Patching Files

For updating files WoW uses bsdiff. Have a look at "http://www.daemonology.net/bsdiff/" or "http://www.pokorra.de/coding/bsdiff.html"

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I had try bsdiff, but it doesn't work.

 1. extract achievement.dbc from enUS\DBFilesClient in Patches\WoW-3.1.3-to-3.2.0-enUS-Win-patch\wow-partial-1.MPQ
 2. rename it to achievement.dbc.patch (45K)
 3. extract achievement.dbc from DBFilesClient in Data\enUS\patch-enUS-2.MPQ
 4. rename it to achievement.dbc.old
 5. bsdiff
   usage: bspatch.exe oldfile newfile patchfile
 6. bsdiff chievement.dbc.old achievement.dbc achievement.dbc.patch
   Corrupt patch
 7. extract achievement.dbc from DBFilesClient in PTR:Data\enUS\patch-enUS-2.MPQ
 8. rename it to achievement.dbc.ptr
 9. bsdiff achievement.dbc.old achievement.dbc.ptr achievement.dbc.patch-ptr (20K)

althought it shows "BSDIFF40" in it's header, but it is not a bsdiff?

-- chuanhsing

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I got some information about files in pre-download mpq. All files inside it are "patch" files.

Followings are for new file patch header:

 0x0000 2 bytes: Size of the patch header (I've only seen 0x18)
 0x0002 2 bytes: Flags
                 * 0x0004 seems always set
                 * 0x0100 unknown, set when new file patch
                 * 0x0400 means BSDIFF40 patch
 0x0004 4 bytes: Looks like CRC
 0x0008 4 bytes: unknown
 0x000C 4 bytes: file size (only if Flags = 0x0100)
 0x0010 8 bytes: timestamp as FILETIME
 ---- body ----
 0x0018 n bytes: the real thing

Followings are for BSDIFF40 patch header:

 0x0000 2 bytes: Size of the patch header (I've only seen 0x18)
 0x0002 2 bytes: Flags
                 * 0x0004 seems always set
                 * 0x0100 unknown
                 * 0x0400 means BSDIFF40 patch
 0x0004 4 bytes: Looks like CRC
 0x0008 4 bytes: unknown
 0x000C 4 bytes: 
 0x0010 8 bytes: timestamp
 ---- body ----
 0x0018 4 bytes: file size
 0x001C 1 byte: unknown
 0x001D 8 bytes: signature, "BSDIFF40"
 0x0025 n bytes: unknown

For the new files, I can skip heading 24 bytes and get the real thing! But I still can't understand the things after BSDIFF40.

-- chuanhsing