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- // Copyright 2017 The go-ethereum Authors
- // This file is part of the go-ethereum library.
- //
- // The go-ethereum library is free software: you can redistribute it and/or modify
- // it under the terms of the GNU Lesser General Public License as published by
- // the Free Software Foundation, either version 3 of the License, or
- // (at your option) any later version.
- //
- // The go-ethereum library is distributed in the hope that it will be useful,
- // but WITHOUT ANY WARRANTY; without even the implied warranty of
- // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- // GNU Lesser General Public License for more details.
- //
- // You should have received a copy of the GNU Lesser General Public License
- // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
- package utils
- import "sync"
- // ExecQueue implements a queue that executes function calls in a single thread,
- // in the same order as they have been queued.
- type ExecQueue struct {
- mu sync.Mutex
- cond *sync.Cond
- funcs []func()
- closeWait chan struct{}
- }
- // NewExecQueue creates a new execution Queue.
- func NewExecQueue(capacity int) *ExecQueue {
- q := &ExecQueue{funcs: make([]func(), 0, capacity)}
- q.cond = sync.NewCond(&q.mu)
- go q.loop()
- return q
- }
- func (q *ExecQueue) loop() {
- for f := q.waitNext(false); f != nil; f = q.waitNext(true) {
- f()
- }
- close(q.closeWait)
- }
- func (q *ExecQueue) waitNext(drop bool) (f func()) {
- q.mu.Lock()
- if drop && len(q.funcs) > 0 {
- // Remove the function that just executed. We do this here instead of when
- // dequeuing so len(q.funcs) includes the function that is running.
- q.funcs = append(q.funcs[:0], q.funcs[1:]...)
- }
- for !q.isClosed() {
- if len(q.funcs) > 0 {
- f = q.funcs[0]
- break
- }
- q.cond.Wait()
- }
- q.mu.Unlock()
- return f
- }
- func (q *ExecQueue) isClosed() bool {
- return q.closeWait != nil
- }
- // CanQueue returns true if more function calls can be added to the execution Queue.
- func (q *ExecQueue) CanQueue() bool {
- q.mu.Lock()
- ok := !q.isClosed() && len(q.funcs) < cap(q.funcs)
- q.mu.Unlock()
- return ok
- }
- // Queue adds a function call to the execution Queue. Returns true if successful.
- func (q *ExecQueue) Queue(f func()) bool {
- q.mu.Lock()
- ok := !q.isClosed() && len(q.funcs) < cap(q.funcs)
- if ok {
- q.funcs = append(q.funcs, f)
- q.cond.Signal()
- }
- q.mu.Unlock()
- return ok
- }
- // Clear drops all queued functions.
- func (q *ExecQueue) Clear() {
- q.mu.Lock()
- q.funcs = q.funcs[:0]
- q.mu.Unlock()
- }
- // Quit stops the exec Queue.
- //
- // Quit waits for the current execution to finish before returning.
- func (q *ExecQueue) Quit() {
- q.mu.Lock()
- if !q.isClosed() {
- q.closeWait = make(chan struct{})
- q.cond.Signal()
- }
- q.mu.Unlock()
- <-q.closeWait
- }
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