Fixed ZIP64 compatibility, now local header filesizes are always set …

…to 0xFFFFFFFF to force reading from extra field, extra field size is now written correctly (was always 0 before)

pyaff4/zip.py

@@ -170,7 +170,9 @@ def empty(self):
 
     def Pack(self):
         # Size of extra less the header.
-        #self.Set("data_size", self.sizeof() - 4)
+        # Data size needs to be set for a zip64 extra field to be compliant with zip specification.
+        self.Set("data_size", self.sizeof() - 4)
+        # Don't think the value set below is used anywhere, might be removable.
         self.data_size = self.sizeof()
         return struct.pack(self.format_string(),
                            *[v for t, _, v in self.fields if v is not None])
@@ -311,22 +313,21 @@ def WriteFileHeader(self, backing_store):
         if USE_UNICODE:
             header.flags = header.flags | (1 << 11)
 
+        # For local header force usage of ZIP64 even when not needed as we do not know the file size, nor what it would
+        # compress to, before writing the header the first time
+        # (similar to how zip works in command line when compressing from stdin)
         # Always calculate and reserve the zip64 header size
         # Alternatively, as the size of the file is not passed on first header creation
         # a file larger than 4GB would triggers creation of the header only after file has been written and would get
         # the first bytes overwritten creating a corrupted container.
-        # Only set header to 0xFFFFFFFF if really needed to look into extra header.
-
         extra_header_64 = Zip64FileHeaderExtensibleField()
-        if self.file_size > ZIP32_MAX_SIZE:
-            header.file_size = 0xFFFFFFFF
+
+        header.file_size = 0xFFFFFFFF
         extra_header_64.Set("file_size", self.file_size)
 
-        if self.compress_size > ZIP32_MAX_SIZE:
-            header.compress_size = 0xFFFFFFFF
+        header.compress_size = 0xFFFFFFFF
         extra_header_64.Set("compress_size", self.compress_size)
 
-        # Write the extra header in any case
         header.extra_field_len = extra_header_64.sizeof()
 
         backing_store.SeekWrite(self.file_header_offset)