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Make `ftp-make-file-seconds' use a correct year instead of 2002.

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This function was using 2002 when there's no year...  Updated it to use
the last occurrence of the guessed date, as described at
  http://files.stairways.com/other/ftp-list-specs-info.txt

This function still looks pretty bogus -- the RFC does *not* say
anything about the format of response to `LIST', so it's whatever
semi-random thing the server does.  (The above link looks like an
attempt to fix it, but I didn't see anything more official than that.)
From some looking around, it looks like ftp clients just try a bunch of
patterns against the text.  Add also warnings in the documentation about
this.
This commit is contained in:
Eli Barzilay 2011-08-04 23:24:50 -04:00
parent 99d48abcf3
commit 234015b34d
2 changed files with 26 additions and 19 deletions
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35
collects/net/ftp-unit.rkt
View File

@ -11,8 +11,6 @@
;; opqaue record to represent an FTP connection:
(define-struct ftp-connection (in out))
(define tzoffset (date-time-zone-offset (seconds->date (current-seconds))))
(define re:multi-response-start #rx#"^[0-9][0-9][0-9]-")
(define re:response-end #rx#"^[0-9][0-9][0-9] ")
@ -75,21 +73,24 @@
(define re:date #rx#"(...) *(.*) (..):(..)|(...) *([0-9]*) +(....)")
(define (ftp-make-file-seconds ftp-date-str)
(let ([date-list (regexp-match re:date (string->bytes/utf-8 ftp-date-str))])
(if (not (list-ref date-list 4))
(find-seconds 0
0
2
(bytes->number (list-ref date-list 6))
(get-month (list-ref date-list 5))
(bytes->number (list-ref date-list 7)))
(+ (find-seconds 0
(bytes->number (list-ref date-list 4))
(bytes->number (list-ref date-list 3))
(bytes->number (list-ref date-list 2))
(get-month (list-ref date-list 1))
2002)
tzoffset))))
(define date-list (regexp-match re:date (string->bytes/utf-8 ftp-date-str)))
(if (not (list-ref date-list 4))
(find-seconds 0 0 0
(bytes->number (list-ref date-list 6))
(get-month (list-ref date-list 5))
(bytes->number (list-ref date-list 7)))
(let* ([cur-secs (current-seconds)]
[cur-date (seconds->date cur-secs)]
[cur-year (date-year cur-date)]
[tzofs (date-time-zone-offset cur-date)]
[minute (bytes->number (list-ref date-list 4))]
[hour (bytes->number (list-ref date-list 3))]
[day (bytes->number (list-ref date-list 2))]
[month (get-month (list-ref date-list 1))]
[guess (+ (find-seconds 0 minute hour day month cur-year) tzofs)])
(if (guess . <= . cur-secs)
guess
(+ (find-seconds 0 minute hour day month (sub1 cur-year)) tzofs)))))
(define re:passive #rx#"\\((.*),(.*),(.*),(.*),(.*),(.*)\\)")

10
collects/net/scribblings/ftp.scrbl
View File

@ -52,14 +52,20 @@ depending on whether the items is a file, directory, or link,
respectively. The second item is the file's date; to convert this
value to seconds consistent with @racket[file-seconds], pass the date
string to @racket[ftp-make-file-seconds], below. The third string is
the name of the file or directory.}
the name of the file or directory.
Warning: the FTP protocol has no specification for the reply format, so
this information can be unreliable.}
@defproc[(ftp-make-file-seconds [ftp-date string?]) exact-integer?]{
Takes a date string produced by @racket[ftp-directory-list] and
converts it to seconds (which can be used with
@racket[seconds->date]).}
@racket[seconds->date]).
Warning: the FTP protocol has no specification for the reply format, so
this information can be unreliable.}
@defproc[(ftp-download-file [ftp-conn ftp-connection?]