc Rohloff [TeamB]" <"on request"> wrote in message 
news:1iwcargjbfba8.dlg@dlg.marcrohloff.com...
> On Thu, 18 Jan 2007 18:04:02 -0000, Ray wrote:
>
>> I am trying to transfer data from one application to another by sending a
>> pointer to a memory block. To test this out I have two applications, a
>> sender and a receiver. The sender fills an integer buffer and sets a 
>> pointer
>> to its address. Then I send a message via the interop SendMessage();.
>>
>> I get the message in the Receiver ok and the pointer value received is 
>> the
>> same as the one sent. But when I try to get the data all I get is 
>> garbage.
>
> You cannot send memory between applications by just sending a pointer.
> Each application addresses its own unique memory space and contents.
>
> You need to use one of:
> 1) TCP/IP
> 2) Webservices, remoting, etc.
> 3) Shared memory, Memory Mapped Files, etc
> 4) The WM_COPYDATA windows message
> 5) Real files
> 6) etc
>
>
> -- 
> Marc Rohloff [TeamB]
> marc rohloff -at- myrealbox -dot- com

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