POEx::Role::Streaming(3)

NAME
POEx::Role::Streaming - Provides behavior for streaming from one filehandle to another

VERSION
version 1.102610

SYNOPSIS
    class MyStreamer with POEx::Role::Streaming {
        ...
    }

    my $streamer = MyStreamer->new
    (
        input_handle => $some_handle,
        output_handle => $some_other_handle.
    );

    POE::Kernel->run();

DESCRIPTION
POEx::Role::Streaming provides a common idiom for streaming data from one filehandle to another. It accomplishes this by making good use of sysread and POE::Wheel::ReadWrite. This Role errs on the side of doing as many blocking reads of the "input_handle" as possible up front (until the high water mark is hit on the Wheel). If this default isn't suitable for the consumer, simply override "get_data_from_input_handle". After Streamer has exhausted the source, and flushed the last of the output, it will clean up after itself by closing the wheel, the handles, and sending all of them out of scope. If an exception happens, it will clean up after itself, and let the DIE signal propagate.

PUBLIC_ATTRIBUTES

  input_handle
    is: ro, isa: FileHandle, required: 1

This is the handle the consumer wants to read

  output_handle
    is: ro, isa: FileHandle, required: 1

This is the handle to which the consumer wants to write

  maximum_buffer_threshold
    is: ro, isa: Int, default: 524288

This is used as the HighMark on the Wheel. Provide a smaller value if the consumer needs to do smaller slurps from the "input_handle"

  minimum_buffer_threshold
    is: ro, isa: Int, default: 32768

This is used as the LowMark on the Wheel. Provide a larger value if the consumer needs to stave off jitter.

PROTECTED_ATTRIBUTES

  filter
    is: ro, isa: Filter, lazy_build: 1

This is the default filter used in the output. It defaults to POE::Filter::Stream. Override _build_filter to provide a different Filter if needed

  wheel
    is: ro, isa: Wheel, lazy_build: 1, handles: qw/ put shutdown_output flush /

wheel stores the constructed wheel for the "output_handle". A few handles are provided as sugar. _build_wheel gathers up "output_handle", a clone of "filter", "maximum_buffer_threshold" and "minimum_buffer_threshold" and constructs a POE::Wheel::ReadWrite. Override this method if more customization is required.

PRIVATE_ATTRIBUTES

  reading_complete
    is: rw, isa: Bool, default: 0

reading_complete is an indicator set during "get_data_from_input_handle" if EOF is reached. This helps "handle_output_flushed" figure out if "read_more_input" should be executed or if it is time to tear everthing down

PROTECTED_METHODS

  after _start
    is Event

_start is advised to spin up the wheel, fill its buffer with initial data, and setup the signal handler for 'DIE' signals (exceptions)

  read_more_input
    is Event

read_more_input fills the "wheel"'s buffer until the HighMark is hit. It does this by looping over "get_data_from_input_handle" until it returns undef

  handle_output_flushed
    is Event

This event is called when the "wheel"'s buffer is empty. If "reading_complete" is set, clean up happens via "done_writing". Otherwise more data is slurped via "read_more_input"

  get_data_from_input_handle
get_data_from_input_handle is the actual implementation for reading from "input_handle". By default, it uses sysread to return a 4k chunk. If EOF is reached, "reading_complete" is set and "done_reading" is executed. If

  done_writing
done_writing is called when the last of the output is flushed and there is nothing left to read. It clears the "wheel", closes the "output_handle", and sends them out of scope

  done_reading
done_reading is called when EOF is reached. It closes the "input_handle" and sends it out of scope.

  handle_output_error
    (Str $action, Int $code, Str $message, WheelID $id) is Event

handle_output_error is an event the "wheel" will call when there is some kind of problem writing. By default it simply dies with the passed information

  die_signal
    (Str $signal, HashRef $ex) is Event

die_signal is our exception handler to which POE delivers DIE signals. By default, it calls "done_reading" and "done_writing". Please note that the signal is not handled and will be propogated.

AUTHOR
Nicholas Perez <nperez@cpan.org>

COPYRIGHT AND LICENSE
This software is copyright (c) 2010 by Infinity Interactive.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.