NAME

attrdb - database of attribute-value pairs

SYNOPSIS

include "bufio.m";
include "attrdb.m";
attrdb := load Attrdb Attrdb->PATH;

Attr: adt {
    attr:   string;
    val:    string;
    tag:    int;        # application-defined data, initially 0
};

Tuples: adt {
    n:  int;
    pairs:  list of ref Attr;

    hasattr:    fn(t: self ref Tuples, attr: string): int;
    haspair:    fn(t: self ref Tuples,
                   attr: string, value: string): int;
    find:       fn(t: self ref Tuples, attr: string): list of ref Attr;
    findbyattr: fn(t: self ref Tuples,
                   attr: string, value: string, rattr: string):
                   list of ref Attr;
};

Dbentry: adt {
    n:  int;
    lines:  list of ref Tuples;

    find:       fn(e: self ref Dbentry, attr: string):
                  list of (ref Tuples, list of ref Attr);
    findfirst:  fn(e: self ref Dbentry, attr: string): string;
    findpair:   fn(e: self ref Dbentry,
                  attr: string, value: string):
                  list of ref Tuples;
    findbyattr: fn(e: self ref Dbentry,
                  attr: string, value: string, rattr: string):
                  list of (ref Tuples, list of ref Attr);
};

Db: adt {
    open:    fn(path: string): ref Db;
    sopen:   fn(data: string): ref Db;
    changed: fn(db: self ref Db): int;
    reopen:  fn(db: self ref Db): int;
    append:  fn(db1: self ref Db, db2: ref Db): ref Db;

    find:       fn(db: self ref Db, start: ref Dbptr,
                  attr: string): (ref Dbentry, ref Dbptr);
    findpair:   fn(db: self ref Db, start: ref Dbptr,
                  attr: string, value: string):
                  (ref Dbentry, ref Dbptr);
    findbyattr: fn(db: self ref Db, start: ref Dbptr,
                  attr: string, value: string, rattr: string):
                  (ref Dbentry, ref Dbptr);
};

init:   fn(): string;

parseentry: fn(s: string, lno: int): (ref Dbentry, int, string);
parseline:  fn(s: string, lno: int): (ref Tuples, string);

DESCRIPTION

Attrdb fetches data from textual databases that contain groups of attribute-value pairs. The format is defined by attrdb(6).

Init must be called before any other function in the module.

Each logical database is represented by a Db value. It can span several physical files, named in the body of a database attribute in the primary file of the database. (If no such attribute appears, there is just the one physical file in the database.)

Db.open(path)

Opens path as a database, and returns a (reference to a) Db value that represents it. On an error, it returns nil and the system error string contains a diagnostic. If path contains a database attribute with associated attributes of the form file=filename, the logical database is formed by (logically) concatenating the contents of each filename in the order listed. See attrdb(6) for details.

Db.sopen(data)

Treat the contents of the string data as a database, and return a Db value representing it.

db1.append(db2)

Return a Db value that represents the result of logically appending the contents of database db2 to db1.

db.changed()

Return true iff one or more of the underlying files have changed since they were last read.

db.reopen()

Discard any cached data, and reopen the database files. Return 0 on success but -1 if any file could not be reopened.

db.find(ptr,attr)

Starting at ptr, look in db for the next entry that contains an attribute attr and return a tuple (e,ptr) where e is a Dbentry value representing the whole entry, and ptr is a database pointer for the next entry. If attr cannot be found, e is nil.

db.findpair(ptr, attr, value)

Starting at ptr, look in db for the next entry that contains the pair attr=value, and return a tuple (e,ptr) where e is a Dbentry value representing the whole entry, and ptr is a database pointer for the next entry. If the given pair cannot be found, e is nil.

db.findbyattr(ptr, attr, value, rattr)

Starting at ptr in db, look for the next entry containing both the pair attr=value and a pair with attribute rattr; return a tuple (e,ptr) where e is a Dbentry value representing the whole entry, and ptr is a database pointer for the next entry. If no such entry can be found, e is nil.

Parseline takes a line containing a set of space-separated attribute=value pairs, and returns a tuple (ts,err). If the line's syntax is correct, ts is a Tuples value that represents the pairs as a list of Attr values. If the syntax is wrong (eg, unmatched quote), ts is nil and err contains a diagnostic.

SOURCE

/appl/lib/attrdb.b

SEE ALSO

cfg(2), attrdb(6), ndb(6)

ATTRDB(2 )

Rev:  Tue Mar 31 02:42:39 GMT 2015