dart_libp2p_bitswap 2.0.0

An implementation of the Bitswap 1.2.0 block exchange protocol for dart_libp2p.

2.0.0

Breaking changes:

• Requires dart_libp2p ^4.12.0 (was ^1.0.0).
• IBlockStore is renamed to BlockStore.
• Bitswap no longer takes peerEventsStream; it subscribes to host.eventBus itself.
• Construction has no side effects. Call await bitswap.start() before use; wantBlocks/getBlock throw StateError if not started or after stop().
• Unsolicited blocks (not on the local wantlist) are discarded instead of stored.
• getBlock takes an optional timeout (default BitswapOptions.getBlockTimeout, 30s). It returns null only on timeout or cancellation; other errors propagate.
• stop() fails pending getBlock calls with StateError, and stops rebroadcasts and queued replies before its first await, so nothing more is sent while it runs.
• The library logs via package:logging and no longer prints.

New:

• BitswapOptions (getBlockTimeout, rebroadcastInterval), Bitswap.cancelWants.
• Blocks hashed with sha3-224/256/384/512, keccak-256/512, blake2b-256/512, blake3 (1–128-byte digests) or identity (up to 128 bytes) are verified and accepted, in addition to sha2-256/512.
• A runnable two-node example (example/dart_libp2p_bitswap_example.dart).
• Optional SizedBlockStore (getSize), which lets Bitswap size blocks without reading them. With one, responses carry pendingBytes (bytes still queued for the peer, counted as boxo does). Received pendingBytes is ignored, as in boxo.
• Bitswap.notifyNewBlock for blocks the application stores itself: serves peers waiting for it and completes local wants.
• Bitswap 1.2.0 want strategy: WANT_BLOCK to one peer and WANT_HAVE to the rest, with sendDontHave; on DONT_HAVE or disconnect, WANT_BLOCK moves to a peer that said HAVE.
• Outstanding wants are rebroadcast periodically, reaching peers that connect after the want was made.
• Later wants to a peer are sent as deltas; only the first message carries full.

Fixes:

• CIDv0 blocks from peers (including go-bitswap) are now accepted.
• Sends to a peer are serialised over one stream, preserving order; a failed write on a reused stream is retried once.
• An outgoing stream the remote closes or resets is dropped as soon as that is seen, so the next send opens a fresh stream instead of first failing a write.
• Inbound messages over 4 MiB are rejected; responses are split to stay under 4 MiB.
• Peers sending WANT_HAVE get a HAVE presence instead of the block, or the block itself when it is at most BitswapOptions.wantHaveReplaceSize bytes (default 1024, as in boxo).
• The wantlist is sent on connect only to peers that speak Bitswap, rather than to every connected peer.
• Serving is bounded and fair: at most maxWantsPerPeer wants per peer (default 1024); peers take turns of up to serveBytesPerTurn (default 1 MiB), highest priority first; serving no longer blocks the peer's read loop; a CANCEL received while a block is being read stops it being sent.
• Concurrent getBlock calls share one want; one caller timing out no longer abandons it for others, and an abandoned want is cancelled with peers.

1.0.0

• Initial version.