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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2014 Ludovic Courtès <ludo@gnu.org>
;;;
;;; 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 build graft)
#:use-module (guix build utils)
#:use-module (rnrs bytevectors)
#:use-module (rnrs io ports)
#:use-module (ice-9 match)
#:use-module (ice-9 ftw)
#:export (replace-store-references
rewrite-directory))
;;; Commentary:
;;;
;;; This module supports "grafts". Grafting a directory means rewriting it,
;;; with references to some specific items replaced by references to other
;;; store items---the grafts.
;;;
;;; This method is used to provide fast security updates as only the leaves of
;;; the dependency graph need to be grafted, even when the security updates
;;; affect a core component such as Bash or libc. It is based on the idea of
;;; 'replace-dependency' implemented by Shea Levy in Nixpkgs.
;;;
;;; Code:
(define* (replace-store-references input output mapping
#:optional (store (%store-directory)))
"Read data from INPUT, replacing store references according to MAPPING, and
writing the result to OUTPUT."
(define pattern
(let ((nix-base32-chars
'(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9
#\a #\b #\c #\d #\f #\g #\h #\i #\j #\k #\l #\m #\n
#\p #\q #\r #\s #\v #\w #\x #\y #\z)))
`(,@(map char-set (string->list store))
,(char-set #\/)
,@(make-list 32 (list->char-set nix-base32-chars))
,(char-set #\-))))
;; We cannot use `regexp-exec' here because it cannot deal with strings
;; containing NUL characters, hence 'fold-port-matches'.
(with-fluids ((%default-port-encoding #f))
(when (file-port? input)
(setvbuf input _IOFBF 65536))
(when (file-port? output)
(setvbuf output _IOFBF 65536))
(let* ((len (+ 34 (string-length store)))
(mapping (map (match-lambda
((origin . replacement)
(unless (string=? (string-drop origin len)
(string-drop replacement len))
(error "invalid replacement" origin replacement))
(cons (string-take origin len)
(string-take replacement len))))
mapping)))
(fold-port-matches (lambda (string result)
(match (assoc-ref mapping string)
(#f
(put-bytevector output (string->utf8 string)))
((= string->utf8 replacement)
(put-bytevector output replacement)))
#t)
#f
pattern
input
(lambda (char result) ;unmatched
(put-u8 output (char->integer char))
result)))))
(define* (rewrite-directory directory output mapping
#:optional (store (%store-directory)))
"Copy DIRECTORY to OUTPUT, replacing strings according to MAPPING, a list of
file name pairs."
(define prefix-len
(string-length directory))
(define (destination file)
(string-append output (string-drop file prefix-len)))
(define (rewrite-leaf file stat result)
(case (stat:type stat)
((symlink)
(let ((target (readlink file)))
(symlink (call-with-output-string
(lambda (output)
(replace-store-references (open-input-string target)
output mapping
store)))
(destination file))))
((regular)
(with-fluids ((%default-port-encoding #f))
(call-with-input-file file
(lambda (input)
(call-with-output-file (destination file)
(lambda (output)
(replace-store-references input output mapping
store)
(chmod output (stat:perms stat))))))))
(else
(error "unsupported file type" stat))))
(file-system-fold (const #t)
rewrite-leaf
(lambda (directory stat result) ;down
(mkdir (destination directory)))
(const #t) ;up
(const #f) ;skip
(lambda (file stat errno result) ;error
(error "read error" file stat errno))
#f
directory
lstat))
;;; graft.scm ends here
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