buffer 复用

package main
 
import (
    "fmt"
    "math/rand"
    "runtime"
    "time"
)
 
func makeBuffer() []byte {
    return make([]byte, rand.Intn(5000000)+5000000)
}
 
func main() {
    pool := make([][]byte, 20)
 
    buffer := make(chan []byte, 5)
 
    var m runtime.MemStats
    makes := 0
    for {
        var b []byte
        select {
        case b = <-buffer:
        default:
            makes += 1
            b = makeBuffer()
        }
 
        i := rand.Intn(len(pool))
        if pool[i] != nil {
            select {
            case buffer <- pool[i]:
                pool[i] = nil
            default:
            }
        }
 
        pool[i] = b
 
        time.Sleep(time.Second)
 
        bytes := 0
        for i := 0; i < len(pool); i++ {
            if pool[i] != nil {
                bytes += len(pool[i])
            }
        }
 
        runtime.ReadMemStats(&m)
        fmt.Printf("%d,%d,%d,%d,%d,%d\n", m.HeapSys, bytes, m.HeapAlloc,
            m.HeapIdle, m.HeapReleased, makes)
    }
}