Re: [boost] [boost::endian] Request for comments/interest

Subject: Re: [boost] [boost::endian] Request for comments/interest
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-06-03 10:56:53

Terry Golubiewski wrote:
> Robert Stewart wrote:
> > Terry Golubiewski wrote:
> > > Robert Stewart wrote:
> > > > Terry Golubiewski wrote:
>
> >> I could make it more helpful; but then it would be called
> >> swap_in_place and would be implemented just like Tomas'!
> >
> > Yours would still be in terms of the endian types.
>
> What inteface would you suggest?

One that takes the raw pointer directly to avoid the reinterpret_cast in user code.

> >> >> --- typed based ---
> >> >>   for (int trial=0; trial != 1000; ++trial) {
> >> >>     {
> >> >>       ifstream input("array.dat", ios::binary);
> >> >>       input.read(reinterpret_cast<char*>(&tmp_array),
> >> >> sizeof(tmp_array));
> >> >>       interface::copy(tmp_array.begin(), tmp_array.end(),
> >> >> array2.begin());
> >> >
> >> > Does this actually swap anything?  Doesn't this just copy
> >> > the data to unswapped objects that *would* swap on access?
> >> > That's hardly a fair comparison.
> >>
> >> array2 is just a plain array<uint32_t, SIZE>.  tmp_array is an
> >> array<endian<big, uint32_t>, SIZE>.  So the conversion/copy
> >> happens in interface::copy.
> >
> > I don't think that's right.  The copy is done in
> > interface::copy(), but the conversion (swap) doesn't occur
> > until you read from the endian objects, right?
>
> Not right. The conversion happens inside of interface::copy which is
> performing a swap-in-place in this example.  After the call to
> interface::copy, array2 is in native-endian format.

OK, I misunderstood what you were doing in interface::copy().

_____
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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