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DecodeMessage: skip bytes Buffer, reducing alloc overhead #175

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merged 2 commits into from
Apr 15, 2016
Merged

DecodeMessage: skip bytes Buffer, reducing alloc overhead #175

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DecodeMessage: skip bytes Buffer, reducing alloc overhead
Dieterbe Apr 15, 2016
877525d
allow empty bodies + document message format
Dieterbe Apr 15, 2016
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32 changes: 17 additions & 15 deletions message.go
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Original file line number Diff line number Diff line change
@@ -1,10 +1,9 @@
package nsq

import (
"bytes"
"encoding/binary"
"errors"
"io"
"io/ioutil"
"sync/atomic"
"time"
)
Expand Down Expand Up @@ -139,24 +138,27 @@ func (m *Message) WriteTo(w io.Writer) (int64, error) {
return total, nil
}

// DecodeMessage deseralizes data (as []byte) and creates a new Message
// DecodeMessage deserializes data (as []byte) and creates a new Message
// message format:
// [x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x][x]...
// | (int64) || || (hex string encoded in ASCII) || (binary)
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Docstring nitpick: message ID is binary w/r/t the protocol. Practically we chose to use ascii printable characters for now.

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(if we want to reword that, that's in the official docs)

// | 8-byte || || 16-byte || N-byte
// ------------------------------------------------------------------------------------------...
// nanosecond timestamp ^^ message ID message body
// (uint16)
// 2-byte
// attempts
func DecodeMessage(b []byte) (*Message, error) {
var msg Message

msg.Timestamp = int64(binary.BigEndian.Uint64(b[:8]))
msg.Attempts = binary.BigEndian.Uint16(b[8:10])

buf := bytes.NewBuffer(b[10:])

_, err := io.ReadFull(buf, msg.ID[:])
if err != nil {
return nil, err
if len(b) < 10+MsgIDLength {
return nil, errors.New("not enough data to decode valid message")
}

msg.Body, err = ioutil.ReadAll(buf)
if err != nil {
return nil, err
}
msg.Timestamp = int64(binary.BigEndian.Uint64(b[:8]))
msg.Attempts = binary.BigEndian.Uint16(b[8:10])
copy(msg.ID[:], b[10:10+MsgIDLength])
msg.Body = b[10+MsgIDLength:]

return &msg, nil
}