feat: Added Reuse and Initialize methods to LinkBuffer

[JHue58]

When used with sharequeue, the nodes of LinkBuffer are set to nil after Append, which prevents reuse and causes GC pressure.

[CLAassistant]

All committers have signed the CLA.

[joway]

the nodes of LinkBuffer are set to nil after Append, which prevents reuse and causes GC pressure.

@Nana-Miko Hi, can you show me your code and how it cause GC pressure?

[JHue58]

the nodes of LinkBuffer are set to nil after Append, which prevents reuse and causes GC pressure.

@Nana-Miko Hi, can you show me your code and how it cause GC pressure?

sure!

queue := mux.NewShardQueue(mux.ShardSize, conn)

	// Simulating pressure environment using for loops
	for {
		var getter mux.WriterGetter = func() (buf Writer, isNil bool) {
			// I can't use sync.Pool to get buf
			// In this func,'var buf = &LinkBuffer{}' will continuously allocate memory
			buf = NewLinkBuffer(128)

			buf.Malloc(128)
			buf.Flush()
			return buf, false
		}
		queue.Add(getter)
	}

In this example, is there any way to reuse LinkBuffer using sync.Pool?