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peer_protocol.Decoder.Decode: Avoid allocating another intermediate reader 

On my system, BenchmarkConnectionMainReadLoop goes from 596 to 1311 MB/s.
This commit is contained in:
Matt Joiner 2016-09-25 10:31:43 +10:00
parent 23efae91e2
commit 47ef753795
1 changed files with 19 additions and 16 deletions
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35
peer_protocol/protocol.go
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@ -128,6 +128,20 @@ type Decoder struct {
MaxLength Integer // TODO: Should this include the length header or not?
}
func readByte(r io.Reader) (b byte, err error) {
var arr [1]byte
n, err := r.Read(arr[:])
b = arr[0]
if n == 1 {
err = nil
return
}
if err == nil {
panic(err)
}
return
}
// io.EOF is returned if the source terminates cleanly on a message boundary.
func (d *Decoder) Decode(msg *Message) (err error) {
var length Integer
@ -146,29 +160,18 @@ func (d *Decoder) Decode(msg *Message) (err error) {
return
}
msg.Keepalive = false
b := make([]byte, length)
_, err = io.ReadFull(d.R, b)
if err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
if err != io.ErrUnexpectedEOF {
err = fmt.Errorf("error reading message: %s", err)
}
return
}
r := bytes.NewReader(b)
r := &io.LimitedReader{d.R, int64(length)}
// Check that all of r was utilized.
defer func() {
if err != nil {
return
}
if r.Len() != 0 {
err = fmt.Errorf("%d bytes unused in message type %d", r.Len(), msg.Type)
if r.N != 0 {
err = fmt.Errorf("%d bytes unused in message type %d", r.N, msg.Type)
}
}()
msg.Keepalive = false
c, err := r.ReadByte()
c, err := readByte(r)
if err != nil {
return
}
@ -210,7 +213,7 @@ func (d *Decoder) Decode(msg *Message) (err error) {
}
msg.Piece = b
case Extended:
msg.ExtendedID, err = r.ReadByte()
msg.ExtendedID, err = readByte(r)
if err != nil {
break
}