;;;; vixie-time.scm -- parse Vixie-style times ;;; Copyright © 2003 Dale Mellor ;;; Copyright © 2018 Mathieu Lirzin ;;; ;;; This file is part of GNU Mcron. ;;; ;;; GNU Mcron 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 3 of the License, or ;;; (at your option) any later version. ;;; ;;; GNU Mcron 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 Mcron. If not, see . (define-module (mcron vixie-time) #:use-module (ice-9 match) #:use-module (ice-9 regex) #:use-module (mcron job-specifier) #:use-module (srfi srfi-1) #:export (parse-vixie-time)) ;; In Vixie-style time specifications three-letter symbols are allowed to stand ;; for the numbers corresponding to months and days of the week. We deal with ;; this by making a textual substitution early on in the processing of the ;; strings. ;; ;; We start by defining, once and for all, a list of cons cells consisting of ;; regexps which will match the symbols - which allow an arbitrary number of ;; other letters to appear after them (so that the user can optionally complete ;; the month and day names; this is an extension of Vixie) - and the value which ;; is to replace the symbol. ;; ;; The procedure then takes a string, and then for each symbol in the ;; parse-symbols list attempts to locate an instance and replace it with an ;; ASCII representation of the value it stands for. The procedure returns the ;; modified string. (Note that each symbol can appear only once, which meets the ;; Vixie specifications technically but still allows silly users to mess things ;; up). (define parse-symbols (map (lambda (symbol-cell) (cons (make-regexp (string-append (car symbol-cell) "[[:alpha:]]*") regexp/icase) (cdr symbol-cell))) '(("jan" . "0") ("feb" . "1") ("mar" . "2") ("apr" . "3") ("may" . "4") ("jun" . "5") ("jul" . "6") ("aug" . "7") ("sep" . "8") ("oct" . "9") ("nov" . "10") ("dec" . "11") ("sun" . "0") ("mon" . "1") ("tue" . "2") ("wed" . "3") ("thu" . "4") ("fri" . "5") ("sat" . "6") ))) (define (vixie-substitute-parse-symbols string) (for-each (lambda (symbol-cell) (let ((match (regexp-exec (car symbol-cell) string))) (if match (set! string (string-append (match:prefix match) (cdr symbol-cell) (match:suffix match)))))) parse-symbols) string) ;; A Vixie time specification is made up of a space-separated list of elements, ;; and the elements consist of a comma-separated list of subelements. The ;; procedure below takes a string holding a subelement, which should have no ;; spaces or symbols (see above) in it, and returns a list of all values which ;; that subelement indicates. There are five distinct cases which must be dealt ;; with: [1] a single '*' which returns a list of all values; [2] a '*' followed ;; by a step specifier; [3] a range and step specifier; [4] a range; and [5] a ;; single number. ;; ;; To perform the computation required for the '*' cases, we need to pass the ;; limit of the allowable range for this subelement as the third argument. As ;; days of the month start at 1 while all the other time components start at 0, ;; we must pass the base of the range to deal with this case also. (define parse-vixie-subelement-regexp (make-regexp "^([[:digit:]]+)(-([[:digit:]]+)(/([[:digit:]]+))?)?$")) (define (parse-vixie-subelement string base limit) (if (char=? (string-ref string 0) #\*) (range base limit (if (> (string-length string) 1) (string->number (substring string 2)) ;; [2] 1)) ;; [1] (let ((match (regexp-exec parse-vixie-subelement-regexp string))) (cond ((not match) (throw 'mcron-error 9 "Bad Vixie-style time specification.")) ((match:substring match 5) (range (string->number (match:substring match 1)) (+ 1 (string->number (match:substring match 3))) (string->number (match:substring match 5)))) ;; [3] ((match:substring match 3) (range (string->number (match:substring match 1)) (+ 1 (string->number (match:substring match 3))))) ;; [4] (else (list (string->number (match:substring match 1)))))))) ;; [5] ;; A Vixie element contains the entire specification, without spaces or symbols, ;; of the acceptable values for one of the time components (minutes, hours, ;; days, months, week days). Here we break the comma-separated list into ;; subelements, and process each with the procedure above. The return value is a ;; list of all the valid values of all the subcomponents. ;; ;; The second and third arguments are the base and upper limit on the values ;; that can be accepted for this time element. ;; ;; The effect of the 'apply append' is to merge a list of lists into a single ;; list. (define (parse-vixie-element string base limit) (apply append (map (lambda (sub-element) (parse-vixie-subelement sub-element base limit)) (string-tokenize string (char-set-complement (char-set #\,)))))) (define (interpolate-weekdays mday-list wday-list month year) "Given a list of days in the month MDAY-LIST and a list of days in the week WDAY-LIST, return an augmented list of days in the month with weekdays accounted for." (let ((t (localtime 0))) (set-tm:mday t 1) (set-tm:mon t month) (set-tm:year t year) (let ((first-day (tm:wday (cdr (mktime t))))) (define (range-wday wday) (let* ((first (- wday first-day)) (first* (if (negative? first) (+ 7 first) first))) (range (1+ first*) 32 7))) (apply append mday-list (map range-wday wday-list))))) ;; Return the number of days in a month. Fix up a tm object for the zero'th day ;; of the next month, rationalize the object and extract the day. (define (days-in-month month year) (let ((t (localtime 0))) (set-tm:mday t 0) (set-tm:mon t (+ month 1)) (set-tm:year t year) (tm:mday (cdr (mktime t))))) ;; We will be working with a list of time-spec's, one for each element of a time ;; specification (minute, hour, ...). Each time-spec holds three pieces of ;; information: a list of acceptable values for this time component, a procedure ;; to get the component from a tm object, and a procedure to set the component ;; in a tm object. (define (time-spec:list time-spec) (vector-ref time-spec 0)) (define (time-spec:getter time-spec) (vector-ref time-spec 1)) (define (time-spec:setter time-spec) (vector-ref time-spec 2)) ;; This procedure modifies the time tm object by setting the component referred ;; to by the time-spec object to its next acceptable value. If this value is not ;; greater than the original (because we have wrapped around the top of the ;; acceptable values list), then the function returns #t, otherwise it returns ;; #f. Thus, if the return value is true then it will be necessary for the ;; caller to increment the next coarser time component as well. ;; ;; The first part of the let block is a concession to humanity; the procedure is ;; simply unreadable without all of these aliases. (define (increment-time-component time time-spec) (let ((time-list (time-spec:list time-spec)) (getter (time-spec:getter time-spec)) (setter (time-spec:setter time-spec)) (find-best-next (@@ (mcron job-specifier) %find-best-next))) (match (find-best-next (getter time) time-list) ((smallest . closest+) (let ((infinite (inf? closest+))) (if infinite (setter time smallest) (setter time closest+)) infinite))))) ;; There now follows a set of procedures for adjusting an element of time, ;; i.e. taking it to the next acceptable value. In each case, the head of the ;; time-spec-list is expected to correspond to the component of time in ;; question. If the adjusted value wraps around its allowed range, then the next ;; biggest element of time must be adjusted, and so on. ;; There is no specification allowed for the year component of ;; time. Therefore, if we have to make an adjustment (presumably because a ;; monthly adjustment has wrapped around the top of its range) we can simply ;; go to the next year. (define (nudge-year! time) (set-tm:year time (+ (tm:year time) 1))) ;; We nudge the month by finding the next allowable value, and if it wraps ;; around we also nudge the year. The time-spec-list will have time-spec ;; objects for month and weekday. (define (nudge-month! time time-spec-list) (and (increment-time-component time (car time-spec-list)) (nudge-year! time))) ;; Try to increment the day component of the time according to the combination ;; of the mday-list and the wday-list. If this wraps around the range, or if ;; this falls outside the current month (31st February, for example), then ;; bump the month, set the day to zero, and recurse on this procedure to find ;; the next day in the new month. ;; ;; The time-spec-list will have time-spec entries for mday, month, and ;; weekday. (define (nudge-day! time time-spec-list) (if (or (increment-time-component time (vector (interpolate-weekdays (time-spec:list (car time-spec-list)) (time-spec:list (caddr time-spec-list)) (tm:mon time) (tm:year time)) tm:mday set-tm:mday)) (> (tm:mday time) (days-in-month (tm:mon time) (tm:year time)))) (begin (nudge-month! time (cdr time-spec-list)) (set-tm:mday time 0) (nudge-day! time time-spec-list)))) ;; The hour is bumped to the next accceptable value, and the day is bumped if ;; the hour wraps around. ;; ;; The time-spec-list holds specifications for hour, mday, month and weekday. (define (nudge-hour! time time-spec-list) (and (increment-time-component time (car time-spec-list)) (nudge-day! time (cdr time-spec-list)))) ;; The minute is bumped to the next accceptable value, and the hour is bumped ;; if the minute wraps around. ;; ;; The time-spec-list holds specifications for minute, hour, day-date, month ;; and weekday. (define (nudge-min! time time-spec-list) (and (increment-time-component time (car time-spec-list)) (nudge-hour! time (cdr time-spec-list)))) ;; This is a procedure which returns a procedure which computes the next time a ;; command should run after the current time, based on the information in the ;; Vixie-style time specification. ;; ;; We start by computing a list of time-spec objects (described above) for the ;; minute, hour, date, month, year and weekday components of the overall time ;; specification [1]. Special care is taken to produce proper values for ;; fields 2 and 4: according to Vixie specification "If both fields are ;; restricted (ie, aren't *), the command will be run when _either_ field ;; matches the current time." This implies that if one of these fields is *, ;; while the other is not, its value should be '() [0], otherwise ;; interpolate-weekdays below will produce incorrect results. ;; When we create the return procedure, it is this list to ;; which references to a time-spec-list will be bound. It will be used by the ;; returned procedure [3] to compute the next time a function should run. Any ;; 7's in the weekday component of the list (the last one) are folded into 0's ;; (both values represent sunday) [2]. Any 0's in the month-day component of the ;; list are removed (this allows a solitary zero to be used to indicate that ;; jobs should only run on certain days of the _week_) [2.1]. ;; ;; The returned procedure itself:- ;; ;; Starts by obtaining the current broken-down time [4], and fixing it to ;; ensure that it is an acceptable value, as follows. Each component from the ;; biggest down is checked for acceptability, and if it is not acceptable it ;; is bumped to the next acceptable value (this may cause higher components to ;; also be bumped if there is range wrap-around) and all the lower components ;; are set to -1 so that it can successfully be bumped up to zero if this is ;; an allowed value. The -1 value will be bumped up subsequently to an allowed ;; value [5]. ;; ;; Once it has been asserted that the current time is acceptable, or has been ;; adjusted to one minute before the next acceptable time, the minute ;; component is then bumped to the next acceptable time, which may ripple ;; through the higher components if necessary [6]. We now have the next time ;; the command needs to run. ;; ;; The new time is then converted back into a UNIX time and returned [7]. (define (parse-vixie-time string) (let ((tokens (string-tokenize (vixie-substitute-parse-symbols string)))) (cond ((> (length tokens) 5) (throw 'mcron-error 9 "Too many fields in Vixie-style time specification")) ((< (length tokens) 5) (throw 'mcron-error 9 "Not enough fields in Vixie-style time specification"))) (let ((time-spec-list (map-in-order (lambda (x) (vector (let* ((n (vector-ref x 0)) (tok (list-ref tokens n))) (cond ((and (= n 4) (string=? tok "*") (not (string=? (list-ref tokens 2) "*"))) '()) ((and (= n 2) (string=? tok "*") (not (string=? (list-ref tokens 4) "*"))) '()) (else (parse-vixie-element tok (vector-ref x 1) (vector-ref x 2))))) ; [0] (vector-ref x 3) (vector-ref x 4))) ;; token range-top+1 getter setter `( #( 0 0 60 ,tm:min ,set-tm:min ) #( 1 0 24 ,tm:hour ,set-tm:hour ) #( 2 1 32 ,tm:mday ,set-tm:mday ) #( 3 0 12 ,tm:mon ,set-tm:mon ) #( 4 0 7 ,tm:wday ,set-tm:wday ))))) ;; [1] (vector-set! (car (last-pair time-spec-list)) 0 (map (lambda (time-spec) (if (eqv? time-spec 7) 0 time-spec)) (vector-ref (car (last-pair time-spec-list)) 0))) ;; [2] (vector-set! (caddr time-spec-list) 0 (remove (lambda (day) (eqv? day 0)) (vector-ref (caddr time-spec-list) 0))) ;; [2.1] (lambda (current-time) ;; [3] (let ((time (localtime current-time))) ;; [4] (if (not (member (tm:mon time) (time-spec:list (cadddr time-spec-list)))) (begin (nudge-month! time (cdddr time-spec-list)) (set-tm:mday time 0))) (if (or (eqv? (tm:mday time) 0) (not (member (tm:mday time) (interpolate-weekdays (time-spec:list (caddr time-spec-list)) (time-spec:list (caddr (cddr time-spec-list))) (tm:mon time) (tm:year time))))) (begin (nudge-day! time (cddr time-spec-list)) (set-tm:hour time -1))) (if (not (member (tm:hour time) (time-spec:list (cadr time-spec-list)))) (begin (nudge-hour! time (cdr time-spec-list)) (set-tm:min time -1))) ;; [5] (set-tm:sec time 0) (nudge-min! time time-spec-list) ;; [6] (car (mktime time))))))) ;; [7]