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

Subject: Re: [boost] [shared_array] Why not in C++11 ?
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2013-07-07 23:27:18

On Monday 08 July 2013 07:22:53 you wrote:
> On Sunday 07 July 2013 21:38:08 Sid Sacek wrote:
> > 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.
> 
> Why not simply use vector or shared_ptr< vector<...> >?

...or even shared_ptr< array<...> >?