Commit | Line | Data |
49293501 |
1 | package Hash::Util; |
2 | |
3 | require 5.007003; |
4 | use strict; |
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5 | use Carp; |
6 | |
7 | require Exporter; |
8 | our @ISA = qw(Exporter); |
9 | our @EXPORT_OK = qw(lock_keys unlock_keys lock_value unlock_value |
10 | lock_hash unlock_hash |
11 | ); |
12 | our $VERSION = 0.04; |
13 | |
49293501 |
14 | =head1 NAME |
15 | |
16 | Hash::Util - A selection of general-utility hash subroutines |
17 | |
18 | =head1 SYNOPSIS |
19 | |
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20 | use Hash::Util qw(lock_keys unlock_keys |
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21 | lock_value unlock_value |
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22 | lock_hash unlock_hash); |
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23 | |
24 | %hash = (foo => 42, bar => 23); |
25 | lock_keys(%hash); |
26 | lock_keys(%hash, @keyset); |
27 | unlock_keys(%hash); |
28 | |
29 | lock_value (%hash, 'foo'); |
30 | unlock_value(%hash, 'foo'); |
31 | |
32 | lock_hash (%hash); |
33 | unlock_hash(%hash); |
34 | |
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35 | =head1 DESCRIPTION |
36 | |
37 | C<Hash::Util> contains special functions for manipulating hashes that |
38 | don't really warrant a keyword. |
39 | |
40 | By default C<Hash::Util> does not export anything. |
41 | |
42 | =head2 Restricted hashes |
43 | |
44 | 5.8.0 introduces the ability to restrict a hash to a certain set of |
45 | keys. No keys outside of this set can be added. It also introduces |
46 | the ability to lock an individual key so it cannot be deleted and the |
47 | value cannot be changed. |
48 | |
49 | This is intended to largely replace the deprecated pseudo-hashes. |
50 | |
51 | =over 4 |
52 | |
53 | =item lock_keys |
54 | |
55 | =item unlock_keys |
56 | |
57 | lock_keys(%hash); |
58 | lock_keys(%hash, @keys); |
59 | |
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60 | Restricts the given %hash's set of keys to @keys. If @keys is not |
61 | given it restricts it to its current keyset. No more keys can be |
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62 | added. delete() and exists() will still work, but will not alter |
63 | the set of allowed keys. B<Note>: the current implementation prevents |
64 | the hash from being bless()ed while it is in a locked state. Any attempt |
65 | to do so will raise an exception. Of course you can still bless() |
66 | the hash before you call lock_keys() so this shouldn't be a problem. |
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67 | |
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68 | unlock_keys(%hash); |
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69 | |
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70 | Removes the restriction on the %hash's keyset. |
71 | |
72 | =cut |
73 | |
74 | sub lock_keys (\%;@) { |
75 | my($hash, @keys) = @_; |
76 | |
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77 | Internals::hv_clear_placeholders %$hash; |
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78 | if( @keys ) { |
79 | my %keys = map { ($_ => 1) } @keys; |
80 | my %original_keys = map { ($_ => 1) } keys %$hash; |
81 | foreach my $k (keys %original_keys) { |
82 | die sprintf "Hash has key '$k' which is not in the new key ". |
83 | "set at %s line %d\n", (caller)[1,2] |
84 | unless $keys{$k}; |
85 | } |
86 | |
87 | foreach my $k (@keys) { |
88 | $hash->{$k} = undef unless exists $hash->{$k}; |
89 | } |
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90 | Internals::SvREADONLY %$hash, 1; |
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91 | |
92 | foreach my $k (@keys) { |
93 | delete $hash->{$k} unless $original_keys{$k}; |
94 | } |
95 | } |
96 | else { |
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97 | Internals::SvREADONLY %$hash, 1; |
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98 | } |
99 | |
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100 | return; |
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101 | } |
102 | |
103 | sub unlock_keys (\%) { |
104 | my($hash) = shift; |
105 | |
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106 | Internals::SvREADONLY %$hash, 0; |
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107 | return; |
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108 | } |
109 | |
110 | =item lock_value |
111 | |
112 | =item unlock_value |
113 | |
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114 | lock_value (%hash, $key); |
115 | unlock_value(%hash, $key); |
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116 | |
117 | Locks and unlocks an individual key of a hash. The value of a locked |
118 | key cannot be changed. |
119 | |
120 | %hash must have already been locked for this to have useful effect. |
121 | |
122 | =cut |
123 | |
124 | sub lock_value (\%$) { |
125 | my($hash, $key) = @_; |
126 | carp "Cannot usefully lock values in an unlocked hash" |
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127 | unless Internals::SvREADONLY %$hash; |
128 | Internals::SvREADONLY $hash->{$key}, 1; |
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129 | } |
130 | |
131 | sub unlock_value (\%$) { |
132 | my($hash, $key) = @_; |
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133 | Internals::SvREADONLY $hash->{$key}, 0; |
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134 | } |
135 | |
136 | |
137 | =item B<lock_hash> |
138 | |
139 | =item B<unlock_hash> |
140 | |
141 | lock_hash(%hash); |
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142 | |
143 | lock_hash() locks an entire hash, making all keys and values readonly. |
144 | No value can be changed, no keys can be added or deleted. |
145 | |
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146 | unlock_hash(%hash); |
147 | |
148 | unlock_hash() does the opposite of lock_hash(). All keys and values |
149 | are made read/write. All values can be changed and keys can be added |
150 | and deleted. |
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151 | |
152 | =cut |
153 | |
154 | sub lock_hash (\%) { |
155 | my($hash) = shift; |
156 | |
157 | lock_keys(%$hash); |
158 | |
159 | foreach my $key (keys %$hash) { |
160 | lock_value(%$hash, $key); |
161 | } |
162 | |
163 | return 1; |
164 | } |
165 | |
166 | sub unlock_hash (\%) { |
167 | my($hash) = shift; |
168 | |
169 | foreach my $key (keys %$hash) { |
170 | unlock_value(%$hash, $key); |
171 | } |
172 | |
173 | unlock_keys(%$hash); |
174 | |
175 | return 1; |
176 | } |
177 | |
178 | |
179 | =back |
180 | |
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181 | =head1 CAVEATS |
182 | |
183 | Note that the trapping of the restricted operations is not atomic: |
184 | for example |
185 | |
186 | eval { %hash = (illegal_key => 1) } |
187 | |
188 | leaves the C<%hash> empty rather than with its original contents. |
189 | |
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190 | =head1 AUTHOR |
191 | |
192 | Michael G Schwern <schwern@pobox.com> on top of code by Nick |
193 | Ing-Simmons and Jeffrey Friedl. |
194 | |
195 | =head1 SEE ALSO |
196 | |
197 | L<Scalar::Util>, L<List::Util>, L<Hash::Util> |
198 | |
199 | =cut |
200 | |
201 | 1; |