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AnyDBM_File - provide framework for multiple DBMs

目次

provide framework for multiple DBMs

名前

AnyDBM_File - 多様な DBM のフレームワークを提供します

AnyDBM_File - provide framework for multiple DBMs

NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File - 様々な DBM の実装

NDBM_File, DB_File, GDBM_File, SDBM_File, ODBM_File - various DBM implementations

使い方

 use AnyDBM_File;

概要

このモジュールは,実装を持たない "純粋仮想基底クラス" です.様々な DBM パッケージから継承するために利用します. Perl 4,Berkeley DB,GDBM,SDBM,ODBM との後方互換性のため,ndbm が好まれます. dbmopen() を経由して NDBM を使うような古いプログラムではそちらが利用されます. しかし,新しいプログラムでは @ISA の要素の順序を変更することができます.
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 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;

複数の DBM 実装を持つことで,データベース形式を複製することが簡単になります.

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;

DBM の比較

DBM Comparisons

これはパッケージごとの特徴の相違点の一覧表です.

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

[0]
on mixed universe machines, may be in the bsd compat library, which is often shunned.
[1]
Can be trimmed if you compile for one access method.
[2]
See DB_File. Requires symbolic links.
[3]
By default, but can be redefined.

SEE ALSO

dbm(3), ndbm(3), DB_File(3), perldbmfilter

 perl v5.8.6                                                  2005-03-28                                              AnyDBM_File(3)