recount-buf.go

package main

import (
	"sync"
	"sync/atomic"
	"time"
)

var pool *sync.Pool

type Packet struct {
	buf []byte
	cnt int32
}

func frob(p *Packet, buf []byte) {
	// FIXME: do stuff with our part
	// do_stuff(buf)

	// Decrement refcount; if we're the last, return to the pool.
	if atomic.AddInt32(&p.cnt, -1) == 0 {
		pool.Put(p)
	}
}

func main() {
	pool = new(sync.Pool)
	pool.New = func() interface{} { return new(Packet) }

	const N = 1000
	for i := 0; i < N; i++ {
		// Get buffer
		p := pool.Get().(*Packet)

		// Ensure it has enough capacity.
		if p.buf == nil || cap(p.buf) < 10 {
			p.buf = make([]byte, 10)
		} else {
			p.buf = p.buf[:0]
		}

		// FIXME: fill buffer with data
		p.buf = append(p.buf, 1, 2, 3, 4, 5, 6, 7, 8)

		// Spawn workers.
		const M = 5
		atomic.StoreInt32(&p.cnt, M)
		for j := 0; j < M; j++ {
			// Pass just a part of the buffer to each worker
			go frob(p, p.buf[j:j+1])
		}
	}
	<-time.After(2 * time.Second)
}