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;;; time-date.el --- date and time handling functions
;; Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;; Masanobu Umeda <umerin@mse.kyutech.ac.jp>
;; Keywords: mail news util
;; This file is part of GNU Emacs.
;; GNU Emacs 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.
;; GNU Emacs 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 GNU Emacs; see the file COPYING. If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.
;;; Commentary:
;;; Code:
(require 'parse-time)
(autoload 'timezone-make-date-arpa-standard "timezone")
;;;###autoload
(defun date-to-time (date)
"Parse a string that represents a date-time and return a time value."
(condition-case ()
(apply 'encode-time
(parse-time-string
;; `parse-time-string' isn't sufficiently general or
;; robust. It fails to grok some of the formats that
;; timzeone does (e.g. dodgy post-2000 stuff from some
;; Elms) and either fails or returns bogus values. Lars
;; reverted this change, but that loses non-trivially
;; often for me. -- fx
(timezone-make-date-arpa-standard date)))
(error (error "Invalid date: %s" date))))
(defun time-to-seconds (time)
"Convert time value TIME to a floating point number.
You can use `float-time' instead."
(+ (* (car time) 65536.0)
(cadr time)
(/ (or (nth 2 time) 0) 1000000.0)))
;;;###autoload
(defun seconds-to-time (seconds)
"Convert SECONDS (a floating point number) to a time value."
(list (floor seconds 65536)
(floor (mod seconds 65536))
(floor (* (- seconds (ffloor seconds)) 1000000))))
;;;###autoload
(defun time-less-p (t1 t2)
"Say whether time value T1 is less than time value T2."
(or (< (car t1) (car t2))
(and (= (car t1) (car t2))
(< (nth 1 t1) (nth 1 t2)))))
;;;###autoload
(defun days-to-time (days)
"Convert DAYS into a time value."
(let* ((seconds (* 1.0 days 60 60 24))
(rest (expt 2 16))
(ms (condition-case nil (floor (/ seconds rest))
(range-error (expt 2 16)))))
(list ms (condition-case nil (round (- seconds (* ms rest)))
(range-error (expt 2 16))))))
;;;###autoload
(defun time-since (time)
"Return the time elapsed since TIME.
TIME should be either a time value or a date-time string."
(when (stringp time)
;; Convert date strings to internal time.
(setq time (date-to-time time)))
(let* ((current (current-time))
(rest (when (< (nth 1 current) (nth 1 time))
(expt 2 16))))
(list (- (+ (car current) (if rest -1 0)) (car time))
(- (+ (or rest 0) (nth 1 current)) (nth 1 time)))))
;;;###autoload
(defalias 'subtract-time 'time-subtract)
;;;###autoload
(defun time-subtract (t1 t2)
"Subtract two time values.
Return the difference in the format of a time value."
(let ((borrow (< (cadr t1) (cadr t2))))
(list (- (car t1) (car t2) (if borrow 1 0))
(- (+ (if borrow 65536 0) (cadr t1)) (cadr t2)))))
;;;###autoload
(defun time-add (t1 t2)
"Add two time values. One should represent a time difference."
(let ((high (car t1))
(low (if (consp (cdr t1)) (nth 1 t1) (cdr t1)))
(micro (if (numberp (car-safe (cdr-safe (cdr t1))))
(nth 2 t1)
0))
(high2 (car t2))
(low2 (if (consp (cdr t2)) (nth 1 t2) (cdr t2)))
(micro2 (if (numberp (car-safe (cdr-safe (cdr t2))))
(nth 2 t2)
0)))
;; Add
(setq micro (+ micro micro2))
(setq low (+ low low2))
(setq high (+ high high2))
;; Normalize
;; `/' rounds towards zero while `mod' returns a positive number,
;; so we can't rely on (= a (+ (* 100 (/ a 100)) (mod a 100))).
(setq low (+ low (/ micro 1000000) (if (< micro 0) -1 0)))
(setq micro (mod micro 1000000))
(setq high (+ high (/ low 65536) (if (< low 0) -1 0)))
(setq low (logand low 65535))
(list high low micro)))
;;;###autoload
(defun date-to-day (date)
"Return the number of days between year 1 and DATE.
DATE should be a date-time string."
(time-to-days (date-to-time date)))
;;;###autoload
(defun days-between (date1 date2)
"Return the number of days between DATE1 and DATE2.
DATE1 and DATE2 should be date-time strings."
(- (date-to-day date1) (date-to-day date2)))
;;;###autoload
(defun date-leap-year-p (year)
"Return t if YEAR is a leap year."
(or (and (zerop (% year 4))
(not (zerop (% year 100))))
(zerop (% year 400))))
;;;###autoload
(defun time-to-day-in-year (time)
"Return the day number within the year corresponding to TIME."
(let* ((tim (decode-time time))
(month (nth 4 tim))
(day (nth 3 tim))
(year (nth 5 tim))
(day-of-year (+ day (* 31 (1- month)))))
(when (> month 2)
(setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
(when (date-leap-year-p year)
(setq day-of-year (1+ day-of-year))))
day-of-year))
;;;###autoload
(defun time-to-days (time)
"The number of days between the Gregorian date 0001-12-31bce and TIME.
TIME should be a time value.
The Gregorian date Sunday, December 31, 1bce is imaginary."
(let* ((tim (decode-time time))
(month (nth 4 tim))
(day (nth 3 tim))
(year (nth 5 tim)))
(+ (time-to-day-in-year time) ; Days this year
(* 365 (1- year)) ; + Days in prior years
(/ (1- year) 4) ; + Julian leap years
(- (/ (1- year) 100)) ; - century years
(/ (1- year) 400)))) ; + Gregorian leap years
;;;###autoload
(defun safe-date-to-time (date)
"Parse a string that represents a date-time and return a time value.
If DATE is malformed, return a time value of zeros."
(condition-case ()
(date-to-time date)
(error '(0 0))))
(provide 'time-date)
;;; arch-tag: addcf07b-b20a-465b-af72-550b8ac5190f
;;; time-date.el ends here
|
