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; "tzfile.scm", Read sysV style (binary) timezone file.
; Copyright (C) 1997 Aubrey Jaffer
;
;Permission to copy this software, to modify it, to redistribute it,
;to distribute modified versions, 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 warranty 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)
(+ (* val 256) (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)
(call-with-open-ports
(open-file path 'rb)
(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)
(byte-set! ra idx (read-byte 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 (bytes-length abbrevs))
(slib:warn 'tzfile:read "format error" abbrevs) #f)
((zero? (byte-ref abbrevs pos))
(substring abbrevs (vector-ref rec 0) pos))
(else (loop (+ 1 pos))))))))
(list path mode-table leap-seconds transition-times transition-types)))))
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