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