Re: [boost] [utility] new auto_buffer class --- RFC

Subject: Re: [boost] [utility] new auto_buffer class --- RFC
From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2009-03-02 13:19:25

Thorsten Ottosen skrev:
> Peter Dimov skrev:

>> The inability to grow also penalizes cases like
>>
>> for # of rows
>>    v.clear()
>>    read number of elements into n
>>    for each element read it into e, v.push_back(e)
>>    process( v.begin(), v.end() )
>>
>> In this case the programmer wants to reuse v between the rows to 
>> minimize the number of heap allocations. But there is no way to know 
>> what the maximum n would end up to be.
> 
> A good points.
> 
> FWIW, stlsoft::auto_buffer is resizeable. It's not that hard to
> add this functionality, though.

I guess your case above should be implemented as

for # of rows
    v.clear();
    v.resize( n );
    for each element read e
       v.push_back_unchecked(e)
    process( v.begin(), v.end() )

where v.resize() should never actually shrink the buffer.
(Do we need another function that does that?), or should we simply
rename v.resize(n) to v.ensure_capacity(n).

But as the example above shows, we do not need a growing push_back()
here. If the name push_back() is problematic, then I'm all for just 
calling it something else. But I don't like adding a growing push_back()
unless we have a use-case.

-Thorsten