[Boost-users] using offset_ptr

Subject: [Boost-users] using offset_ptr
From: Rex Battenberg (Rex.Battenberg_at_[hidden])
Date: 2009-04-23 15:03:43

Hi,
I am having trouble using offset_ptr.  I want to dynamically allocate 
memory in windows shared memory and create a point to it so it can be 
used by two different processes.  I figures I would create a named 
object in the shaed memory to contain the pointer to the memmory, but 
when I try it I get a compile error.  Here is the code I have so far.  
Note the the the shared memory is created elsewhere and it is big enough.

    bip::managed_windows_shared_memory* pAldisSharedMemory = new 
bip::managed_windows_shared_memory(bip::open_only, 
ALDIS_SHARED_MEMORY_NAME.c_str());
    if (pAldisSharedMemory)
    {
        bip::offset_ptr<char> pImageData;

//
//  This line causes the following error.  Error    1    error C2440: 
'initializing' : cannot convert from //' 
//boost::interprocess::offset_ptr<PointedType> *' to 'char *'    
//C:\stopbar\3rdParty\boost\include\boost\interprocess\offset_ptr.hpp    
111    AldisHardware
//
        pImageData = 
pAldisSharedMemory->find_or_construct<bip::offset_ptr<char>>("ImageData")();

//        char * *pImageData = 
pAldisSharedMemory->find_or_construct<char *>("ImageData")();

        if (pImageData == NULL)
        {
            //
            // This value will be unuseable by other processes, need to 
use an offset_ptr here, but I have not figured
            // out yet how to make them work.
            //
            pImageData = (char *)pAldisSharedMemory->allocate(1280 * 860 
* 3);
        }

I have really no idea what is wrong or how to do this.  If anybody has 
any examples, that would be great.

Thanks

Rex