1;;; time-date.el --- Date and time handling functions
2
3;; Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
4;;   Free Software Foundation, Inc.
5
6;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
7;;	Masanobu Umeda <umerin@mse.kyutech.ac.jp>
8;; Keywords: mail news util
9
10;; This file is part of GNU Emacs.
11
12;; GNU Emacs is free software; you can redistribute it and/or modify
13;; it under the terms of the GNU General Public License as published by
14;; the Free Software Foundation; either version 2, or (at your option)
15;; any later version.
16
17;; GNU Emacs is distributed in the hope that it will be useful,
18;; but WITHOUT ANY WARRANTY; without even the implied warranty of
19;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the
20;; GNU General Public License for more details.
21
22;; You should have received a copy of the GNU General Public License
23;; along with GNU Emacs; see the file COPYING.  If not, write to the
24;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
25;; Boston, MA 02110-1301, USA.
26
27;;; Commentary:
28
29;; Time values come in three formats.  The oldest format is a cons
30;; cell of the form (HIGH . LOW).  This format is obsolete, but still
31;; supported.  The two other formats are the lists (HIGH LOW) and
32;; (HIGH LOW MICRO).  The first two formats specify HIGH * 2^16 + LOW
33;; seconds; the third format specifies HIGH * 2^16 + LOW + MICRO /
34;; 1000000 seconds.  We should have 0 <= MICRO < 1000000 and 0 <= LOW
35;; < 2^16.  If the time value represents a point in time, then HIGH is
36;; nonnegative.  If the time value is a time difference, then HIGH can
37;; be negative as well.  The macro `with-decoded-time-value' and the
38;; function `encode-time-value' make it easier to deal with these
39;; three formats.  See `time-subtract' for an example of how to use
40;; them.
41
42;;; Code:
43
44(defmacro with-decoded-time-value (varlist &rest body)
45  "Decode a time value and bind it according to VARLIST, then eval BODY.
46
47The value of the last form in BODY is returned.
48
49Each element of the list VARLIST is a list of the form
50\(HIGH-SYMBOL LOW-SYMBOL MICRO-SYMBOL [TYPE-SYMBOL] TIME-VALUE).
51The time value TIME-VALUE is decoded and the result it bound to
52the symbols HIGH-SYMBOL, LOW-SYMBOL and MICRO-SYMBOL.
53
54The optional TYPE-SYMBOL is bound to the type of the time value.
55Type 0 is the cons cell (HIGH . LOW), type 1 is the list (HIGH
56LOW), and type 3 is the list (HIGH LOW MICRO)."
57  (declare (indent 1)
58	   (debug ((&rest (symbolp symbolp symbolp &or [symbolp form] form))
59		   body)))
60  (if varlist
61      (let* ((elt (pop varlist))
62	     (high (pop elt))
63	     (low (pop elt))
64	     (micro (pop elt))
65	     (type (unless (eq (length elt) 1)
66		     (pop elt)))
67	     (time-value (car elt))
68	     (gensym (make-symbol "time")))
69	`(let* ,(append `((,gensym ,time-value)
70			  (,high (pop ,gensym))
71			  ,low ,micro)
72			(when type `(,type)))
73	   (if (consp ,gensym)
74	       (progn
75		 (setq ,low (pop ,gensym))
76		 (if ,gensym
77		     ,(append `(setq ,micro (car ,gensym))
78			      (when type `(,type 2)))
79		   ,(append `(setq ,micro 0)
80			    (when type `(,type 1)))))
81	     ,(append `(setq ,low ,gensym ,micro 0)
82		      (when type `(,type 0))))
83	   (with-decoded-time-value ,varlist ,@body)))
84    `(progn ,@body)))
85
86(defun encode-time-value (high low micro type)
87  "Encode HIGH, LOW, and MICRO into a time value of type TYPE.
88Type 0 is the cons cell (HIGH . LOW), type 1 is the list (HIGH LOW),
89and type 3 is the list (HIGH LOW MICRO)."
90  (cond
91   ((eq type 0) (cons high low))
92   ((eq type 1) (list high low))
93   ((eq type 2) (list high low micro))))
94
95(autoload 'parse-time-string "parse-time")
96(autoload 'timezone-make-date-arpa-standard "timezone")
97
98;;;###autoload
99(defun date-to-time (date)
100  "Parse a string that represents a date-time and return a time value."
101  (condition-case ()
102      (apply 'encode-time
103	     (parse-time-string
104	      ;; `parse-time-string' isn't sufficiently general or
105	      ;; robust.  It fails to grok some of the formats that
106	      ;; timezone does (e.g. dodgy post-2000 stuff from some
107	      ;; Elms) and either fails or returns bogus values.  Lars
108	      ;; reverted this change, but that loses non-trivially
109	      ;; often for me.  -- fx
110	      (timezone-make-date-arpa-standard date)))
111    (error (error "Invalid date: %s" date))))
112
113;;;###autoload
114(defun time-to-seconds (time)
115  "Convert time value TIME to a floating point number.
116You can use `float-time' instead."
117  (with-decoded-time-value ((high low micro time))
118    (+ (* 1.0 high 65536)
119       low
120       (/ micro 1000000.0))))
121
122;;;###autoload
123(defun seconds-to-time (seconds)
124  "Convert SECONDS (a floating point number) to a time value."
125  (list (floor seconds 65536)
126	(floor (mod seconds 65536))
127	(floor (* (- seconds (ffloor seconds)) 1000000))))
128
129;;;###autoload
130(defun time-less-p (t1 t2)
131  "Say whether time value T1 is less than time value T2."
132  (with-decoded-time-value ((high1 low1 micro1 t1)
133			    (high2 low2 micro2 t2))
134    (or (< high1 high2)
135	(and (= high1 high2)
136	     (or (< low1 low2)
137		 (and (= low1 low2)
138		      (< micro1 micro2)))))))
139
140;;;###autoload
141(defun days-to-time (days)
142  "Convert DAYS into a time value."
143  (let* ((seconds (* 1.0 days 60 60 24))
144	 (high (condition-case nil (floor (/ seconds 65536))
145		 (range-error most-positive-fixnum))))
146    (list high (condition-case nil (floor (- seconds (* 1.0 high 65536)))
147		 (range-error 65535)))))
148
149;;;###autoload
150(defun time-since (time)
151  "Return the time elapsed since TIME.
152TIME should be either a time value or a date-time string."
153  (when (stringp time)
154    ;; Convert date strings to internal time.
155    (setq time (date-to-time time)))
156  (time-subtract (current-time) time))
157
158;;;###autoload
159(defalias 'subtract-time 'time-subtract)
160
161;;;###autoload
162(defun time-subtract (t1 t2)
163  "Subtract two time values.
164Return the difference in the format of a time value."
165  (with-decoded-time-value ((high low micro type t1)
166			    (high2 low2 micro2 type2 t2))
167    (setq high (- high high2)
168	  low (- low low2)
169	  micro (- micro micro2)
170	  type (max type type2))
171    (when (< micro 0)
172      (setq low (1- low)
173	    micro (+ micro 1000000)))
174    (when (< low 0)
175      (setq high (1- high)
176	    low (+ low 65536)))
177    (encode-time-value high low micro type)))
178
179;;;###autoload
180(defun time-add (t1 t2)
181  "Add two time values.  One should represent a time difference."
182  (with-decoded-time-value ((high low micro type t1)
183			    (high2 low2 micro2 type2 t2))
184    (setq high (+ high high2)
185	  low (+ low low2)
186	  micro (+ micro micro2)
187	  type (max type type2))
188    (when (>= micro 1000000)
189      (setq low (1+ low)
190	    micro (- micro 1000000)))
191    (when (>= low 65536)
192      (setq high (1+ high)
193	    low (- low 65536)))
194    (encode-time-value high low micro type)))
195
196;;;###autoload
197(defun date-to-day (date)
198  "Return the number of days between year 1 and DATE.
199DATE should be a date-time string."
200  (time-to-days (date-to-time date)))
201
202;;;###autoload
203(defun days-between (date1 date2)
204  "Return the number of days between DATE1 and DATE2.
205DATE1 and DATE2 should be date-time strings."
206  (- (date-to-day date1) (date-to-day date2)))
207
208;;;###autoload
209(defun date-leap-year-p (year)
210  "Return t if YEAR is a leap year."
211  (or (and (zerop (% year 4))
212	   (not (zerop (% year 100))))
213      (zerop (% year 400))))
214
215;;;###autoload
216(defun time-to-day-in-year (time)
217  "Return the day number within the year corresponding to TIME."
218  (let* ((tim (decode-time time))
219	 (month (nth 4 tim))
220	 (day (nth 3 tim))
221	 (year (nth 5 tim))
222	 (day-of-year (+ day (* 31 (1- month)))))
223    (when (> month 2)
224      (setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
225      (when (date-leap-year-p year)
226	(setq day-of-year (1+ day-of-year))))
227    day-of-year))
228
229;;;###autoload
230(defun time-to-days (time)
231  "The number of days between the Gregorian date 0001-12-31bce and TIME.
232TIME should be a time value.
233The Gregorian date Sunday, December 31, 1bce is imaginary."
234  (let* ((tim (decode-time time))
235	 (month (nth 4 tim))
236	 (day (nth 3 tim))
237	 (year (nth 5 tim)))
238    (+ (time-to-day-in-year time)	; 	Days this year
239       (* 365 (1- year))		;	+ Days in prior years
240       (/ (1- year) 4)			;	+ Julian leap years
241       (- (/ (1- year) 100))		;	- century years
242       (/ (1- year) 400))))		;	+ Gregorian leap years
243
244(defun time-to-number-of-days (time)
245  "Return the number of days represented by TIME.
246The number of days will be returned as a floating point number."
247  (/ (time-to-seconds time) (* 60 60 24)))
248
249;;;###autoload
250(defun safe-date-to-time (date)
251  "Parse a string that represents a date-time and return a time value.
252If DATE is malformed, return a time value of zeros."
253  (condition-case ()
254      (date-to-time date)
255    (error '(0 0))))
256
257(provide 'time-date)
258
259;;; arch-tag: addcf07b-b20a-465b-af72-550b8ac5190f
260;;; time-date.el ends here
261