mirror of https://github.com/golang/go.git
82 lines
2.0 KiB
Go
82 lines
2.0 KiB
Go
// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package lsp
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import (
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"sync"
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"time"
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)
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type debounceFunc struct {
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order uint64
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done chan struct{}
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}
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type debouncer struct {
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mu sync.Mutex
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funcs map[string]*debounceFunc
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}
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func newDebouncer() *debouncer {
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return &debouncer{
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funcs: make(map[string]*debounceFunc),
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}
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}
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// debounce waits timeout before running f, if no subsequent call is made with
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// the same key in the intervening time. If a later call to debounce with the
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// same key occurs while the original call is blocking, the original call will
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// return immediately without running its f.
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//
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// If order is specified, it will be used to order calls logically, so calls
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// with lesser order will not cancel calls with greater order.
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func (d *debouncer) debounce(key string, order uint64, timeout time.Duration, f func()) {
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if timeout == 0 {
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// Degenerate case: no debouncing.
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f()
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return
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}
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// First, atomically acquire the current func, cancel it, and insert this
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// call into d.funcs.
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d.mu.Lock()
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current, ok := d.funcs[key]
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if ok && current.order > order {
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// If we have a logical ordering of events (as is the case for snapshots),
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// don't overwrite a later event with an earlier event.
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d.mu.Unlock()
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return
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}
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if ok {
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close(current.done)
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}
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done := make(chan struct{})
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next := &debounceFunc{
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order: order,
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done: done,
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}
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d.funcs[key] = next
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d.mu.Unlock()
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// Next, wait to be cancelled or for our wait to expire. There is a race here
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// that we must handle: our timer could expire while another goroutine holds
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// d.mu.
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select {
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case <-done:
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case <-time.After(timeout):
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d.mu.Lock()
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if d.funcs[key] != next {
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// We lost the race: another event has arrived for the key and started
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// waiting. We could reasonably choose to run f at this point, but doing
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// nothing is simpler.
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d.mu.Unlock()
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return
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}
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delete(d.funcs, key)
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d.mu.Unlock()
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f()
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}
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}
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