HAKERIS 11/HAKERIS 11.ISO/linux/system/LinuxConsole 0.4/linuxconsole0.4install-en.iso/guile0.4.lcm/share/guile/slib/tzfile.scm

Text File | 2004-01-06 | 5.2 KB | 139 lines

; "tzfile.scm", Read sysV style (binary) timezone file.
; Copyright (c) 1997 Aubrey Jaffer
;
;Permission to copy this software, to redistribute it, and to use it
;for any purpose is granted, subject to the following restrictions and
;understandings.
;
;1.  Any copy made of this software must include this copyright notice
;in full.
;
;2.  I have made no warrantee or representation that the operation of
;this software will be error-free, and I am under no obligation to
;provide any services, by way of maintenance, update, or otherwise.
;
;3.  In conjunction with products arising from the use of this
;material, there shall be no use of my name in any advertising,
;promotional, or sales literature without prior written consent in
;each case.

(require 'byte)

(define (tzfile:read-long port)
  (let ((hibyte (read-byte port)))
    (do ((idx 3 (+ -1 idx))
     (val (if (> hibyte 127) (+ #x-100 hibyte) hibyte)
          (+ (ash val 8) (read-byte port))))
    ((zero? idx) val))))
(define (tzfile:read-longs len port)
  (define ra (make-vector len 0))
  (do ((idx 0 (+ 1 idx)))
      ((>= idx len) ra)
    (vector-set! ra idx (tzfile:read-long port))))

(define (tzfile:read-bool port)
  (let ((c (read-char port)))
    (if (eof-object? c) c (if (zero? (char->integer c)) #f #t))))

(define (tzfile:read path)
  (define null (integer->char 0))
  (call-with-input-file path
    (lambda (port)
      (do ((idx 0 (+ 1 idx)))        ;reserved.
      ((>= idx 20))
    (read-char port))
      (let* ((ttisgmtcnt (tzfile:read-long port))
         (ttisstdcnt (tzfile:read-long port))
         (leapcnt (tzfile:read-long port))
         (timecnt (tzfile:read-long port))
         (typecnt (tzfile:read-long port))
         (charcnt (tzfile:read-long port))
         (transition-times (tzfile:read-longs timecnt port))
         (transition-types
          (do ((ra (make-vector timecnt 0))
           (idx 0 (+ 1 idx)))
          ((>= idx timecnt) ra)
        (vector-set! ra idx (read-byte port))))
         ;;(printf "  typecnt = %d\n" typecnt)
         (mode-table (do ((tt (make-vector typecnt #f))
                  (idx 0 (+ 1 idx)))
                 ((>= idx typecnt) tt)
               (let* ((gmt-offset (tzfile:read-long port))
                  (isdst (tzfile:read-bool port))
                  (abbrev-index (read-byte port)))
                 (vector-set! tt idx
                      (vector abbrev-index gmt-offset
                          isdst #f #f)))))
         ;;(printf "  %d bytes of abbreviations:\n" charcnt)
         (abbrevs (do ((ra (make-bytes charcnt 0))
               (idx 0 (+ 1 idx)))
              ((>= idx charcnt) ra)
            (string-set! ra idx (read-char port))))
         (leap-seconds (tzfile:read-longs (* 2 leapcnt) port)))
    (cond ((not (or (eqv? 0 ttisstdcnt) (eqv? typecnt ttisstdcnt)))
           (slib:warn 'tzfile:read "format error" ttisstdcnt typecnt)))
    (cond ((not (or (eqv? 0 ttisgmtcnt) (eqv? typecnt ttisgmtcnt)))
           (slib:warn 'tzfile:read "format error" ttisgmtcnt typecnt)))
    ;;(printf " reading %d transition attributes\n" ttisstdcnt)
    (do ((idx 0 (+ 1 idx)))
        ((>= idx ttisstdcnt))
      (vector-set! (vector-ref mode-table idx) 3 (tzfile:read-bool port)))
    ;;(printf " reading %d transition attributes\n" ttisgmtcnt)
    (do ((idx 0 (+ 1 idx)))
        ((>= idx ttisgmtcnt))
      (vector-set! (vector-ref mode-table idx) 4 (tzfile:read-bool port)))
    (cond ((not (eof-object? (peek-char port)))
           (slib:warn 'tzfile:read "bytes left at end")))
    (do ((idx 0 (+ 1 idx)))
        ((>= idx ttisstdcnt))
      (let ((rec (vector-ref mode-table idx)))
        (vector-set!
         rec 0 (let loop ((pos (vector-ref rec 0)))
             (cond ((>= pos (string-length abbrevs))
                (slib:warn 'tzfile:read "format error" abbrevs) #f)
               ((char=? null (string-ref abbrevs pos))
                (substring abbrevs (vector-ref rec 0) pos))
               (else (loop (+ 1 pos))))))))
    (list path mode-table leap-seconds transition-times transition-types)
    ))))

(define (tzfile:transition-index time zone)
  (and zone
       (apply
    (lambda (path mode-table leap-seconds transition-times transition-types)
      (let ((ntrns (vector-length transition-times)))
        (if (zero? ntrns) -1
        (let loop ((lidx (ash (+ 1 ntrns) -1))
               (jmp (ash (+ 1 ntrns) -2)))
          (let* ((idx (max 0 (min lidx (+ -1 ntrns))))
             (idx-time (vector-ref transition-times idx)))
            (cond ((<= jmp 0)
               (+ idx (if (>= time idx-time) 0 -1)))
              ((= time idx-time) idx)
              ((and (zero? idx) (< time idx-time)) -1)
              ((and (not (= idx lidx)) (not (< time idx-time))) idx)
              (else
               (loop ((if (< time idx-time) - +) idx jmp)
                 (if (= 1 jmp) 0 (ash (+ 1 jmp) -1))))))))))
    (cdr (vector->list zone)))))

(define (tzfile:get-std-spec mode-table)
  (do ((type-idx 0 (+ 1 type-idx)))
      ((or (>= type-idx (vector-length mode-table))
       (not (vector-ref (vector-ref mode-table type-idx) 2)))
       (if (>= type-idx (vector-length mode-table))
       (vector-ref mode-table 0)
       (vector-ref mode-table type-idx)))))

(define (tzfile:get-zone-spec time zone)
  (apply
   (lambda (path mode-table leap-seconds transition-times transition-types)
     (let* ((trans-idx (tzfile:transition-index time zone)))
       (if (zero? (vector-length transition-types))
       (vector-ref mode-table 0)
       (if (negative? trans-idx)
           (tzfile:get-std-spec mode-table)
           (vector-ref mode-table
               (vector-ref transition-types trans-idx))))))
   (cdr (vector->list zone))))