1 files changed, 86 insertions, 0 deletions
diff --git a/git/index/util.py b/git/index/util.py
new file mode 100644
index 00000000..bd5fcc03
--- /dev/null
+++ b/git/index/util.py
@@ -0,0 +1,86 @@
+"""Module containing index utilities"""
+import struct
+import tempfile
+import os
+
+__all__ = ( 'TemporaryFileSwap', 'post_clear_cache', 'default_index', 'git_working_dir' )
+
+#{ Aliases 
+pack = struct.pack
+unpack = struct.unpack
+
+
+#} END aliases
+
+class TemporaryFileSwap(object):
+	"""Utility class moving a file to a temporary location within the same directory
+	and moving it back on to where on object deletion."""
+	__slots__ = ("file_path", "tmp_file_path")
+
+	def __init__(self, file_path):
+		self.file_path = file_path
+		self.tmp_file_path = self.file_path + tempfile.mktemp('','','')
+		# it may be that the source does not exist
+		try:
+			os.rename(self.file_path, self.tmp_file_path)
+		except OSError:
+			pass
+
+	def __del__(self):
+		if os.path.isfile(self.tmp_file_path):
+			if os.name == 'nt' and os.path.exists(self.file_path):
+				os.remove(self.file_path)
+			os.rename(self.tmp_file_path, self.file_path)
+		# END temp file exists
+
+
+#{ Decorators 
+
+def post_clear_cache(func):
+	"""Decorator for functions that alter the index using the git command. This would
+	invalidate our possibly existing entries dictionary which is why it must be
+	deleted to allow it to be lazily reread later.
+
+	:note:
+		This decorator will not be required once all functions are implemented
+		natively which in fact is possible, but probably not feasible performance wise.
+	"""
+	def post_clear_cache_if_not_raised(self, *args, **kwargs):
+		rval = func(self, *args, **kwargs)
+		self._delete_entries_cache()
+		return rval
+
+	# END wrapper method
+	post_clear_cache_if_not_raised.__name__ = func.__name__
+	return post_clear_cache_if_not_raised
+
+def default_index(func):
+	"""Decorator assuring the wrapped method may only run if we are the default
+	repository index. This is as we rely on git commands that operate
+	on that index only. """
+	def check_default_index(self, *args, **kwargs):
+		if self._file_path != self._index_path():
+			raise AssertionError( "Cannot call %r on indices that do not represent the default git index" % func.__name__ )
+		return func(self, *args, **kwargs)
+	# END wrpaper method
+
+	check_default_index.__name__ = func.__name__
+	return check_default_index
+
+def git_working_dir(func):
+	"""Decorator which changes the current working dir to the one of the git 
+	repository in order to assure relative paths are handled correctly"""
+	def set_git_working_dir(self, *args, **kwargs):
+		cur_wd = os.getcwd()
+		os.chdir(self.repo.working_tree_dir)
+		try:
+			return func(self, *args, **kwargs)
+		finally:
+			os.chdir(cur_wd)
+		# END handle working dir
+	# END wrapper
+	
+	set_git_working_dir.__name__ = func.__name__
+	return set_git_working_dir
+
+#} END decorators