1 files changed, 79 insertions, 0 deletions
diff --git a/pym/portage/util/writeable_check.py b/pym/portage/util/writeable_check.py
new file mode 100644
index 000000000..e6ddce680
--- /dev/null
+++ b/pym/portage/util/writeable_check.py
@@ -0,0 +1,79 @@
+#-*- coding:utf-8 -*-
+# Copyright 2014 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+"""
+Methods to check whether Portage is going to write to read-only filesystems.
+Since the methods are not portable across different OSes, each OS needs its
+own method. To expand RO checking for different OSes, add a method which
+accepts a list of directories and returns a list of mounts which need to be
+remounted RW, then add "elif ostype == (the ostype value for your OS)" to
+get_ro_checker().
+"""
+from __future__ import unicode_literals
+
+import io
+import logging
+import re
+
+from portage import _encodings
+from portage.util import writemsg_level
+from portage.localization import _
+from portage.data import ostype
+
+
+def get_ro_checker():
+	"""
+	Uses the system type to find an appropriate method for testing whether Portage
+	is going to write to any read-only filesystems.
+
+	@return:
+	1. A method for testing for RO filesystems appropriate to the current system.
+	"""
+	return _CHECKERS.get(ostype, empty_ro_checker)
+
+
+def linux_ro_checker(dir_list):
+	"""
+	Use /proc/mounts to check that no directories installed by the ebuild are set
+	to be installed to a read-only filesystem.
+
+	@param dir_list: A list of directories installed by the ebuild.
+	@type dir_list: List
+	@return:
+	1. A list of filesystems which are both set to be written to and are mounted
+	read-only, may be empty.
+	"""
+	ro_filesystems = set()
+
+	try:
+		with io.open("/proc/mounts", mode='r', encoding=_encodings['content'],
+			errors='replace') as f:
+			roregex = re.compile(r'(\A|,)ro(\Z|,)')
+			for line in f:
+				if roregex.search(line.split(" ")[3].strip()) is not None:
+					romount = line.split(" ")[1].strip()
+					ro_filesystems.add(romount)
+
+	# If /proc/mounts can't be read, assume that there are no RO
+	# filesystems and return.
+	except EnvironmentError:
+		writemsg_level(_("!!! /proc/mounts cannot be read"),
+			level=logging.WARNING, noiselevel=-1)
+		return []
+
+	return set.intersection(ro_filesystems, set(dir_list))
+
+
+def empty_ro_checker(dir_list):
+	"""
+	Always returns [], this is the fallback function if the system does not have
+	an ro_checker method defined.
+	"""
+	return []
+
+
+# _CHECKERS is a map from ostype output to the appropriate function to return
+# in get_ro_checker.
+_CHECKERS = {
+	"Linux": linux_ro_checker,
+}