On 2017-11-17, at 18:56:20, Charles Mills wrote:
> Okay, in response to absolutely no popular requests, here is how to convert
> a TOD to a UNIX time:
>
> Add CVTLSO. There's your all-important leap seconds, affine or otherwise.
>
Subtract?
>
> ...to save a couple of cycles in the case of
> repetitive conversions you could adjust that constant for CVTLSO and only do
> one subtract.
>
Taking care that CVTLSO hasn't changed midstream, which might devour the saving.
BTW, how does one ensure that CVTLSO hasn't changed between the STCK and the
access of CVTLSO?
> ...
> If the result is negative you are out of luck. The C library routines do not
> support negative times (times before 1/1/1970).
>
I believe that (used to be) a POSIX requirement, but many non-IBM UNIXen
tolerate the violation. In:
http://pubs.opengroup.org/onlinepubs/9699919799/functions/localtime.html#tag_16_299_05
ERRORS
The localtime() [CX] and localtime_r() functions shall fail if:
[EOVERFLOW]
The result cannot be represented.
... no mention of negative argument.
This leaves the bugbear "-1", returned as an error by mktime(). But is
that 1969-12-31 23:59:59. I suppose returned value is -1 but errno is
> -----Original Message-----
> From: Paul Gilmartin
> Sent: Friday, November 17, 2017 7:14 AM
>>
> That might be an affine transformation of STCK-CVTLSO.
-- gil
