MOBI Output: Ensure that MOBI files always have 8KB worth of null bytes at the end of record 0. This appears to be necessary for Amazon to be able to add DRM to calibre generated MOBI files sent to their publishing service.

src/calibre/ebooks/metadata/mobi.py

@@ -259,6 +259,7 @@ def create_exth(self, new_title=None, exth=None):
         trail = len(new_record0.getvalue()) % 4
         pad = '\0' * (4 - trail) # Always pad w/ at least 1 byte
         new_record0.write(pad)
+        new_record0.write('\0'*(1024*8))
 
         # Rebuild the stream, update the pdbrecords pointers
         self.patchSection(0,new_record0.getvalue())

src/calibre/ebooks/mobi/debug.py

@@ -274,7 +274,7 @@ def __init__(self, record0):
             self.exth = EXTHHeader(self.raw[self.exth_offset:])
 
             self.end_of_exth = self.exth_offset + self.exth.length
-            self.bytes_after_exth = len(self.raw) - self.end_of_exth
+            self.bytes_after_exth = self.fullname_offset - self.end_of_exth
 
     def __str__(self):
         ans = ['*'*20 + ' MOBI Header '+ '*'*20]
@@ -321,6 +321,9 @@ def __str__(self):
             ans += '\n\n' + str(self.exth)
             ans += '\n\nBytes after EXTH: %d'%self.bytes_after_exth
 
+        ans += '\nNumber of bytes after full name: %d' % (len(self.raw) - (self.fullname_offset +
+                self.fullname_length))
+
         ans += '\nRecord 0 length: %d'%len(self.raw)
         return ans
 

src/calibre/ebooks/mobi/writer.py

@@ -1511,7 +1511,7 @@ def _generate_record0(self):
         record0.write(exth)
         record0.write(title)
         record0 = record0.getvalue()
-        self._records[0] = record0 + ('\0' * (2452 - len(record0)))
+        self._records[0] = record0 + ('\0' * (1024*8))
 
     def _build_exth(self):
         oeb = self._oeb