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utils: Add 'ar-file?'. 

* guix/build/utils.scm (%ar-magic-bytes): New variable.
  (ar-file?): New procedure.
This commit is contained in:
Ludovic Courtès 2014-11-22 21:44:59 +01:00
parent 50b87bd54b
commit 91ee959b03
1 changed files with 16 additions and 0 deletions
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16
guix/build/utils.scm
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@ -37,6 +37,7 @@
executable-file? executable-file?
call-with-ascii-input-file call-with-ascii-input-file
elf-file? elf-file?
ar-file?
with-directory-excursion with-directory-excursion
mkdir-p mkdir-p
copy-recursively copy-recursively
@ -118,6 +119,21 @@ return values of applying PROC to the port."
(equal? (get-header) (equal? (get-header)
#vu8(#x7f #x45 #x4c #x46))) ;"\177ELF" #vu8(#x7f #x45 #x4c #x46))) ;"\177ELF"
(define %ar-magic-bytes
;; Magic bytes of archives created by 'ar'. See <ar.h>.
(u8-list->bytevector (map char->integer (string->list "!<arch>\n"))))
(define (ar-file? file)
"Return true if FILE starts with the magic bytes of archives as created by
'ar'."
(define (get-header)
(call-with-input-file file
(lambda (port)
(get-bytevector-n port 8))
#:binary #t #:guess-encoding #f))
(equal? (get-header) %ar-magic-bytes))
(define-syntax-rule (with-directory-excursion dir body ...) (define-syntax-rule (with-directory-excursion dir body ...)
"Run BODY with DIR as the process's current directory." "Run BODY with DIR as the process's current directory."
(let ((init (getcwd))) (let ((init (getcwd)))