X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcode%2Ftime.lisp;h=fb35b183eb50ab97e4033e56d80dca7c7e1e130f;hb=b7cfa0e5e726c2037ba2c6cb32406ff7e9764dd2;hp=5ddfde3be5cb01f5e0fcbfff532281d0f8686dd2;hpb=148e3820ad314a9b59d0133c1d60eaac4af9118b;p=sbcl.git diff --git a/src/code/time.lisp b/src/code/time.lisp index 5ddfde3..fb35b18 100644 --- a/src/code/time.lisp +++ b/src/code/time.lisp @@ -27,8 +27,8 @@ (defun get-internal-real-time () #!+sb-doc - "Return the real time in the internal time format. This is useful for - finding elapsed time. See INTERNAL-TIME-UNITS-PER-SECOND." + "Return the real time in the internal time format. (See + INTERNAL-TIME-UNITS-PER-SECOND.) This is useful for finding elapsed time." (multiple-value-bind (ignore seconds useconds) (sb!unix:unix-gettimeofday) (declare (ignore ignore) (type (unsigned-byte 32) seconds useconds)) (let ((base *internal-real-time-base-seconds*) @@ -47,8 +47,8 @@ (defun get-internal-run-time () #!+sb-doc - "Return the run time in the internal time format. This is useful for - finding CPU usage." + "Return the run time in the internal time format. (See + INTERNAL-TIME-UNITS-PER-SECOND.) This is useful for finding CPU usage." (declare (values (unsigned-byte 32))) (multiple-value-bind (ignore utime-sec utime-usec stime-sec stime-usec) (sb!unix:unix-fast-getrusage sb!unix:rusage_self) @@ -70,6 +70,43 @@ ;;;; Encode and decode universal times. +;;; In August 2003, work was done in this file for more plausible +;;; timezone handling after the unix timezone database runs out in +;;; 2038. We assume that timezone rules are trending sane rather than +;;; insane, so for all years after the end of time_t we apply the +;;; rules for 2035/2036 instead of the actual date asked for. Making +;;; the same assumption about the early 1900s would be less +;;; reasonable, however, so please note that we're still broken for +;;; local time between 1900-1-1 and 1901-12-13 + +;;; It should be noted that 64 bit machines don't actually fix this +;;; problem, at least as of 2003, because the Unix zonefiles are +;;; specified in terms of 32 bit fields even on, say, the Alpha. So, +;;; references to the range of time_t elsewhere in this file should +;;; rightly be read as shorthand for the range of an signed 32 bit +;;; number of seconds since 1970-01-01 + +;;; I'm obliged to Erik Naggum's "Long, Painful History of Time" paper +;;; for the choice of epoch +;;; here. By starting the year in March, we avoid having to test the month +;;; whenever deciding whether to account for a leap day. 2000 is especially +;;; special, because it's disvisible by 400, hence the start of a 400 year +;;; leap year cycle + +;;; If a universal-time is after time_t runs out, we find its offset +;;; from 1st March of whichever year it falls in, then add that to +;;; 2035-3-1. This date has two relevant properties: (1) somewhere +;;; near the end of time_t, and (2) preceding a leap year. Thus a +;;; date which is e.g. 365.5 days from March 1st in its year will be +;;; treated for timezone lookup as if it were Feb 29th 2036 + +;;; This epoch is used only for fixing the timezones-outside-time_t +;;; problem. Someday it would be nice to come back to this code and +;;; see if the rest of the file and its references to Spice Lisp +;;; history (Perq time base?) could be cleaned up any on this basis. +;;; -- dan, 2003-08-08 + + ;;; Subtract from the returned Internal-Time to get the universal ;;; time. The offset between our time base and the Perq one is 2145 ;;; weeks and five days. @@ -98,6 +135,35 @@ (daylight savings times) or NIL (standard time), and timezone." (decode-universal-time (get-universal-time))) +(defconstant +mar-1-2000+ #.(encode-universal-time 0 0 0 1 3 2000 0)) +(defconstant +mar-1-2035+ #.(encode-universal-time 0 0 0 1 3 2035 0)) + +(defun years-since-mar-2000 (utime) + "Returns number of complete years since March 1st 2000, and remainder in seconds" + (let* ((days-in-year (* 86400 365)) + (days-in-4year (+ (* 4 days-in-year) 86400)) + (days-in-100year (- (* 25 days-in-4year) 86400)) + (days-in-400year (+ (* 4 days-in-100year) 86400)) + (offset (- utime +mar-1-2000+)) + (year 0)) + (labels ((whole-num (x y inc max) + (let ((w (truncate x y))) + (when (and max (> w max)) (setf w max)) + (incf year (* w inc)) + (* w y)))) + (decf offset (whole-num offset days-in-400year 400 nil)) + (decf offset (whole-num offset days-in-100year 100 3)) + (decf offset (whole-num offset days-in-4year 4 25)) + (decf offset (whole-num offset days-in-year 1 3)) + (values year offset)))) + +(defun truncate-to-unix-range (utime) + (let ((unix-time (- utime unix-to-universal-time))) + (if (< unix-time (ash 1 31)) + unix-time + (multiple-value-bind (year offset) (years-since-mar-2000 utime) + (+ +mar-1-2035+ (- unix-to-universal-time) offset))))) + (defun decode-universal-time (universal-time &optional time-zone) #!+sb-doc "Converts a universal-time to decoded time format returning the following @@ -118,10 +184,9 @@ (daylight NIL) (timezone (cond ((null time-zone) - (multiple-value-bind - (ignore minwest dst) - (sb!unix::get-timezone (- universal-time - unix-to-universal-time)) + (multiple-value-bind (ignore minwest dst) + (sb!unix::get-timezone + (truncate-to-unix-range universal-time)) (declare (ignore ignore)) (declare (fixnum minwest)) (setf daylight dst) @@ -180,6 +245,7 @@ (incf sum days-in-month)) (coerce (nreverse reversed-result) 'simple-vector))) + (defun encode-universal-time (second minute hour date month year &optional time-zone) #!+sb-doc @@ -204,14 +270,29 @@ (hours (+ hour (* days 24)))) (if time-zone (+ second (* (+ minute (* (+ hours time-zone) 60)) 60)) - (let* ((minwest-guess - (sb!unix::unix-get-minutes-west (- (* hours 60 60) - unix-to-universal-time))) - (guess (+ minute (* hours 60) minwest-guess)) - (minwest - (sb!unix::unix-get-minutes-west (- (* guess 60) - unix-to-universal-time)))) - (+ second (* (+ guess (- minwest minwest-guess)) 60)))))) + ;; can't ask unix for times after 2037: this is only a problem + ;; if we need to query the system timezone + (if (> year 2037) + (labels ((leap-year-p (year) + (cond ((zerop (mod year 400)) t) + ((zerop (mod year 100)) t) + ((zerop (mod year 4)) t) + (t nil)))) + (let* ((fake-year (if (leap-year-p year) 2036 2037)) + (fake-time (encode-universal-time second minute hour + date month fake-year))) + (+ fake-time + (* 86400 (+ (* 365 (- year fake-year)) + (- (leap-years-before year) + (leap-years-before fake-year))))))) + (let* ((minwest-guess + (sb!unix::unix-get-minutes-west + (- (* hours 60 60) unix-to-universal-time))) + (guess (+ minute (* hours 60) minwest-guess)) + (minwest + (sb!unix::unix-get-minutes-west + (- (* guess 60) unix-to-universal-time)))) + (+ second (* (+ guess (- minwest minwest-guess)) 60))))))) ;;;; TIME