NAME

Cfg, Record, Tuple, Attr - configuration file parser

SYNOPSIS

include "cfg.m";
cfg := load Cfg Cfg->PATH;

Attr: adt {
	name: string;
	value: string;
};

Tuple: adt {
	lnum: int;
	attrs: list of Attr;
	lookup: fn(t: self ref Tuple, name: string): string;
};

Record: adt {
	tuples: list of ref Tuple;
	lookup: fn(r: self ref Record, name: string)
		: (string, ref Tuple);
};

init: fn(path: string): string;
lookup: fn(name: string): list of (string, ref Record);
getkeys: fn(): list of string;

DESCRIPTION

Cfg parses its configuration file format into a set of Records.

Each line of the configuration file is comprised of a tuple of attributes. Comments are introduced by the '#' character and run to the end of the input line. Empty lines and comments are ignored.

An attribute has a name followed by an optional value. The value is specified by separating the name and value by an '=' character. Attribute names and values are input words. A word is delimited by spacing characters and the '=' character. If a word needs to include any of these characters then the word may be quoted using single or double quotes. The start and end quotes must be the same. The quoting character may be included in the word by appearing twice.

Examples:

	'a b c'	yields	a b c
	"a b c"	yields	a b c
	'a " c'	yields	a " c
	'a '' c'	yields	a ' c

The name of the first attribute of a tuple is its key. The primary tuple value is the value of its first attribute.

Tuples whose first attribute name appears at the start of a line (having no preceeding spacing characters) are treated as the start of a new record. A record incorporates all tuples up to the start of the next record. The record key is defined to be the name of its first attribute. The primary record value is the value of the first attribute.

The adt types Attr, Tuple and Record are direct analogues of the constructs defined above.

init(path)

Init initialises the Cfg module, causing it to open and parse the configuration file given by the path argument. If an error is encountered in processing the file then an error string is returned. If there are no errors init returns nil.

lookup(name)

Lookup returns the set of Records whose key matches the name argument. The return value is a list of (primary record value, record) pairs.

getkeys()

Getkeys returns a list of the record keys that appear in the configuration file. Note that more than one record can have the same key. Duplicate key names are not returned by getkeys().

record.lookup(name)

Returns the first tuple in record whose key matches name. The return value is (primary tuple value, tuple). If no matching tuple is found then the value (nil, nil) is returned. Note that more than one tuple of the record could have a key that matches name. Only the first matching tuple is returned. If an application makes use of multiple tuples with the same key then the record.tuple list will have to be handled explicitly by the application.

tuple.lookup(name)

Returns the first attribute in tuple whose name matches name. The return value is the value of the attribute or nil if no matching attribute was found.

SOURCE

/appl/lib/cfg.b

CFG(2 )

Rev:  Tue Mar 31 02:42:39 GMT 2015