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+; "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:vicinity (make-vicinity "/usr/lib/zoneinfo/"))
+
+(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))))