https://perl5.git.perl.org / perl5.git / blame
| Commit | Line | Data |
|---|---|---|
| a0d0e21e LW |
1 | package AnyDBM_File; |
| 2 | ||
| 3 | @ISA = qw(NDBM_File DB_File GDBM_File SDBM_File ODBM_File) unless @ISA; | |
| 4 | ||
| 5 | eval { require NDBM_File } || | |
| 6 | eval { require DB_File } || | |
| 7 | eval { require GDBM_File } || | |
| 8 | eval { require SDBM_File } || | |
| 9 | eval { require ODBM_File }; | |
| f06db76b AD |
10 | |
| 11 | =head1 NAME | |
| 12 | ||
| 13 | AnyDBM_File - provide framework for multiple DBMs | |
| 14 | ||
| 15 | NDBM_File, ODBM_File, SDBM_File, GDBM_File - various DBM implementations | |
| 16 | ||
| 17 | =head1 SYNOPSIS | |
| 18 | ||
| 19 | use AnyDBM_File; | |
| 20 | ||
| 21 | =head1 DESCRIPTION | |
| 22 | ||
| 23 | This module is a "pure virtual base class"--it has nothing of its own. | |
| 24 | It's just there to inherit from one of the various DBM packages. It | |
| 25 | prefers ndbm for compatibility reasons with Perl 4, then Berkeley DB (See | |
| 26 | L<DB_File>), GDBM, SDBM (which is always there--it comes with Perl), and | |
| 27 | finally ODBM. This way old programs that used to use NDBM via dbmopen() | |
| 28 | can still do so, but new ones can reorder @ISA: | |
| 29 | ||
| 30 | @AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File); | |
| 31 | ||
| 32 | Note, however, that an explicit use overrides the specified order: | |
| 33 | ||
| 34 | use GDBM_File; | |
| 35 | @AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File); | |
| 36 | ||
| 37 | will only find GDBM_File. | |
| 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 | ||
| 90 | dbm(3), ndbm(3), DB_File(3) | |
| 91 | ||
| 92 | =cut |