Anybody have opinions on this?
Good idea? Bad idea? You like?
-- lg
On Mar 27, 2012, at 1:10 AM, Larry Gritz wrote:
> In the continuing quest to make create/open more efficient, here are two
> minor API changes:
>
> 1. In almost all uses, an app calls ImageInput::create() to get an II*, then
> immediately calls in->open() to open the file, which, if you think carefully
> about the fact that create() does an open to verify that the II is capable of
> opening the file, means that open() ends up getting called twice. Very
> wasteful. So the first change is that we change the ImageInput::create()
> function prototype to include a do_open flag -- if true, it returns the file
> already opened, not needing a separate call to open(). If false (and this is
> sometimes useful), it behaves as before, returning an ImageInput* that can be
> opened, but is not presently. This also simplifies the source of apps just a
> bit, since the common "create & open" sequence can now be accomplished with
> just a call to create.
>
> 2. To further streamline, we add a new optional method,
> ImageInput::valid_file(filename), which returns true if the named file
> appears to be a valid file of that format (in a way that's less expensive
> than doing a full open and header read -- for example, just checking the
> first few bytes that contain a "magic number" or whatever). Not all plugins
> supply this function, and it's not required; the ones that do must return
> true for supports("valid_file"). I've included implementations for OpenEXR
> and TIFF that are considerably less expensive than a full header read.
>
> The combination of these should reduce a lot of the overhead for identifying
> which type of ImageInput is appropriate for a given file and creating it,
> generally avoiding at least one redundant open and header read for exr and
> tif files.
>
> Note that this is a break in ABI compatibility. It will not be merged into
> 1.0, only master, and so will be a 1.1 feature. I believe that it should be
> source-back-compatible, however.
>
>
>
> You can merge this Pull Request by running:
>
> git pull https://github.com/lgritz/oiio lg-validfile
>
> Or you can view, comment on it, or merge it online at:
>
> https://github.com/OpenImageIO/oiio/pull/265
>
> -- Commit Summary --
>
> * Change ImageInput::create() to allow the caller to request the file to be
> returned already opened.
> * Make OpenImageIO::geterror() return a thread-specific error, so multiple
> threads calling ImageInput::create() can't clobber each other's error
> messages.
> * Add ImageInput::valid_file() and supports("valid_file") -- test whether a
> file is a valid file of that format, cheaper than a full open.
>
> -- File Changes --
>
> M src/doc/imageinput.tex (162)
> M src/doc/imageioapi.tex (3)
> M src/doc/writingplugins.tex (17)
> M src/iconvert/iconvert.cpp (2)
> M src/igrep/igrep.cpp (13)
> M src/iinfo/iinfo.cpp (16)
> M src/include/imageio.h (52)
> M src/libOpenImageIO/imageio.cpp (25)
> M src/libOpenImageIO/imageioplugin.cpp (51)
> M src/libtexture/imagecache.cpp (2)
> M src/oiiotool/printinfo.cpp (13)
> M src/openexr.imageio/exrinput.cpp (20)
> M src/python/py_imageinput.cpp (4)
> M src/tiff.imageio/tiffinput.cpp (34)
>
> -- Patch Links --
>
> https://github.com/OpenImageIO/oiio/pull/265.patch
> https://github.com/OpenImageIO/oiio/pull/265.diff
>
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/OpenImageIO/oiio/pull/265
>
> --
> Larry Gritz
> [email protected]
>
>
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> Oiio-dev mailing list
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--
Larry Gritz
[email protected]
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