Golang Writer.wait_for_stop方法代碼示例

// Starts a process of building the torrent file. This function does everything
// in a separate goroutine and uses up to 'nworkers' of goroutines to perform
// SHA1 hashing. Therefore it will return almost immedately. It returns two
// channels, the first one is for completion awaiting, the second one is for
// getting status reports. Status report is a number of bytes hashed, you can
// get the total amount of bytes by inspecting the Batch.TotalSize method return
// value.
func (b *Batch) Start(w io.Writer, nworkers int) (<-chan error, <-chan int64) {
	if nworkers <= 0 {
		nworkers = 1
	}

	completion := make(chan error)
	status := make(chan int64)

	go func() {
		// prepare workers
		workers := make([]*worker, nworkers)
		free_workers := make(chan *worker, nworkers)
		for i := 0; i < nworkers; i++ {
			workers[i] = new_worker(free_workers)
		}
		stop_workers := func() {
			for _, w := range workers {
				w.stop()
			}
			for _, w := range workers {
				w.wait_for_stop()
			}
		}

		// prepare files for reading
		fr := files_reader{files: b.files}
		npieces := b.total_size/b.piece_length + 1
		b.pieces = make([]byte, 20*npieces)
		hashed := int64(0)

		// read all the pieces passing them to workers for hashing
		var data []byte
		for i := int64(0); i < npieces; i++ {
			if data == nil {
				data = make([]byte, b.piece_length)
			}

			nr, err := fr.Read(data)
			if err != nil {
				// EOF is not an eror if it was the last piece
				if err == io.EOF {
					if i != npieces-1 {
						stop_workers()
						completion <- err
						return
					}
				} else {
					stop_workers()
					completion <- err
					return
				}
			}

			// cut the data slice to the amount of actual data read
			data = data[:nr]
			w := <-free_workers
			data = w.queue(data, b.pieces[20*i:20*i+20])

			// update and try to send the status report
			if data != nil {
				hashed += int64(len(data))
				data = data[:cap(data)]

				select {
				case status <- hashed:
				default:
				}
			}
		}
		stop_workers()

		// at this point the hash was calculated and we're ready to
		// write the torrent file
		err := b.write_torrent(w)
		if err != nil {
			completion <- err
			return
		}
		completion <- nil
	}()
	return completion, status
}