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 23:22:53

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<...> >?