Re: [boost] [shared_array] Why not in C++11 ?

Subject: Re: [boost] [shared_array] Why not in C++11 ?
From: Sid Sacek (ssacek_at_[hidden])
Date: 2013-07-07 21:38:08

Peter Dimov wrote:
> > > > Once C++14 becomes an official standard, it'd become possible for
> > > > N3640 to be discussed and, hopefully, accepted;
> > >
> >
> > I then tried to get the buffer length (in code) but hit a brick wall.
> >
> >	int len = buffer.length;     // doesn't exist
> >	int len = buffer.length();   // doesn't exist
> >	int len = buffer.capacity;   // doesn't exist
> >	int len = buffer.capacity(); // doesn't exist
> >	int len = buffer.size;       // doesn't exist
> >	int len = buffer.size();     // doesn't exist
> >
>
> I thought about it a little, and I guess I could write a wrapper class around shared_ptr<> to provide buffering features.
>
> class shared_buffer : public shared_ptr< unsigned char [] > {
>	size_t capacity;
>	...
> }

I can't stop thinking about this.  What would be the harm in providing a 'capacity()' member ?

        buffer = boost::make_shared< unsigned char[] >( 1234 );

        int capacity = buffer.capacity();

It can be designed such that that no matter how the new 'shared_ptr<T[]>' object is instantiated, the size of the array is always known, and hence the capacity should always be available.

I don't know how big of a change this is to the existing classes, but it could be made into a requirement. And even if it could not be made a requirement, buffers with unknown sizes would simply return -1.  That means that coders who care about the capacity() would supply it in their code, and those who don't care would use the classes in the old fashioned way.
-Sid