1IO::Handle::Util(3pm) User Contributed Perl DocumentationIO::Handle::Util(3pm)
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6 IO::Handle::Util - Functions for working with IO::Handle like objects.
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9 # make something that looks like a filehandle from a random data:
10 my $io = io_from_any $some_data;
11 # or from a callback that returns strings:
13 my $io = io_from_getline sub { return $another_line };
14 # create a callback that iterates through the handle
16 my $read_cb = io_to_read_cb $io;
17
19 This module provides a number of helpful routines to manipulate or
20 create IO::Handle like objects.
21
23 Coercions resulting in IO objects
24 These are available using the ":io_from" export group.
25 io_from_any $whatever
27 Inspects the value of "whatever" and calls the appropriate coercion
28 function on it, either "io_from_ref" or "io_from_string".
29 io_from_ref $some_ref
31 Depending on the reference type of $some_ref invokes either
32 "io_from_object", "io_from_array" or "io_from_scalar_ref".
33 Code references are not coerced automatically because either
35 "io_from_thunk" or "io_from_getline" or "io_from_write_cb" could
36 all make sense.
37 Globs are returned as is only if they have a valid "IO" slot.
39 io_from_object $obj
41 Depending on the class of $obj either returns or coerces the
42 object.
43 Objects that are passed through include anything that subclasses
45 IO::Handle or seems to duck type (supports the "print" and
46 "getline" methods, which might be a bit too permissive).
47 Objects that are coerced currently only include Path::Class::File,
49 which will have the "openr" method invoked on it.
50 Anything else is an error.
52 io_from_string $str
54 Instantiates an IO::String object using $str as the buffer.
55 Note that $str is not passed as an alias, so writing to the IO
57 object will not modify string. For that see "io_from_scalar_ref".
58 io_from_array \@array
60 Creates an IO::Handle::Iterator that will return the elements of
61 @array one by one.
62 Note that a copy of @array is made.
64 In order to be able to append more elements to the array or remove
66 the ones that have been returned use IO::Handle::Iterator yourself
67 directly.
68 io_from_scalar_ref \$str
70 Creates an IO::String object using $str as the buffer.
71 Writing to the IO object will modify $str.
73 io_from_thunk sub { ... }
75 Invokes the callback once in list context the first time it's
76 needed, and then returns each element of the list like
77 "io_from_array" would.
78 io_from_getline sub { ... }
80 Creates an IO::Handle::Iterator object using the callback.
81 io_from_write_cb sub { ... }
83 Creates an IO::Handle::Prototype::Fallback using the callback.
84 The callback will always be invoked with one string argument and
86 with the values of $, and "$\" localized to "undef".
87 Coercions utilizing IO objects
89 These coercions will actually call "io_from_any" on their argument
90 first. This allows you to do things like:
91 my $str = '';
93 my $sub = io_to_write_cb(\$str);
94 $sub->("foo");
96 These are available using the ":io_to" export group.
98 io_to_write_cb $thing
100 Creates a code ref that will invoke "print" on the handle with the
101 arguments to the callback.
102 $, and "$\" will both be localized to "undef".
104 io_to_read_cb $thing
106 Creates a code ref that will invoke "getline" on the handle.
107 $/ will not be localized and should probably be set to a reference
109 to a number if you want efficient iteration. See perlvar for
110 details.
111 io_to_string $thing
113 Slurps a string out of the IO object by reading all the data.
114 If a string was passed it is returned as is.
116 io_to_array $thing
118 Returns an array reference containing all the lines of the IO
119 object.
120 If an array reference was passed it is returned as is.
122 io_to_list $thing
124 Returns the list of lines from the IO object.
125 Warns if not invoked in list context.
127 If an array reference was passed it is dereferenced an its elements
129 are returned.
130 io_to_glob $thing
132 If the filehandle is an unblessed glob returns it as is, otherwise
133 returns a new glob which is tied to delegate to the OO interface.
134 This lets you use most of the builtins without the method syntax:
136 my $fh = io_to_glob($some_kind_of_OO_handle);
138 while ( defined( my $line = <$fh> ) ) {
140 ...
141 }
142 Misc functions
144 io_prototype %callbacks
145 Given a key-value pair list of named callbacks, constructs an
146 IO::Handle::Prototype::Fallback object with those callbacks.
147 For example:
149 my $io = io_prototype print => sub {
151 my $self = shift;
152 no warnings 'uninitialized';
154 $string .= join($,, @_) . $\;
155 };
156 $io->say("Hello"); # $string now has "Hello\n"
158 See IO::Handle::Prototype::Fallback for more details.
160 is_real_fh $io
162 Returns true if the IO handle probably could be passed to something
163 like AnyEvent::Handle which would break encapsulation.
164 Checks for the following conditions:
166 · The handle has a reftype of either a "GLOB" with an "IO" slot,
168 or is an "IO" itself.
169 · The handle's "fileno" method returns a positive number,
171 corresponding to a filedescriptor.
172 · The "fileno" builtin returns the same thing as "fileno" invoked
174 as a method.
175 If these conditions hold the handle is probably OK to work with
177 using the IO builtins directly, or passing the filedescriptor to C
178 land, instead of by invoking methods on it.
179
181 IO::Handle, FileHandle, IO::String, perlio, "open" in perlfunc
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184 <http://github.com/nothingmuch/io-handle-util>
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187 Yuval Kogman
188
190 Copyright (c) 2009 Yuval Kogman. All rights reserved
191 This program is free software; you can redistribute
192 it and/or modify it under the same terms as Perl itself.
193perl v5.30.1 2020-01-30 IO::Handle::Util(3pm)