RTM-JSON conversion script

# This script requires Python 3.x
# It will convert a RTM-file (Operation Flashpoint animation) to a JSON-file
# and back.
#
# Examples:
#     python rtm.py cesnapilot.rtm
# this creates a "cesnapilot.js"
#
#     python rtm.py cesnapilot.js
# this creates a "cesnapilot.rtm"

import struct
import json

def clean_string(s):
   return s[:s.find(b"\0")]

class RtmLoadException(Exception):
   pass

class RTM:
   def __init__(self):
      self.move = [0.0, 0.0, 0.0]
      self.bones = []
      self.frames = []

   def readFromPath(self, path):
      with open(path, "rb") as file:
         self.readFromFile(file)

   def readFromFile(self, file):
      magic = struct.unpack("8s", file.read(8))[0]
      if magic != b"RTM_0101":
         raise RtmLoadException("Unexpected magic value %s" % magic)

      self.move = struct.unpack("fff", file.read(4*3))
      number_of_frames = struct.unpack("i", file.read(4))[0]
      number_of_bones = struct.unpack("i", file.read(4))[0]

      for i in range(number_of_bones):
         name = clean_string(struct.unpack("32s", file.read(32))[0]).decode("cp1252")
         self.bones.append(name)

      for i in range(number_of_frames):
         frame_time = struct.unpack("f", file.read(4))[0]
         bone_transform = {}
         for ib in range(number_of_bones):
            bone = clean_string(struct.unpack("32s", file.read(32))[0]).decode("cp1252")
            transform = struct.unpack("ffffffffffff", file.read(12*4))
            bone_transform[bone] = transform
         self.frames.append({"frame_time": frame_time, "transforms": bone_transform})

   def writeToPath(self, path):
      with open(path, "wb") as file:
         self.writeToFile(file)

   def writeToFile(self, file):
      file.write(b"RTM_0101")
      file.write(struct.pack("fff", *self.move))

      file.write(struct.pack("i", len(self.frames)))
      file.write(struct.pack("i", len(self.bones)))

      for b in self.bones:
         file.write(struct.pack("32s", b.encode("cp1252")))

      for frame in self.frames:
         file.write(struct.pack("f", frame["frame_time"]))
         for bone, transform in frame["transforms"].items():
            file.write(struct.pack("32s", bone.encode("cp1252")))
            file.write(struct.pack("ffffffffffff", *transform))

   def to_json(self):
      return json.dumps({
         "move": self.move,
         "bones": self.bones,
         "frames": self.frames
         }, sort_keys=True, indent=4)

   def from_json(self, json_string):
      data = json.loads(json_string)
      self.move = data["move"]
      self.bones = data["bones"]
      self.frames = data["frames"]

if __name__ == '__main__':
   import sys
   if len(sys.argv) <= 1:
      print("USAGE:")
      print("python rtm.py INPUT.rtm")
      print("\tConverts to JSON, creates INPUT.js\n")
      print("python rtm.py INPUT.js")
      print("\tConverts to RTM, creates INPUT.rtm")
   else:
      import os.path
      import_path = sys.argv[1]
      root, ext = os.path.splitext(import_path)
      ext = ext.lower()

      rtm = RTM()

      if ext == ".rtm":
         export_path = "{}.js".format(root)
         rtm.readFromPath(import_path)
         with open(export_path, "w", encoding="utf-8") as file:
            file.write(rtm.to_json())
            print("Exported {} successfully to {}".format(import_path, export_path))
      elif ext == ".js":
         export_path = "{}.rtm".format(root)
         rtm.from_json(open(import_path,"r",encoding="utf-8").read())
         rtm.writeToPath(export_path)
         print("Exported {} successfully to {}".format(import_path, export_path))