attrdb - database of attribute-value pairs .EX 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); 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.

/appl/lib/attrdb.b cfg (2), attrdb (6), ndb (6)