From 77361444108f2e7ab3825ece60df4cd522d8d393 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 15 Apr 2011 15:31:55 -0600
Subject: [PATCH] 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 | 1 +
 src/calibre/ebooks/mobi/debug.py    | 5 ++++-
 src/calibre/ebooks/mobi/writer.py   | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/calibre/ebooks/metadata/mobi.py b/src/calibre/ebooks/metadata/mobi.py
index ffdef77d11..15fdceff15 100644
--- a/src/calibre/ebooks/metadata/mobi.py
+++ b/src/calibre/ebooks/metadata/mobi.py
@@ -259,6 +259,7 @@ class MetadataUpdater(object):
         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())
diff --git a/src/calibre/ebooks/mobi/debug.py b/src/calibre/ebooks/mobi/debug.py
index 36aba39d65..86ed3e9ef9 100644
--- a/src/calibre/ebooks/mobi/debug.py
+++ b/src/calibre/ebooks/mobi/debug.py
@@ -274,7 +274,7 @@ class MOBIHeader(object):
             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 @@ class MOBIHeader(object):
             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
 
diff --git a/src/calibre/ebooks/mobi/writer.py b/src/calibre/ebooks/mobi/writer.py
index fc47b26c02..ddcba63eca 100644
--- a/src/calibre/ebooks/mobi/writer.py
+++ b/src/calibre/ebooks/mobi/writer.py
@@ -1511,7 +1511,7 @@ class MobiWriter(object):
         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