multi: add buffer.Write and pool.WriteBuffer, make GCQueue generic

pool/recycle.go

@@ -0,0 +1,52 @@
+package pool
+
+import (
+	"time"
+
+	"github.com/lightningnetwork/lnd/queue"
+)
+
+// Recycler is an interface that allows an object to be reclaimed without
+// needing to be returned to the runtime.
+type Recycler interface {
+	// Recycle resets the object to its default state.
+	Recycle()
+}
+
+// Recycle is a generic queue for recycling objects implementing the Recycler
+// interface. It is backed by an underlying queue.GCQueue, and invokes the
+// Recycle method on returned objects before returning them to the queue.
+type Recycle struct {
+	queue *queue.GCQueue
+}
+
+// NewRecycle initializes a fresh Recycle instance.
+func NewRecycle(newItem func() interface{}, returnQueueSize int,
+	gcInterval, expiryInterval time.Duration) *Recycle {
+
+	return &Recycle{
+		queue: queue.NewGCQueue(
+			newItem, returnQueueSize,
+			gcInterval, expiryInterval,
+		),
+	}
+}
+
+// Take returns an element from the pool.
+func (r *Recycle) Take() interface{} {
+	return r.queue.Take()
+}
+
+// Return returns an item implementing the Recycler interface to the pool. The
+// Recycle method is invoked before returning the item to improve performance
+// and utilization under load.
+func (r *Recycle) Return(item Recycler) {
+	// Recycle the item to ensure that a dirty instance is never offered
+	// from Take. The call is done here so that the CPU cycles spent
+	// clearing the buffer are owned by the caller, and not by the queue
+	// itself. This makes the queue more likely to be available to deliver
+	// items in the free list.
+	item.Recycle()
+
+	r.queue.Return(item)
+}