ring.go

package main

import (
	"container/ring"
	"fmt"
	"math/rand"
	"strconv"
	"sync/atomic"
	"unsafe"
)

type Val struct {
	Ptr unsafe.Pointer
}

type Entry struct {
	URL string
}

func main() {
	buffer := ring.New(10)
	for i := 0; i < buffer.Len(); i++ {
		buffer.Value = &Val{}
		buffer = buffer.Next()
	}
	// producer
	go func() {
		for cur := buffer; ; cur = cur.Next() {
			if out := SwapOut(cur, &Entry{URL: strconv.Itoa(rand.Int())}); out != nil {
				fmt.Println("clean cuckoo")
			}
		}
	}()
	// consumer
	for cur := buffer; ; cur = cur.Next() {
		if out := SwapOut(cur, nil); out != nil {
			fmt.Println("scan:", out.URL)
		}
	}
}

func SwapOut(r *ring.Ring, n *Entry) *Entry {
	return (*Entry)(atomic.SwapPointer(&r.Value.(*Val).Ptr, unsafe.Pointer(n)))
}