/
sender.go
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/
sender.go
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// Copyright © 2018 MG <mailtomasterg@gmail.com>
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package server
import (
"encoding/binary"
"errors"
"go.uber.org/zap"
)
var (
// ErrorSendEmptyPacket error while sending empty packet
ErrorSendEmptyPacket = errors.New("sending invalid packet (nil)")
// ErrorQueueFull error while tx queue is full
ErrorQueueFull = errors.New("sending queue is full")
)
// ConnWriteFunc writes data to connection, for standard socket and web socket
type ConnWriteFunc func([]byte) (int, error)
// Sender send packets to the client
type Sender struct {
ctrl chan struct{} // exit signal
pending chan []byte // pending packets
writer ConnWriteFunc // connection writer function
cache []byte // for combined syscall write
}
// NewSender create and returns a sender instance
func NewSender(ctrl chan struct{}, queueSize, sendCacheSize int, writer ConnWriteFunc) *Sender {
return &Sender{
ctrl: ctrl,
writer: writer,
pending: make(chan []byte, queueSize),
cache: make([]byte, sendCacheSize),
}
}
// EnqueueOutgoing push data to the sender's pending channel
func (buf *Sender) EnqueueOutgoing(pkg []byte) error {
if len(pkg) == 0 {
return ErrorSendEmptyPacket
}
// queue the data for sending
select {
case buf.pending <- pkg:
default:
log.Warn("sending queue is full", zap.Error(ErrorQueueFull))
return ErrorQueueFull
}
return nil
}
// actual send logic
func (buf *Sender) actualSend(data []byte) bool {
// write packet size, uint16, (these 2 bytes are excluded)
size := len(data)
binary.BigEndian.PutUint16(buf.cache, uint16(size))
copy(buf.cache[2:], data)
// write data
n, err := buf.writer(buf.cache[:size+2])
if err != nil {
log.Error("error while sending data", zap.Int("bytes", n), zap.Error(err))
return false
}
return true
}
// SendLoop packets sending routine
func (buf *Sender) SendLoop() {
for {
select {
case data := <-buf.pending: // dequeue data for sending
buf.actualSend(data)
case <-buf.ctrl: // control signal received
return
}
}
}