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1 | package Tie::Array; |
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2 | |
3 | use 5.005_64; |
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4 | use strict; |
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5 | use Carp; |
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6 | our $VERSION = '1.01'; |
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7 | |
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8 | # Pod documentation after __END__ below. |
9 | |
10 | sub DESTROY { } |
11 | sub EXTEND { } |
12 | sub UNSHIFT { shift->SPLICE(0,0,@_) } |
13 | sub SHIFT { shift->SPLICE(0,1) } |
14 | sub CLEAR { shift->STORESIZE(0) } |
15 | |
16 | sub PUSH |
17 | { |
18 | my $obj = shift; |
19 | my $i = $obj->FETCHSIZE; |
20 | $obj->STORE($i++, shift) while (@_); |
21 | } |
22 | |
23 | sub POP |
24 | { |
25 | my $obj = shift; |
26 | my $newsize = $obj->FETCHSIZE - 1; |
27 | my $val; |
28 | if ($newsize >= 0) |
29 | { |
30 | $val = $obj->FETCH($newsize); |
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31 | $obj->STORESIZE($newsize); |
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32 | } |
33 | $val; |
34 | } |
35 | |
36 | sub SPLICE |
37 | { |
38 | my $obj = shift; |
39 | my $sz = $obj->FETCHSIZE; |
40 | my $off = (@_) ? shift : 0; |
41 | $off += $sz if ($off < 0); |
42 | my $len = (@_) ? shift : $sz - $off; |
43 | my @result; |
44 | for (my $i = 0; $i < $len; $i++) |
45 | { |
46 | push(@result,$obj->FETCH($off+$i)); |
47 | } |
48 | if (@_ > $len) |
49 | { |
50 | # Move items up to make room |
51 | my $d = @_ - $len; |
52 | my $e = $off+$len; |
53 | $obj->EXTEND($sz+$d); |
54 | for (my $i=$sz-1; $i >= $e; $i--) |
55 | { |
56 | my $val = $obj->FETCH($i); |
57 | $obj->STORE($i+$d,$val); |
58 | } |
59 | } |
60 | elsif (@_ < $len) |
61 | { |
62 | # Move items down to close the gap |
63 | my $d = $len - @_; |
64 | my $e = $off+$len; |
65 | for (my $i=$off+$len; $i < $sz; $i++) |
66 | { |
67 | my $val = $obj->FETCH($i); |
68 | $obj->STORE($i-$d,$val); |
69 | } |
70 | $obj->STORESIZE($sz-$d); |
71 | } |
72 | for (my $i=0; $i < @_; $i++) |
73 | { |
74 | $obj->STORE($off+$i,$_[$i]); |
75 | } |
76 | return @result; |
77 | } |
78 | |
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79 | sub EXISTS { |
80 | my $pkg = ref $_[0]; |
81 | croak "$pkg dosn't define an EXISTS method"; |
82 | } |
83 | |
84 | sub DELETE { |
85 | my $pkg = ref $_[0]; |
86 | croak "$pkg dosn't define a DELETE method"; |
87 | } |
88 | |
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89 | package Tie::StdArray; |
90 | use vars qw(@ISA); |
91 | @ISA = 'Tie::Array'; |
92 | |
93 | sub TIEARRAY { bless [], $_[0] } |
94 | sub FETCHSIZE { scalar @{$_[0]} } |
95 | sub STORESIZE { $#{$_[0]} = $_[1]-1 } |
96 | sub STORE { $_[0]->[$_[1]] = $_[2] } |
97 | sub FETCH { $_[0]->[$_[1]] } |
98 | sub CLEAR { @{$_[0]} = () } |
99 | sub POP { pop(@{$_[0]}) } |
100 | sub PUSH { my $o = shift; push(@$o,@_) } |
101 | sub SHIFT { shift(@{$_[0]}) } |
102 | sub UNSHIFT { my $o = shift; unshift(@$o,@_) } |
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103 | sub EXISTS { exists $_[0]->[$_[1]] } |
104 | sub DELETE { delete $_[0]->[$_[1]] } |
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105 | |
106 | sub SPLICE |
107 | { |
108 | my $ob = shift; |
109 | my $sz = $ob->FETCHSIZE; |
110 | my $off = @_ ? shift : 0; |
111 | $off += $sz if $off < 0; |
112 | my $len = @_ ? shift : $sz-$off; |
113 | return splice(@$ob,$off,$len,@_); |
114 | } |
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115 | |
116 | 1; |
117 | |
118 | __END__ |
119 | |
120 | =head1 NAME |
121 | |
122 | Tie::Array - base class for tied arrays |
123 | |
124 | =head1 SYNOPSIS |
125 | |
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126 | package NewArray; |
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127 | use Tie::Array; |
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128 | @ISA = ('Tie::Array'); |
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129 | |
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130 | # mandatory methods |
131 | sub TIEARRAY { ... } |
132 | sub FETCH { ... } |
133 | sub FETCHSIZE { ... } |
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134 | |
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135 | sub STORE { ... } # mandatory if elements writeable |
136 | sub STORESIZE { ... } # mandatory if elements can be added/deleted |
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137 | sub EXISTS { ... } # mandatory if exists() expected to work |
138 | sub DELETE { ... } # mandatory if delete() expected to work |
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139 | |
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140 | # optional methods - for efficiency |
141 | sub CLEAR { ... } |
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142 | sub PUSH { ... } |
143 | sub POP { ... } |
144 | sub SHIFT { ... } |
145 | sub UNSHIFT { ... } |
146 | sub SPLICE { ... } |
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147 | sub EXTEND { ... } |
148 | sub DESTROY { ... } |
149 | |
150 | package NewStdArray; |
151 | use Tie::Array; |
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152 | |
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153 | @ISA = ('Tie::StdArray'); |
154 | |
155 | # all methods provided by default |
156 | |
157 | package main; |
158 | |
159 | $object = tie @somearray,Tie::NewArray; |
160 | $object = tie @somearray,Tie::StdArray; |
161 | $object = tie @somearray,Tie::NewStdArray; |
162 | |
163 | |
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164 | |
165 | =head1 DESCRIPTION |
166 | |
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167 | This module provides methods for array-tying classes. See |
168 | L<perltie> for a list of the functions required in order to tie an array |
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169 | to a package. The basic B<Tie::Array> package provides stub C<DESTROY>, |
170 | and C<EXTEND> methods that do nothing, stub C<DELETE> and C<EXISTS> |
171 | methods that croak() if the delete() or exists() builtins are ever called |
172 | on the tied array, and implementations of C<PUSH>, C<POP>, C<SHIFT>, |
173 | C<UNSHIFT>, C<SPLICE> and C<CLEAR> in terms of basic C<FETCH>, C<STORE>, |
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174 | C<FETCHSIZE>, C<STORESIZE>. |
175 | |
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176 | The B<Tie::StdArray> package provides efficient methods required for tied arrays |
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177 | which are implemented as blessed references to an "inner" perl array. |
178 | It inherits from B<Tie::Array>, and should cause tied arrays to behave exactly |
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179 | like standard arrays, allowing for selective overloading of methods. |
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180 | |
181 | For developers wishing to write their own tied arrays, the required methods |
182 | are briefly defined below. See the L<perltie> section for more detailed |
183 | descriptive, as well as example code: |
184 | |
185 | =over |
186 | |
187 | =item TIEARRAY classname, LIST |
188 | |
189 | The class method is invoked by the command C<tie @array, classname>. Associates |
190 | an array instance with the specified class. C<LIST> would represent |
191 | additional arguments (along the lines of L<AnyDBM_File> and compatriots) needed |
192 | to complete the association. The method should return an object of a class which |
193 | provides the methods below. |
194 | |
195 | =item STORE this, index, value |
196 | |
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197 | Store datum I<value> into I<index> for the tied array associated with |
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198 | object I<this>. If this makes the array larger then |
199 | class's mapping of C<undef> should be returned for new positions. |
200 | |
201 | =item FETCH this, index |
202 | |
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203 | Retrieve the datum in I<index> for the tied array associated with |
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204 | object I<this>. |
205 | |
206 | =item FETCHSIZE this |
207 | |
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208 | Returns the total number of items in the tied array associated with |
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209 | object I<this>. (Equivalent to C<scalar(@array)>). |
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210 | |
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211 | =item STORESIZE this, count |
212 | |
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213 | Sets the total number of items in the tied array associated with |
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214 | object I<this> to be I<count>. If this makes the array larger then |
215 | class's mapping of C<undef> should be returned for new positions. |
216 | If the array becomes smaller then entries beyond count should be |
217 | deleted. |
218 | |
219 | =item EXTEND this, count |
220 | |
221 | Informative call that array is likely to grow to have I<count> entries. |
222 | Can be used to optimize allocation. This method need do nothing. |
223 | |
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224 | =item EXISTS this, key |
225 | |
226 | Verify that the element at index I<key> exists in the tied array I<this>. |
227 | |
228 | The B<Tie::Array> implementation is a stub that simply croaks. |
229 | |
230 | =item DELETE this, key |
231 | |
232 | Delete the element at index I<key> from the tied array I<this>. |
233 | |
234 | The B<Tie::Array> implementation is a stub that simply croaks. |
235 | |
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236 | =item CLEAR this |
237 | |
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238 | Clear (remove, delete, ...) all values from the tied array associated with |
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239 | object I<this>. |
240 | |
241 | =item DESTROY this |
242 | |
243 | Normal object destructor method. |
244 | |
245 | =item PUSH this, LIST |
246 | |
247 | Append elements of LIST to the array. |
248 | |
249 | =item POP this |
250 | |
251 | Remove last element of the array and return it. |
252 | |
253 | =item SHIFT this |
254 | |
255 | Remove the first element of the array (shifting other elements down) |
256 | and return it. |
257 | |
258 | =item UNSHIFT this, LIST |
259 | |
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260 | Insert LIST elements at the beginning of the array, moving existing elements |
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261 | up to make room. |
262 | |
263 | =item SPLICE this, offset, length, LIST |
264 | |
265 | Perform the equivalent of C<splice> on the array. |
266 | |
267 | I<offset> is optional and defaults to zero, negative values count back |
268 | from the end of the array. |
269 | |
270 | I<length> is optional and defaults to rest of the array. |
271 | |
272 | I<LIST> may be empty. |
273 | |
274 | Returns a list of the original I<length> elements at I<offset>. |
275 | |
276 | =back |
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277 | |
278 | =head1 CAVEATS |
279 | |
280 | There is no support at present for tied @ISA. There is a potential conflict |
281 | between magic entries needed to notice setting of @ISA, and those needed to |
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282 | implement 'tie'. |
283 | |
284 | Very little consideration has been given to the behaviour of tied arrays |
285 | when C<$[> is not default value of zero. |
286 | |
287 | =head1 AUTHOR |
288 | |
289 | Nick Ing-Simmons E<lt>nik@tiuk.ti.comE<gt> |
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290 | |
291 | =cut |
292 | |