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file-systems: Fix F2FS volume name accessor.

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Follow-up to 23b37c3d40.

* gnu/build/file-systems.scm (bytevector-utf16-length): New procedure.
(null-terminated-utf16->string): New procedure.
(f2fs-superblock-volume-name): Use it.
This commit is contained in:
Danny Milosavljevic 2020-05-03 17:29:39 +02:00
parent f8a0065ae3
commit f73f4b3a2d
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1 changed files with 19 additions and 1 deletions
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20
gnu/build/file-systems.scm
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@ -98,6 +98,22 @@ takes a bytevector and returns #t when it's a valid superblock."
(define null-terminated-latin1->string
(cut latin1->string <> zero?))
(define (bytevector-utf16-length bv)
"Given a bytevector BV containing a NUL-terminated UTF16-encoded string,
determine where the NUL terminator is and return its index. If there's no
NUL terminator, return the size of the bytevector."
(let ((length (bytevector-length bv)))
(let loop ((index 0))
(if (< index length)
(if (zero? (bytevector-u16-ref bv index 'little))
index
(loop (+ index 2)))
length))))
(define (null-terminated-utf16->string bv endianness)
(utf16->string (sub-bytevector bv 0 (bytevector-utf16-length bv))
endianness))
;;;
;;; Ext2 file systems.
@ -377,7 +393,9 @@ if DEVICE does not contain an F2FS file system."
(define (f2fs-superblock-volume-name sblock)
"Return the volume name of SBLOCK as a string of at most 512 characters, or
#f if SBLOCK has no volume name."
(utf16->string (sub-bytevector sblock (- (+ #x470 12) #x400) 512) %f2fs-endianness))
(null-terminated-utf16->string
(sub-bytevector sblock (- (+ #x470 12) #x400) 512)
%f2fs-endianness))
(define (check-f2fs-file-system device)
"Return the health of a F2FS file system on DEVICE."