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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2014, 2015, 2016 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 threads)
#: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 (rename-matching-files directory mapping)
"Apply MAPPING to the names of all the files in DIRECTORY, where MAPPING is
a list of store file name pairs."
(let* ((mapping (map (match-lambda
((source . target)
(cons (basename source) (basename target))))
mapping))
(matches (find-files directory
(lambda (file stat)
(assoc-ref mapping (basename file)))
#:directories? #t)))
;; XXX: This is not quite correct: if MAPPING contains "foo", and
;; DIRECTORY contains "bar/foo/foo", we first rename "bar/foo" and then
;; "bar/foo/foo" no longer exists so we fail. Oh well, surely that's good
;; enough!
(for-each (lambda (file)
(let ((target (assoc-ref mapping (basename file))))
(rename-file file
(string-append (dirname file) "/" target))))
matches)))
(define (exit-on-exception proc)
"Return a procedure that wraps PROC so that 'primitive-exit' is called when
an exception is caught."
(lambda (arg)
(catch #t
(lambda ()
(proc arg))
(lambda (key . args)
;; Since ports are not thread-safe as of Guile 2.0, reopen stderr.
(let ((port (fdopen 2 "w0")))
(print-exception port #f key args)
(primitive-exit 1))))))
(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)
(let ((stat (lstat file))
(dest (destination file)))
(mkdir-p (dirname dest))
(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)))
dest)))
((regular)
(with-fluids ((%default-port-encoding #f))
(call-with-input-file file
(lambda (input)
(call-with-output-file dest
(lambda (output)
(replace-store-references input output mapping
store)
(chmod output (stat:perms stat))))))))
((directory)
(mkdir-p dest))
(else
(error "unsupported file type" stat)))))
;; XXX: Work around occasional "suspicious ownership or permission" daemon
;; errors that arise when we create the top-level /gnu/store/… directory as
;; #o777.
(umask #o022)
;; Use 'exit-on-exception' to force an exit upon I/O errors, given that
;; 'n-par-for-each' silently swallows exceptions.
;; See <http://bugs.gnu.org/23581>.
(n-par-for-each (parallel-job-count)
(exit-on-exception rewrite-leaf)
(find-files directory (const #t)
#:directories? #t))
(rename-matching-files output mapping))
;;; graft.scm ends here
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