Re: [Boost-users] [gil] New format guidelines about custom Device

Subject: Re: [Boost-users] [gil] New format guidelines about custom Device
From: Mateusz Loskot (mateusz_at_[hidden])
Date: 2010-12-22 17:03:33

On 22/12/10 20:01, Christian Henning wrote:
> On Wed, Dec 22, 2010 at 2:36 PM, Mateusz Loskot <mateusz_at_[hidden]> wrote:
>> Hi,
>>
>> I'm implementing new image format support for Boost.GIL
>> based on the new IO implementation which has been
>> reviewed [1] lately.
>>
>> [1] http://lists.boost.org/boost-announce/2010/11/0273.php
>>
>> What would be the guidelines regarding custom Device implementation?
>> Currently, only TIFF format implements it.
>> When it is required to implement custom Device for the IO?
>> When recommended as a good practice?
> 
> Right now, io_new is providing support for FILE*, std::istream, and
> std::ostream. For TIFF I had to add another device type for TIFF*
> since that's the one used in libtiff. All devices are registered using
> c++ metafunctions, like is_output_device<...> and
> is_input_device<...>.
> 
> You would have to add another device if the your one is missing. For
> instance, boost::iostream is not there yet.

OK, so as a simple rule I can take that if a format implementation
library defines it's own file/resource descriptor, then additional
Device is most likely needed.

For instance, if a library manages files like this:

MyFormatFile* OpenMyFormatFile(...);

then device for MyFormatFile should be provided, for convenience.

Thanks!

Regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org
Member of ACCU, http://accu.org