IO::Handle::Prototype:UserlContributed Perl IO::Handle::Prototype::Fallback(3)NAMEIO::Handle::Prototype::Fallback - Create IO::Handle like objects using
a set of callbacks.
SYNOPSIS
my $fh = IO::Handle::Prototype::Fallback->new(
getline => sub {
my $fh = shift;
...
},
);
DESCRIPTION
This class provides a way to define a filehandle based on callbacks.
Fallback implementations are provided to the extent possible based on
the provided callbacks, for both writing and reading.
SPECIAL CALLBACKS
This class provides two additional methods on top of IO::Handle,
designed to let you implement things with a minimal amount of baggage.
The fallback methods are all best implemented using these, though these
can be implemented in terms of Perl's standard methods too.
However, to provide the most consistent semantics, it's better to do
this:
IO::Handle::Prototype::Fallback->new(
__read => sub {
shift @array;
},
);
Than this:
IO::Handle::Prototype::Fallback->new(
getline => sub {
shift @array;
},
);
Because the fallback implementation of "getline" implements all of the
extra crap you'd need to handle to have a fully featured
implementation.
__read
Return a chunk of data of any size (could use $/ or not, it depends
on you, unlike "getline" which probably should respect the value of
$/).
This avoids the annoying "substr" stuff you need to do with "read".
__write $string
Write out a string.
This is like a simplified "print", which can disregard $, and "$\"
as well as multiple argument forms, and does not have the extra
"substr" annoyance of "write" or "syswrite".
WRAPPING
If you provide a single reading related callback ("__read", "getline"
or "read") then your callback will be used to implement all of the
other reading primitives using a string buffer.
These implementations handle $/ in all forms ("undef", ref to number
and string), all the funny calling conventions for "read", etc.
FALLBACKS
Any callback that can be defined purely in terms of other callbacks in
a way will be added. For instance "getc" can be implemented in terms of
"read", "say" can be implemented in terms of "print", "print" can be
implemented in terms of "write", "write" can be implemented in terms of
"print", etc.
None of these require special wrapping and will always be added if
their dependencies are present.
GLOB OVERLOADING
When overloaded as a glob a tied handle will be returned. This allows
you to use the handle in Perl's IO builtins. For instance:
my $line = <$fh>
will not call the "getline" method natively, but the tied interface
arranges for that to happen.
perl v5.14.12009-09-29IO::Handle::Prototype::Fallback(3)
