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authorReinhard Kotucha <reinhard.kotucha@web.de>2008-01-05 21:23:03 +0000
committerReinhard Kotucha <reinhard.kotucha@web.de>2008-01-05 21:23:03 +0000
commit61700e8be90ff6f495c0b1a9835fe07e9848de8d (patch)
treeba85dbc1413d5f834a501a8828e3b67678ba8524 /Master/tlpkg/tlperl/lib/AnyDBM_File.pm
parent270728c6f3efcac6728d2c335c79824c356f428d (diff)
tlperl: Perl for scripts provided by TeX Live.
git-svn-id: svn://tug.org/texlive/trunk@6046 c570f23f-e606-0410-a88d-b1316a301751
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+package AnyDBM_File;
+
+use 5.006_001;
+our $VERSION = '1.00';
+our @ISA = qw(NDBM_File DB_File GDBM_File SDBM_File ODBM_File) unless @ISA;
+
+my $mod;
+for $mod (@ISA) {
+ if (eval "require $mod") {
+ @ISA = ($mod); # if we leave @ISA alone, warnings abound
+ return 1;
+ }
+}
+
+die "No DBM package was successfully found or installed";
+#return 0;
+
+=head1 NAME
+
+AnyDBM_File - provide framework for multiple DBMs
+
+NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File - various DBM implementations
+
+=head1 SYNOPSIS
+
+ use AnyDBM_File;
+
+=head1 DESCRIPTION
+
+This module is a "pure virtual base class"--it has nothing of its own.
+It's just there to inherit from one of the various DBM packages. It
+prefers ndbm for compatibility reasons with Perl 4, then Berkeley DB (See
+L<DB_File>), GDBM, SDBM (which is always there--it comes with Perl), and
+finally ODBM. This way old programs that used to use NDBM via dbmopen()
+can still do so, but new ones can reorder @ISA:
+
+ BEGIN { @AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File) }
+ use AnyDBM_File;
+
+Having multiple DBM implementations makes it trivial to copy database formats:
+
+ use POSIX; use NDBM_File; use DB_File;
+ tie %newhash, 'DB_File', $new_filename, O_CREAT|O_RDWR;
+ tie %oldhash, 'NDBM_File', $old_filename, 1, 0;
+ %newhash = %oldhash;
+
+=head2 DBM Comparisons
+
+Here's a partial table of features the different packages offer:
+
+ odbm ndbm sdbm gdbm bsd-db
+ ---- ---- ---- ---- ------
+ Linkage comes w/ perl yes yes yes yes yes
+ Src comes w/ perl no no yes no no
+ Comes w/ many unix os yes yes[0] no no no
+ Builds ok on !unix ? ? yes yes ?
+ Code Size ? ? small big big
+ Database Size ? ? small big? ok[1]
+ Speed ? ? slow ok fast
+ FTPable no no yes yes yes
+ Easy to build N/A N/A yes yes ok[2]
+ Size limits 1k 4k 1k[3] none none
+ Byte-order independent no no no no yes
+ Licensing restrictions ? ? no yes no
+
+
+=over 4
+
+=item [0]
+
+on mixed universe machines, may be in the bsd compat library,
+which is often shunned.
+
+=item [1]
+
+Can be trimmed if you compile for one access method.
+
+=item [2]
+
+See L<DB_File>.
+Requires symbolic links.
+
+=item [3]
+
+By default, but can be redefined.
+
+=back
+
+=head1 SEE ALSO
+
+dbm(3), ndbm(3), DB_File(3), L<perldbmfilter>
+
+=cut