Companion
Properties
Hard cap on blocks per piece (15-bit counter in upstream). max_blocks_per_piece.
Cap on partial pieces scanned by the end-game tail (upstream's TORRENT_ALLOCA cap).
Anti-sprawl cap: force OPTION_PRIORITIZE_PARTIALS once partial pieces hold more than this many blocks (2048 blocks = 32 MiB at 16 KiB). Matches the constant in pick_pieces.
The peer is on parole: only exclusive picks, no end-game tail. on_parole.
Drain partially-downloaded pieces before opening new ones. prioritize_partials.
Pick rarest pieces first (the normal steady-state mode). rarest_first.
Walk the pick order backwards, most common pieces first. reverse.
Pick pieces in index order (streaming). sequential.
Multiplier creating 3 sub-levels per availability. piece_picker::prio_factor.
Number of priority levels (0..7). piece_picker::priority_levels.