1 files changed, 50 insertions, 0 deletions
diff --git a/Tools/freeze/bkfile.py b/Tools/freeze/bkfile.py
new file mode 100644
index 0000000..6d0ccde
--- /dev/null
+++ b/Tools/freeze/bkfile.py
@@ -0,0 +1,50 @@
+_orig_open = open
+
+class _BkFile:
+	def __init__(self, file, mode, bufsize):
+		import os
+		self.__filename = file
+		self.__backup = file + '~'
+		try:
+			os.unlink(self.__backup)
+		except os.error:
+			pass
+		try:
+			os.rename(file, self.__backup)
+		except os.error:
+			self.__backup = None
+		self.__file = _orig_open(file, mode, bufsize)
+		self.closed = self.__file.closed
+		self.fileno = self.__file.fileno
+		self.flush = self.__file.flush
+		self.isatty = self.__file.isatty
+		self.mode = self.__file.mode
+		self.name = self.__file.name
+		self.read = self.__file.read
+		self.readinto = self.__file.readinto
+		self.readline = self.__file.readline
+		self.readlines = self.__file.readlines
+		self.seek = self.__file.seek
+		self.softspace = self.__file.softspace
+		self.tell = self.__file.tell
+		self.truncate = self.__file.truncate
+		self.write = self.__file.write
+		self.writelines = self.__file.writelines
+
+	def close(self):
+		self.__file.close()
+		if self.__backup is None:
+			return
+		import cmp
+		# don't use cmp.cmp because of NFS bugs :-( and
+		# anyway, the stat mtime values differ so do_cmp will
+		# most likely be called anyway
+		if cmp.do_cmp(self.__backup, self.__filename):
+			import os
+			os.unlink(self.__filename)
+			os.rename(self.__backup, self.__filename)
+
+def open(file, mode = 'r', bufsize = -1):
+	if 'w' not in mode:
+		return _orig_open(file, mode, bufsize)
+	return _BkFile(file, mode, bufsize)