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