We basically cast a struct timespec pointer to a time_t pointer when we pass the clock_settime() paramter to localtime(). Explicitly express that in the source code.
The CIA TOD only stores the time but not the date. Therefore the date set by clock_settime() ist just stored inside the C library for retrieval via clock_gettime().
The "very special" handling of 12AM/PM is based on https://groups.google.com/d/msg/comp.sys.cbm/ysVYSX4AMbc/vHrXCWEhCOUJ saying:
==========
24hr: Wr => Rd => Nx
--------------------
0 : 92 => 12 => 01 <= Switch from 00 to 01 (24-hour notation)
1 : 01 => 01 => 02
2 : 02 => 02 => 03
11 : 11 => 11 => 92
12 : 12 => 92 => 81 <= Switch from 12 to 13 (24-hour notation)
13 : 81 => 81 => 82
14 : 82 => 82 => 83
23 : 91 => 91 => 12
1. column ("24hr"): hour to be tested (decimal)
2. column ("Wr"): hour written to TOD register (BCD)
3. column ("Rd"): hour read from TOD register (BCD) immediately after writing the value in column 2 to see the conversion between AM/PM, if any
4. column ("Nx"): next hour (BCD) after the hour switch
==========
Thanks Paul!
We want to add the capability to not only get the time but also set the time, but there's no "setter" for the "getter" time().
The first ones that come into mind are gettimeofday() and settimeofday(). However, they take a struct timezone argument that doesn't make sense - even the man pages says "The use of the timezone structure is obsolete; the tz argument should normally be specified as NULL." And POSIX says "Applications should use the clock_gettime() function instead of the obsolescent gettimeofday() function."
The ...timeofday() functions work with microseconds while the clock_...time() functions work with nanoseconds. Given that we expect our targets to support only 1/10 of seconds the microseconds look preferable at first sight. However, already microseconds require the cc65 data type 'long' so it's not such a relevant difference to nanoseconds. Additionally clock_getres() seems useful.
In order to avoid code duplication clock_gettime() takes over the role of the actual time getter from _systime(). So time() now calls clock_gettime() instead of _systime().
For some reason beyond my understanding _systime() was mentioned in time.h. _systime() worked exactly like e.g. _sysremove() and those _sys...() functions are all considered internal. The only reason I could see would be a performance gain of bypassing the time() wrapper. However, all known _systime() implementations internally called mktime(). And mktime() is implemented in C using an iterative algorithm so I really can't see what would be left to gain here. From that perspective I decided to just remove _systime().
All but one TGI drivers didn't use IRQs. Especially when the TGI driver kernel was the only .interruptor this meant quite some unnecessary overhead because it pulled in the whole IRQ infrastructure.
The one driver using IRQs (the graphics driver for the 160x102x16 mode on the Lynx) now uses a library reference to set up a JMP to its IRQ handler.
All but one joystick drivers didn't use IRQs. Espsecially when the joystick driver kernel was the only .interruptor this meant quite some unnecessary overhead because it pulled in the whole IRQ infrastructure.
I was told that the one driver using IRQs (the DXS/HIT-4 Player joystick driver for the C64) can be reworked to not do it. Until this is done that driver is defunct.
As discussed in https://github.com/cc65/cc65/pull/452 after my premature merge the two functions in question don't work as expected.
Additionally I adjusted several style deviations in the pull request in question.
