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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 = '1.02'; |
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7 | |
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8 | # Pod documentation after __END__ below. |
9 | |
10 | sub DESTROY { } |
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11 | sub EXTEND { } |
12 | sub UNSHIFT { scalar shift->SPLICE(0,0,@_) } |
13 | sub SHIFT { shift->SPLICE(0,1) } |
14 | #sub SHIFT { (shift->SPLICE(0,1))[0] } |
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15 | sub CLEAR { shift->STORESIZE(0) } |
16 | |
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17 | sub PUSH |
18 | { |
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19 | my $obj = shift; |
20 | my $i = $obj->FETCHSIZE; |
21 | $obj->STORE($i++, shift) while (@_); |
22 | } |
23 | |
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24 | sub POP |
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25 | { |
26 | my $obj = shift; |
27 | my $newsize = $obj->FETCHSIZE - 1; |
28 | my $val; |
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29 | if ($newsize >= 0) |
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30 | { |
31 | $val = $obj->FETCH($newsize); |
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32 | $obj->STORESIZE($newsize); |
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33 | } |
34 | $val; |
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35 | } |
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36 | |
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37 | sub SPLICE { |
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 | $len += $sz - $off if $len < 0; |
44 | my @result; |
45 | for (my $i = 0; $i < $len; $i++) { |
46 | push(@result,$obj->FETCH($off+$i)); |
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47 | } |
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48 | $off = $sz if $off > $sz; |
49 | $len -= $off + $len - $sz if $off + $len > $sz; |
50 | if (@_ > $len) { |
51 | # Move items up to make room |
52 | my $d = @_ - $len; |
53 | my $e = $off+$len; |
54 | $obj->EXTEND($sz+$d); |
55 | for (my $i=$sz-1; $i >= $e; $i--) { |
56 | my $val = $obj->FETCH($i); |
57 | $obj->STORE($i+$d,$val); |
58 | } |
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59 | } |
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60 | elsif (@_ < $len) { |
61 | # Move items down to close the gap |
62 | my $d = $len - @_; |
63 | my $e = $off+$len; |
64 | for (my $i=$off+$len; $i < $sz; $i++) { |
65 | my $val = $obj->FETCH($i); |
66 | $obj->STORE($i-$d,$val); |
67 | } |
68 | $obj->STORESIZE($sz-$d); |
69 | } |
70 | for (my $i=0; $i < @_; $i++) { |
71 | $obj->STORE($off+$i,$_[$i]); |
72 | } |
73 | return @result; |
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74 | } |
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75 | |
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76 | sub EXISTS { |
77 | my $pkg = ref $_[0]; |
78 | croak "$pkg dosn't define an EXISTS method"; |
79 | } |
80 | |
81 | sub DELETE { |
82 | my $pkg = ref $_[0]; |
83 | croak "$pkg dosn't define a DELETE method"; |
84 | } |
85 | |
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86 | package Tie::StdArray; |
87 | use vars qw(@ISA); |
88 | @ISA = 'Tie::Array'; |
89 | |
90 | sub TIEARRAY { bless [], $_[0] } |
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91 | sub FETCHSIZE { scalar @{$_[0]} } |
92 | sub STORESIZE { $#{$_[0]} = $_[1]-1 } |
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93 | sub STORE { $_[0]->[$_[1]] = $_[2] } |
94 | sub FETCH { $_[0]->[$_[1]] } |
95 | sub CLEAR { @{$_[0]} = () } |
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96 | sub POP { pop(@{$_[0]}) } |
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97 | sub PUSH { my $o = shift; push(@$o,@_) } |
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98 | sub SHIFT { shift(@{$_[0]}) } |
99 | sub UNSHIFT { my $o = shift; unshift(@$o,@_) } |
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100 | sub EXISTS { exists $_[0]->[$_[1]] } |
101 | sub DELETE { delete $_[0]->[$_[1]] } |
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102 | |
103 | sub SPLICE |
104 | { |
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105 | my $ob = shift; |
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106 | my $sz = $ob->FETCHSIZE; |
107 | my $off = @_ ? shift : 0; |
108 | $off += $sz if $off < 0; |
109 | my $len = @_ ? shift : $sz-$off; |
110 | return splice(@$ob,$off,$len,@_); |
111 | } |
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112 | |
113 | 1; |
114 | |
115 | __END__ |
116 | |
117 | =head1 NAME |
118 | |
119 | Tie::Array - base class for tied arrays |
120 | |
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121 | =head1 SYNOPSIS |
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122 | |
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123 | package NewArray; |
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124 | use Tie::Array; |
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125 | @ISA = ('Tie::Array'); |
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126 | |
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127 | # mandatory methods |
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128 | sub TIEARRAY { ... } |
129 | sub FETCH { ... } |
130 | sub FETCHSIZE { ... } |
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131 | |
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132 | sub STORE { ... } # mandatory if elements writeable |
133 | sub STORESIZE { ... } # mandatory if elements can be added/deleted |
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134 | sub EXISTS { ... } # mandatory if exists() expected to work |
135 | sub DELETE { ... } # mandatory if delete() expected to work |
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136 | |
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137 | # optional methods - for efficiency |
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138 | sub CLEAR { ... } |
139 | sub PUSH { ... } |
140 | sub POP { ... } |
141 | sub SHIFT { ... } |
142 | sub UNSHIFT { ... } |
143 | sub SPLICE { ... } |
144 | sub EXTEND { ... } |
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145 | sub DESTROY { ... } |
146 | |
147 | package NewStdArray; |
148 | use Tie::Array; |
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149 | |
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150 | @ISA = ('Tie::StdArray'); |
151 | |
152 | # all methods provided by default |
153 | |
154 | package main; |
155 | |
156 | $object = tie @somearray,Tie::NewArray; |
157 | $object = tie @somearray,Tie::StdArray; |
158 | $object = tie @somearray,Tie::NewStdArray; |
159 | |
160 | |
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161 | |
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162 | =head1 DESCRIPTION |
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163 | |
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164 | This module provides methods for array-tying classes. See |
165 | L<perltie> for a list of the functions required in order to tie an array |
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166 | to a package. The basic B<Tie::Array> package provides stub C<DESTROY>, |
167 | and C<EXTEND> methods that do nothing, stub C<DELETE> and C<EXISTS> |
168 | methods that croak() if the delete() or exists() builtins are ever called |
169 | on the tied array, and implementations of C<PUSH>, C<POP>, C<SHIFT>, |
170 | C<UNSHIFT>, C<SPLICE> and C<CLEAR> in terms of basic C<FETCH>, C<STORE>, |
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171 | C<FETCHSIZE>, C<STORESIZE>. |
172 | |
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173 | The B<Tie::StdArray> package provides efficient methods required for tied arrays |
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174 | which are implemented as blessed references to an "inner" perl array. |
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175 | It inherits from B<Tie::Array>, and should cause tied arrays to behave exactly |
176 | like standard arrays, allowing for selective overloading of methods. |
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177 | |
178 | For developers wishing to write their own tied arrays, the required methods |
179 | are briefly defined below. See the L<perltie> section for more detailed |
180 | descriptive, as well as example code: |
181 | |
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182 | =over 4 |
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183 | |
184 | =item TIEARRAY classname, LIST |
185 | |
186 | The class method is invoked by the command C<tie @array, classname>. Associates |
187 | an array instance with the specified class. C<LIST> would represent |
188 | additional arguments (along the lines of L<AnyDBM_File> and compatriots) needed |
189 | to complete the association. The method should return an object of a class which |
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190 | provides the methods below. |
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191 | |
192 | =item STORE this, index, value |
193 | |
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194 | Store datum I<value> into I<index> for the tied array associated with |
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195 | object I<this>. If this makes the array larger then |
196 | class's mapping of C<undef> should be returned for new positions. |
197 | |
198 | =item FETCH this, index |
199 | |
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200 | Retrieve the datum in I<index> for the tied array associated with |
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201 | object I<this>. |
202 | |
203 | =item FETCHSIZE this |
204 | |
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205 | Returns the total number of items in the tied array associated with |
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206 | object I<this>. (Equivalent to C<scalar(@array)>). |
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207 | |
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208 | =item STORESIZE this, count |
209 | |
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210 | Sets the total number of items in the tied array associated with |
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211 | object I<this> to be I<count>. If this makes the array larger then |
212 | class's mapping of C<undef> should be returned for new positions. |
213 | If the array becomes smaller then entries beyond count should be |
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214 | deleted. |
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215 | |
216 | =item EXTEND this, count |
217 | |
218 | Informative call that array is likely to grow to have I<count> entries. |
219 | Can be used to optimize allocation. This method need do nothing. |
220 | |
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221 | =item EXISTS this, key |
222 | |
223 | Verify that the element at index I<key> exists in the tied array I<this>. |
224 | |
225 | The B<Tie::Array> implementation is a stub that simply croaks. |
226 | |
227 | =item DELETE this, key |
228 | |
229 | Delete the element at index I<key> from the tied array I<this>. |
230 | |
231 | The B<Tie::Array> implementation is a stub that simply croaks. |
232 | |
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233 | =item CLEAR this |
234 | |
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235 | Clear (remove, delete, ...) all values from the tied array associated with |
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236 | object I<this>. |
237 | |
238 | =item DESTROY this |
239 | |
240 | Normal object destructor method. |
241 | |
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242 | =item PUSH this, LIST |
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243 | |
244 | Append elements of LIST to the array. |
245 | |
246 | =item POP this |
247 | |
248 | Remove last element of the array and return it. |
249 | |
250 | =item SHIFT this |
251 | |
252 | Remove the first element of the array (shifting other elements down) |
253 | and return it. |
254 | |
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255 | =item UNSHIFT this, LIST |
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256 | |
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257 | Insert LIST elements at the beginning of the array, moving existing elements |
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258 | up to make room. |
259 | |
260 | =item SPLICE this, offset, length, LIST |
261 | |
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262 | Perform the equivalent of C<splice> on the array. |
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263 | |
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264 | I<offset> is optional and defaults to zero, negative values count back |
265 | from the end of the array. |
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266 | |
267 | I<length> is optional and defaults to rest of the array. |
268 | |
269 | I<LIST> may be empty. |
270 | |
271 | Returns a list of the original I<length> elements at I<offset>. |
272 | |
273 | =back |
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274 | |
275 | =head1 CAVEATS |
276 | |
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277 | There is no support at present for tied @ISA. There is a potential conflict |
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278 | between magic entries needed to notice setting of @ISA, and those needed to |
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279 | implement 'tie'. |
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280 | |
281 | Very little consideration has been given to the behaviour of tied arrays |
282 | when C<$[> is not default value of zero. |
283 | |
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284 | =head1 AUTHOR |
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285 | |
286 | Nick Ing-Simmons E<lt>nik@tiuk.ti.comE<gt> |
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287 | |
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288 | =cut |