Store 'diff' bytes by run-length encoding zeros....

courgette/third_party/bsdiff.h

 /*-
  * Copyright 2003,2004 Colin Percival
  * All rights reserved
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted providing that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 56 matching lines @@
 
 // The following declarations are common to the patch-creation and
 // patch-application code.
 
 // The patch stream starts with a MBSPatchHeader.
 typedef struct MBSPatchHeader_ {
   char tag[8];       // Contains MBS_PATCH_HEADER_TAG
   uint32 slen;       // Length of the file to be patched.
   uint32 scrc32;     // CRC32 of the file to be patched.
   uint32 dlen;       // Length of the result file.
-  uint32 cblen;      // Length of the control block in bytes.
-  uint32 difflen;    // Length of the diff block in bytes.
-  uint32 extralen;   // Length of the extra block in bytes.
 } MBSPatchHeader;
 
 // This is the value for the tag field.  Must match length exactly, not counting
 // null at end of string.
 #define MBS_PATCH_HEADER_TAG "GBSDIF42"
 
 }  // namespace
 #endif  // COURGETTE_BSDIFF_H_