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| package main
import (
"crypto/rand"
"crypto/sha256"
"encoding/binary"
"encoding/hex"
"errors"
"fmt"
"hash"
"io"
"log"
"math/bits"
"net"
"sync"
"sync/atomic"
)
var (
pool = new(BufferPool)
)
// Conn 是你需要实现的一种连接类型，它支持下面描述的若干接口；
// 为了实现这些接口，你需要设计一个基于 TCP 的简单协议；
type Conn struct {
c net.Conn
nextID uint32
lock sync.Mutex
err error
closeChan chan struct{}
writeDoneChan chan struct{}
writeBuffChan chan []byte
readDoneChan chan struct{}
readBuffChan chan []byte
acceptChan chan *Stream
streamLock sync.Mutex
streams map[uint32]*Stream
closeOnce sync.Once
}
// Send 传入一个 key 表示发送者将要传输的数据对应的标识；
// 返回 writer 可供发送者分多次写入大量该 key 对应的数据；
// 当发送者已将该 key 对应的所有数据写入后，调用 writer.Close 告知接收者：该 key 的数据已经完全写入；
func (conn *Conn) Send(key string) (io.WriteCloser, error) {
s := &Stream{
key: key,
streamID: conn.nextID,
state: Open,
sendChan: conn.writeBuffChan,
recvChan: make(chan []byte, 64),
}
atomic.AddUint32(&conn.nextID, 1)
log.Println("open new stream", s.streamID)
conn.streamLock.Lock()
conn.streams[s.streamID] = s
conn.streamLock.Unlock()
buff := pool.Get(HeaderSize + len(key))
h := encode(OpenStream, s.streamID, uint32(len(key)))
copy(buff, h[:])
copy(buff[HeaderSize:], key)
select {
case conn.writeBuffChan <- buff:
return s, nil
case <-conn.closeChan:
return nil, errors.New("connection closed")
}
}
// Receive 返回一个 key 表示接收者将要接收到的数据对应的标识；
// 返回的 reader 可供接收者多次读取该 key 对应的数据；
// 当 reader 返回 io.EOF 错误时，表示接收者已经完整接收该 key 对应的数据；
func (conn *Conn) Receive() (key string, reader io.Reader, err error) {
select {
case stream := <-conn.acceptChan:
return stream.key, stream, nil
case <-conn.closeChan:
conn.lock.Lock()
err = conn.err
conn.lock.Unlock()
return "", nil, err
}
}
// Close 关闭你实现的连接对象及其底层的 TCP 连接
func (conn *Conn) Close() {
conn.closeOnce.Do(func() {
close(conn.closeChan)
conn.streamLock.Lock()
defer conn.streamLock.Unlock()
for _, stream := range conn.streams {
stream.Close()
}
<-conn.writeDoneChan
conn.c.Close()
<-conn.readDoneChan
})
}
func (conn *Conn) sendLoop() {
defer close(conn.writeDoneChan)
for {
select {
case writeBuff := <-conn.writeBuffChan:
size := len(writeBuff)
offset := 0
for offset < size {
write, err := conn.c.Write(writeBuff)
if err != nil {
log.Println("write error:", err)
go conn.Close()
conn.lock.Lock()
conn.err = err
conn.lock.Unlock()
return
}
offset += write
}
default:
select {
case _, ok := <-conn.closeChan:
if !ok {
log.Println("connection closed")
return
}
default:
}
}
}
}
func (conn *Conn) recvLoop() {
defer close(conn.readDoneChan)
var h header
loop:
for {
_, err := io.ReadFull(conn.c, h[:])
if err != nil {
log.Println("read error:", err)
go conn.Close()
conn.lock.Lock()
conn.err = err
conn.lock.Unlock()
return
}
if h.Version() != protoVersion {
log.Println("invalid version:", h.Version())
return
}
id := h.StreamID()
switch MsgType(h.MsgType()) {
case OpenStream:
if id != conn.nextID {
log.Println("invalid stream id ", id)
continue loop
}
atomic.AddUint32(&conn.nextID, 1)
key := pool.Get(int(h.Length()))
read, err := io.ReadFull(conn.c, key)
if err != nil {
log.Println("read error:", err)
return
}
if read != int(h.Length()) {
log.Println("invalid read length:", read)
return
}
stream := &Stream{
key: string(key),
streamID: id,
state: Open,
sendChan: conn.writeBuffChan,
recvChan: make(chan []byte, 64),
}
conn.streamLock.Lock()
conn.streams[id] = stream
conn.streamLock.Unlock()
log.Printf("receive new stream: id: %d, key: %s", id, stream.key)
select {
case conn.acceptChan <- stream:
case <-conn.closeChan:
return
}
case DataFrame:
conn.streamLock.Lock()
stream, ok := conn.streams[id]
conn.streamLock.Unlock()
if !ok || stream == nil {
log.Println("invalid stream id ", id)
continue loop
}
buff := pool.Get(int(h.Length()))
read, err := io.ReadFull(conn.c, buff)
if err != nil {
log.Println("read error:", err)
return
}
if read != int(h.Length()) {
log.Println("invalid read length:", read)
return
}
select {
case stream.recvChan <- buff:
case <-conn.closeChan:
return
}
case CloseStream:
conn.streamLock.Lock()
stream, ok := conn.streams[id]
conn.streamLock.Unlock()
if !ok || stream == nil {
log.Println("invalid stream id ", id)
continue loop
}
log.Printf("close stream: id: %d, key: %s", id, stream.key)
stream.lock.Lock()
stream.state = Close
stream.lock.Unlock()
default:
log.Println("invalid msg type:", MsgType(h.MsgType()))
}
}
}
// NewConn 从一个 TCP 连接得到一个你实现的连接对象
func NewConn(conn net.Conn) *Conn {
c := &Conn{
c: conn,
nextID: 0,
closeChan: make(chan struct{}),
writeDoneChan: make(chan struct{}),
writeBuffChan: make(chan []byte, 64),
readDoneChan: make(chan struct{}),
readBuffChan: make(chan []byte, 64),
acceptChan: make(chan *Stream, 10),
streamLock: sync.Mutex{},
streams: make(map[uint32]*Stream),
}
go c.sendLoop()
go c.recvLoop()
return c
}
type MsgType uint8
const (
Unknown MsgType = iota
OpenStream
DataFrame
CloseStream
)
const (
MaxDataLength = 1<<32 - 1
protoVersion = 1
SizeOfVersion = 1
SizeOfMsgType = 1
SizeOfStreamID = 4
SizeOfDataLength = 4
HeaderSize = SizeOfVersion + SizeOfMsgType + SizeOfStreamID + SizeOfDataLength
)
type StreamState uint8
const (
Open StreamState = iota
Close
)
type header [HeaderSize]byte
func (h header) Version() uint8 {
return h[0]
}
func (h header) MsgType() uint8 {
return h[1]
}
func (h header) StreamID() uint32 {
return binary.BigEndian.Uint32(h[2:6])
}
func (h header) Length() uint32 {
return binary.BigEndian.Uint32(h[6:10])
}
func (h header) String() string {
return fmt.Sprintf("Vsn:%d Type:%d StreamID:%d Length:%d",
h.Version(), h.MsgType(), h.StreamID(), h.Length())
}
func encode(msgType MsgType, streamID uint32, length uint32) header {
var h header
h[0] = protoVersion
h[1] = byte(msgType)
binary.BigEndian.PutUint32(h[2:6], streamID)
binary.BigEndian.PutUint32(h[6:10], length)
return h
}
type Stream struct {
value atomic.Value
key string
streamID uint32
lock sync.Mutex
err error
state StreamState
sendChan chan []byte
lastReadOffset int
lastReadBuff []byte
recvChan chan []byte
}
func (s *Stream) Close() error {
buf := pool.Get(HeaderSize)
h := encode(CloseStream, s.streamID, 0)
copy(buf, h[:])
select {
case s.sendChan <- buf:
s.lock.Lock()
s.state = Close
s.lock.Unlock()
}
return nil
}
func (s *Stream) Write(buff []byte) (n int, err error) {
s.lock.Lock()
state := s.state
s.lock.Unlock()
if state == Close {
return 0, fmt.Errorf("stream closed")
}
if s.err != nil {
return 0, s.err
}
writeLen := len(buff)
offset := 0
for offset < writeLen {
size := min(MaxDataLength, len(buff)-offset)
buf := pool.Get(HeaderSize + size)
h := encode(DataFrame, s.streamID, uint32(size))
copy(buf, h[:])
copy(buf[HeaderSize:], buff[offset:offset+size])
select {
case s.sendChan <- buf:
offset += size
}
}
return offset, nil
}
func (s *Stream) Read(buff []byte) (n int, err error) {
size := len(buff)
if len(s.lastReadBuff) != 0 {
copy(buff, s.lastReadBuff[s.lastReadOffset:s.lastReadOffset+size])
s.lastReadOffset += size
if s.lastReadOffset == len(s.lastReadBuff) {
s.lastReadOffset = 0
pool.Put(s.lastReadBuff)
s.lastReadBuff = nil
}
return size, nil
}
if s.err != nil {
return 0, s.err
}
for {
select {
case buf := <-s.recvChan:
if len(buf) <= size {
copy(buff, buf)
pool.Put(buf)
return len(buf), nil
} else {
copy(buff, buf[:size])
s.lastReadOffset = size
s.lastReadBuff = buf
return size, nil
}
default:
s.lock.Lock()
state := s.state
s.lock.Unlock()
if state == Close {
return 0, io.EOF
}
}
}
}
// BufferPool
type BufferPool struct {
pools [32]sync.Pool // a list of singlePools
ptrs sync.Pool
}
type bufp struct {
buf []byte
}
func (p *BufferPool) Get(length int) []byte {
if length == 0 {
return nil
}
// Calling this function with a negative length is invalid.
// make will panic if length is negative, so we don't have to.
if length > MaxDataLength || length < 0 {
return make([]byte, length)
}
idx := nextLogBase2(uint32(length))
if ptr := p.pools[idx].Get(); ptr != nil {
bp := ptr.(*bufp)
buf := bp.buf[:uint32(length)]
bp.buf = nil
p.ptrs.Put(ptr)
return buf
}
return make([]byte, 1<<idx)[:uint32(length)]
}
func (p *BufferPool) Put(buf []byte) {
capacity := cap(buf)
if capacity == 0 || capacity > MaxDataLength {
return // drop it
}
idx := prevLogBase2(uint32(capacity))
var bp *bufp
if ptr := p.ptrs.Get(); ptr != nil {
bp = ptr.(*bufp)
} else {
bp = new(bufp)
}
bp.buf = buf
p.pools[idx].Put(bp)
}
// Log of base two, round up (for v > 0).
func nextLogBase2(v uint32) uint32 {
return uint32(bits.Len32(v - 1))
}
// Log of base two, round down (for v > 0)
func prevLogBase2(num uint32) uint32 {
next := nextLogBase2(num)
if num == (1 << next) {
return next
}
return next - 1
}
// 除了上面规定的接口，你还可以自行定义新的类型，变量和函数以满足实现需求
// ////////////////////////////////////////////
// /////// 接下来的代码为测试代码，请勿修改 /////////
// ////////////////////////////////////////////
// 连接到测试服务器，获得一个你实现的连接对象
func dial(serverAddr string) *Conn {
conn, err := net.Dial("tcp", serverAddr)
if err != nil {
panic(err)
}
return NewConn(conn)
}
// 启动测试服务器
func startServer(handle func(*Conn)) net.Listener {
ln, err := net.Listen("tcp", ":8080")
if err != nil {
panic(err)
}
go func() {
for {
conn, err := ln.Accept()
if err != nil {
fmt.Println("[WARNING] ln.Accept", err)
return
}
go handle(NewConn(conn))
}
}()
return ln
}
// 简单断言
func assertEqual[T comparable](actual T, expected T) {
if actual != expected {
panic(fmt.Sprintf("actual:%v expected:%v\n", actual, expected))
}
}
// 简单 case：单连接，双向传输少量数据
func testCase0() {
const (
key = "Bible"
data = `Then I heard the voice of the Lord saying, “Whom shall I send? And who will go for us?”
And I said, “Here am I. Send me!”
Isaiah 6:8`
)
ln := startServer(func(conn *Conn) {
// 服务端等待客户端进行传输
_key, reader, err := conn.Receive()
if err != nil {
panic(err)
}
assertEqual(_key, key)
dataB, err := io.ReadAll(reader)
if err != nil {
panic(err)
}
assertEqual(string(dataB), data)
// 服务端向客户端进行传输
writer, err := conn.Send(key)
if err != nil {
panic(err)
}
n, err := writer.Write([]byte(data))
if err != nil {
panic(err)
}
if n != len(data) {
panic(n)
}
conn.Close()
})
//goland:noinspection GoUnhandledErrorResult
defer ln.Close()
conn := dial(ln.Addr().String())
// 客户端向服务端传输
writer, err := conn.Send(key)
if err != nil {
panic(err)
}
n, err := writer.Write([]byte(data))
if n != len(data) {
panic(n)
}
err = writer.Close()
if err != nil {
panic(err)
}
// 客户端等待服务端传输
_key, reader, err := conn.Receive()
if err != nil {
panic(err)
}
assertEqual(_key, key)
dataB, err := io.ReadAll(reader)
if err != nil {
panic(err)
}
assertEqual(string(dataB), data)
conn.Close()
}
// 生成一个随机 key
func newRandomKey() string {
buf := make([]byte, 8)
_, err := rand.Read(buf)
if err != nil {
panic(err)
}
return hex.EncodeToString(buf)
}
// 读取随机数据，并返回随机数据的校验和：用于验证数据是否完整传输
func readRandomData(reader io.Reader, hash hash.Hash) (checksum string) {
hash.Reset()
var buf = make([]byte, 23<<20) // 调用者读取时的 buf 大小不是固定的，你的实现中不可假定 buf 为固定值
for {
n, err := reader.Read(buf)
if err == io.EOF {
break
}
if err != nil {
panic(err)
}
_, err = hash.Write(buf[:n])
if err != nil {
panic(err)
}
}
checksum = hex.EncodeToString(hash.Sum(nil))
return checksum
}
// 写入随机数据，并返回随机数据的校验和：用于验证数据是否完整传输
func writeRandomData(writer io.Writer, hash hash.Hash) (checksum string) {
hash.Reset()
const (
dataSize = 500 << 20 // 一个 key 对应 500MB 随机二进制数据，dataSize 也可以是其他值，你的实现中不可假定 dataSize 为固定值
bufSize = 1 << 20 // 调用者写入时的 buf 大小不是固定的，你的实现中不可假定 buf 为固定值
)
var (
buf = make([]byte, bufSize)
size = 0
)
for i := 0; i < dataSize/bufSize; i++ {
_, err := rand.Read(buf)
if err != nil {
panic(err)
}
_, err = hash.Write(buf)
if err != nil {
panic(err)
}
n, err := writer.Write(buf)
if err != nil {
panic(err)
}
size += n
}
if size != dataSize {
panic(size)
}
checksum = hex.EncodeToString(hash.Sum(nil))
return checksum
}
// 复杂 case：多连接，双向传输，大量数据，多个不同的 key
func testCase1() {
var (
mapKeyToChecksum = map[string]string{}
lock sync.Mutex
)
ln := startServer(func(conn *Conn) {
// 服务端等待客户端进行传输
key, reader, err := conn.Receive()
if err != nil {
panic(err)
}
var (
h = sha256.New()
_checksum = readRandomData(reader, h)
)
lock.Lock()
checksum, keyExist := mapKeyToChecksum[key]
lock.Unlock()
if !keyExist {
panic(fmt.Sprintln(key, "not exist"))
}
assertEqual(_checksum, checksum)
// 服务端向客户端连续进行 2 次传输
for _, key := range []string{newRandomKey(), newRandomKey()} {
writer, err := conn.Send(key)
if err != nil {
panic(err)
}
checksum := writeRandomData(writer, h)
lock.Lock()
mapKeyToChecksum[key] = checksum
lock.Unlock()
err = writer.Close() // 表明该 key 的所有数据已传输完毕
if err != nil {
panic(err)
}
}
conn.Close()
})
//goland:noinspection GoUnhandledErrorResult
defer ln.Close()
conn := dial(ln.Addr().String())
// 客户端向服务端传输
var (
key = newRandomKey()
h = sha256.New()
)
writer, err := conn.Send(key)
if err != nil {
panic(err)
}
checksum := writeRandomData(writer, h)
lock.Lock()
mapKeyToChecksum[key] = checksum
lock.Unlock()
err = writer.Close()
if err != nil {
panic(err)
}
// 客户端等待服务端的多次传输
keyCount := 0
for {
key, reader, err := conn.Receive()
if err == io.EOF {
// 服务端所有的数据均传输完毕，关闭连接
break
}
if err != nil {
panic(err)
}
_checksum := readRandomData(reader, h)
lock.Lock()
checksum, keyExist := mapKeyToChecksum[key]
lock.Unlock()
if !keyExist {
panic(fmt.Sprintln(key, "not exist"))
}
assertEqual(_checksum, checksum)
keyCount++
}
assertEqual(keyCount, 2)
conn.Close()
}
func main() {
testCase0()
testCase1()
}
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