PDB (Palm OS)


PDB is a container format for record databases in Palm OS, Garnet OS and Access Linux Platform. Its structure is similar to PRC resource databases. The PalmDOC eBook format is a special version of the PDB format.

Structure of PDB file

A PDB file contains a PDB header, PDB record headers and records.

PDB Header

The PDB header is located at the beginning of the file and contains meta-information on the file:
OffsetNameTypeSize
0x00namechar 32 Bytes
0x20file attributesinteger2 Bytes
0x22versioninteger2 Bytes
0x24creation time32bit integer - PDB Datetime4 Bytes
0x28modification time32bit integer - PDB Datetime4 Bytes
0x2cbackup time32bit integer - PDB Datetime4 Bytes
0x30modification numberinteger4 Bytes
0x34app_infointeger4 Bytes
0x38sort_infointeger4 Bytes
0x3ctypeinteger4 Bytes
0x40creatorinteger4 Bytes
0x44unique_id_seedinteger4 Bytes
0x48next_record_listinteger4 Bytes
0x4cnum_recordsinteger2 Bytes

PDB Record Header

For every record, there is an eight byte record header, containing:
nametypesizenotes
offsetinteger4 bytesByte number in the PDB file, where the record is located
attributesbyte1 byteAttributes of the record
UniqueIDinteger3 bytesAlways 0

PDB Records

Now the records themselves follow. The usual order is AppInfoArea, SortInfoArea and records, sequentially.

PDB Datetimes

Many PDB format files used times counting in seconds from 1904-01-01T00:00:00. This is the base time used by the original Macintosh. It may be noted that there were close links between Palm OS and Mac OS during early development. Using an unsigned 32-bit integer and the 1904 epoch, integer overflow will overflow will occur sometime in 2040.
Others may be observed to be counting from 1970-01-01T00:00:00, and uses a signed 32-bit integer which will overflow sometime in 2038.
For either system, overflow will occur in around 30 years time.
calls the dates calculated from 1904 "old Palm epoch", and the dates calculated from 1970 "UNIX epoch". Protein C also provides functions, and time_t_to_palm_seconds ) for converting between the two.
even suggest some very old files may use times counting from 1900.
This conflict between old Palm epoch and UNIX epoch is unfortunate, the following heuristic may be useful when examining a file copied from a Palm OS device:
This is based on the idea that, otherwise the time would be before 1972 or before 1970 and the PDB format wasn't around then.
The utility and other software uses this rule-of-thumb when reading files.