Method getOrInit

engine/filesync/change_cache.go:38–90

(
	ctx context.Context,
	callKey string,
	fn func(context.Context) (*ChangeWithStat, error),
)

}

func (c *changeCache) getOrInit(
	ctx context.Context,
	callKey string,
	fn func(context.Context) (*ChangeWithStat, error),
) (*cachedChange, error) {
	if callKey == "" {
		return nil, fmt.Errorf("cache call key is empty")
	}

	c.mu.Lock()
	if c.ongoingCalls == nil {
		c.ongoingCalls = make(map[string]*cachedChange)
	}
	if c.completedCalls == nil {
		c.completedCalls = make(map[string]*cachedChange)
	}

	if res, ok := c.completedCalls[callKey]; ok {
		res.refCount++
		c.mu.Unlock()
		return res, nil
	}

	if res, ok := c.ongoingCalls[callKey]; ok {
		res.waiters++
		c.mu.Unlock()
		return c.wait(ctx, res)
	}

	callCtx, cancel := context.WithCancelCause(context.WithoutCancel(ctx))
	res := &cachedChange{
		cache: c,

		callKey: callKey,

		waitCh:  make(chan struct{}),
		cancel:  cancel,
		waiters: 1,
	}
	c.ongoingCalls[callKey] = res

	go func() {
		defer close(res.waitCh)
		val, err := fn(callCtx)
		res.err = err
		if err == nil {
			res.val = val
		}
	}()

	c.mu.Unlock()
	return c.wait(ctx, res)
}

func (c *changeCache) wait(ctx context.Context, res *cachedChange) (*cachedChange, error) {
	var err error