Make blendfile.py reading/parsing slightly more robust/helpful in bro…

…ken .blend files cases.

io_blend_utils/blend/blendfile.py

@@ -123,6 +123,8 @@ def __init__(self, handle):
  self.block_header_struct = self.header.create_block_header_struct()
  self.blocks = []
  self.code_index = {}
+ self.structs = []
+ self.sdna_index_from_id = {}
 
  block = BlendFileBlock(handle, self)
  while block.code != b'ENDB':
@@ -140,6 +142,9 @@ def __init__(self, handle):
  self.is_modified = False
  self.blocks.append(block)
 
+ if not self.structs:
+ raise Exception("No DNA1 block in file, this is not a valid .blend file!")
+
  # cache (could lazy init, incase we never use?)
  self.block_from_offset = {block.addr_old: block for block in self.blocks if block.code != b'ENDB'}
 
@@ -311,12 +316,21 @@ def __init__(self, handle, bfile):
  self.user_data = None
 
  data = handle.read(bfile.block_header_struct.size)
+
+ if len(data) != bfile.block_header_struct.size:
+ print("WARNING! Blend file seems to be badly truncated!")
+ self.code = b'ENDB'
+ self.size = 0
+ self.addr_old = 0
+ self.sdna_index = 0
+ self.count = 0
+ self.file_offset = 0
+ return
  # header size can be 8, 20, or 24 bytes long
  # 8: old blend files ENDB block (exception)
  # 20: normal headers 32 bit platform
  # 24: normal headers 64 bit platform
  if len(data) > 15:
-
  blockheader = bfile.block_header_struct.unpack(data)
  self.code = blockheader[0].partition(b'\0')[0]
  if self.code != b'ENDB':