Re: [Boost-users] [interprocess] shared_memory_object opened or created?

From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2008-03-18 16:23:39

Boris wrote:
> If I instantiate a shared_memory_object with open_or_create how do I know  
> if it was opened or created? I ask as if it was created I need to create a  
> structure in the mapped region. If it was opened though I must not create  
> a structure (as another program created the structure before and I might  
> overwrite data).
> 
> I ran into this problem after creating a reader and writer. They exchange  
> data using a shared_memory_object. It would be great if I could start the  
> two programs in any order. But currently the programs don't know which one  
> created and which one opened the shared memory. Do I miss anything or was  
> open_or_create added for another use case?
> 
> Boris

Since you must create an object to share between both, use 
find_or_construct<> on both processes (supposing both have enough 
information to create the shared structure) before doing anything. If 
the object is already created, the function will return a pointer to the 
already created structure.

Regards,

Ion