Fix reading directly from the disc

Getting the file size with os.stat() does not work with block devices.

You can now:

  libray -i /dev/sg0 -o test.iso

README.md

@@ -56,10 +56,17 @@ required arguments:
   -i ISO, --iso ISO     Path to .iso file
 ```
 
-Rip a PS3 to .ISO with an appropriate blu-ray drive: https://rpcs3.net/quickstart (see "Compatible Blu-ray disc drives section"). 
+You need to use an appropriate blu-ray drive: https://rpcs3.net/quickstart (see "Compatible Blu-ray disc drives section").
-Then just feed the .ISO to libray which will try to download an IRD decryption file for your iso. 
 
-Example:
+On some systems (eg. Linux), you can decrypt directly from the disc.
+
+```
+libray -i /dev/sr0 -o ps3_game_decrypted.iso
+```
+
+Libray will try to download an IRD decryption file for your iso:
+
+Alternatively, you can first rip the disc to an ISO file and then decrypt from the ISO file:
 
 ```
 libray -i ps3_game.iso -o ps3_game_decrypted.iso

libray/core.py

@@ -58,7 +58,10 @@ ISO_IV = to_bytes("69474772af6fdab342743aefaa186287")
 
 def filesize(filename):
   """Get size of a file in bytes from os.stat"""
-  return os.stat(filename).st_size
+  try:
+    return open(filename, "rb").seek(0, 2)
+  except:
+    return os.stat(filename).st_size
 
 
 def read_seven_bit_encoded_int(fileobj, order):