NAME

Palmfile: Categories, DBInfo, Doc, Entry, Pfile, Record - read Palm™ file formats

SYNOPSIS

include "bufio.m";
include "palmfile.m";
palmfile := load Palmfile Palmfile->PATH;
Pfile: adt {


    fname:  string;


    appinfo:  array of byte;


    sortinfo: array of int;


    entries:  array of ref Entry;


    open:   fn(name: string, mode: int): (ref Pfile, string);


    close:  fn(pf: self ref Pfile): int;


    read:   fn(pf: self ref Pfile, index: int): (ref Record, string);


    stat:   fn(pf: self ref Pfile): ref DBInfo;
};
DBInfo: adt {


    name:    string; # database name on Palm


    attr:    int;    # file attributes (defined below)


    dtype:   string; # database type (byte[4])


    version: int;    # version of data layout, defined by application


    creator: string; # creating application (byte[4])


    ctime:   int;    # creation time


    mtime:   int;    # modification time


    btime:   int;    # last backup


    modno:   int;    # modification number


    uidseed: int;    # unique record ID seed


    new:     fn(name: string, attr: int, dtype: string,


                   version: int, creator: string): ref DBInfo;
};
Entry: adt {


    id: int;        # resource: id; record: unique ID


    offset: int;    # offset in file


    size:   int;    # size in bytes


    name:   int;    # resource entry only


    attr:   int;    # record entry only
};
Record: adt {


    id:     int;    # resource: ID; data: unique record ID


    index:  int;    # record index (origin 0)


    name:   int;    # byte[4]: resource record only


    attr:   int;    # attributes, defined below, data record only


    cat:    int;    # category, data record only


    data:   array of byte;   # content of record
};
Categories: adt {


    renamed: int;    # which categories have been renamed


    labels:  array of string; # category names


    uids:    array of int;    # corresponding unique IDs


    lastuid: int;             # last unique ID assigned


    appdata: array of byte;   # remaining application-specific data


    new:     fn(labels: array of string): ref Categories;


    unpack:  fn(a: array of byte): ref Categories;


    pack:    fn(c: self ref Categories): array of byte;
};
Doc: adt {


    version:  int;


    length:   int;  # uncompressed


    nrec:     int;  # text records only


    recsize:  int;  # uncompressed


    position: int;


    sizes:    array of int;   # sizes of uncompressed records


    open:     fn(file: ref Pfile): (ref Doc, string);


    read:     fn(doc: self ref Doc, i: int): (string, string);


    iscompressed:  fn(doc: self ref Doc): int;


    unpacktext: fn(doc: self ref Doc, a: array of byte):


                   (string, string);


    textlength: fn(doc: self ref Doc, a: array of byte): int;
};
init:     fn(): string;
filename: fn(s: string): string;
dbname:   fn(s: string): string;
gets:     fn(a: array of byte): string;
puts:     fn(a: array of byte, s: string);
get2:     fn(a: array of byte): int;
get3:     fn(a: array of byte): int;
get4:     fn(a: array of byte): int;
put2:     fn(a: array of byte, v: int);
put3:     fn(a: array of byte, v: int);
put4:     fn(a: array of byte, v: int);

DESCRIPTION

Palmfile provides read-only access to files in the Palm™ database and document formats. It currently handles three types of files: Palm Database (.pdb) files, which store data for applications; Palm Resource (.prc) files, which store code resources and user interface resource elements; and Palm Doc (.doc) files, which store compressed documents for the Palm document and e-book readers. Database and resource files have a similar structure, with slight differences in representation, and differing mainly in how the contents are used.

Init must be called before any other function in the file. It returns a diagnostic if it cannot initialise the module.

Pfile represents an open Palm file of any type:

open(): Opens file name with the given mode (which must currently be Sys->OREAD) and returns a tuple (pf,err). Pf is a new Pfile instance giving access to the file, or nil if the open failed, in which case the err string contains a diagnostic.
pf.close(): Close the file (needed only when writing to a file is eventually supported).
pf.read(index): Returns a tuple (rec, err) where rec is a Record containing the data of the record with the given index (origin 0), or nil if no such record index exists or it cannot be read. In the latter case, err is a diagnostic string.
pf.stat(): Return the database information for pf.
entries: An array of Entry values (see below), one per record. The length of the array is consequently the length of the file in records. It can be nil or empty.
appinfo: Optional application-specific data (see Categories below).
sortinfo: Optional application-specific data (typically an array of record IDs in a chosen sorting order).
fname: File name given to Pfile.open.

DBInfo gives the database information for a file:

name: Database name used on the Palm, maximum of 31 characters.
attr: A bit set of file attributes, containing the following values:

Fresource: File is a resource file (.prc) not a database file (.pdb).
Fronly: File is read only.
Fappinfodirty: Application information has changed.
Fbackup: No conduit program exists (the whole file must be backed up).
Foverwrite: Overwrite older copy if present.
Freset: Reset PDA after installing this file.
Fprivate: Don't allow copy of this file to be beamed.

dtype: String identifying database type (up to 4 characters). It is usually the string "appI" for resource files.
version: Identifies the version of the data format (application specific).
creator: String identifying creating application (up to 4 characters).
ctime: File creation time, in seconds from the Inferno epoch (see daytime (2)).
mtime: Time file last modified, in seconds from the epoch.
btime: Time file last backed up, in seconds from the epoch.
uidseed: Seed for generating unique record IDs (typically set to 0 for database files, always 0 for resource files).
new(name, attr, dtype, creator): Return a new DBInfo with the given values.

In some applications, it is useful to use a data base name (ie, DBInfo.name) as a component of an Inferno file name. The device allows space and slash characters in names, though, which makes it hard to use the name directly. Filename maps each space character in s to U+00A0 (unpaddable space) and each slash character to U+2215 (`division /'), and returns the result. Dbname maps the other way.

Entries and Records

Each record in the file is represented by an Entry in memory, which holds the record's essential attributes, leaving the data on file. The meaning of some of the elements depends on whether the file is a data file or a resource file.

id: Resource ID, 16 bits (resource file); unique record ID, 24 bits (data file).
offset: Offset in file, in bytes.
size: Size of record in bytes.
name: Name of the resource (resource record only).
attrs: Record attributes (data record only):

Rdelete: Delete the record when file next synchronised.
Rdirty: Record has been modified.
Rinuse: Record in use (not typically used in Inferno).
Rsecret: Record is secret (shown on the device only with use of a password).
Rarchive: Archive this record when file next synchronised.
Rmcat: Mask for the 4-bit category field (in Entry.attrs only).

Records read from the file are represented by a Record adt containing its data and associated values. Some fields are valid only for particular classes of records.

id: Resource or record ID, as for Entry.
index: Index (origin 0) of the record in the file.
name: Resource name (resource record only).
attr: Record attributes, as above (data record only).
cat: Record's category ID (data record only).
data: The actual data.

Application data

The contents of both the ``application information'' and ``sort information'' sections of the file are defined by an application in general. Even so, both have conventional uses with many Palm applications. The Palm software often assigns data records to particular categories (eg, ``Business'' or ``Personal''), and stores up to 16 category names and IDs in the application data in a fixed format (possibly followed by further data that is application specific). This is represented by an instance of Categories, which provides the following:

renamed: Bit set indicating which categories have been renamed (for category 0, bit 1<<0, for 1, bit 1<<1, and so on).
labels: Array of 16 category labels.
uids: Array of 16 category IDs, each in the range 0 to 255. (It is said that the Palm itself assigns 0 to 127 and desktop applications assign 128 to 255.)
lastuid: Last unique category ID assigned.
appdata: Any data that remained after unpacking the category data.
new(labels): Return a new Categories value for the given array of labels, assigning unique IDs to each in turn, starting from 128. There can be at most 16 labels; if there are fewer, the remaining labels will be marked as unused (empty strings).
unpack(a): Unpack the application data in array a (typically pf.appinfo for some Pfile pf), returning a reference to a new Categories instance. A nil value is returned if the array is too short to hold valid category data.
c.pack(): Pack c into a form suitable for writing back to a file's application information area.

Binary data in Palm files is typically encoded in big-endian form. Palmfile functions account for that internally, but some Palm applications might use big-endian data in their own data records. Several functions are therefore provided to decode and encode big-endian data: getn retrieves an integer from the first n bytes of array a; putn stores a big-endian representation of the value v in the first n bytes of array a.

Strings are stored in fixed-length arrays of bytes, always terminated by a zero byte. The character encoding is (apparently) Latin-1 (ISO 8859-1), not UTF-8, so functions gets and puts are provided to convert between that representation and a Limbo string.

Documents

Doc provides read-only access to Palm documents and (unencrypted) e-books:

open(file): Given a Pfile file, return a tuple (doc, err) where doc is a new Doc instance giving access to the document contents in file. If an error occurs, in particular if file does not appear to be a valid Palm document, doc is nil and the string err diagnoses the error.
doc.iscompressed(): Returns true (non-zero) if the document is compressed; returns false (zero) otherwise.
doc.read(i): Read text record with index i (origin 0), returning a tuple (s, err) where s is the uncompressed text for record i, or nil if the record does not exist (or there is an error reading it). On any error, err is a diagnostic string. Note that i is an index into the set of text records, and is not an index into the set of all records. It must be no greater than doc.nrec. doc.unpacktext(a) Returns a tuple (s, err) where s is the text in array a, after uncompressing if doc contains compressed records. Following Palm conventions, the text is assumed to be written in the Latin-1 encoding (ISO-8859-1). If it is compressed but the data in a is corrupt (cannot be uncompressed), s is nil and err diagnoses the problem.
doc.textlength(a): Returns the number of bytes required to store the text in array a once it has been uncompressed (if necessary).
version: The document's version number.
length: The length of the whole document in bytes, when uncompressed.
nrec: Number of text records in the document.
recsize: Size of uncompressed text records.
position: Possibly records the position where reading last stopped.
sizes: Array giving sizes of all text records, once uncompressed.

Most document-reading applications require only Doc.open and Doc.read, and perhaps Doc.length to guide the construction of scroll bars (for instance).

SOURCE

/appl/lib/palmfile.b