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guix/guix/cpio.scm

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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2015 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2021 Tobias Geerinckx-Rice <me@tobias.gr>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (guix cpio)
#:use-module ((guix build syscalls) #:select (device-number
device-number->major+minor))
#:use-module ((guix build utils) #:select (dump-port))
#:use-module (srfi srfi-9)
#:use-module (srfi srfi-11)
#:use-module (rnrs bytevectors)
#:use-module (rnrs io ports)
#:use-module (ice-9 match)
#:export (cpio-header?
make-cpio-header
file->cpio-header
file->cpio-header*
special-file->cpio-header*
write-cpio-header
read-cpio-header
write-cpio-archive))
;;; Commentary:
;;;
;;; This module implements the cpio "new ASCII" format, bit-for-bit identical
;;; to GNU cpio with the '-H newc' option.
;;;
;;; Code:
;; Values for 'mode', OR'd together.
(define C_IRUSR #o000400)
(define C_IWUSR #o000200)
(define C_IXUSR #o000100)
(define C_IRGRP #o000040)
(define C_IWGRP #o000020)
(define C_IXGRP #o000010)
(define C_IROTH #o000004)
(define C_IWOTH #o000002)
(define C_IXOTH #o000001)
(define C_ISUID #o004000)
(define C_ISGID #o002000)
(define C_ISVTX #o001000)
(define C_FMT #o170000) ;bit mask
(define C_ISBLK #o060000)
(define C_ISCHR #o020000)
(define C_ISDIR #o040000)
(define C_ISFIFO #o010000)
(define C_ISSOCK #o0140000)
(define C_ISLNK #o0120000)
(define C_ISCTG #o0110000)
(define C_ISREG #o0100000)
(define MAGIC
;; The "new" portable format with ASCII header, as produced by GNU cpio with
;; '-H newc'.
(string->number "070701" 16))
(define (read-header-field size port)
(string->number (get-string-n port size) 16))
(define (write-header-field value size port)
(put-bytevector port
(string->utf8
(string-pad (string-upcase (number->string value 16))
size #\0))))
(define-syntax define-pack
(syntax-rules ()
((_ type ctor pred write read (field-names field-sizes field-getters) ...)
(begin
(define-record-type type
(ctor field-names ...)
pred
(field-names field-getters) ...)
(define (read port)
(set-port-encoding! port "ISO-8859-1")
(ctor (read-header-field field-sizes port)
...))
(define (write obj port)
(let* ((size (+ field-sizes ...)))
(match obj
(($ type field-names ...)
(write-header-field field-names field-sizes port)
...))))))))
;; cpio header in "new ASCII" format, without checksum.
(define-pack <cpio-header>
%make-cpio-header cpio-header?
write-cpio-header read-cpio-header
(magic 6 cpio-header-magic)
(ino 8 cpio-header-inode)
(mode 8 cpio-header-mode)
(uid 8 cpio-header-uid)
(gid 8 cpio-header-gid)
(nlink 8 cpio-header-nlink)
(mtime 8 cpio-header-mtime)
(file-size 8 cpio-header-file-size)
(dev-maj 8 cpio-header-device-major)
(dev-min 8 cpio-header-device-minor)
(rdev-maj 8 cpio-header-rdevice-major)
(rdev-min 8 cpio-header-rdevice-minor)
(name-size 8 cpio-header-name-size)
(checksum 8 cpio-header-checksum)) ;0 for "newc" format
(define* (make-cpio-header #:key
(inode 0)
(mode (logior C_ISREG C_IRUSR))
(uid 0) (gid 0)
(nlink 1) (mtime 0) (size 0)
(dev 0) (rdev 0) (name-size 0))
"Return a new cpio file header."
(let-values (((major minor) (device-number->major+minor dev))
((rmajor rminor) (device-number->major+minor rdev)))
(%make-cpio-header MAGIC
inode mode uid gid
nlink mtime
(if (or (= C_ISLNK (logand mode C_FMT))
(= C_ISREG (logand mode C_FMT)))
size
0)
major minor rmajor rminor
(+ name-size 1) ;include trailing zero
0))) ;checksum
(define (mode->type mode)
"Given the number MODE, return a symbol representing the kind of file MODE
denotes, similar to 'stat:type'."
(let ((fmt (logand mode C_FMT)))
(cond ((= C_ISREG fmt) 'regular)
((= C_ISDIR fmt) 'directory)
((= C_ISLNK fmt) 'symlink)
((= C_ISBLK fmt) 'block-special)
((= C_ISCHR fmt) 'char-special)
(else
(error "unsupported file type" mode)))))
(define* (file->cpio-header file #:optional (file-name file)
#:key (stat lstat))
"Return a cpio header corresponding to the info returned by STAT for FILE,
using FILE-NAME as its file name."
(let ((st (stat file)))
(make-cpio-header #:inode (stat:ino st)
#:mode (stat:mode st)
#:uid (stat:uid st)
#:gid (stat:gid st)
#:nlink (stat:nlink st)
#:mtime (stat:mtime st)
#:size (stat:size st)
#:dev (stat:dev st)
#:rdev (stat:rdev st)
#:name-size (string-length file-name))))
(define* (file->cpio-header* file
#:optional (file-name file)
#:key (stat lstat))
"Similar to 'file->cpio-header', but return a header with a zeroed
modification time, inode number, UID/GID, etc. This allows archives to be
produced in a deterministic fashion."
(let ((st (stat file)))
(make-cpio-header #:mode (stat:mode st)
#:nlink (stat:nlink st)
#:size (stat:size st)
#:name-size (string-length file-name))))
(define* (special-file->cpio-header* file
device-type
device-major
device-minor
permission-bits
#:optional (file-name file))
"Create a character or block device header.
DEVICE-TYPE is either 'char-special or 'block-special.
The number of hard links is assumed to be 1."
(make-cpio-header #:mode (logior (match device-type
('block-special C_ISBLK)
('char-special C_ISCHR))
permission-bits)
#:nlink 1
#:rdev (device-number device-major device-minor)
#:name-size (string-length file-name)))
(define %trailer
"TRAILER!!!")
(define %last-header
;; The header that marks the end of the archive.
(make-cpio-header #:mode 0
#:name-size (string-length %trailer)))
(define* (write-cpio-archive files port
#:key (file->header file->cpio-header))
"Write to PORT a cpio archive in \"new ASCII\" format containing all of FILES.
The archive written to PORT is intended to be bit-identical to what GNU cpio
produces with the '-H newc' option."
(define (write-padding offset port)
(let ((padding (modulo (- 4 (modulo offset 4)) 4)))
(put-bytevector port (make-bytevector padding))))
(define (pad-block port)
;; Write padding to PORT such that we finish with a 512-byte block.
;; XXX: We rely on PORT's internal state, assuming it's a file port.
(let* ((offset (seek port 0 SEEK_CUR))
(padding (modulo (- 512 (modulo offset 512)) 512)))
(put-bytevector port (make-bytevector padding))))
(define (dump-file file)
(let* ((header (file->header file))
(size (cpio-header-file-size header)))
(write-cpio-header header port)
(put-bytevector port (string->utf8 file))
(put-u8 port 0)
;; We're padding the header + following file name + trailing zero, and
;; the header is 110 byte long.
(write-padding (+ 110 1 (string-length file)) port)
(case (mode->type (cpio-header-mode header))
((regular)
(call-with-input-file file
(lambda (input)
(dump-port input port))))
((symlink)
(let ((target (readlink file)))
(put-string port target)))
((directory)
#t)
((block-special)
#t)
((char-special)
#t)
(else
(error "file type not supported")))
;; Pad the file content.
(write-padding size port)))
(set-port-encoding! port "ISO-8859-1")
(for-each dump-file files)
(write-cpio-header %last-header port)
(put-bytevector port (string->utf8 %trailer))
(write-padding (string-length %trailer) port)
;; Pad so the last block is 512-byte long.
(pad-block port))
;;; cpio.scm ends here
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