1 | package SDBM_File;
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2 |
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3 | use strict;
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4 | use warnings;
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5 |
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6 | require Tie::Hash;
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7 | use XSLoader ();
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8 |
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9 | our @ISA = qw(Tie::Hash);
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10 | our $VERSION = "1.05";
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11 |
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12 | XSLoader::load 'SDBM_File', $VERSION;
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13 |
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14 | 1;
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15 |
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16 | __END__
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17 |
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18 | =head1 NAME
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19 |
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20 | SDBM_File - Tied access to sdbm files
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21 |
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22 | =head1 SYNOPSIS
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23 |
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24 | use Fcntl; # For O_RDWR, O_CREAT, etc.
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25 | use SDBM_File;
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26 |
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27 | tie(%h, 'SDBM_File', 'filename', O_RDWR|O_CREAT, 0666)
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28 | or die "Couldn't tie SDBM file 'filename': $!; aborting";
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29 |
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30 | # Now read and change the hash
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31 | $h{newkey} = newvalue;
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32 | print $h{oldkey};
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33 | ...
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34 |
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35 | untie %h;
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36 |
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37 | =head1 DESCRIPTION
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38 |
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39 | C<SDBM_File> establishes a connection between a Perl hash variable and
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40 | a file in SDBM_File format;. You can manipulate the data in the file
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41 | just as if it were in a Perl hash, but when your program exits, the
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42 | data will remain in the file, to be used the next time your program
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43 | runs.
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44 |
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45 | Use C<SDBM_File> with the Perl built-in C<tie> function to establish
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46 | the connection between the variable and the file. The arguments to
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47 | C<tie> should be:
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48 |
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49 | =over 4
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50 |
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51 | =item 1.
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52 |
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53 | The hash variable you want to tie.
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54 |
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55 | =item 2.
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56 |
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57 | The string C<"SDBM_File">. (Ths tells Perl to use the C<SDBM_File>
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58 | package to perform the functions of the hash.)
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59 |
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60 | =item 3.
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61 |
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62 | The name of the file you want to tie to the hash.
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63 |
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64 | =item 4.
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65 |
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66 | Flags. Use one of:
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67 |
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68 | =over 2
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69 |
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70 | =item C<O_RDONLY>
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71 |
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72 | Read-only access to the data in the file.
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73 |
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74 | =item C<O_WRONLY>
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75 |
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76 | Write-only access to the data in the file.
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77 |
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78 | =item C<O_RDWR>
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79 |
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80 | Both read and write access.
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81 |
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82 | =back
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83 |
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84 | If you want to create the file if it does not exist, add C<O_CREAT> to
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85 | any of these, as in the example. If you omit C<O_CREAT> and the file
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86 | does not already exist, the C<tie> call will fail.
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87 |
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88 | =item 5.
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89 |
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90 | The default permissions to use if a new file is created. The actual
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91 | permissions will be modified by the user's umask, so you should
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92 | probably use 0666 here. (See L<perlfunc/umask>.)
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93 |
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94 | =back
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95 |
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96 | =head1 DIAGNOSTICS
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97 |
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98 | On failure, the C<tie> call returns an undefined value and probably
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99 | sets C<$!> to contain the reason the file could not be tied.
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100 |
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101 | =head2 C<sdbm store returned -1, errno 22, key "..." at ...>
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102 |
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103 | This warning is emitted when you try to store a key or a value that
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104 | is too long. It means that the change was not recorded in the
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105 | database. See BUGS AND WARNINGS below.
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106 |
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107 | =head1 BUGS AND WARNINGS
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108 |
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109 | There are a number of limits on the size of the data that you can
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110 | store in the SDBM file. The most important is that the length of a
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111 | key, plus the length of its associated value, may not exceed 1008
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112 | bytes.
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113 |
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114 | See L<perlfunc/tie>, L<perldbmfilter>, L<Fcntl>
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115 |
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116 | =cut
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