func main() {
_, err := OutFunc()
if err != nil {
log.Printf("error is : %v", err)
}
fmt.Printf("End of main")
data := []int{0, 1, 2, 3, 4}
s1 := data[:2]
fmt.Printf("data ptr is %p, s1 ptr is %p", &data, &s1)
s2 := append(s1, 100, 200)
fmt.Println("\n", data)
fmt.Println(s1)
fmt.Println(s2)
fmt.Printf("data ptr is %p, s1 ptr is %p, s2 ptr is %p \n", &data, &s1, &s2)
var pool *sync.Pool
pool = new(sync.Pool)
pool.New = func() interface{} {
return 1
}
//pool.Put(1)
i := pool.Get()
if i == nil {
fmt.Println("pool.Get is non-block function. nil could be returned. not cool")
} else {
fmt.Println("number is ", i)
}
}
func Gzip(level int) gin.HandlerFunc {
var gzPool sync.Pool
gzPool.New = func() interface{} {
gz, err := gzip.NewWriterLevel(ioutil.Discard, level)
if err != nil {
panic(err)
}
return gz
}
return func(c *gin.Context) {
if !shouldCompress(c.Request) {
return
}
gz := gzPool.Get().(*gzip.Writer)
defer gzPool.Put(gz)
gz.Reset(c.Writer)
c.Header("Content-Encoding", "gzip")
c.Header("Vary", "Accept-Encoding")
c.Writer = &gzipWriter{c.Writer, gz}
defer func() {
c.Header("Content-Length", "0")
gz.Close()
}()
c.Next()
}
}
func (p person) dine(wg *sync.WaitGroup, foodPool *sync.Pool) {
for {
if !foodRemains() {
break
}
potentialDish := foodPool.Get()
if potentialDish == nil {
fmt.Printf("%s recieved a nil dish\n", p.Name)
break
}
someDish, ok := potentialDish.(dish)
if !ok {
fmt.Printf("%s was unable to turn a potential dish into a real dish\n", p.Name)
continue
}
p.consume(&someDish)
if someDish.Bites <= 0 {
fmt.Printf("%s finished %s\n", p.Name, someDish.Name)
} else {
foodPool.Put(someDish)
}
}
wg.Done()
}
func NewByteArraySize(pool *sync.Pool, size int) []byte {
if v := pool.Get(); v != nil {
ba := v.([]byte)
return ba
}
return make([]byte, size)
}
func (s *Server) ReadSocket(packetPool *sync.Pool) {
// each goroutine gets its own socket
// if the sockets support SO_REUSEPORT, then this will cause the
// kernel to distribute datagrams across them, for better read
// performance
s.logger.WithField("address", s.UDPAddr).Info("UDP server listening")
serverConn, err := NewSocket(s.UDPAddr, s.RcvbufBytes)
if err != nil {
// if any goroutine fails to create the socket, we can't really
// recover, so we just blow up
// this probably indicates a systemic issue, eg lack of
// SO_REUSEPORT support
s.logger.WithError(err).Fatal("Error listening for UDP")
}
for {
buf := packetPool.Get().([]byte)
n, _, err := serverConn.ReadFrom(buf)
if err != nil {
s.logger.WithError(err).Error("Error reading from UDP")
continue
}
s.HandlePacket(buf[:n])
// the Metric struct created by HandlePacket has no byte slices in it,
// only strings
// therefore there are no outstanding references to this byte slice, we
// can return it to the pool
packetPool.Put(buf)
}
}
// Example use of a pool to manage a free list of numbers
func ExampleNumberPool_1() {
// Create a Context
ctx := dec.NewContext(dec.InitDecimal128, 0)
// New() function for the pool to create new numbers
newFunc := func() interface{} { return dec.NewNumber(ctx.Digits()) }
// create a pool. Either dec.Pool or sync.Pool will do
syncPool := sync.Pool{New: newFunc}
// We can use Get().(*dec.Number) to get new or reusable numbers
number := syncPool.Get().(*dec.Number)
fmt.Printf("from sync.Pool: %s\n", number.Zero())
// We're done with it, put it back in the pool
syncPool.Put(number)
// Or, wrap it with a NumberPool so that Get() returns *Number instead of interface{}.
// NumberPool also helps keeping track of the context.
pool := &dec.NumberPool{&syncPool, ctx}
// and benefit: no need to type-cast
number = pool.Get()
// Introducing the idiomatic code: defer Put() the *Number right after Get()
defer pool.Put(number)
fmt.Printf("from sync.Pool: %s\n", number.FromString("1243", pool.Context))
// Output:
// from sync.Pool: 0
// from sync.Pool: 1243
}
// Middleware encodes the response using Gzip encoding and sets all the appropriate
// headers. If the Content-Type is not set, it will be set by calling
// http.DetectContentType on the data being written.
func Middleware(level int) goa.Middleware {
gzipPool := sync.Pool{
New: func() interface{} {
gz, err := gzip.NewWriterLevel(ioutil.Discard, level)
if err != nil {
panic(err)
}
return gz
},
}
return func(h goa.Handler) goa.Handler {
return func(ctx *goa.Context) (err error) {
r := ctx.Request()
// Skip compression if the client doesn't accept gzip encoding, is
// requesting a WebSocket or the data is already compressed.
if !strings.Contains(r.Header.Get(headerAcceptEncoding), encodingGzip) ||
len(r.Header.Get(headerSecWebSocketKey)) > 0 ||
ctx.Header().Get(headerContentEncoding) == encodingGzip {
return h(ctx)
}
// Set the appropriate gzip headers.
ctx.Header().Set(headerContentEncoding, encodingGzip)
ctx.Header().Set(headerVary, headerAcceptEncoding)
// Retrieve gzip writer from the pool. Reset it to use the ResponseWriter.
// This allows us to re-use an already allocated buffer rather than
// allocating a new buffer for every request.
gz := gzipPool.Get().(*gzip.Writer)
// Get the original http.ResponseWriter
w := ctx.SetResponseWriter(nil)
// Reset our gzip writer to use the http.ResponseWriter
gz.Reset(w)
// Wrap the original http.ResponseWriter with our gzipResponseWriter
grw := gzipResponseWriter{
ResponseWriter: w,
gzw: gz,
}
// Set the new http.ResponseWriter
ctx.SetResponseWriter(grw)
// Call the next handler supplying the gzipResponseWriter instead of
// the original.
err = h(ctx)
if err != nil {
return
}
// Delete the content length after we know we have been written to.
grw.Header().Del(headerContentLength)
gz.Close()
gzipPool.Put(gz)
return
}
}
}
// TODO
func NewBufioReaderSize(pool *sync.Pool, r io.Reader, size int) *bufio.Reader {
if v := pool.Get(); v != nil {
br := v.(*bufio.Reader)
br.Reset(r)
return br
}
return bufio.NewReaderSize(r, size)
}
func NewBufioWriterSize(pool *sync.Pool, w io.Writer, size int) *bufio.Writer {
if v := pool.Get(); v != nil {
bw := v.(*bufio.Writer)
bw.Reset(w)
return bw
}
return bufio.NewWriterSize(w, size)
}
func BenchmarkAllocSyncPool(b *testing.B) {
var p sync.Pool
s := make([]byte, 10)
for i := 0; i < b.N; i++ {
p.Put(s)
s = p.Get().([]byte)
}
}
func BenchmarkRuntimeCallersSyncPool(b *testing.B) {
pool := sync.Pool{New: func() interface{} { return make([]uintptr, 32) }}
for i := 0; i < b.N; i++ {
pcs := pool.Get().([]uintptr)
runtime.Callers(0, pcs[:])
pcs = pcs[0:]
pool.Put(pcs)
}
}
func newWriterLevel(pool *sync.Pool, w io.Writer, level int) *gzip.Writer {
if v := pool.Get(); v != nil {
zw := v.(*gzip.Writer)
zw.Reset(w)
return zw
}
zw, _ := gzip.NewWriterLevel(w, level)
return zw
}
func main() {
var pool sync.Pool
var a = 1
pool.Put(a)
pool.Put(new(User))
fmt.Println(pool.Get())
runtime.GC()
fmt.Println(pool.Get())
fmt.Println(pool.Get())
}
func main() {
var rp sync.Pool
var wp sync.Pool
for i := 0; i < 1024; i++ {
rb := new([]byte)
*rb = make([]byte, 2048)
rp.Put(rb)
}
var counter uint32
log.Fatal(nsk.ListenAndServe(":8000", func(conn *net.TCPConn) {
var s string
var c uint32
var rb *[]byte
var w *bufio.Writer
if v := wp.Get(); v != nil {
w = v.(*bufio.Writer)
w.Reset(conn)
} else {
w = bufio.NewWriter(conn)
}
if v := rp.Get(); v != nil {
rb = v.(*[]byte)
} else {
rb = new([]byte)
*rb = make([]byte, 2048)
}
n, err := conn.Read(*rb)
if err != nil || n <= 0 {
goto E
}
c = atomic.AddUint32(&counter, 1)
s = strconv.FormatUint(uint64(c), 10)
w.WriteString("HTTP/1.1 200 OK\r\n")
w.WriteString("Connection: close\r\n")
w.WriteString(fmt.Sprintf("Content-Length: %d\r\n\r\n", len(s)))
w.WriteString(s)
w.Flush()
E:
conn.Close()
rp.Put(rb)
wp.Put(w)
}))
}
func benchPool(i int, b *testing.B) {
pool := sync.Pool{New: func() interface{} {
return make([]int, 0, i)
}}
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
s := pool.Get().([]int)[:0]
pool.Put(s)
}
})
}
func BenchmarkAllocSyncPool(b *testing.B) {
var p sync.Pool
s := make([]byte, 10)
for i := 0; i < b.N; i++ {
p.Put(s)
si := p.Get()
var ok bool
s, ok = si.([]byte)
if !ok {
s = make([]byte, 10)
}
}
}
func main() {
// 禁用GC，并保证在main函数执行结束前恢复GC
defer debug.SetGCPercent(debug.SetGCPercent(-1))
var count int32
newFunc := func() interface{} {
return atomic.AddInt32(&count, 1)
}
pool := sync.Pool{New: newFunc}
// New 字段值的作用
v1 := pool.Get()
fmt.Printf("v1: %v\n", v1)
// 临时对象池的存取
pool.Put(newFunc())
pool.Put(newFunc())
pool.Put(newFunc())
v2 := pool.Get()
fmt.Printf("v2: %v\n", v2)
// 垃圾回收对临时对象池的影响
debug.SetGCPercent(100)
runtime.GC()
v3 := pool.Get()
fmt.Printf("v3: %v\n", v3)
pool.New = nil
v4 := pool.Get()
fmt.Printf("v4: %v\n", v4)
}
func callServer(clientPool *sync.Pool, s rpcx.ClientSelector) {
client := clientPool.Get().(*rpcx.Client)
args := &Args{7, 8}
var reply Reply
err := client.Call("Arith.Mul", args, &reply)
if err != nil {
fmt.Printf("error for Arith: %d*%d, %v \n", args.A, args.B, err)
} else {
fmt.Printf("Arith: %d*%d=%d, client: %p \n", args.A, args.B, reply.C, client)
}
clientPool.Put(client)
}
func (t *Transport) fromtxpool(async bool, pool *sync.Pool) (arg *txproto) {
if async {
arg = pool.Get().(*txproto)
arg.flush, arg.async = false, false
arg.n, arg.err, arg.respch = 0, nil, nil
if arg.packet == nil {
arg.packet = make([]byte, t.buffersize)
}
} else {
arg = pool.Get().(*txproto)
arg.packet, arg.flush, arg.async = nil, false, false
arg.n, arg.err, arg.respch = 0, nil, nil
}
return arg
}
func main() {
var pool sync.Pool
pool.New = func() interface{} {
return person{name: "name", timestamp: time.Now()}
}
var p, q, r person
p = pool.Get().(person)
fmt.Println(p.timestamp.String())
pool.Put(p)
r = pool.Get().(person)
q = pool.Get().(person)
fmt.Println(r.timestamp.String())
fmt.Println(q.timestamp.String())
}
func main() {
// Task 1: Define a pool (of ints). Just as the task says, a sync.Pool
// allocates individually and can free as a group.
p := sync.Pool{New: func() interface{} {
fmt.Println("pool empty")
return new(int)
}}
// Task 2: Allocate some ints.
i := new(int)
j := new(int)
// Show that they're usable.
*i = 1
*j = 2
fmt.Println(*i + *j) // prints 3
// Task 2 continued: Put allocated ints in pool p.
// Task explanation: Variable p has a pool as its value. Another pool
// could be be created and assigned to a different variable. You choose
// a pool simply by using the appropriate variable, p here.
p.Put(i)
p.Put(j)
// Drop references to i and j. This allows them to be garbage collected;
// that is, freed as a group.
i = nil
j = nil
// Get ints for i and j again, this time from the pool. P.Get may reuse
// an object allocated above as long as objects haven't been garbage
// collected yet; otherwise p.Get will allocate a new object.
i = p.Get().(*int)
j = p.Get().(*int)
*i = 4
*j = 5
fmt.Println(*i + *j) // prints 9
// One more test, this time forcing a garbage collection.
p.Put(i)
p.Put(j)
i = nil
j = nil
runtime.GC()
i = p.Get().(*int)
j = p.Get().(*int)
*i = 7
*j = 8
fmt.Println(*i + *j) // prints 15
}
func main() {
runtime.GOMAXPROCS(runtime.NumCPU())
pool := sync.Pool{
New: func() interface{} {
data := new(Data)
data.tag = "new"
data.buffer = make([]int, 10)
return data
},
}
for i := 0; i < 10; i++ {
go func() {
data := pool.Get().(*Data)
for index := range data.buffer {
data.buffer[index] = rand.Intn(100)
}
fmt.Println(data)
data.tag = "used"
pool.Put(data)
}()
}
for i := 0; i < 10; i++ {
go func() {
data := pool.Get().(*Data)
n := 0
for index := range data.buffer {
data.buffer[index] = n
n += 2
}
fmt.Println(data)
data.tag = "used"
pool.Put(data)
}()
}
fmt.Scanln()
}
func init() {
// Private data
var pool sync.Pool
const bufSize = 32768
bufPool.Get = func() []byte {
b, ok := pool.Get().([]byte)
if !ok || len(b) < bufSize {
b = make([]byte, bufSize)
}
return b
}
bufPool.Free = func(b []byte) {
if len(b) >= bufSize {
pool.Put(b)
}
}
}
func acquirePipelineWork(pool *sync.Pool, timeout time.Duration) *pipelineWork {
v := pool.Get()
if v == nil {
v = &pipelineWork{
done: make(chan struct{}, 1),
}
}
w := v.(*pipelineWork)
if timeout > 0 {
if w.t == nil {
w.t = time.NewTimer(timeout)
} else {
w.t.Reset(timeout)
}
w.deadline = time.Now().Add(timeout)
} else {
w.deadline = zeroTime
}
return w
}
func main() {
runtime.GOMAXPROCS(runtime.NumCPU()) // 모든 CPU 사용
pool := sync.Pool{ // 풀 할당
New: func() interface{} { // Get 함수를 사용했을 때 호출될 함수 정의
data := new(Data) // 새 메모리 할당
data.tag = "new" // 태그 설정
data.buffer = make([]int, 10) // 슬라이스 공간 할당
return data // 할당한 메모리(객체) 리턴
},
}
for i := 0; i < 10; i++ {
go func() { // 고루틴 10개 생성
data := pool.Get().(*Data) // 풀에서 *Data 타입으로 데이터를 가져옴
for index := range data.buffer {
data.buffer[index] = rand.Intn(100) // 슬라이스에 랜덤 값 저장
}
fmt.Println(data) // data 내용 출력
data.tag = "used" // 객체가 사용되었다는 태그 설정
pool.Put(data) // 풀에 객체를 보관
}()
}
for i := 0; i < 10; i++ {
go func() { // 고루틴 10개 생성
data := pool.Get().(*Data) // 풀에서 *Data 타입으로 데이터를 가져옴
n := 0
for index := range data.buffer {
data.buffer[index] = n // 슬라이스에 짝수 저장
n += 2
}
fmt.Println(data) // data 내용 출력
data.tag = "used" // 객체가 사용되었다는 태그 설정
pool.Put(data) // 풀에 객체 보관
}()
}
fmt.Scanln()
}
// Handle provides on-the-fly gzip encoding for other handlers.
//
// Usage:
//
// func DL1Handler(w http.ResponseWriter, req *http.Request) {
// fmt.Fprintln(w, "foobar")
// }
//
// func DL2Handler(w http.ResponseWriter, req *http.Request) {
// fmt.Fprintln(w, "zzz")
// }
//
//
// func main() {
// http.HandleFunc("/download1", DL1Handler)
// http.HandleFunc("/download2", DL2Handler)
// http.ListenAndServe(":8080", Gzip(http.DefaultServeMux))
// }
func Gzip(h http.Handler) http.HandlerFunc {
var pool sync.Pool
pool.New = func() interface{} {
return gzip.NewWriter(ioutil.Discard)
}
return func(w http.ResponseWriter, r *http.Request) {
// Do nothing on a HEAD request
if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") || r.Method == "HEAD" ||
w.Header().Get("Content-Encoding") == "gzip" { // Skip compression if already compressed
h.ServeHTTP(w, r)
return
}
w.Header().Set("Content-Encoding", "gzip")
gz := pool.Get().(*gzip.Writer)
defer pool.Put(gz)
gz.Reset(w)
h.ServeHTTP(IOResponseWriter{Writer: gz, ResponseWriter: WrapWriter(w)}, r)
gz.Close()
}
}
func BenchmarkJsonDecoderWithPool(b *testing.B) {
f, err := os.Open(httpTestFilename)
decoder := &HttpJSONDecoder{}
if err != nil {
b.Fatal(err)
}
defer f.Close()
r := bufio.NewReader(f)
jsonDoc, isPrefix, err := r.ReadLine()
if err != nil || isPrefix {
b.Fatal(errors.New("Couldn't properly read ammo sample from data file"))
}
var a Ammo
pool := sync.Pool{
New: func() interface{} { return &Http{} },
}
for n := 0; n < b.N; n++ {
h := pool.Get().(*Http)
a, _ = decoder.Decode(jsonDoc, h)
pool.Put(h)
}
_ = a
}
// GzipLevel returns a middleware which compresses HTTP response using gzip compression
// scheme using the level specified
func GzipLevel(level int) lars.HandlerFunc {
// test gzip level, then don't have to each time one is created
// in the pool
if _, err := gzip.NewWriterLevel(ioutil.Discard, level); err != nil {
panic(err)
}
var pool = sync.Pool{
New: func() interface{} {
z, _ := gzip.NewWriterLevel(ioutil.Discard, level)
return z
},
}
return func(c lars.Context) {
c.Response().Header().Add(lars.Vary, lars.AcceptEncoding)
if strings.Contains(c.Request().Header.Get(lars.AcceptEncoding), lars.Gzip) {
w := pool.Get().(*gzip.Writer)
w.Reset(c.Response().Writer())
defer func() {
w.Close()
pool.Put(w)
}()
gw := gzipWriter{Writer: w, ResponseWriter: c.Response().Writer()}
c.Response().Header().Set(lars.ContentEncoding, lars.Gzip)
c.Response().SetWriter(gw)
}
c.Next()
}
}
func test1() {
//Pool内存缓存 GC时将被清除
var bp sync.Pool
var looks sync.RWMutex
bp.New = func() interface{} {
return &bytes.Buffer{}
}
buf := bp.Get().(*bytes.Buffer)
buf.WriteString("test")
fmt.Println(buf.String())
bp.Put(buf) //记录至缓存
limit := make(chan struct{}, 10)
go func() {
buf := bp.Get().(*bytes.Buffer)
buf.WriteString("tttt")
looks.Lock()
bp.Put(buf)
looks.Unlock()
}()
time.Sleep(1 * time.Second)
for {
limit <- struct{}{}
go func() {
//提取以后必须再次Put 否则将被清除
buf := bp.Get().(*bytes.Buffer)
if buf.Len() != 0 {
fmt.Println(buf.String())
looks.Lock()
bp.Put(buf)
looks.Unlock()
//runtime.GC()
}
<-limit
}()
}
return
runtime.GC() //手动启动GC
buf = bp.Get().(*bytes.Buffer) //由于缓存被清空 反问内容为空
fmt.Println(buf.String())
}
n := c.pn.Next()
if n == nil {
// Done!
bufPool.Put(c.buf)
return nil
}
if proc, ok := c.procs[n.inode]; ok {
n.Proc = proc
}
return n
}
// cbConnections sets Connections()
var cbConnections = func(processes bool) (ConnIter, error) {
// buffer for contents of /proc/<pid>/net/tcp
buf := bufPool.Get().(*bytes.Buffer)
buf.Reset()
var procs map[uint64]Proc
if processes {
var err error
if procs, err = walkProcPid(buf); err != nil {
return nil, err
}
}
if buf.Len() == 0 {
readFile(procRoot+"/net/tcp", buf)
readFile(procRoot+"/net/tcp6", buf)
}