Re: [Boost-users] a question on correct way to assign using scoped_array

31 Dec 2004

      Adam Peterson wrote:
...
Essentially, I'm passing a function a scoped_array and I want to
assign data to it.  It seems like there isn't a way to copy a chunk
of data to the scoped_array except when it is created.  Functionaly
I'm where I want to be, but I'm thinking I must be misunderstanding
the correct way to do this.  I'm getting the data from a DLL that
allocates its own memory, so I have to copy the data locally, then
call the DLL's function to release the memory.  Is this the best way
to accomplish what I'm after?
It seems to me that you've missed scoped_array::reset:
...
scoped_array<APPRIGHTITEM> saTemp ( sap );
saGroups.swap( saTemp );
is exactly what saGroups.reset( sap ) would do.

You could also return a shared_array to avoid the local copy:

shared_array<APPRIGHTITEM> blah( ... )
{
    LPAPPRIGHTITEM  lp = NULL;
    DWORD dw = 0;

    get_my_data( &lp, &dw );

    if( lp )
    {
        return shared_array<APPRIGHTITEM>( lp, FreeList );
    }
    else
    {
        return shared_array<APPRIGHTITEM>();
    }
}

Depending on how get_my_data and FreeList are specified, you may not need 
the if. This approach also makes the code exception-safe; the original seems 
to leak the list when new throws.

And of course if you needed the item count, you would've returned a 
std::vector. :-)

Re: [Boost-users] a question on correct way to assign using scoped_array

Peter Dimov