Method Read

batch.go:140–185

Read reads the value of the next message from the batch into b, returning the number of bytes read, or an error if the next message couldn't be read. If an error is returned the batch cannot be used anymore and calling Read again will keep returning that error. All errors except io.EOF (indicating

(b []byte)

// The method fails with io.ErrShortBuffer if the buffer passed as argument is
// too small to hold the message value.
func (batch *Batch) Read(b []byte) (int, error) {
	n := 0

	batch.mutex.Lock()
	offset := batch.offset

	_, _, _, err := batch.readMessage(
		func(r *bufio.Reader, size int, nbytes int) (int, error) {
			if nbytes < 0 {
				return size, nil
			}
			return discardN(r, size, nbytes)
		},
		func(r *bufio.Reader, size int, nbytes int) (int, error) {
			if nbytes < 0 {
				return size, nil
			}
			// make sure there are enough bytes for the message value.  return
			// errShortRead if the message is truncated.
			if nbytes > size {
				return size, errShortRead
			}
			n = nbytes // return value
			if nbytes > cap(b) {
				nbytes = cap(b)
			}
			if nbytes > len(b) {
				b = b[:nbytes]
			}
			nbytes, err := io.ReadFull(r, b[:nbytes])
			if err != nil {
				return size - nbytes, err
			}
			return discardN(r, size-nbytes, n-nbytes)
		},
	)

	if err == nil && n > len(b) {
		n, err = len(b), io.ErrShortBuffer
		batch.err = io.ErrShortBuffer
		batch.offset = offset // rollback
	}

	batch.mutex.Unlock()
	return n, err
}

// ReadMessage reads and return the next message from the batch.
//