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Net-BitTorrent-v2.0.0
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/ Net::BitTorrent::Torrent::PiecePicker

NAME

Net::BitTorrent::Torrent::PiecePicker - Intelligent Piece Selection

SYNOPSIS

use Net::BitTorrent::Torrent::PiecePicker;
use Net::BitTorrent::Types qw[:pick];

my $picker = Net::BitTorrent::Torrent::PiecePicker->new(
    bitfield => $my_bitfield,
    strategy => PICK_RAREST_FIRST
);

# Update global swarm availability
$picker->update_availability($peer_bitfield, 1); # peer joined
$picker->update_availability($peer_bitfield, -1); # peer left

# Pick the next piece to request from a peer
my ($idx, $off, $len) = $picker->pick_block($peer, \%blocks_pending);

DESCRIPTION

Net::BitTorrent::Torrent::PiecePicker implements the selection logic used to decide which torrent piece or block to request next. A good picker is essential for swarm health and performance.

SELECTION STRATEGIES

  • PICK_RAREST_FIRST (Default)

    Prioritizes pieces that have the lowest availability in the local swarm. This ensures that rare pieces are replicated quickly, preventing "stalled" torrents where the last few pieces are missing.

  • PICK_SEQUENTIAL

    Picks pieces in simple numerical order. Useful for linear media playback where early data is needed first.

  • PICK_STREAMING

    A hybrid approach that prioritizes early pieces while still respecting per-piece priorities.

METHODS

new( %params )

Creates a new PiecePicker object.

my $picker = Net::BitTorrent::Torrent::PiecePicker->new(
    bitfield => $bitfield
);

Expected parameters:

bitfield

The Acme::Bitfield object representing the local client's pieces.

piece_priorities - optional

An array reference of priority levels for each piece.

strategy - optional

The selection strategy constant. Defaults to PICK_RAREST_FIRST.

update_availability( $peer_bitfield, $delta )

Updates internal availability counts when a peer's bitfield changes.

$picker->update_availability( $bf, 1 );

Expected parameters:

$peer_bitfield

The bitfield object representing the peer's pieces.

$delta

The change in availability (usually 1 when a peer connects/has, -1 when a peer disconnects).

set_priority( $index, $priority )

Sets the priority for a specific piece.

$picker->set_priority( 0, 2 );

Expected parameters:

$index

The piece index.

$priority

The priority level (0 = skip, 1 = normal, higher = higher).

get_priority( $index )

Returns the priority of a piece.

my $p = $picker->get_priority( 0 );

Expected parameters:

$index

The piece index.

get_availability( $index )

Returns the number of peers that have a specific piece.

my $count = $picker->get_availability( 0 );

Expected parameters:

$index

The piece index.

is_interesting( $peer )

Checks if a peer has any pieces that we lack and want.

if ($picker->is_interesting( $peer )) { ... }

Expected parameters:

$peer

The Peer object to check.

pick_piece( $peer_bitfield, $blocks_pending )

Selects a piece to request from a peer based on the current strategy.

my $idx = $picker->pick_piece( $p_bf, $pending );

Expected parameters:

$peer_bitfield

The peer's bitfield.

$blocks_pending

Hash reference of currently pending blocks.

pick_block( $peer, $blocks_pending )

Selects a specific block (16KiB) to request from a specific peer.

my ($idx, $off, $len) = $picker->pick_block( $peer, $pending );

Iterates through prioritized piece candidates and returns the first block that is not already pending or received.

Expected parameters:

$peer

The Peer object.

$blocks_pending

Hash reference of currently pending blocks.

enter_end_game( )

Enables End Game mode.

$picker->enter_end_game();

In this mode, the picker becomes more aggressive, allowing requests for the same block to be sent to multiple peers simultaneously to finish the torrent faster.

strategy( )

Returns or sets the picking strategy.

my $s = $picker->strategy();
$picker->strategy( PICK_SEQUENTIAL );

Expected parameters:

$strategy - optional

The new strategy constant.

end_game( )

Returns true if in end game mode.

if ($picker->end_game) { ... }

AUTHOR

Sanko Robinson <sanko@cpan.org>

COPYRIGHT

Copyright (C) 2008-2026 by Sanko Robinson.

This library is free software; you can redistribute it and/or modify it under the terms of the Artistic License 2.0.