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

From: Boris (boriss_at_[hidden])
Date: 2008-03-18 18:13:11

On Tue, 18 Mar 2008 21:23:39 +0100, Ion Gaztañaga <igaztanaga_at_[hidden]>  
wrote:

> 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.

Can I use find_or_construct<> also with the shared_memory_object? It seems  
like I must use managed memory segments then?

Boris