kitetorrent/io.github.yuroyami.kitetorrent.extensions/MetadataTransfer

MetadataTransfer

class MetadataTransfer(val totalSize: Int)

Reassembles the metadata (info) blob from incoming UtMetadata data pieces and verifies it against the expected info-hash. This is the codec-side counterpart of ut_metadata_plugin::received_metadata / metadata_request in ut_metadata.cpp.

Construct it once the total size is known (from the first data message's total_size, or from the peer's metadata_size handshake field), feed pieces with addPiece, then once isComplete call verify to check the assembled bytes against the torrent's info-hash. libtorrent does the equivalent check via torrent::set_metadata (which hashes and compares); the expensive-invariant block at the top of ut_metadata_plugin::metadata() shows the exact hashes used: hasher(info) == v1 and hasher256(info) == v2.

This helper is deliberately self-contained and does no networking; it just owns the buffer and the per-piece "have" bitfield.

Parameters

totalSize

the full length of the metadata blob, in bytes (must be > 0).

Constructors

MetadataTransfer

constructor(totalSize: Int)

Properties

isComplete

val isComplete: Boolean

True once every piece has been received.

pieceCount

val pieceCount: Int

The number of 16 KiB pieces this metadata spans.

totalSize

val totalSize: Int

Functions

addMessage

fun addMessage(msg: UtMetadata.Message): Boolean

Convenience: accept a parsed UtMetadata.Message. Only UtMetadata.Type.DATA messages contribute; anything else returns false.

addPiece

fun addPiece(piece: Int, data: ByteArray): Boolean

Store the bytes of one metadata piece. Mirrors the validity checks in received_metadata:

assembled

fun assembled(): ByteArray

The assembled metadata bytes. Only meaningful once isComplete; before then it still returns the (partially-filled) buffer so callers can hash-check incrementally if they wish.

hasPiece

fun hasPiece(piece: Int): Boolean

True if piece piece has already been stored.

missingPieces

fun missingPieces(): List<Int>

The list of piece indices still missing. Use it to drive UtMetadata.encodeRequest.

verify

fun verify(expected: Digest32): Boolean

Verify against whichever info-hash width expected is: a 20-byte digest is treated as a v1 (SHA-1) hash, a 32-byte digest as a v2 (SHA-256) hash. Any other width returns false.

verifySha1

fun verifySha1(expected: Sha1Hash): Boolean

Verify the assembled metadata against an expected v1 (SHA-1) info-hash, that is hasher(info).final() == info_hashes().v1. Returns false if not yet isComplete.

verifySha256

fun verifySha256(expected: Sha256Hash): Boolean

Verify the assembled metadata against an expected v2 (SHA-256) info-hash, that is hasher256(info).final() == info_hashes().v2. Returns false if not yet isComplete.