/
decode.go
218 lines (179 loc) · 4.78 KB
/
decode.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
package eventstream
import (
"bytes"
"encoding/binary"
"encoding/hex"
"encoding/json"
"fmt"
"github.com/aws/smithy-go/logging"
"hash"
"hash/crc32"
"io"
)
// DecoderOptions is the Decoder configuration options.
type DecoderOptions struct {
Logger logging.Logger
LogMessages bool
}
// Decoder provides decoding of an Event Stream messages.
type Decoder struct {
options DecoderOptions
}
// NewDecoder initializes and returns a Decoder for decoding event
// stream messages from the reader provided.
func NewDecoder(optFns ...func(*DecoderOptions)) *Decoder {
options := DecoderOptions{}
for _, fn := range optFns {
fn(&options)
}
return &Decoder{
options: options,
}
}
// Decode attempts to decode a single message from the event stream reader.
// Will return the event stream message, or error if decodeMessage fails to read
// the message from the stream.
//
// payloadBuf is a byte slice that will be used in the returned Message.Payload. Callers
// must ensure that the Message.Payload from a previous decode has been consumed before passing in the same underlying
// payloadBuf byte slice.
func (d *Decoder) Decode(reader io.Reader, payloadBuf []byte) (m Message, err error) {
if d.options.Logger != nil && d.options.LogMessages {
debugMsgBuf := bytes.NewBuffer(nil)
reader = io.TeeReader(reader, debugMsgBuf)
defer func() {
logMessageDecode(d.options.Logger, debugMsgBuf, m, err)
}()
}
m, err = decodeMessage(reader, payloadBuf)
return m, err
}
// decodeMessage attempts to decode a single message from the event stream reader.
// Will return the event stream message, or error if decodeMessage fails to read
// the message from the reader.
func decodeMessage(reader io.Reader, payloadBuf []byte) (m Message, err error) {
crc := crc32.New(crc32IEEETable)
hashReader := io.TeeReader(reader, crc)
prelude, err := decodePrelude(hashReader, crc)
if err != nil {
return Message{}, err
}
if prelude.HeadersLen > 0 {
lr := io.LimitReader(hashReader, int64(prelude.HeadersLen))
m.Headers, err = decodeHeaders(lr)
if err != nil {
return Message{}, err
}
}
if payloadLen := prelude.PayloadLen(); payloadLen > 0 {
buf, err := decodePayload(payloadBuf, io.LimitReader(hashReader, int64(payloadLen)))
if err != nil {
return Message{}, err
}
m.Payload = buf
}
msgCRC := crc.Sum32()
if err := validateCRC(reader, msgCRC); err != nil {
return Message{}, err
}
return m, nil
}
func logMessageDecode(logger logging.Logger, msgBuf *bytes.Buffer, msg Message, decodeErr error) {
w := bytes.NewBuffer(nil)
defer func() { logger.Logf(logging.Debug, w.String()) }()
fmt.Fprintf(w, "Raw message:\n%s\n",
hex.Dump(msgBuf.Bytes()))
if decodeErr != nil {
fmt.Fprintf(w, "decodeMessage error: %v\n", decodeErr)
return
}
rawMsg, err := msg.rawMessage()
if err != nil {
fmt.Fprintf(w, "failed to create raw message, %v\n", err)
return
}
decodedMsg := decodedMessage{
rawMessage: rawMsg,
Headers: decodedHeaders(msg.Headers),
}
fmt.Fprintf(w, "Decoded message:\n")
encoder := json.NewEncoder(w)
if err := encoder.Encode(decodedMsg); err != nil {
fmt.Fprintf(w, "failed to generate decoded message, %v\n", err)
}
}
func decodePrelude(r io.Reader, crc hash.Hash32) (messagePrelude, error) {
var p messagePrelude
var err error
p.Length, err = decodeUint32(r)
if err != nil {
return messagePrelude{}, err
}
p.HeadersLen, err = decodeUint32(r)
if err != nil {
return messagePrelude{}, err
}
if err := p.ValidateLens(); err != nil {
return messagePrelude{}, err
}
preludeCRC := crc.Sum32()
if err := validateCRC(r, preludeCRC); err != nil {
return messagePrelude{}, err
}
p.PreludeCRC = preludeCRC
return p, nil
}
func decodePayload(buf []byte, r io.Reader) ([]byte, error) {
w := bytes.NewBuffer(buf[0:0])
_, err := io.Copy(w, r)
return w.Bytes(), err
}
func decodeUint8(r io.Reader) (uint8, error) {
type byteReader interface {
ReadByte() (byte, error)
}
if br, ok := r.(byteReader); ok {
v, err := br.ReadByte()
return v, err
}
var b [1]byte
_, err := io.ReadFull(r, b[:])
return b[0], err
}
func decodeUint16(r io.Reader) (uint16, error) {
var b [2]byte
bs := b[:]
_, err := io.ReadFull(r, bs)
if err != nil {
return 0, err
}
return binary.BigEndian.Uint16(bs), nil
}
func decodeUint32(r io.Reader) (uint32, error) {
var b [4]byte
bs := b[:]
_, err := io.ReadFull(r, bs)
if err != nil {
return 0, err
}
return binary.BigEndian.Uint32(bs), nil
}
func decodeUint64(r io.Reader) (uint64, error) {
var b [8]byte
bs := b[:]
_, err := io.ReadFull(r, bs)
if err != nil {
return 0, err
}
return binary.BigEndian.Uint64(bs), nil
}
func validateCRC(r io.Reader, expect uint32) error {
msgCRC, err := decodeUint32(r)
if err != nil {
return err
}
if msgCRC != expect {
return ChecksumError{}
}
return nil
}