util

type Queue interface {
	// Put puts item into the queue and keeps blocking if the queue is full.
	// It will return immediately and do nothing if the item is nil.
	Put(item interface{})

	// PutTimeout puts item into the queue and waits for timeout if the queue is full.
	// If timeout <= 0, it will return false immediately when queue is full.
	// It will return immediately and do nothing if the item is nil.
	PutTimeout(item interface{}, timeout time.Duration) bool

	// Poll gets an item from the queue and keeps blocking if the queue is empty.
	Poll() interface{}

	// PollTimeout gets an item from the queue and waits for timeout if the queue is empty.
	// If timeout <= 0, it will return (nil, bool) immediately when queue is empty.
	PollTimeout(timeout time.Duration) (interface{}, bool)

	// Len returns the current size of the queue.
	Len() int
}

type StdPrinter struct {
	Out io.Writer
}