diff options
Diffstat (limited to 'guix/build/utils.scm')
| -rw-r--r-- | guix/build/utils.scm | 35 |
1 files changed, 33 insertions, 2 deletions
diff --git a/guix/build/utils.scm b/guix/build/utils.scm index dd5a91f52f..5ea3b98353 100644 --- a/guix/build/utils.scm +++ b/guix/build/utils.scm @@ -3,11 +3,11 @@ ;;; Copyright © 2013 Andreas Enge <andreas@enge.fr> ;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org> ;;; Copyright © 2015, 2018, 2021 Mark H Weaver <mhw@netris.org> -;;; Copyright © 2018 Arun Isaac <arunisaac@systemreboot.net> +;;; Copyright © 2018, 2022 Arun Isaac <arunisaac@systemreboot.net> ;;; Copyright © 2018, 2019 Ricardo Wurmus <rekado@elephly.net> ;;; Copyright © 2020 Efraim Flashner <efraim@flashner.co.il> ;;; Copyright © 2020, 2021 Maxim Cournoyer <maxim.cournoyer@gmail.com> -;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be> +;;; Copyright © 2021, 2022 Maxime Devos <maximedevos@telenet.be> ;;; Copyright © 2021 Brendan Tildesley <mail@brendan.scot> ;;; ;;; This file is part of GNU Guix. @@ -60,8 +60,11 @@ directory-exists? executable-file? symbolic-link? + switch-symlinks call-with-temporary-output-file call-with-ascii-input-file + file-header-match + png-file? elf-file? ar-file? gzip-file? @@ -238,6 +241,25 @@ introduce the version part." "Return #t if FILE is a symbolic link (aka. \"symlink\".)" (eq? (stat:type (lstat file)) 'symlink)) +(define (switch-symlinks link target) + "Atomically switch LINK, a symbolic link, to point to TARGET. Works +both when LINK already exists and when it does not." + (let ((pivot (string-append link ".new"))) + ;; Create pivot link, deleting it if it already exists. This can + ;; happen if a previous switch-symlinks was interrupted. + (let symlink/remove-old () + (catch 'system-error + (lambda () + (symlink target pivot)) + (lambda args + (if (= (system-error-errno args) EEXIST) + (begin + ;; Remove old link and retry. + (delete-file pivot) + (symlink/remove-old)) + (apply throw args))))) + (rename-file pivot link))) + (define (call-with-temporary-output-file proc) "Call PROC with a name of a temporary file and open output port to that file; close the file and delete it when leaving the dynamic extent of this @@ -291,6 +313,15 @@ with the bytes in HEADER, a bytevector." #f ;FILE is a directory (apply throw args)))))) +(define %png-magic-bytes + ;; Magic bytes of PNG images, see ‘5.2 PNG signatures’ in + ;; ‘Portable Network Graphics (PNG) Specification (Second Edition)’ + ;; on <https://www.w3.org/TR/PNG/>. + #vu8(137 80 78 71 13 10 26 10)) + +(define png-file? + (file-header-match %png-magic-bytes)) + (define %elf-magic-bytes ;; Magic bytes of ELF files. See <elf.h>. (u8-list->bytevector (map char->integer (string->list "\x7FELF")))) |