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Commit	Line	Data
	1	package AnyDBM_File;
	2	use warnings;
	3	use strict;
	4
	5	use 5.006_001;
	6	our $VERSION = '1.01';
	7	our @ISA = qw(NDBM_File DB_File GDBM_File SDBM_File ODBM_File) unless @ISA;
	8
	9	my $mod;
	10	for $mod (@ISA) {
	11	if (eval "require $mod") {
	12	@ISA = ($mod); # if we leave @ISA alone, warnings abound
	13	return 1;
	14	}
	15	}
	16
	17	die "No DBM package was successfully found or installed";
	18
	19	__END__
	20
	21	=head1 NAME
	22
	23	AnyDBM_File - provide framework for multiple DBMs
	24
	25	NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File - various DBM implementations
	26
	27	=head1 SYNOPSIS
	28
	29	use AnyDBM_File;
	30
	31	=head1 DESCRIPTION
	32
	33	This module is a "pure virtual base class"--it has nothing of its own.
	34	It's just there to inherit from one of the various DBM packages. It
	35	prefers ndbm for compatibility reasons with Perl 4, then Berkeley DB (See
	36	L<DB_File>), GDBM, SDBM (which is always there--it comes with Perl), and
	37	finally ODBM. This way old programs that used to use NDBM via dbmopen()
	38	can still do so, but new ones can reorder @ISA:
	39
	40	BEGIN { @AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File) }
	41	use AnyDBM_File;
	42
	43	Having multiple DBM implementations makes it trivial to copy database formats:
	44
	45	use Fcntl; use NDBM_File; use DB_File;
	46	tie %newhash, 'DB_File', $new_filename, O_CREAT\|O_RDWR;
	47	tie %oldhash, 'NDBM_File', $old_filename, 1, 0;
	48	%newhash = %oldhash;
	49
	50	=head2 DBM Comparisons
	51
	52	Here's a partial table of features the different packages offer:
	53
	54	odbm ndbm sdbm gdbm bsd-db
	55	---- ---- ---- ---- ------
	56	Linkage comes w/ perl yes yes yes yes yes
	57	Src comes w/ perl no no yes no no
	58	Comes w/ many unix os yes yes[0] no no no
	59	Builds ok on !unix ? ? yes yes ?
	60	Code Size ? ? small big big
	61	Database Size ? ? small big? ok[1]
	62	Speed ? ? slow ok fast
	63	FTPable no no yes yes yes
	64	Easy to build N/A N/A yes yes ok[2]
	65	Size limits 1k 4k 1k[3] none none
	66	Byte-order independent no no no no yes
	67	Licensing restrictions ? ? no yes no
	68
	69
	70	=over 4
	71
	72	=item [0]
	73
	74	on mixed universe machines, may be in the bsd compat library,
	75	which is often shunned.
	76
	77	=item [1]
	78
	79	Can be trimmed if you compile for one access method.
	80
	81	=item [2]
	82
	83	See L<DB_File>.
	84	Requires symbolic links.
	85
	86	=item [3]
	87
	88	By default, but can be redefined.
	89
	90	=back
	91
	92	=head1 SEE ALSO
	93
	94	dbm(3), ndbm(3), DB_File(3), L<perldbmfilter>
	95
	96	=cut