Commit | Line | Data |
---|---|---|
a0d0e21e LW |
1 | package AnyDBM_File; |
2 | ||
3b825e41 | 3 | use 5.006_001; |
b75c8c73 | 4 | our $VERSION = '1.00'; |
17f410f9 | 5 | our @ISA = qw(NDBM_File DB_File GDBM_File SDBM_File ODBM_File) unless @ISA; |
a0d0e21e | 6 | |
ca4f5ef1 | 7 | my $mod; |
8 | for $mod (@ISA) { | |
34d04c8d CS |
9 | if (eval "require $mod") { |
10 | @ISA = ($mod); # if we leave @ISA alone, warnings abound | |
11 | return 1; | |
12 | } | |
ca4f5ef1 | 13 | } |
14 | ||
15 | die "No DBM package was successfully found or installed"; | |
16 | #return 0; | |
f06db76b AD |
17 | |
18 | =head1 NAME | |
19 | ||
20 | AnyDBM_File - provide framework for multiple DBMs | |
21 | ||
34d04c8d | 22 | NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File - various DBM implementations |
f06db76b AD |
23 | |
24 | =head1 SYNOPSIS | |
25 | ||
26 | use AnyDBM_File; | |
27 | ||
28 | =head1 DESCRIPTION | |
29 | ||
30 | This module is a "pure virtual base class"--it has nothing of its own. | |
31 | It's just there to inherit from one of the various DBM packages. It | |
32 | prefers ndbm for compatibility reasons with Perl 4, then Berkeley DB (See | |
33 | L<DB_File>), GDBM, SDBM (which is always there--it comes with Perl), and | |
34 | finally ODBM. This way old programs that used to use NDBM via dbmopen() | |
35 | can still do so, but new ones can reorder @ISA: | |
36 | ||
34d04c8d CS |
37 | BEGIN { @AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File) } |
38 | use AnyDBM_File; | |
f06db76b AD |
39 | |
40 | Having multiple DBM implementations makes it trivial to copy database formats: | |
41 | ||
42 | use POSIX; use NDBM_File; use DB_File; | |
c954a603 | 43 | tie %newhash, 'DB_File', $new_filename, O_CREAT|O_RDWR; |
44 | tie %oldhash, 'NDBM_File', $old_filename, 1, 0; | |
f06db76b AD |
45 | %newhash = %oldhash; |
46 | ||
47 | =head2 DBM Comparisons | |
48 | ||
49 | Here's a partial table of features the different packages offer: | |
50 | ||
51 | odbm ndbm sdbm gdbm bsd-db | |
52 | ---- ---- ---- ---- ------ | |
53 | Linkage comes w/ perl yes yes yes yes yes | |
54 | Src comes w/ perl no no yes no no | |
55 | Comes w/ many unix os yes yes[0] no no no | |
56 | Builds ok on !unix ? ? yes yes ? | |
57 | Code Size ? ? small big big | |
58 | Database Size ? ? small big? ok[1] | |
59 | Speed ? ? slow ok fast | |
60 | FTPable no no yes yes yes | |
61 | Easy to build N/A N/A yes yes ok[2] | |
62 | Size limits 1k 4k 1k[3] none none | |
63 | Byte-order independent no no no no yes | |
64 | Licensing restrictions ? ? no yes no | |
65 | ||
66 | ||
67 | =over 4 | |
68 | ||
69 | =item [0] | |
70 | ||
71 | on mixed universe machines, may be in the bsd compat library, | |
72 | which is often shunned. | |
73 | ||
74 | =item [1] | |
75 | ||
76 | Can be trimmed if you compile for one access method. | |
77 | ||
78 | =item [2] | |
79 | ||
80 | See L<DB_File>. | |
81 | Requires symbolic links. | |
82 | ||
83 | =item [3] | |
84 | ||
85 | By default, but can be redefined. | |
86 | ||
87 | =back | |
88 | ||
89 | =head1 SEE ALSO | |
90 | ||
9fe6733a | 91 | dbm(3), ndbm(3), DB_File(3), L<perldbmfilter> |
f06db76b AD |
92 | |
93 | =cut |