1 files changed, 65 insertions, 0 deletions
diff --git a/cloudinit/includer.py b/cloudinit/includer.py
new file mode 100644
index 00000000..d1022c5a
--- /dev/null
+++ b/cloudinit/includer.py
@@ -0,0 +1,65 @@
+import os
+import re
+
+from cloudinit import downloader as down
+from cloudinit import exceptions as excp
+from cloudinit import log as logging
+from cloudinit import shell as sh
+
+INCLUDE_PATT = re.compile("^#(opt_include|include)[ \t](.*)$", re.MULTILINE)
+OPT_PATS = ['opt_include']
+
+LOG = logging.getLogger(__name__)
+
+
+class Includer(object):
+
+    def __init__(self, root_fn, stack_limit=10):
+        self.root_fn = root_fn
+        self.stack_limit = stack_limit
+
+    def _read_file(self, fname):
+        return sh.read_file(fname)
+
+    def _read(self, fname, stack, rel):
+        if len(stack) >= self.stack_limit:
+            raise excp.StackExceeded("Stack limit of %s reached while including %s" % (self.stack_limit, fname))
+
+        canon_fname = self._canon_name(fname, rel)
+        if canon_fname in stack:
+            raise excp.RecursiveInclude("File %s recursively included" % (canon_fname))
+
+        stack.add(canon_fname)
+        new_rel = os.path.dirname(canon_fname)
+        contents = self._read_file(canon_fname)
+
+        def include_cb(match):
+            is_optional = (match.group(1).lower() in OPT_PATS)
+            fn = match.group(2).strip()
+            if not fn:
+                # Should we die??
+                return match.group(0)
+            else:
+                try:
+                    LOG.debug("Including file %s", fn)
+                    return self._read(fn, stack, new_rel)
+                except IOError:
+                    if is_optional:
+                        return ''
+                    else:
+                        raise
+
+        adjusted_contents = INCLUDE_PATT.sub(include_cb, contents)
+        stack.remove(fname)
+        return adjusted_contents
+
+    def _canon_name(self, fname, rel):
+        fname = fname.strip()
+        if not fname.startswith("/"):
+            fname = os.path.sep.join([rel, fname])
+        return os.path.realpath(fname)
+
+    def read(self, relative_to="."):
+        stack = set()
+        return self._read(self.root_fn, stack, rel=relative_to)
+