func decode()

in play.go [110:176]

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

func decode(kind string, output []byte) ([]event, error) {
	var (
		magic     = []byte{0, 0, 'P', 'B'}
		headerLen = 8 + 4
		last      = epoch
		events    []event
	)
	add := func(t time.Time, b []byte) {
		var prev *event
		if len(events) > 0 {
			prev = &events[len(events)-1]
		}
		if prev != nil && t.Equal(prev.time) {
			// Merge this event with previous event, to avoid
			// sending a lot of events for a big output with no
			// significant timing information.
			prev.msg = append(prev.msg, b...)
		} else {
			e := event{msg: b, kind: kind, time: t}
			events = append(events, e)
		}
		last = t
	}
	for i := 0; i < len(output); {
		if !bytes.HasPrefix(output[i:], magic) {
			// Not a header; find next header.
			j := bytes.Index(output[i:], magic)
			if j < 0 {
				// No more headers; bail.
				add(last, output[i:])
				break
			}
			add(last, output[i:i+j])
			i += j
		}
		i += len(magic)

		// Decode header.
		if len(output)-i < headerLen {
			return nil, errors.New("short header")
		}
		header := output[i : i+headerLen]
		nanos := int64(binary.BigEndian.Uint64(header[0:]))
		t := time.Unix(0, nanos)
		if t.Before(last) {
			// Force timestamps to be monotonic. (This could
			// be an encoding error, which we ignore now but will
			// will likely be picked up when decoding the length.)
			t = last
		}
		n := int(binary.BigEndian.Uint32(header[8:]))
		if n < 0 {
			return nil, fmt.Errorf("bad length: %v", n)
		}
		i += headerLen

		// Slurp output.
		// Truncated output is OK (probably caused by sandbox limits).
		end := i + n
		if end > len(output) {
			end = len(output)
		}
		add(t, output[i:end])
		i += n
	}
	return events, nil
}