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;;;; date.jl -- Date manipulation
;;; Copyright (C) 1997 John Harper <john@dcs.warwick.ac.uk>
;;; $Id: date.jl,v 1.3 1999/12/11 21:08:24 john Exp $
;;; This file is part of Jade.
;;; Jade is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 2, or (at your option)
;;; any later version.
;;; Jade is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;; You should have received a copy of the GNU General Public License
;;; along with Jade; see the file COPYING. If not, write to
;;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
(provide 'date)
(defvar date-month-alist '(("Jan" . 1) ("Feb" . 2) ("Mar" . 3) ("Apr" . 4)
("May" . 5) ("Jun" . 6) ("Jul" . 7) ("Aug" . 8)
("Sep" . 9) ("Oct" . 10) ("Nov" . 11) ("Dec" . 12)
("January" . 1) ("February" . 2) ("March" . 3)
("April" . 4) ("June" . 6) ("July" . 7)
("August" . 8) ("September" . 9) ("October" . 10)
("November" . 11) ("December" . 12))
"Alist of (MONTH-NAME . MONTH-NUM).")
(defvar date-timezone-alist
'(("UT" . 0) ("GMT" . 0)
("EST" . -300) ("EDT" . -240)
("CST" . -360) ("CDT" . -300)
("MST" . -420) ("MDT" . -360)
("PST" . -480) ("PDT" . -420))
"Alist of (TIMEZONE . MINUTES-DIFFERENCE).")
(defvar date-two-digit-year-prefix (substring (current-time-string) 20 22)
"A two-digit string that will be prepended to year specifications that
only have two, lower order, digits. This is picked up automatically from
the current year, i.e. 1997 -> \"19\", 2001 -> \"20\".")
;; Date parsing
;; Constants defining date structure fields
(defconst date-vec-day-abbrev 0)
(defconst date-vec-day 1)
(defconst date-vec-month-abbrev 2)
(defconst date-vec-month 3)
(defconst date-vec-year 4)
(defconst date-vec-hour 5)
(defconst date-vec-minute 6)
(defconst date-vec-second 7)
(defconst date-vec-timezone 8)
(defconst date-vec-epoch-time 9)
;; Parse the date header at position POINT in STRING, returns vector
;; [DAY-ABBREV DAY MONTH-ABBREV MONTH YEAR HOUR MINUTE SECOND TZ-STRING TIME_T]
(defun parse-date (string &optional point)
"Parse the date specifiction in STRING, optionally starting at the POINT'th
character in the string. This will parse dates in RFC-822 mail messages."
(unless point (setq point 0))
(let
((day-abbrev "")
(day -1)
(month-abbrev "")
(month -1)
(year -1)
(hour 0)
(minute 0)
(second 0)
(timezone 0)
time_t tem)
(while (< point (length string))
(cond
((string-looking-at "[\t ]*([0-9]+)([\t ]+|$)" string point)
(let*
((start (match-start 1))
(end (match-end 1))
(value (read-from-string (substring string start end))))
;; Could be year or day of month
(if (or (>= day 0) (> (- end start) 2))
;; Assume year
(if (= (- end start) 2)
;; two-digit year
(setq year (+ (* 100 (read-from-string
date-two-digit-year-prefix)) value))
(setq year value))
(setq day value))
(setq point end)))
((string-looking-at
"[\t ]*([0-9]+):([0-9]+)(:[0-9]+)?[\t ]*([A-Z]+|[+-][0-9]+)?[\t ]*"
string point)
;; Time spec.
(setq point (match-end))
(setq hour (read-from-string (substring string (match-start 1)
(match-end 1)))
minute (read-from-string (substring string (match-start 2)
(match-end 2)))
second (if (equal (match-start 3) (match-end 3))
0
(read-from-string (substring string (1+ (match-start 3))
(match-end 3))))
timezone (if (equal (match-start 4) (match-end 4))
"UT"
(substring string (match-start 4) (match-end 4))))
(if (setq tem (assoc timezone date-timezone-alist))
(setq timezone (cdr tem))
;; Try +-HHMM
(if (string-looking-at "[+-]([0-9][0-9])([0-9][0-9])" timezone)
(setq timezone (* (if (= (aref timezone 0) ?+) 1 -1)
(+ (* 60 (read-from-string
(substring timezone
(match-start 1)
(match-end 1))))
(read-from-string
(substring timezone
(match-start 2)
(match-end 2))))))
;; whatever..
(setq timezone 0))))
((string-looking-at
"[\t ]*(Mon|Tue|Wed|Thu|Fri|Sat|Sun)[a-z]*[\t ]*,?[\t ]*"
string point t)
;; Found day spec
(setq day-abbrev (substring string (match-start 1) (match-end 1)))
(setq point (match-end)))
((string-looking-at
"[\t ]*(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)[a-z]*[\t ]*"
string point t)
;; Month name
(setq month-abbrev (substring string (match-start 1) (match-end 1)))
(setq month (cdr (assoc month-abbrev date-month-alist)))
(setq point (match-end)))
((string-looking-at
"[\t ]*([0-9][0-9][0-9][0-9])-([0-9][0-9])-([0-9][0-9])[\t ]*"
string point)
;; ISO 8601 calendar date YYYY-MM-DD
(setq year (read-from-string (expand-last-match "\\1")))
(setq month (read-from-string (expand-last-match "\\2")))
(setq month-abbrev (car (rassq month date-month-alist)))
(setq day (read-from-string (expand-last-match "\\3")))
;; XXX day of week calculation
(setq point (match-end)))
(t
;; Garbage in -- garbage out
(setq point (length string)))))
(when (< year 0)
(setq year (read-from-string (current-time-string nil "%Y"))))
(when (< month 0)
(setq month (read-from-string (current-time-string nil "%m"))))
(when (< day 0)
(setq day (read-from-string (current-time-string nil "%d"))))
;; Use Gauss' algorithm (?) to find seconds since 1970
;; This subroutine is copied from my VMM operating system,
;; which was in turn copied from Linux
(let
((g-month (- month 2))
(g-year year)
total-seconds total-days)
(when (>= 0 g-month)
;; Put feb last since it has leap day
(setq g-month (+ g-month 12)
g-year (1- g-year)))
;; (DAYS . SECONDS)
(setq total-days (+ (- (/ g-year 4)
(/ g-year 100))
(/ g-year 400)
(/ (* 367 g-month) 12)
day
(* g-year 365)
-719499)
total-seconds (+ second (* 60 (+ minute
(- timezone)
(* 60 hour)))))
(setq time_t (fix-time (cons total-days total-seconds))))
(when (and (string= day-abbrev "") time_t)
;; January 1, 1970 was a Thursday
(let
((dow (% (+ (car time_t) 4) 7)))
(when (< dow 0)
(setq dow (+ dow 7)))
(setq day-abbrev
(aref ["Sun" "Mon" "Tue" "Wed" "Thu" "Fri" "Sat"] dow))))
(vector day-abbrev day month-abbrev month
year hour minute second timezone time_t)))
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