1package main
2
3import (
4	"bytes"
5	"crypto/rand"
6	"encoding/hex"
7	"fmt"
8)
9
10// These constants help to indicate the type of payload
11const (
12	RequestPayload          = '1'
13	ResponsePayload         = '2'
14	ReplayedResponsePayload = '3'
15)
16
17func randByte(len int) []byte {
18	b := make([]byte, len/2)
19	rand.Read(b)
20
21	h := make([]byte, len)
22	hex.Encode(h, b)
23
24	return h
25}
26
27func uuid() []byte {
28	return randByte(24)
29}
30
31var payloadSeparator = "\n������\n"
32
33func payloadScanner(data []byte, atEOF bool) (advance int, token []byte, err error) {
34	if atEOF && len(data) == 0 {
35		return 0, nil, nil
36	}
37
38	if i := bytes.Index(data, []byte(payloadSeparator)); i >= 0 {
39		// We have a full newline-terminated line.
40		return i + len([]byte(payloadSeparator)), data[0:i], nil
41	}
42
43	if atEOF {
44		return len(data), data, nil
45	}
46	return 0, nil, nil
47}
48
49// Timing is request start or round-trip time, depending on payloadType
50func payloadHeader(payloadType byte, uuid []byte, timing int64, latency int64) (header []byte) {
51	//Example:
52	//  3 f45590522cd1838b4a0d5c5aab80b77929dea3b3 13923489726487326 1231\n
53	return []byte(fmt.Sprintf("%c %s %d %d\n", payloadType, uuid, timing, latency))
54}
55
56func payloadBody(payload []byte) []byte {
57	headerSize := bytes.IndexByte(payload, '\n')
58	return payload[headerSize+1:]
59}
60
61func payloadMeta(payload []byte) [][]byte {
62	headerSize := bytes.IndexByte(payload, '\n')
63	if headerSize < 0 {
64		return nil
65	}
66	return bytes.Split(payload[:headerSize], []byte{' '})
67}
68
69func payloadID(payload []byte) (id []byte) {
70	meta := payloadMeta(payload)
71
72	if len(meta) < 2 {
73		return
74	}
75	// id is encoded in hex, we need to revert to how it was
76	id = make([]byte, 20)
77	hex.Decode(id, meta[1])
78	return
79}
80
81func isOriginPayload(payload []byte) bool {
82	switch payload[0] {
83	case RequestPayload, ResponsePayload:
84		return true
85	default:
86		return false
87	}
88}
89
90func isRequestPayload(payload []byte) bool {
91	return payload[0] == RequestPayload
92}
93