Use a set of helper/parsing classes to perform system configuration

Previously file modification of system configuration was done
in a functional and hard to test manner. Now instead this patch
allows for a manner that provides a nice object oriented
interface to those objects as well as makes it possible to test
those parsing entities without having to invoke distro class code.
   - Created parsers for:
    - /etc/sysconfig
    - /etc/hostname
    - resolv.conf
    - /etc/hosts

Moved duplicated functionality into the root level distro class including:
 - apply_hostname
 - set_hostname
 - *various shared configuration file names/paths*

1 files changed, 113 insertions, 0 deletions

diff --git a/cloudinit/distros/parsers/sys_conf.py b/cloudinit/distros/parsers/sys_conf.py
new file mode 100644
index 00000000..20ca1871
--- /dev/null
+++ b/cloudinit/distros/parsers/sys_conf.py
@@ -0,0 +1,113 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from StringIO import StringIO
+
+import pipes
+import re
+
+# This library is used to parse/write
+# out the various sysconfig files edited (best attempt effort)
+#
+# It has to be slightly modified though
+# to ensure that all values are quoted/unquoted correctly
+# since these configs are usually sourced into
+# bash scripts...
+import configobj
+
+# See: http://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap08.html
+# or look at the 'param_expand()' function in the subst.c file in the bash
+# source tarball...
+SHELL_VAR_RULE = r'[a-zA-Z_]+[a-zA-Z0-9_]*'
+SHELL_VAR_REGEXES = [
+    # Basic variables
+    re.compile(r"\$" + SHELL_VAR_RULE),
+    # Things like $?, $0, $-, $@
+    re.compile(r"\$[0-9#\?\-@\*]"),
+    # Things like ${blah:1} - but this one
+    # gets very complex so just try the
+    # simple path
+    re.compile(r"\$\{.+\}"),
+]
+
+
+def _contains_shell_variable(text):
+    for r in SHELL_VAR_REGEXES:
+        if r.search(text):
+            return True
+    return False
+
+
+class SysConf(configobj.ConfigObj):
+    def __init__(self, contents):
+        configobj.ConfigObj.__init__(self, contents,
+                                     interpolation=False,
+                                     write_empty_values=True)
+
+    def __str__(self):
+        contents = self.write()
+        out_contents = StringIO()
+        if isinstance(contents, (list, tuple)):
+            out_contents.write("\n".join(contents))
+        else:
+            out_contents.write(str(contents))
+        return out_contents.getvalue()
+
+    def _quote(self, value, multiline=False):
+        if not isinstance(value, (str, basestring)):
+            raise ValueError('Value "%s" is not a string' % (value))
+        if len(value) == 0:
+            return ''
+        quot_func = None
+        if value[0] in ['"', "'"] and value[-1] in ['"', "'"]:
+            if len(value) == 1:
+                quot_func = (lambda x:
+                                self._get_single_quote(x) % x)
+        else:
+            # Quote whitespace if it isn't the start + end of a shell command
+            if value.strip().startswith("$(") and value.strip().endswith(")"):
+                pass
+            else:
+                if re.search(r"[\t\r\n ]", value):
+                    if _contains_shell_variable(value):
+                        # If it contains shell variables then we likely want to
+                        # leave it alone since the pipes.quote function likes
+                        # to use single quotes which won't get expanded...
+                        if re.search(r"[\n\"']", value):
+                            quot_func = (lambda x:
+                                            self._get_triple_quote(x) % x)
+                        else:
+                            quot_func = (lambda x:
+                                            self._get_single_quote(x) % x)
+                    else:
+                        quot_func = pipes.quote
+        if not quot_func:
+            return value
+        return quot_func(value)
+
+    def _write_line(self, indent_string, entry, this_entry, comment):
+        # Ensure it is formatted fine for
+        # how these sysconfig scripts are used
+        val = self._decode_element(self._quote(this_entry))
+        key = self._decode_element(self._quote(entry))
+        cmnt = self._decode_element(comment)
+        return '%s%s%s%s%s' % (indent_string,
+                               key,
+                               self._a_to_u('='),
+                               val,
+                               cmnt)