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protocol.go
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protocol.go
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// Copyright (C) 2019 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// This protocol is mirrored in gapii/cc/protocol.h
package client
import (
"context"
"io"
"net"
"sync/atomic"
"time"
)
const messageHeaderSize uint = 6
const messageDataBytes uint = 5
type messageType byte
const (
messageData messageType = 0x00
messageStartTrace messageType = 0x01
messageEndTrace messageType = 0x02
messageError messageType = 0x03
messageInvalid messageType = 0xff
)
var startTraceMessage [messageHeaderSize]byte = [messageHeaderSize]byte{byte(messageStartTrace)}
var endTraceMessage [messageHeaderSize]byte = [messageHeaderSize]byte{byte(messageEndTrace)}
func readHeader(conn net.Conn) (msgType messageType, dataSize uint64, err error) {
msgType = messageInvalid
now := time.Now()
conn.SetReadDeadline(now.Add(time.Millisecond * 500)) // Allow for stop event and UI refreshes.
buf := make([]byte, messageHeaderSize)
if _, err = io.ReadFull(conn, buf); err == nil {
// first header byte contains the message type
msgType = messageType(buf[0])
// next messageDataBytes contain the data size as little-endian unsigned integer
for i := uint(0); i < messageDataBytes; i++ {
dataSize += uint64(buf[i+1]) << (i * 8)
}
}
return
}
func readData(ctx context.Context, conn net.Conn, dataSize uint64, w io.Writer, written *int64) (read siSize, err error) {
const maxBufSize siSize = 64 * 1024
for read < siSize(dataSize) {
copyCount := siSize(dataSize) - read
if copyCount > maxBufSize {
copyCount = maxBufSize
}
now := time.Now()
conn.SetReadDeadline(now.Add(time.Millisecond * 500)) // Allow for stop event and UI refreshes.
writeCount, copyErr := io.CopyN(w, conn, int64(copyCount))
read += siSize(writeCount)
atomic.AddInt64(written, writeCount)
if abort, abortErr := handleCommError(ctx, copyErr, true); abort {
err = abortErr
return
}
}
return
}
func readError(conn net.Conn, dataSize uint64) (errorMsg string, err error) {
now := time.Now()
conn.SetReadDeadline(now.Add(time.Millisecond * 500)) // Allow for stop event and UI refreshes.
buf := make([]byte, dataSize)
if _, err = io.ReadFull(conn, buf); err == nil {
errorMsg = string(buf)
}
return
}
func writeStartTrace(conn net.Conn) error {
_, err := conn.Write(startTraceMessage[:])
return err
}
func writeEndTrace(conn net.Conn) error {
_, err := conn.Write(endTraceMessage[:])
return err
}