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1 | package Tie::Handle; |
2 | |
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3 | use 5.005_64; |
4 | our $VERSION = '1.0'; |
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5 | |
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6 | =head1 NAME |
7 | |
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8 | Tie::Handle, Tie::StdHandle - base class definitions for tied handles |
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9 | |
10 | =head1 SYNOPSIS |
11 | |
12 | package NewHandle; |
13 | require Tie::Handle; |
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14 | |
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15 | @ISA = (Tie::Handle); |
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16 | |
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17 | sub READ { ... } # Provide a needed method |
18 | sub TIEHANDLE { ... } # Overrides inherited method |
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19 | |
20 | |
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21 | package main; |
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22 | |
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23 | tie *FH, 'NewHandle'; |
24 | |
25 | =head1 DESCRIPTION |
26 | |
27 | This module provides some skeletal methods for handle-tying classes. See |
28 | L<perltie> for a list of the functions required in tying a handle to a package. |
29 | The basic B<Tie::Handle> package provides a C<new> method, as well as methods |
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30 | C<TIEHANDLE>, C<PRINT>, C<PRINTF> and C<GETC>. |
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31 | |
32 | For developers wishing to write their own tied-handle classes, the methods |
33 | are summarized below. The L<perltie> section not only documents these, but |
34 | has sample code as well: |
35 | |
36 | =over |
37 | |
38 | =item TIEHANDLE classname, LIST |
39 | |
40 | The method invoked by the command C<tie *glob, classname>. Associates a new |
41 | glob instance with the specified class. C<LIST> would represent additional |
42 | arguments (along the lines of L<AnyDBM_File> and compatriots) needed to |
43 | complete the association. |
44 | |
45 | =item WRITE this, scalar, length, offset |
46 | |
47 | Write I<length> bytes of data from I<scalar> starting at I<offset>. |
48 | |
49 | =item PRINT this, LIST |
50 | |
51 | Print the values in I<LIST> |
52 | |
53 | =item PRINTF this, format, LIST |
54 | |
55 | Print the values in I<LIST> using I<format> |
56 | |
57 | =item READ this, scalar, length, offset |
58 | |
59 | Read I<length> bytes of data into I<scalar> starting at I<offset>. |
60 | |
61 | =item READLINE this |
62 | |
63 | Read a single line |
64 | |
65 | =item GETC this |
66 | |
67 | Get a single character |
68 | |
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69 | =item CLOSE this |
70 | |
71 | Close the handle |
72 | |
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73 | =item OPEN this, filename |
74 | |
75 | (Re-)open the handle |
76 | |
77 | =item BINMODE this |
78 | |
79 | Specify content is binary |
80 | |
81 | =item EOF this |
82 | |
83 | Test for end of file. |
84 | |
85 | =item TELL this |
86 | |
87 | Return position in the file. |
88 | |
89 | =item SEEK this, offset, whence |
90 | |
91 | Position the file. |
92 | |
93 | Test for end of file. |
94 | |
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95 | =item DESTROY this |
96 | |
97 | Free the storage associated with the tied handle referenced by I<this>. |
98 | This is rarely needed, as Perl manages its memory quite well. But the |
99 | option exists, should a class wish to perform specific actions upon the |
100 | destruction of an instance. |
101 | |
102 | =back |
103 | |
104 | =head1 MORE INFORMATION |
105 | |
106 | The L<perltie> section contains an example of tying handles. |
107 | |
108 | =cut |
109 | |
110 | use Carp; |
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111 | use warnings::register; |
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112 | |
113 | sub new { |
114 | my $pkg = shift; |
115 | $pkg->TIEHANDLE(@_); |
116 | } |
117 | |
118 | # "Grandfather" the new, a la Tie::Hash |
119 | |
120 | sub TIEHANDLE { |
121 | my $pkg = shift; |
122 | if (defined &{"{$pkg}::new"}) { |
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123 | warnings::warn "WARNING: calling ${pkg}->new since ${pkg}->TIEHANDLE is missing" |
124 | if warnings::enabled(); |
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125 | $pkg->new(@_); |
126 | } |
127 | else { |
128 | croak "$pkg doesn't define a TIEHANDLE method"; |
129 | } |
130 | } |
131 | |
132 | sub PRINT { |
133 | my $self = shift; |
134 | if($self->can('WRITE') != \&WRITE) { |
135 | my $buf = join(defined $, ? $, : "",@_); |
136 | $buf .= $\ if defined $\; |
137 | $self->WRITE($buf,length($buf),0); |
138 | } |
139 | else { |
140 | croak ref($self)," doesn't define a PRINT method"; |
141 | } |
142 | } |
143 | |
144 | sub PRINTF { |
145 | my $self = shift; |
146 | |
147 | if($self->can('WRITE') != \&WRITE) { |
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148 | my $buf = sprintf(shift,@_); |
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149 | $self->WRITE($buf,length($buf),0); |
150 | } |
151 | else { |
152 | croak ref($self)," doesn't define a PRINTF method"; |
153 | } |
154 | } |
155 | |
156 | sub READLINE { |
157 | my $pkg = ref $_[0]; |
158 | croak "$pkg doesn't define a READLINE method"; |
159 | } |
160 | |
161 | sub GETC { |
162 | my $self = shift; |
163 | |
164 | if($self->can('READ') != \&READ) { |
165 | my $buf; |
166 | $self->READ($buf,1); |
167 | return $buf; |
168 | } |
169 | else { |
170 | croak ref($self)," doesn't define a GETC method"; |
171 | } |
172 | } |
173 | |
174 | sub READ { |
175 | my $pkg = ref $_[0]; |
176 | croak "$pkg doesn't define a READ method"; |
177 | } |
178 | |
179 | sub WRITE { |
180 | my $pkg = ref $_[0]; |
181 | croak "$pkg doesn't define a WRITE method"; |
182 | } |
183 | |
184 | sub CLOSE { |
185 | my $pkg = ref $_[0]; |
186 | croak "$pkg doesn't define a CLOSE method"; |
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187 | } |
188 | |
189 | package Tie::StdHandle; |
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190 | our @ISA = 'Tie::Handle'; |
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191 | use Carp; |
192 | |
193 | sub TIEHANDLE |
194 | { |
195 | my $class = shift; |
196 | my $fh = do { \local *HANDLE}; |
197 | bless $fh,$class; |
198 | $fh->OPEN(@_) if (@_); |
199 | return $fh; |
200 | } |
201 | |
202 | sub EOF { eof($_[0]) } |
203 | sub TELL { tell($_[0]) } |
204 | sub FILENO { fileno($_[0]) } |
205 | sub SEEK { seek($_[0],$_[1],$_[2]) } |
206 | sub CLOSE { close($_[0]) } |
207 | sub BINMODE { binmode($_[0]) } |
208 | |
209 | sub OPEN |
210 | { |
211 | $_[0]->CLOSE if defined($_[0]->FILENO); |
212 | open($_[0],$_[1]); |
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213 | } |
214 | |
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215 | sub READ { read($_[0],$_[1],$_[2]) } |
216 | sub READLINE { my $fh = $_[0]; <$fh> } |
217 | sub GETC { getc($_[0]) } |
218 | |
219 | sub WRITE |
220 | { |
221 | my $fh = $_[0]; |
222 | print $fh substr($_[1],0,$_[2]) |
223 | } |
224 | |
225 | |
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226 | 1; |