bootloader: Factorize write-file-on-device.

* gnu/bootloader/extlinux.scm (install-extlinux): Factorize bootloader
writing in a new procedure write-file-on-device defined in (gnu build
bootloader).
* gnu/build/bootloader.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add new file.
* gnu/system/vm.scm (qemu-img): Adapt to import and use (gnu build bootloader)
module during derivation building.
* gnu/scripts/system.scm (bootloader-installer-derivation): Ditto.

1 files changed, 37 insertions, 0 deletions

diff --git a/gnu/build/bootloader.scm b/gnu/build/bootloader.scm
new file mode 100644
index 0000000000..d00674dd40
--- /dev/null
+++ b/gnu/build/bootloader.scm
@@ -0,0 +1,37 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
+;;;
+;;; 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 (gnu build bootloader)
+  #:use-module (ice-9 binary-ports)
+  #:export (write-file-on-device))
+
+
+;;;
+;;; Writing utils.
+;;;
+
+(define (write-file-on-device file size device offset)
+  "Write SIZE bytes from FILE to DEVICE starting at OFFSET."
+  (call-with-input-file file
+    (lambda (input)
+      (let ((bv (get-bytevector-n input size)))
+        (call-with-output-file device
+          (lambda (output)
+            (seek output offset SEEK_SET)
+            (put-bytevector output bv))
+          #:binary #t)))))