XMP Specification Part 3: Storage in Files - Adobe

struct MasterPage {
// 16 byte GUID identifying this as an InDesign database
// Must be: 0606EDF5-D81D-46e5-BD31-EFE7FE74B71D
char fGUID [16];
// 8 bytes; type of database (for example "DOCUMENT")
char fMagicBytes [8];
// Endian of object streams, 1=little endian, 2=big endian
char fObjectStreamEndian;
// Irrelevant stuff
char fIrrelevant1 [239];
// Master page sequence number. The master page with
// the larger value is the current master page
LittleEndianUnsignedInt64 fSequenceNumber;
// More irrelevant stuff
char fIrrelevant2 [8];
// The number of pages in the file. fFilePages * 4096
// is the absolute file offset in bytes of where any
// contiguous data storage would begin (provided this
// master page is the current master page).
LittleEndianUnsignedInt32 fFilePages;
// More irrelevant stuff
char fIrrelevant3 [3812];
};
Table 13 describes the fields in a master page.
Table 13 — Master page fields
fGUID The first 16 bytes of each master page (and thus the first 16 bytes of the file)
are set to a GUID that identifies the file as an InDesign database.
The ID value of the master page is:
0606EDF5-D81D-46e5-BD31-EFE7FE74B71D
You must check for this value. If it is not present, something has changed in
an incompatible way in the file format and you can make no further
assumptions. You can search the entire file to find XMP metadata, but you
cannot add additional metadata beyond any padding provided in the packet.
fMagicBytes Contains an 8-byte sequence identifying the type of database file.
This can be useful if you want this information and cannot get it from the file
extension or type and creator. The 8 characters "DOCUMENT" designate a
database that contains an InDesign document and would normally have a
.indd extension.
fObjectStreamEndian The byte order (big-endian or little-endian) in which integers in an object
stream are written, which depends on the creation platform of the database.
You must use this byte-order to interpret the packet-length value if you
enlarge XMP packets and rewrite the file format; see 2.4.2.2, “Rewriting XMP
data beyond the packet padding”.
You do not need it to find or interpret the XMP data; all integer values in the
storage structures themselves are uniformly little-endian.
38 ©Adobe Systems Incorporated, 2010