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1 | package Tie::Array; |
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2 | |
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3 | use 5.006_001; |
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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) } |
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14 | sub CLEAR { shift->STORESIZE(0) } |
15 | |
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16 | sub PUSH |
17 | { |
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18 | my $obj = shift; |
19 | my $i = $obj->FETCHSIZE; |
20 | $obj->STORE($i++, shift) while (@_); |
21 | } |
22 | |
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23 | sub POP |
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24 | { |
25 | my $obj = shift; |
26 | my $newsize = $obj->FETCHSIZE - 1; |
27 | my $val; |
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28 | if ($newsize >= 0) |
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29 | { |
30 | $val = $obj->FETCH($newsize); |
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31 | $obj->STORESIZE($newsize); |
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32 | } |
33 | $val; |
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34 | } |
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35 | |
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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)); |
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46 | } |
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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 | } |
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58 | } |
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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 | } |
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72 | return wantarray ? @result : pop @result; |
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73 | } |
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74 | |
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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 | |
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85 | package Tie::StdArray; |
86 | use vars qw(@ISA); |
87 | @ISA = 'Tie::Array'; |
88 | |
89 | sub TIEARRAY { bless [], $_[0] } |
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90 | sub FETCHSIZE { scalar @{$_[0]} } |
91 | sub STORESIZE { $#{$_[0]} = $_[1]-1 } |
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92 | sub STORE { $_[0]->[$_[1]] = $_[2] } |
93 | sub FETCH { $_[0]->[$_[1]] } |
94 | sub CLEAR { @{$_[0]} = () } |
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95 | sub POP { pop(@{$_[0]}) } |
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96 | sub PUSH { my $o = shift; push(@$o,@_) } |
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97 | sub SHIFT { shift(@{$_[0]}) } |
98 | sub UNSHIFT { my $o = shift; unshift(@$o,@_) } |
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99 | sub EXISTS { exists $_[0]->[$_[1]] } |
100 | sub DELETE { delete $_[0]->[$_[1]] } |
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101 | |
102 | sub SPLICE |
103 | { |
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104 | my $ob = shift; |
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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 | } |
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111 | |
112 | 1; |
113 | |
114 | __END__ |
115 | |
116 | =head1 NAME |
117 | |
118 | Tie::Array - base class for tied arrays |
119 | |
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120 | =head1 SYNOPSIS |
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121 | |
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122 | package NewArray; |
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123 | use Tie::Array; |
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124 | @ISA = ('Tie::Array'); |
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125 | |
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126 | # mandatory methods |
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127 | sub TIEARRAY { ... } |
128 | sub FETCH { ... } |
129 | sub FETCHSIZE { ... } |
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130 | |
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131 | sub STORE { ... } # mandatory if elements writeable |
132 | sub STORESIZE { ... } # mandatory if elements can be added/deleted |
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133 | sub EXISTS { ... } # mandatory if exists() expected to work |
134 | sub DELETE { ... } # mandatory if delete() expected to work |
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135 | |
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136 | # optional methods - for efficiency |
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137 | sub CLEAR { ... } |
138 | sub PUSH { ... } |
139 | sub POP { ... } |
140 | sub SHIFT { ... } |
141 | sub UNSHIFT { ... } |
142 | sub SPLICE { ... } |
143 | sub EXTEND { ... } |
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144 | sub DESTROY { ... } |
145 | |
146 | package NewStdArray; |
147 | use Tie::Array; |
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148 | |
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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 | |
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160 | |
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161 | =head1 DESCRIPTION |
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162 | |
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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 |
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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>, |
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170 | C<FETCHSIZE>, C<STORESIZE>. |
171 | |
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172 | The B<Tie::StdArray> package provides efficient methods required for tied arrays |
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173 | which are implemented as blessed references to an "inner" perl array. |
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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. |
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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 | |
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181 | =over 4 |
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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 |
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189 | provides the methods below. |
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190 | |
191 | =item STORE this, index, value |
192 | |
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193 | Store datum I<value> into I<index> for the tied array associated with |
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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 | |
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199 | Retrieve the datum in I<index> for the tied array associated with |
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200 | object I<this>. |
201 | |
202 | =item FETCHSIZE this |
203 | |
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204 | Returns the total number of items in the tied array associated with |
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205 | object I<this>. (Equivalent to C<scalar(@array)>). |
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206 | |
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207 | =item STORESIZE this, count |
208 | |
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209 | Sets the total number of items in the tied array associated with |
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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 |
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213 | deleted. |
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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 | |
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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 | |
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232 | =item CLEAR this |
233 | |
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234 | Clear (remove, delete, ...) all values from the tied array associated with |
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235 | object I<this>. |
236 | |
237 | =item DESTROY this |
238 | |
239 | Normal object destructor method. |
240 | |
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241 | =item PUSH this, LIST |
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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 | |
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254 | =item UNSHIFT this, LIST |
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255 | |
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256 | Insert LIST elements at the beginning of the array, moving existing elements |
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257 | up to make room. |
258 | |
259 | =item SPLICE this, offset, length, LIST |
260 | |
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261 | Perform the equivalent of C<splice> on the array. |
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262 | |
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263 | I<offset> is optional and defaults to zero, negative values count back |
264 | from the end of the array. |
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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 |
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273 | |
274 | =head1 CAVEATS |
275 | |
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276 | There is no support at present for tied @ISA. There is a potential conflict |
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277 | between magic entries needed to notice setting of @ISA, and those needed to |
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278 | implement 'tie'. |
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279 | |
280 | Very little consideration has been given to the behaviour of tied arrays |
281 | when C<$[> is not default value of zero. |
282 | |
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283 | =head1 AUTHOR |
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284 | |
285 | Nick Ing-Simmons E<lt>nik@tiuk.ti.comE<gt> |
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286 | |
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287 | =cut |