Commit | Line | Data |
---|---|---|
a0d0e21e LW |
1 | package AnyDBM_File; |
2 | ||
34d04c8d | 3 | use vars qw(@ISA); |
a0d0e21e LW |
4 | @ISA = qw(NDBM_File DB_File GDBM_File SDBM_File ODBM_File) unless @ISA; |
5 | ||
ca4f5ef1 | 6 | my $mod; |
7 | for $mod (@ISA) { | |
34d04c8d CS |
8 | if (eval "require $mod") { |
9 | @ISA = ($mod); # if we leave @ISA alone, warnings abound | |
10 | return 1; | |
11 | } | |
ca4f5ef1 | 12 | } |
13 | ||
14 | die "No DBM package was successfully found or installed"; | |
15 | #return 0; | |
f06db76b AD |
16 | |
17 | =head1 NAME | |
18 | ||
19 | AnyDBM_File - provide framework for multiple DBMs | |
20 | ||
34d04c8d | 21 | NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File - various DBM implementations |
f06db76b AD |
22 | |
23 | =head1 SYNOPSIS | |
24 | ||
25 | use AnyDBM_File; | |
26 | ||
27 | =head1 DESCRIPTION | |
28 | ||
29 | This module is a "pure virtual base class"--it has nothing of its own. | |
30 | It's just there to inherit from one of the various DBM packages. It | |
31 | prefers ndbm for compatibility reasons with Perl 4, then Berkeley DB (See | |
32 | L<DB_File>), GDBM, SDBM (which is always there--it comes with Perl), and | |
33 | finally ODBM. This way old programs that used to use NDBM via dbmopen() | |
34 | can still do so, but new ones can reorder @ISA: | |
35 | ||
34d04c8d CS |
36 | BEGIN { @AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File) } |
37 | use AnyDBM_File; | |
f06db76b AD |
38 | |
39 | Having multiple DBM implementations makes it trivial to copy database formats: | |
40 | ||
41 | use POSIX; use NDBM_File; use DB_File; | |
c954a603 | 42 | tie %newhash, 'DB_File', $new_filename, O_CREAT|O_RDWR; |
43 | tie %oldhash, 'NDBM_File', $old_filename, 1, 0; | |
f06db76b AD |
44 | %newhash = %oldhash; |
45 | ||
46 | =head2 DBM Comparisons | |
47 | ||
48 | Here's a partial table of features the different packages offer: | |
49 | ||
50 | odbm ndbm sdbm gdbm bsd-db | |
51 | ---- ---- ---- ---- ------ | |
52 | Linkage comes w/ perl yes yes yes yes yes | |
53 | Src comes w/ perl no no yes no no | |
54 | Comes w/ many unix os yes yes[0] no no no | |
55 | Builds ok on !unix ? ? yes yes ? | |
56 | Code Size ? ? small big big | |
57 | Database Size ? ? small big? ok[1] | |
58 | Speed ? ? slow ok fast | |
59 | FTPable no no yes yes yes | |
60 | Easy to build N/A N/A yes yes ok[2] | |
61 | Size limits 1k 4k 1k[3] none none | |
62 | Byte-order independent no no no no yes | |
63 | Licensing restrictions ? ? no yes no | |
64 | ||
65 | ||
66 | =over 4 | |
67 | ||
68 | =item [0] | |
69 | ||
70 | on mixed universe machines, may be in the bsd compat library, | |
71 | which is often shunned. | |
72 | ||
73 | =item [1] | |
74 | ||
75 | Can be trimmed if you compile for one access method. | |
76 | ||
77 | =item [2] | |
78 | ||
79 | See L<DB_File>. | |
80 | Requires symbolic links. | |
81 | ||
82 | =item [3] | |
83 | ||
84 | By default, but can be redefined. | |
85 | ||
86 | =back | |
87 | ||
88 | =head1 SEE ALSO | |
89 | ||
9fe6733a | 90 | dbm(3), ndbm(3), DB_File(3), L<perldbmfilter> |
f06db76b AD |
91 | |
92 | =cut |