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Diffstat (limited to 'Master/xemtex/perl/lib/AnyDBM_File.pm')
-rw-r--r-- | Master/xemtex/perl/lib/AnyDBM_File.pm | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/Master/xemtex/perl/lib/AnyDBM_File.pm b/Master/xemtex/perl/lib/AnyDBM_File.pm new file mode 100644 index 00000000000..d73abab0f9e --- /dev/null +++ b/Master/xemtex/perl/lib/AnyDBM_File.pm @@ -0,0 +1,93 @@ +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 |