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1 | package Tie::Array; |
2 | ||
3 | use 5.006_001; | |
4 | use strict; | |
5 | use Carp; | |
6 | our $VERSION = '1.02'; | |
7 | ||
8 | # Pod documentation after __END__ below. | |
9 | ||
10 | sub DESTROY { } | |
11 | sub EXTEND { } | |
12 | sub UNSHIFT { scalar 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); | |
31 | $obj->STORESIZE($newsize); | |
32 | } | |
33 | $val; | |
34 | } | |
35 | ||
36 | sub SPLICE { | |
37 | my $obj = shift; | |
38 | my $sz = $obj->FETCHSIZE; | |
39 | my $off = (@_) ? shift : 0; | |
40 | $off += $sz if ($off < 0); | |
41 | my $len = (@_) ? shift : $sz - $off; | |
42 | $len += $sz - $off if $len < 0; | |
43 | my @result; | |
44 | for (my $i = 0; $i < $len; $i++) { | |
45 | push(@result,$obj->FETCH($off+$i)); | |
46 | } | |
47 | $off = $sz if $off > $sz; | |
48 | $len -= $off + $len - $sz if $off + $len > $sz; | |
49 | if (@_ > $len) { | |
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 | my $val = $obj->FETCH($i); | |
56 | $obj->STORE($i+$d,$val); | |
57 | } | |
58 | } | |
59 | elsif (@_ < $len) { | |
60 | # Move items down to close the gap | |
61 | my $d = $len - @_; | |
62 | my $e = $off+$len; | |
63 | for (my $i=$off+$len; $i < $sz; $i++) { | |
64 | my $val = $obj->FETCH($i); | |
65 | $obj->STORE($i-$d,$val); | |
66 | } | |
67 | $obj->STORESIZE($sz-$d); | |
68 | } | |
69 | for (my $i=0; $i < @_; $i++) { | |
70 | $obj->STORE($off+$i,$_[$i]); | |
71 | } | |
72 | return wantarray ? @result : pop @result; | |
73 | } | |
74 | ||
75 | sub EXISTS { | |
76 | my $pkg = ref $_[0]; | |
77 | croak "$pkg dosn't define an EXISTS method"; | |
78 | } | |
79 | ||
80 | sub DELETE { | |
81 | my $pkg = ref $_[0]; | |
82 | croak "$pkg dosn't define a DELETE method"; | |
83 | } | |
84 | ||
85 | package Tie::StdArray; | |
86 | use vars qw(@ISA); | |
87 | @ISA = 'Tie::Array'; | |
88 | ||
89 | sub TIEARRAY { bless [], $_[0] } | |
90 | sub FETCHSIZE { scalar @{$_[0]} } | |
91 | sub STORESIZE { $#{$_[0]} = $_[1]-1 } | |
92 | sub STORE { $_[0]->[$_[1]] = $_[2] } | |
93 | sub FETCH { $_[0]->[$_[1]] } | |
94 | sub CLEAR { @{$_[0]} = () } | |
95 | sub POP { pop(@{$_[0]}) } | |
96 | sub PUSH { my $o = shift; push(@$o,@_) } | |
97 | sub SHIFT { shift(@{$_[0]}) } | |
98 | sub UNSHIFT { my $o = shift; unshift(@$o,@_) } | |
99 | sub EXISTS { exists $_[0]->[$_[1]] } | |
100 | sub DELETE { delete $_[0]->[$_[1]] } | |
101 | ||
102 | sub SPLICE | |
103 | { | |
104 | my $ob = shift; | |
105 | my $sz = $ob->FETCHSIZE; | |
106 | my $off = @_ ? shift : 0; | |
107 | $off += $sz if $off < 0; | |
108 | my $len = @_ ? shift : $sz-$off; | |
109 | return splice(@$ob,$off,$len,@_); | |
110 | } | |
111 | ||
112 | 1; | |
113 | ||
114 | __END__ | |
115 | ||
116 | =head1 NAME | |
117 | ||
118 | Tie::Array - base class for tied arrays | |
119 | ||
120 | =head1 SYNOPSIS | |
121 | ||
122 | package Tie::NewArray; | |
123 | use Tie::Array; | |
124 | @ISA = ('Tie::Array'); | |
125 | ||
126 | # mandatory methods | |
127 | sub TIEARRAY { ... } | |
128 | sub FETCH { ... } | |
129 | sub FETCHSIZE { ... } | |
130 | ||
131 | sub STORE { ... } # mandatory if elements writeable | |
132 | sub STORESIZE { ... } # mandatory if elements can be added/deleted | |
133 | sub EXISTS { ... } # mandatory if exists() expected to work | |
134 | sub DELETE { ... } # mandatory if delete() expected to work | |
135 | ||
136 | # optional methods - for efficiency | |
137 | sub CLEAR { ... } | |
138 | sub PUSH { ... } | |
139 | sub POP { ... } | |
140 | sub SHIFT { ... } | |
141 | sub UNSHIFT { ... } | |
142 | sub SPLICE { ... } | |
143 | sub EXTEND { ... } | |
144 | sub DESTROY { ... } | |
145 | ||
146 | package Tie::NewStdArray; | |
147 | use Tie::Array; | |
148 | ||
149 | @ISA = ('Tie::StdArray'); | |
150 | ||
151 | # all methods provided by default | |
152 | ||
153 | package main; | |
154 | ||
155 | $object = tie @somearray,Tie::NewArray; | |
156 | $object = tie @somearray,Tie::StdArray; | |
157 | $object = tie @somearray,Tie::NewStdArray; | |
158 | ||
159 | ||
160 | ||
161 | =head1 DESCRIPTION | |
162 | ||
163 | This module provides methods for array-tying classes. See | |
164 | L<perltie> for a list of the functions required in order to tie an array | |
165 | to a package. The basic B<Tie::Array> package provides stub C<DESTROY>, | |
166 | and C<EXTEND> methods that do nothing, stub C<DELETE> and C<EXISTS> | |
167 | methods that croak() if the delete() or exists() builtins are ever called | |
168 | on the tied array, and implementations of C<PUSH>, C<POP>, C<SHIFT>, | |
169 | C<UNSHIFT>, C<SPLICE> and C<CLEAR> in terms of basic C<FETCH>, C<STORE>, | |
170 | C<FETCHSIZE>, C<STORESIZE>. | |
171 | ||
172 | The B<Tie::StdArray> package provides efficient methods required for tied arrays | |
173 | which are implemented as blessed references to an "inner" perl array. | |
174 | It inherits from B<Tie::Array>, and should cause tied arrays to behave exactly | |
175 | like standard arrays, allowing for selective overloading of methods. | |
176 | ||
177 | For developers wishing to write their own tied arrays, the required methods | |
178 | are briefly defined below. See the L<perltie> section for more detailed | |
179 | descriptive, as well as example code: | |
180 | ||
181 | =over 4 | |
182 | ||
183 | =item TIEARRAY classname, LIST | |
184 | ||
185 | The class method is invoked by the command C<tie @array, classname>. Associates | |
186 | an array instance with the specified class. C<LIST> would represent | |
187 | additional arguments (along the lines of L<AnyDBM_File> and compatriots) needed | |
188 | to complete the association. The method should return an object of a class which | |
189 | provides the methods below. | |
190 | ||
191 | =item STORE this, index, value | |
192 | ||
193 | Store datum I<value> into I<index> for the tied array associated with | |
194 | object I<this>. If this makes the array larger then | |
195 | class's mapping of C<undef> should be returned for new positions. | |
196 | ||
197 | =item FETCH this, index | |
198 | ||
199 | Retrieve the datum in I<index> for the tied array associated with | |
200 | object I<this>. | |
201 | ||
202 | =item FETCHSIZE this | |
203 | ||
204 | Returns the total number of items in the tied array associated with | |
205 | object I<this>. (Equivalent to C<scalar(@array)>). | |
206 | ||
207 | =item STORESIZE this, count | |
208 | ||
209 | Sets the total number of items in the tied array associated with | |
210 | object I<this> to be I<count>. If this makes the array larger then | |
211 | class's mapping of C<undef> should be returned for new positions. | |
212 | If the array becomes smaller then entries beyond count should be | |
213 | deleted. | |
214 | ||
215 | =item EXTEND this, count | |
216 | ||
217 | Informative call that array is likely to grow to have I<count> entries. | |
218 | Can be used to optimize allocation. This method need do nothing. | |
219 | ||
220 | =item EXISTS this, key | |
221 | ||
222 | Verify that the element at index I<key> exists in the tied array I<this>. | |
223 | ||
224 | The B<Tie::Array> implementation is a stub that simply croaks. | |
225 | ||
226 | =item DELETE this, key | |
227 | ||
228 | Delete the element at index I<key> from the tied array I<this>. | |
229 | ||
230 | The B<Tie::Array> implementation is a stub that simply croaks. | |
231 | ||
232 | =item CLEAR this | |
233 | ||
234 | Clear (remove, delete, ...) all values from the tied array associated with | |
235 | object I<this>. | |
236 | ||
237 | =item DESTROY this | |
238 | ||
239 | Normal object destructor method. | |
240 | ||
241 | =item PUSH this, LIST | |
242 | ||
243 | Append elements of LIST to the array. | |
244 | ||
245 | =item POP this | |
246 | ||
247 | Remove last element of the array and return it. | |
248 | ||
249 | =item SHIFT this | |
250 | ||
251 | Remove the first element of the array (shifting other elements down) | |
252 | and return it. | |
253 | ||
254 | =item UNSHIFT this, LIST | |
255 | ||
256 | Insert LIST elements at the beginning of the array, moving existing elements | |
257 | up to make room. | |
258 | ||
259 | =item SPLICE this, offset, length, LIST | |
260 | ||
261 | Perform the equivalent of C<splice> on the array. | |
262 | ||
263 | I<offset> is optional and defaults to zero, negative values count back | |
264 | from the end of the array. | |
265 | ||
266 | I<length> is optional and defaults to rest of the array. | |
267 | ||
268 | I<LIST> may be empty. | |
269 | ||
270 | Returns a list of the original I<length> elements at I<offset>. | |
271 | ||
272 | =back | |
273 | ||
274 | =head1 CAVEATS | |
275 | ||
276 | There is no support at present for tied @ISA. There is a potential conflict | |
277 | between magic entries needed to notice setting of @ISA, and those needed to | |
278 | implement 'tie'. | |
279 | ||
280 | Very little consideration has been given to the behaviour of tied arrays | |
281 | when C<$[> is not default value of zero. | |
282 | ||
283 | =head1 AUTHOR | |
284 | ||
285 | Nick Ing-Simmons E<lt>nik@tiuk.ti.comE<gt> | |
286 | ||
287 | =cut |