Support ProDOS 2.5 extended file dates

[inexorabletash]

ProDOS 2.5 smuggles in a few extra year bits

Add support in the date decode routine, hereabouts: https://github.com/a2stuff/a2d/blob/master/desktop/desktop_main.s#L8223

There may be other places...

[inexorabletash]

Specifically per @JohnMBrooks - "Basic displays extended dates (10-bit year 1940 to 2964) by appending the 3 top bits from the hour byte to the 7-bit year"

So old GET/SET_FILE_INFO, mod/create_date/time and File Entry creation/last_mod fields:

       byte 1            byte 0
  7 6 5 4 3 2 1 0   7 6 5 4 3 2 1 0
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 |    Year     |  Month  |   Day   |
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+

       byte 1            byte 0
  7 6 5 4 3 2 1 0   7 6 5 4 3 2 1 0
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 |0 0 0|  Hour   | |0 0|  Minute   |
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+

For files created with 2.5, this becomes:

       byte 1            byte 0
  7 6 5 4 3 2 1 0   7 6 5 4 3 2 1 0
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 |    Year     |  Month  |   Day   |
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+

       byte 1            byte 0
  7 6 5 4 3 2 1 0   7 6 5 4 3 2 1 0
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
 |YearX|  Hour   | |0 0|  Minute   |
 +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+

Where the YearX bits are prepended to the Year bits, giving 10 bits range total (0...1023). The date is stored -1900, so this gives dates 1900 through 2923. 🎉

Proposed algorithm:

• If (DateLo | DateHi) == 0
  • Final Year = 0
• Else, if YearX is non-zero
  • Final Year = 1900 + Year + (YearX << 7)
• Else, if Year < 40
  • Final Year = 2000 + Year (per ProDOS Tech Note # 28)
• Else
  • Final Year = 1900 + Year

[inexorabletash]

For posterity: ProDOS 8 2.4.2 SET_FILE_INFO calls seemingly fail to set the modified date if the upper byte is clear, i.e. if the year is 1900 (or 2000, if you follow Tech Note #28) and the month is < 8.

[c0mmander8]

The ProDOS 2.5 extended date and time format seems to have changed. Please see https://prodos8.com/releases/prodos-25/.

[inexorabletash]

That page is talking about the global page format. This is issue is talking about the file metadata format. Unfortunately in 2.5 they differ from each other.

[inexorabletash]

You were right, it has changed. The code will need updating.

At least the global page/file stamp formats are the same now.

[inexorabletash]

Should be fixed by 92c0414