On Fri, 23 Jul 2010 16:03:16 -0500 Denis Kenzior <[email protected]> wrote:
> Hi Kristen, > > On 07/23/2010 03:52 PM, Kristen Carlson Accardi wrote: > > On Fri, 23 Jul 2010 15:03:59 -0500 > > Denis Kenzior <[email protected]> wrote: > >> > >> This also brings up another point. You're assuming that the caller is > >> appending the CLUT right after the image data and massaging the clut > >> offset appropriately. This is a really bad idea since the caller will > >> have to do some significant pre-processing. > >> > >> You can handle this in one of two ways: > >> > >> 1. Assume the calling logic will read the entire image file before > >> calling this function. In this case, modifying the signature as follows > >> might be a good idea: > >> > >> char *stk_image_to_xpm(const unsigned char *file, > >> unsigned short file_len, > >> enum stk_img_scheme scheme, > >> unsigned short img_offset, > >> unsigned short img_len); > >> > >> 2. Assume the calling logic is clever and will optimize reading of the > >> file, including peeking into the image header to determine the where the > >> CLUT is located and reading it. In this case you can either reuse the > >> signature from 1 above, or come up with something else. > >> > >> Remember, reading from the SIM is extremely slow, so any and all clever > >> optimization tricks are definitely wanted. > > > > So, is it likely given normal usage that we'll access an image a single > > image at a time, or is it more likely that we'll access a bunch of images > > all at once? It may be better to read an entire image data file (with > > multiple images) and keep it cached if we are likely to immediately > > need the other images. In which case I'd be inclined to just pass > > in the entire data image file and the offset like you have above. If > > we are only likely to use a single image for any given length of time, > > then it seems better to have the caller be smart and pass us the clut. > > The problem is we just don't know, so we have to assume the worst case. > Anything that minimizes the number of reads is a good thing (TM). > > For instance, you might have couple of dozen images from EFimg dispersed > among multiple EFiidf files. Each EFiidf file might be 65K in length, > but EFimg files might only refer to about 10k from all of them. > > It is perfectly OK for EFiidf to contain mostly garbage (e.g. for future > updates, installation of new SIM Toolkit applications on the SIM + > associated image data, etc) So you simply can't assume any sort of > packing or efficient storage use. > > In this case, a clever algorithm that minimizes the number of SIM > fetches is needed. > > Regards, > -Denis If that is the case then I propose we assume a smart algorithm fetched our data for us and change the signature to something like this: unsigned char *stk_image_to_xpm(const unsigned char *image_body, enum stk_image_scheme scheme, unsigned int height, unsigned int width, unsigned int ncolors, const unsigned char *clut); We would assume that the caller has done all the sanity checking on the file and handed us a clut of appropriate size as well. _______________________________________________ ofono mailing list [email protected] http://lists.ofono.org/listinfo/ofono
