Re: [pdf-devel] Some thoughts on the time module...

[Aleksander Morgado]

>    > Could you specify which are the functions needed? The time module is the
>    > right place to put them.
>
>    We'll need something that will take the two DWORDS that windows uses (a high and 
>    a low) and return a pdf_time_t.

That's probably easy to do.

First we must convert file-time to system-time, changing the timescale:
http://msdn.microsoft.com/en-us/library/ms724228(VS.85).aspx

In this way we get a time_t (Unix time).


>    For the UNIX time, is time_t equivalent to pdf_time_t? If so, then nothing is 
>    needed there, but if they're not then we need something that'll take a time_t 
>    and return a pdf_time_t.

They are equivalent internally, but the pdf_time_t must be used as an 
opaque type. The simplest option would be to use a span to set up the 
seconds since unix timescale origin, and add it to a newly created 
pdf_time_t:

pdf_time_t newtime = pdf_time_new();
pdf_time_span_t newspan = pdf_time_span_new();

/* This will work until 2038... */
pdf_time_span_set_from_i32(&newspan, (pdf_i32_t)time_t);

/* Or using pdf_time_span_set() to set the high dword and
 * the low dword) */

/* And finally set the correct date */
pdf_time_add_span(newtime, newspan);



> Both functions can be implemented in the pdf_time module.

Yes, maybe could be easier to directly update the API with two new 
functions, both passing as argument the number of seconds since unix 
timescale origin:

pdf_time_set_from_i32(pdf_time_t time_object,
                      pdf_i32_t seconds);

pdf_time_set(pdf_time_t time_object, \
             pdf_i32_t high, pdf_u32_t low);

Plus maybe an additional one to be used in Windows, which involves also 
the timescale change (filetime to systime):
pdf_time_set_from_filetime(pdf_time_t time_object, \
                           pdf_i32_t high, pdf_u32_t low);

Cheers,
-Aleksander