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% Copyright (C) 2020-2021, 2022 John E. Davis
%
% This file is part of the S-Lang Library and may be distributed under the
% terms of the GNU General Public License. See the file COPYING for
% more information.
%---------------------------------------------------------------------------
% The code here attemps to convert a human readable representation of a
% timestamp, such as Wed May 13 02:38:34 2020 to a Unix time (number
% of secs since the Unix epoch)
%
% Public funtions:
%
% timestamp_parse:
% Parses a timestamp and Returns the number of seconds since
% the Unix EPOCH (1970-01-01T00:00:00Z)
%
private variable Months
= ["jan", "feb", "mar", "apr", "may", "jun",
"jul", "aug", "sep", "oct", "nov", "dec"];
% There is an extensive list of timezone abbreviations at
% <https://www.timeanddate.com/time/zones/>. The problem with
% abbreviations is that they are not unique. For example, CST
% could refer to Austrailia, North America, or China.
% The ones here are used by slrn.
private variable TZMap = Assoc_Type[Int_Type, 0];
TZMap["EDT"] = -400; % US Eastern Daylight Time
TZMap["EST"] = -500; % US Eastern Standard Time
TZMap["CDT"] = -500; % US Central Daylight Time
TZMap["CST"] = -600; % US Central
TZMap["MDT"] = -600; % US Mountain Daylight Time
TZMap["MST"] = -700; % US Mountain
TZMap["PDT"] = -700; % US Pacific Daylight Time
TZMap["PST"] = -800; % US Pacific
TZMap["GMT"] = 0;
TZMap["UTC"] = 0;
TZMap["Z"] = 0;
TZMap["CET"] = 100; % Central European
TZMap["MET"] = 100; % Middle European
TZMap["MEZ"] = 100; % Middle European
TZMap["EET"] = 200; % Eastern European
TZMap["MSK"] = 300; % Moscow
TZMap["HKT"] = 800; % Hong Kong
TZMap["JST"] = 900; % Japan Standard
TZMap["KST"] = 900; % Korean Standard
TZMap["CAST"] = 930; % Central Autsralian
TZMap["EAST"] = 1000; % Eastern Autsralian
TZMap["NZST"] = 1200; % New Zealand Autsralian
private define map_tzstr_string (tzstr)
{
return TZMap[strtrim (strup(tzstr))];
}
private variable Cumulative_Days_Per_Month =
int (cumsum ([0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]));
private variable TS_Formats = {};
private define add_ts_format (re, indices, month_is_int)
{
variable s = struct
{
re = re,
month_is_int = month_is_int,
indices = indices,
};
list_append (TS_Formats, s);
}
% Tue 12 May 2020 04:37:54 [PM] EDT
add_ts_format (`^[a-zA-Z,]*` % weekday
+ ` *\(\d\d?\)[ -]\([a-zA-Z]+\)[ -]\(\d\d\d*\),?` % day month year
+ ` *\(\d\d?\)[:.]\(\d\d\)[:.]?\(\d*\)` % hh:mm:ss
+ ` *\(.*\)`, % AM/PM + tz
[1,2,3,4,5,6,7], 0);
% Sun, Dec 04, 1994 11:05:52 GMT
add_ts_format (`^[a-zA-Z,]+`
+ ` +\([a-zA-Z]\{3,\}\) \(\d+\),? *\(\d\d\d*\)`% month, day, year
+ ` +\(\d\d?\):\(\d\d\):?\(\d*\)`% hh:mm:ss
+ ` *\(.*\)`, % tz
[2,1,3,4,5,6,7], 0);
% Dec 04, 1994 11:05:52 GMT
add_ts_format (`^\([a-zA-Z]\{3,\}\) \(\d+\),? *\(\d\d\d*\)`% month, day, year
+ ` +\(\d\d?\):\(\d\d\):?\(\d*\)`% hh:mm:ss
+ ` *\(.*\)`, % tz
[2,1,3,4,5,6,7], 0);
% 2020-09-12T21:17:30 <tz-offset>
add_ts_format (`^\(\d\d\d\d\)-?\(\d\d\)-?\(\d\d\)`
+ `T\(\d\d\):?\(\d\d\):?\(\d\d\)`
+ ` *\(.*\)`,
[3,2,1,4,5,6,7], 1);
% 5/12/2020, 5:31:57 PM
add_ts_format (`\(\d\d?\)/\(\d\d?\)/\(\d\d\d*\),?`
+ ` *\(\d\d?\):\(\d\d\):?\(\d*\)`
+ ` *\(.*\)`,
[2,1,3,4,5,6,7], 1);
% Dec 4 11:05:52 2020
add_ts_format (`^\([a-zA-Z]\{3,\}\) +\(\d+\),?` % month, day
+ ` +\(\d\d?\):\(\d\d\):?\(\d*\),?`% hh:mm:ss
+ ` +\(\d\d\d*\)` % year
+ ` *\(.*\)`, % tz
[2,1,6,3,4,5,7], 0);
% Tue Dec 4 11:05:52 2020
add_ts_format (`^[A-Za-z,]+`
+ ` +\([a-zA-Z]\{3,\}\) +\(\d+\),?` % month, day
+ ` +\(\d\d?\):\(\d\d\):?\(\d*\),?`% hh:mm:ss
+ ` +\(\d\d\d*\)` % year
+ ` *\(.*\)`, % tz
[2,1,6,3,4,5,7], 0);
private variable Last_TS_Index = 0;
private define guess_local_timezone_offset ()
{
variable now = _time(), tm = gmtime(now);
tm.tm_isdst = -1; % Force a lookup to see if DST is in effect
variable secs = now - mktime (tm);
variable hours = secs/3600;
return 100*hours + (secs - 3600*hours)/60;
}
define timestamp_parse (timestamp)
{
timestamp = strtrim (timestamp);
variable day, month, year, hours, minutes, secs, tz, tzstr;
variable num = length (TS_Formats);
loop (num)
{
variable fmt = TS_Formats[Last_TS_Index];
variable matches = string_matches (timestamp, fmt.re);
if (matches == NULL)
{
Last_TS_Index = (Last_TS_Index + 1) mod num;
continue;
}
variable ind = fmt.indices;
day = atoi (matches[ind[0]]);
month = matches[ind[1]];
year = atoi (matches[ind[2]]);
hours = atoi (matches[ind[3]]);
minutes = atoi (matches[ind[4]]);
secs = atoi (matches[ind[5]]);
tzstr = matches[ind[6]];
if (fmt.month_is_int)
month = atoi (month) - 1; % 0 to 11
else
{
if (strbytelen (month) > 3) month = month[[0,1,2]];
month = wherefirst (Months == strlow(month));
if (month == NULL) return NULL;
}
break;
}
then return NULL;
if (year < 100)
{
% No century
year += 1900;
if (year < 1950) year += 100;
}
tzstr = strtrim (tzstr);
% Take care of AM/PM
if (((tzstr[0] == 'A') || (tzstr[0] == 'P'))
&& (tzstr[1] == 'M')
&& ((tzstr[2] == 0) || (tzstr[2] == ' ')))
{
if (tzstr[0] == 'P')
hours += 12;
tzstr = strtrim (tzstr[[2:]]);
}
tzstr = strreplace (tzstr, ":", "");
if (tzstr == "")
tz = guess_local_timezone_offset ();
else
{
tz = atoi (tzstr);
if ((tz == 0) && (tzstr[0] != '+') && (tzstr[0] != '-'))
tz = map_tzstr_string (tzstr);
}
day--; % offset from 0
% Compute the cumulative number of days, accounting for a leap year
day += Cumulative_Days_Per_Month[month];
if ((month >= 2) % month runs 0 .. 11
&& (0 == (year mod 4))
&& ((year mod 100) || (0 == (year mod 400))))
day++;
year -= 1970; % Unix EPOCH
day += 365*year + (year+1)/4; % leap year, every 4 years from 72
% The TZ is hhmm form, so 600 is 6 hours, and 0 minutes
hours -= tz/100;
minutes -= tz mod 100;
return secs + 60L*(minutes + 60L*(hours + 24L*day));
}
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