Add a deoptimize option to add a file in non sequential chains

MFS.py

@@ -344,13 +344,16 @@ def removeFile(self, id):
       self.data_ids[chain - self.num_files] = 0
       chain = next_chain
 
-  def addFile(self, id, data):
+  def addFile(self, id, data, optimize=True):
     self.removeFile(id)
     file = MFSFile(id)
     size = len(data)
     data_chain = []
     for offset in xrange(0, size, MFS.CHUNK_SIZE):
-      chain = self.getNextFreeDataChunk()
+      if optimize:
+        chain = self.getNextFreeDataChunk()
+      else:
+        chain = self.getLastFreeDataChunk()
       if chain == -1:
         # If not enough space, free previously set chains
         for chain in data_chain:
@@ -374,6 +377,12 @@ def getNextFreeDataChunk(self):
         return i
     return -1
 
+  def getLastFreeDataChunk(self):
+    for i, chain in reversed(list(enumerate(self.data_ids))):
+      if chain == 0:
+        return i
+    return -1
+
   def generate(self):
     data = self.SYSTEM_VOLUME_HEADER_FMT.pack(self.signature, self.version,
                                                    self.capacity, self.num_files) + \

MFSUtil.py

@@ -44,6 +44,8 @@ def main():
                       "0 : packed.\n"
                       "1 : align all files on chunk start.\n"
                       "2 : align end of files on end of chunk.")
+  parser.add_argument("--deoptimize", dest="optimize", action="store_false",
+                      help="De-optimize chain sequences when adding a file to MFS.")
 
   group = parser.add_mutually_exclusive_group(required=True)
   group.add_argument("-m", "--mfs", dest="mfs", type=argparse.FileType('rb'),
@@ -93,7 +95,7 @@ def main():
         print "File ID %d already exists in the MFS System Volume" % args.file_id
         sys.exit(-1)
       data = args.add.read()
-      mfs.getSystemVolume().addFile(args.file_id, data)
+      mfs.getSystemVolume().addFile(args.file_id, data, args.optimize)
       mfs.generate()
       with argparse.FileType("wb")(args.output) as f: f.write(mfs.data)
     elif args.zip: