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MRAMBERG

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1 non-PAUSE user.

Chase Whitener
and 2 contributors

NAME

UV::Loop - Looping with libuv

SYNOPSIS

  #!/usr/bin/env perl
  use strict;
  use warnings;

  use UV;

  # A new loop
  my $loop = UV::Loop->new();

  # default loop
  my $loop = UV::Loop->default_loop(); # convenience constructor
  my $loop = UV::Loop->new(1); # Tell the constructor you want the default loop

  # run a loop with one of three options:
  # UV_RUN_DEFAULT, UV_RUN_ONCE, UV_RUN_NOWAIT
  $loop->run(); # runs with UV_RUN_DEFAULT
  $loop->run(UV::Loop::UV_RUN_DEFAULT); # explicitly state UV_RUN_DEFAULT
  $loop->run(UV::Loop::UV_RUN_ONCE);
  $loop->run(UV::Loop::UV_RUN_NOWAIT);

DESCRIPTION

This module provides an interface to libuv's loop. We will try to document things here as best as we can, but we also suggest you look at the libuv docs directly for more details on how things work.

Event loops that work properly on all platforms. YAY!

CONSTANTS

RUN MODE CONSTANTS

UV_RUN_DEFAULT

UV_RUN_NOWAIT

UV_RUN_ONCE

CONFIGURE CONSTANTS

SIGPROF

UV_LOOP_BLOCK_SIGNAL

METHODS

UV::Loop makes the following methods available.

new

    my $loop = UV::Loop->new();
    my $default_loop = UV::Loop->new(1);
    my $default_loop = UV::Loop->default_loop();
    my $default_loop = UV::Loop->default();

This constructor either returns the default loop (singleton object), or creates a new event loop and initializes it.

Please look at the documentation from libuv.

alive

    my $int = $loop->alive();

The alive method returns a non-zero value if there are active handles or requests in the loop.

backend_fd

    my $int = $loop->backend_fd();

The backend_fd method returns the backend file descriptor. Only kqueue, epoll and event ports are supported.

This can be used in conjunction with "run" in UV::Loop and UV_RUN_NOWAIT to poll in one thread and run the event loop's callbacks in another.

* Note: Embedding a kqueue fd in another kqueue pollset doesn't work on all platforms. It's not an error to add the fd but it never generates events.

backend_timeout

    my $int = $loop->backend_timeout();

The backend_timeout method returns the poll timeout. The return value is in milliseconds, or -1 for no timeout.

close

    $loop->close();

The close method releases all internal loop resources. Call this method only when the loop has finished executing and all open handles and requests have been closed, or it will return UV::UV_EBUSY. After this method returns, the user can free the memory allocated for the loop.

configure

    my $int = $loop->configure();

The configure method sets additional loop options. You should normally call this before the first call to "run" in UV::Loop unless mentioned otherwise.

Returns 0 on success or a UV/"CONSTANTS" error code on failure. Be prepared to handle UV::UV_ENOSYS; it means the loop option is not supported by the platform.

Supported options:

  • UV_LOOP_BLOCK_SIGNAL: Block a signal when polling for new events. The second argument to $loop->configure is the signal number.

    This operation is currently only implemented for SIGPROF signals, to suppress unnecessary wakeups when using a sampling profiler. Requesting other signals will fail with UV::UV_EINVAL.

default

    # simply a synonym for ->new(1)
    my $default_loop = UV::Loop->default();

A synonym for the "new" in UV::Loop constructor.

default_loop

    # simply a synonym for ->new(1)
    my $default_loop = UV::Loop->default_loop();

A synonym for the "new" in UV::Loop constructor.

loop_alive

    my $int = $loop->loop_alive();

This is just a synonym for "alive" in UV::Loop.

loop_configure

    my $int = $loop->configure(UV::Loop::UV_LOOP_BLOCK_SIGNAL, SIGPROF);

This is just a synonym for "configure" in UV::Loop.

now

    my $uint64_t = $loop->now();

The now method returns the current timestamp in milliseconds. The timestamp is cached at the start of the event loop tick, see "update_loop" in UV::Loop for details and rationale.

The timestamp increases monotonically from some arbitrary point in time. Don't make assumptions about the starting point, you will only get disappointed.

* Note: Use "hrtime" in UV if you need sub-millisecond granularity.

run

    # use UV_RUN_DEFAULT by default
    my $int = $loop->run();
    # or, explicitly use it:
    my $int = $loop->run(UV::Loop::UV_RUN_DEFAULT);
    # run in UV_RUN_NOWAIT mode
    my $int = $loop->run(UV::Loop::UV_RUN_NOWAIT);
    # run in UV_RUN_ONCE mode
    my $int = $loop->run(UV::Loop::UV_RUN_ONCE);

The run method runs the event loop. It will act differently depending on the specified mode:

  • UV_RUN_DEFAULT Runs the event loop until there are no more active and referenced handles or requests. Returns non-zero if "stop" in UV::Loop was called and there are still active handles or requests. Returns zero in all other cases.

  • UV_RUN_NOWAIT Poll for i/o once but don't block if there are no pending callbacks. Returns zero if done (no active handles or requests left), or non-zero if more callbacks are expected (meaning you should run the event loop again sometime in the future).

  • UV_RUN_ONCE Poll for i/o once. Note that this function blocks if there are no pending callbacks. Returns zero when done (no active handles or requests left), or non-zero if more callbacks are expected (meaning you should run the event loop again sometime in the future).

stop

    $loop->stop();

The stop method stops the event loop, causing "run" in UV::Loop to end as soon as possible. This will happen not sooner than the next loop iteration. If this function was called before blocking for i/o, the loop won't block for i/o on this iteration.

update_time

    $loop->update_time();

The update_time method updates the event loop's concept of "now" in UV::Loop. Libuv caches the current time at the start of the event loop tick in order to reduce the number of time-related system calls.

You won't normally need to call this method unless you have callbacks that block the event loop for longer periods of time, where "longer" is somewhat subjective but probably on the order of a millisecond or more.

walk

    # although you can do it, calling ->walk() without a callback is pretty
    # useless.
    # call with no callback
    $loop->walk();
    $loop->walk(undef);
    $loop->walk(sub {});

    # instead, let's walk the loop and cleanup any handles attached and then
    # completely close the loop.
    $loop->walk(sub {
        my $handle = shift;
        # check to make sure the handle can stop
        $handle->stop() if $handle->can('stop');
        $handle->close() unless $handle->closing();
        $loop->run(UV::Loop::UV_RUN_DEFAULT);
        $loop->close();
    });

The walk method will walk the list of handles and fire off the callback supplied.

This is an excellent way to ensure your loop is completely cleaned up.

AUTHOR

Chase Whitener <capoeirab@cpan.org>

AUTHOR EMERITUS

Daisuke Murase <typester@cpan.org>

COPYRIGHT AND LICENSE

Copyright 2012, Daisuke Murase.

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