wg

Documentation

Overview

Package wg implements a channel-enabled WaitGroup.

Index

• type WaitGroup
  • func (w *WaitGroup) Add(delta int)
  • func (w *WaitGroup) C() <-chan struct{}
  • func (w *WaitGroup) Done()
  • func (w *WaitGroup) N() int

Types

type WaitGroup

type WaitGroup struct {
	// contains filtered or unexported fields
}

A WaitGroup waits for a collection of goroutines to finish. The main goroutine calls Add to set the number of goroutines to wait for. Then each of the goroutines runs and calls Done when finished. At the same time, Wait can be used to block until all goroutines have finished. A WaitGroup must not be copied after first use.

TODO(marius): this could be made more efficient by using atomics.

func (*WaitGroup) Add

func (w *WaitGroup) Add(delta int)

Add adds delta, which may be negative, to the WaitGroup counter. If the counter becomes zero, all goroutines blocked on Wait are released. If the counter goes negative, Add panics.

Note that calls with a positive delta that occur when the counter is zero must happen before a Wait. Calls with a negative delta, or calls with a positive delta that start when the counter is greater than zero, may happen at any time. Typically this means the calls to Add should execute before the statement creating the goroutine or other event to be waited for. If a WaitGroup is reused to wait for several independent sets of events, new Add calls must happen after all previous Wait calls have returned. See the WaitGroup example.

func (*WaitGroup) C

func (w *WaitGroup) C() <-chan struct{}

C returns a channel that is closed when the waitgroup count is 0.

func (*WaitGroup) Done

func (w *WaitGroup) Done()

Done decrements the WaitGroup counter.

func (*WaitGroup) N

func (w *WaitGroup) N() int

N returns the current number of waiters.