Subject: Re: [boost] Interest in a simple buffer abstraction?
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2011-01-28 09:24:39
Boris Kolpackov wrote:
> "Stewart, Robert" <Robert.Stewart_at_[hidden]> writes:
> > > std::vector<char> data_store_;
> > > boost::buffer data_;
> > Why would you have both?
> Because I want the packet to own the data and to be able to access
> it using a natural interface. With your approach I would have to
> write gratuitous code like this.
No you wouldn't. As I showed in the portion of my reply that you cut, if your packet owns its data, then it would have a container of that data. The point of my idea is that you can create a packet type that *doesn't* own the data or even know how the data is stored because the adaptor would abstract the underlying storage type and provide a useful interface permitting the packet to append, copy, etc.
I understand that your idea is for a type that owns the data. I'm proposing an alternative view of the problem.
> > which requires that some other code create a std::vector<char> or
> > other container for the packet to use.
> This goes down the slippery slop of someone else owning the memory
> and making sure it is not gone while other objects still reference
When you want performance, you don't want to copy data. Your model requires that the data be copied. Mine references data allocated elsewhere. As I noted, that does indeed mean that the reference mustn't outlive the allocation, but with that responsibility comes improved performance and greater flexibility.
> If that's the functionality you want, then why bother with the
> buffer class at all? Simply store a pair: const void*, size_t; it
> will be just as convenient.
As I noted (in what you snipped), the adaptor type can still provide the additional functionality you had proposed: appending, copying, etc. You get none of that with such a pair.
When sharing a buffer among libraries, using my suggestion, memory need only be allocated in one place whilst various functions from different libraries can all reference that memory using a type-erased, feature rich, standardized reference to it.
Rob Stewart robert.stewart_at_[hidden]
Software Engineer, Core Software using std::disclaimer;
Susquehanna International Group, LLP http://www.sig.com
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