"Kenny Riddile" <kfriddile@gmail.com> wrote in message news:idj944$lk7$1@dough.gmane.org...
Yes, implementations of a spec are free to implement their requirements however they like (assuming no other requirements are violated). That being said, I just looked at the implementation of array_source and it appears that none of the data in the array is being copied.
Yes, AFAICT also, the array_source implementation does not copy the input data (in fact, even if the documentation does not state it explicitly, it would IMO be common sense to assume so...as if it did actually copy the data this would constitute a performance bug by any standard)... However, redundant copying is only part of the issue here (in some use cases possibly even a less important one) as boost::iostreams::array_source still uses the std::iostreams infrastructure which means that includes all of its redundant horrors (locales, mutexes, virtual functions, RTTI, dynamic memory allocation, exceptions, transformations......)... Simply looking at/stepping through the release-mode generated assembly for merely the boost::iostreams::stream<array_source> constructor will make most heads dizzy... A proper (and zero overhead at that) way to model an in memory image would be a plain boost::iterator_range<> ... Not only because it is free of all the iostream monstrosities but because with backends like LibJPEG and LibTIFF reading an image from a boost::iterator_range<> can be accomplished without the LibXXX backend making a single seek/read callback (back to the GIL.IO 'device' that is in this case a boost::iterator_range<> or a transparent wrapper around it) because it already has all the data readily available... Additionally with the boost::iterator_range<> approach it is easy to add memory mapped file support for reading images (where the input image/file is again represented with a plain boost::iterator_range<> with all the benefits outlined above)... -- "What Huxley teaches is that in the age of advanced technology, spiritual devastation is more likely to come from an enemy with a smiling face than from one whose countenance exudes suspicion and hate." Neil Postman