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file/untar: allow \0s for user and group ids

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Some .tar packer (on Windows?) zeros out the user and group fields,
and `file/untar` doesn't use them anyway.
This commit is contained in:
Matthew Flatt 2018-12-19 19:32:18 -07:00
parent 8ce8058796
commit b38d437a00
1 changed files with 7 additions and 3 deletions
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10
racket/collects/file/untar.rkt
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@ -55,8 +55,8 @@
link-target-from-extended-attributes)
(define name-bytes (read-bytes* 100 in))
(define mode (tar-bytes->number (read-bytes* 8 in) in))
(define owner (tar-bytes->number (read-bytes* 8 in) in))
(define group (tar-bytes->number (read-bytes* 8 in) in))
(define owner (tar-bytes->number (read-bytes* 8 in) in #:allow-zeros? #t))
(define group (tar-bytes->number (read-bytes* 8 in) in #:allow-zeros? #t))
(define size (tar-bytes->number (read-bytes* 12 in) in))
(define mod-time (tar-bytes->number (read-bytes* 12 in) in))
(define checksum-bytes (read-bytes* 8 in))
@ -199,13 +199,17 @@
(write-bytes bstr out 0 size))
(loop (- amt size))))))
(define (tar-bytes->number bstr in)
(define (tar-bytes->number bstr in #:allow-zeros? [allow-zeros? #f])
(define len (bytes-length bstr))
(cond
[(bitwise-bit-set? (bytes-ref bstr 0) 7)
;; base-256:
(for/fold ([v 0]) ([i (in-range 1 len)])
(+ (* v 256) v))]
[(and allow-zeros?
(for/and ([b (in-bytes bstr)])
(zero? b)))
#f]
[else
;; traditional:
(define skip-tail