https://github.com/etcd-io/etcd
Tip revision: d42e8589e1305d893eeec9e7db746f6f4a76c250 authored by Sam Batschelet on 03 October 2021, 15:47:37 UTC
version: 3.5.1
version: 3.5.1
Tip revision: d42e858
wait.go
// Copyright 2015 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package wait provides utility functions for polling, listening using Go
// channel.
package wait
import (
"log"
"sync"
)
const (
// To avoid lock contention we use an array of list struct (rw mutex & map)
// for the id argument, we apply mod operation and uses its remainder to
// index into the array and find the corresponding element.
defaultListElementLength = 64
)
// Wait is an interface that provides the ability to wait and trigger events that
// are associated with IDs.
type Wait interface {
// Register waits returns a chan that waits on the given ID.
// The chan will be triggered when Trigger is called with
// the same ID.
Register(id uint64) <-chan interface{}
// Trigger triggers the waiting chans with the given ID.
Trigger(id uint64, x interface{})
IsRegistered(id uint64) bool
}
type list struct {
e []listElement
}
type listElement struct {
l sync.RWMutex
m map[uint64]chan interface{}
}
// New creates a Wait.
func New() Wait {
res := list{
e: make([]listElement, defaultListElementLength),
}
for i := 0; i < len(res.e); i++ {
res.e[i].m = make(map[uint64]chan interface{})
}
return &res
}
func (w *list) Register(id uint64) <-chan interface{} {
idx := id % defaultListElementLength
newCh := make(chan interface{}, 1)
w.e[idx].l.Lock()
defer w.e[idx].l.Unlock()
if _, ok := w.e[idx].m[id]; !ok {
w.e[idx].m[id] = newCh
} else {
log.Panicf("dup id %x", id)
}
return newCh
}
func (w *list) Trigger(id uint64, x interface{}) {
idx := id % defaultListElementLength
w.e[idx].l.Lock()
ch := w.e[idx].m[id]
delete(w.e[idx].m, id)
w.e[idx].l.Unlock()
if ch != nil {
ch <- x
close(ch)
}
}
func (w *list) IsRegistered(id uint64) bool {
idx := id % defaultListElementLength
w.e[idx].l.RLock()
defer w.e[idx].l.RUnlock()
_, ok := w.e[idx].m[id]
return ok
}
type waitWithResponse struct {
ch <-chan interface{}
}
func NewWithResponse(ch <-chan interface{}) Wait {
return &waitWithResponse{ch: ch}
}
func (w *waitWithResponse) Register(id uint64) <-chan interface{} {
return w.ch
}
func (w *waitWithResponse) Trigger(id uint64, x interface{}) {}
func (w *waitWithResponse) IsRegistered(id uint64) bool {
panic("waitWithResponse.IsRegistered() shouldn't be called")
}