reduce websocket read allocations

See #2037

irc/ircconn.go

@@ -5,6 +5,7 @@ package irc
 
 import (
 	"bytes"
+	"io"
 	"net"
 	"unicode/utf8"
 
@@ -93,21 +94,25 @@ func (cc *IRCStreamConn) Close() (err error) {
 // IRCWSConn is an IRCConn over a websocket.
 type IRCWSConn struct {
 	conn   *websocket.Conn
+	buf    []byte
 	binary bool
 }
 
-func NewIRCWSConn(conn *websocket.Conn) IRCWSConn {
-	binary := conn.Subprotocol() == "binary.ircv3.net"
-	return IRCWSConn{conn: conn, binary: binary}
+func NewIRCWSConn(conn *websocket.Conn) *IRCWSConn {
+	return &IRCWSConn{
+		conn:   conn,
+		binary: conn.Subprotocol() == "binary.ircv3.net",
+		buf:    make([]byte, maxReadQBytes()),
+	}
 }
 
-func (wc IRCWSConn) UnderlyingConn() *utils.WrappedConn {
+func (wc *IRCWSConn) UnderlyingConn() *utils.WrappedConn {
 	// just assume that the type is OK
 	wConn, _ := wc.conn.UnderlyingConn().(*utils.WrappedConn)
 	return wConn
 }
 
-func (wc IRCWSConn) WriteLine(buf []byte) (err error) {
+func (wc *IRCWSConn) WriteLine(buf []byte) (err error) {
 	buf = bytes.TrimSuffix(buf, crlf)
 	// #1483: if we have websockets at all, then we're enforcing utf8
 	messageType := websocket.TextMessage
@@ -117,7 +122,7 @@ func (wc IRCWSConn) WriteLine(buf []byte) (err error) {
 	return wc.conn.WriteMessage(messageType, buf)
 }
 
-func (wc IRCWSConn) WriteLines(buffers [][]byte) (err error) {
+func (wc *IRCWSConn) WriteLines(buffers [][]byte) (err error) {
 	for _, buf := range buffers {
 		err = wc.WriteLine(buf)
 		if err != nil {
@@ -127,20 +132,35 @@ func (wc IRCWSConn) WriteLines(buffers [][]byte) (err error) {
 	return
 }
 
-func (wc IRCWSConn) ReadLine() (line []byte, err error) {
-	messageType, line, err := wc.conn.ReadMessage()
-	if err == nil {
+func (wc *IRCWSConn) ReadLine() (line []byte, err error) {
+	messageType, reader, err := wc.conn.NextReader()
+	switch err {
+	case nil:
+		// OK
+	case websocket.ErrReadLimit:
+		return line, ircreader.ErrReadQ
+	default:
+		return line, err
+	}
+
+	n, err := io.ReadFull(reader, wc.buf)
+	line = wc.buf[:n]
+	switch err {
+	case io.ErrUnexpectedEOF, io.EOF:
+		// these are OK. io.ErrUnexpectedEOF is the good case:
+		// it means we read the full message and it consumed less than the full wc.buf
 		if messageType == websocket.BinaryMessage && !utf8.Valid(line) {
 			return line, errInvalidUtf8
 		}
 		return line, nil
-	} else if err == websocket.ErrReadLimit {
+	case nil, websocket.ErrReadLimit:
+		// nil means we filled wc.buf without exhausting the reader:
 		return line, ircreader.ErrReadQ
-	} else {
+	default:
 		return line, err
 	}
 }
 
-func (wc IRCWSConn) Close() (err error) {
+func (wc *IRCWSConn) Close() (err error) {
 	return wc.conn.Close()
 }