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116 lines
2.6 KiB
116 lines
2.6 KiB
package SDBM_File;
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use strict;
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use warnings;
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require Tie::Hash;
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use XSLoader ();
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our @ISA = qw(Tie::Hash);
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our $VERSION = "1.03" ;
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XSLoader::load 'SDBM_File', $VERSION;
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1;
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__END__
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=head1 NAME
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SDBM_File - Tied access to sdbm files
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=head1 SYNOPSIS
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use Fcntl; # For O_RDWR, O_CREAT, etc.
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use SDBM_File;
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tie(%h, 'SDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
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or die "Couldn't tie SDBM file 'filename': $!; aborting";
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# Now read and change the hash
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$h{newkey} = newvalue;
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print $h{oldkey};
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...
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untie %h;
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=head1 DESCRIPTION
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C<SDBM_File> establishes a connection between a Perl hash variable and
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a file in SDBM_File format;. You can manipulate the data in the file
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just as if it were in a Perl hash, but when your program exits, the
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data will remain in the file, to be used the next time your program
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runs.
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Use C<SDBM_File> with the Perl built-in C<tie> function to establish
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the connection between the variable and the file. The arguments to
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C<tie> should be:
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=over 4
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=item 1.
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The hash variable you want to tie.
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=item 2.
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The string C<"SDBM_File">. (Ths tells Perl to use the C<SDBM_File>
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package to perform the functions of the hash.)
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=item 3.
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The name of the file you want to tie to the hash.
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=item 4.
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Flags. Use one of:
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=over 2
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=item C<O_RDONLY>
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Read-only access to the data in the file.
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=item C<O_WRONLY>
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Write-only access to the data in the file.
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=item C<O_RDWR>
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Both read and write access.
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=back
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If you want to create the file if it does not exist, add C<O_CREAT> to
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any of these, as in the example. If you omit C<O_CREAT> and the file
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does not already exist, the C<tie> call will fail.
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=item 5.
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The default permissions to use if a new file is created. The actual
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permissions will be modified by the user's umask, so you should
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probably use 0666 here. (See L<perlfunc/umask>.)
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=back
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=head1 DIAGNOSTICS
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On failure, the C<tie> call returns an undefined value and probably
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sets C<$!> to contain the reason the file could not be tied.
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=head2 C<sdbm store returned -1, errno 22, key "..." at ...>
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This warning is emmitted when you try to store a key or a value that
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is too long. It means that the change was not recorded in the
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database. See BUGS AND WARNINGS below.
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=head1 BUGS AND WARNINGS
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There are a number of limits on the size of the data that you can
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store in the SDBM file. The most important is that the length of a
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key, plus the length of its associated value, may not exceed 1008
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bytes.
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See L<perlfunc/tie>, L<perldbmfilter>, L<Fcntl>
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=cut
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