func()

in lib/torrent/storage/agentstorage/torrent.go [202:249]

• 34 lines of code
• 11 McCabe index (conditional complexity)

func (t *Torrent) WritePiece(src storage.PieceReader, pi int) error {
	piece, err := t.getPiece(pi)
	if err != nil {
		return err
	}
	if int64(src.Length()) != t.PieceLength(pi) {
		return fmt.Errorf(
			"invalid piece length: expected %d, got %d", t.PieceLength(pi), src.Length())
	}

	// Exit quickly if the piece is not writable.
	if piece.complete() {
		return storage.ErrPieceComplete
	}
	if piece.dirty() {
		return errWritePieceConflict
	}

	dirty, complete := piece.tryMarkDirty()
	if dirty {
		return errWritePieceConflict
	} else if complete {
		return storage.ErrPieceComplete
	}

	// At this point, we've determined that the piece is not complete and ensured
	// we are the only thread which may write the piece. We do not block other
	// threads from checking if the piece is writable.

	if err := t.writePiece(src, pi); err != nil {
		// Allow other threads to write this piece since we mysteriously failed.
		piece.markEmpty()
		return fmt.Errorf("write piece: %s", err)
	}

	if int(t.numComplete.Load()) == len(t.pieces) {
		// Multiple threads may attempt to move the download file to cache, however
		// only one will succeed while the others will receive (and ignore) file exist
		// error.
		err := t.cads.MoveDownloadFileToCache(t.metaInfo.Digest().Hex())
		if err != nil && !os.IsExist(err) {
			return fmt.Errorf("download completed but failed to move file to cache directory: %s", err)
		}
		t.committed.Store(true)
	}

	return nil
}