[sane-devel] [RFC][PATCH] sanei configuration framework extension

[m. allan noah]

On Mon, Jun 23, 2008 at 3:36 PM, stef <stef.dev at free.fr> wrote:
> Le Thursday 19 June 2008 15:36:59 m. allan noah, vous avez écrit :
>> pretty good, but i have two comments:
>>
>> 1. i think calling the struct SANE_Config instead of something with
>> sanei in it, makes it look too much like something that should be in
>> the SANE standard, instead of the internal-use function that it is.
>>
>> 2. some backends seem to have dozens of options, that struct is going
>> to become quite large if it is extending to hold everything. does it
>> instead make more sense for the callback to be run for each line
>> extracted from the file, with a flag indicating that it was an option
>> instead of an attach line?
>>
>> allan
>>
>
>        Hello,
>
>        here's a new take at config option parsing. The struct is now called
> SANEI_Config, and holds an array of SANE_Option_Descriptor and an array of
> placeholder for the values of the options.

brilliant. enables us to reuse lots of code, and keep a familiar
interface. bravo.

> To parse options, a backend first
> creates a list of the options it wants using SANE_Option_Descriptor.

great.

> Then it calls sanei_configure_initialize() which creates the placeholders.
>        When the SANEI_Config is ready, the backend calls sanei_configure_attach()
> which opens the configuration, parse it according to the given descriptors.
> Whenever a line no recognized as an option is met, the
> sanei_configure_attach() calls the backend provided (*attach)(SANEI_Config *,
> char *devname) attach function. This backend specific function calls the
> usb/scsi/parport attach functions allready provided by sanei library. As a
> parameter it has the currently parsed options in the config struct and so may
> use them during the attach. A sanei_configure_get_value() helper is given to
> access the values of the options.
>        Once parsing is done, there is a sanei_configure_dispose() function to
> release allocated ressources.

i would rather that the backend provided the placeholder memory if
possible, for two reasons: 1. to keep all the memory allocations in
one place, 2. so that the placeholders can be pre-loaded with default
values by the backend.

>        By doing this way, configuration is parsed only with the options the backend
> needs. The existing sanei_check_value() may be reused to check if constraints
> are respected.  Only a couple options that need a complex syntax couldn't be
> handled right now (such as 'calibrate /path/name port' from canon_pp) but
> could be handled by a SANE_TYPE_STRING_LIST to be created.
>
>        The appended patch currently only manage SANE_TYPE_STRING options and as been
> tested with a modified rts8891 backend.

this sounds quite good- thank you very much for taking on the task!

allan
-- 
"The truth is an offense, but not a sin"