mirror of https://github.com/perkeep/perkeep.git
121 lines
2.6 KiB
Go
121 lines
2.6 KiB
Go
/*
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Copyright 2012 The Perkeep Authors.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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*/
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package chanworker // import "perkeep.org/internal/chanworker"
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import (
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"container/list"
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"sync"
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)
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type chanWorker struct {
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c chan interface{}
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donec chan bool
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workc chan interface{}
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fn func(n interface{}, ok bool)
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buf *list.List
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}
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// TODO: make it configurable if need be. Although so far in camput it wasn't.
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const buffered = 16
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// NewWorker starts nWorkers goroutines running fn on incoming
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// items sent on the returned channel. fn may block; writes to the
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// channel will buffer.
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// If nWorkers is negative, a new goroutine running fn is called for each
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// item sent on the returned channel.
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// When the returned channel is closed, fn is called with (nil, false)
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// after all other calls to fn have completed.
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// If nWorkers is zero, NewWorker will panic.
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func NewWorker(nWorkers int, fn func(el interface{}, ok bool)) chan<- interface{} {
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if nWorkers == 0 {
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panic("NewChanWorker: invalid value of 0 for nWorkers")
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}
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retc := make(chan interface{}, buffered)
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if nWorkers < 0 {
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// Unbounded number of workers.
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go func() {
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var wg sync.WaitGroup
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for w := range retc {
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wg.Add(1)
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go func(w interface{}) {
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fn(w, true)
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wg.Done()
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}(w)
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}
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wg.Wait()
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fn(nil, false)
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}()
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return retc
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}
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w := &chanWorker{
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c: retc,
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workc: make(chan interface{}, buffered),
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donec: make(chan bool), // when workers finish
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fn: fn,
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buf: list.New(),
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}
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go w.pump()
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for i := 0; i < nWorkers; i++ {
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go w.work()
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}
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go func() {
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for i := 0; i < nWorkers; i++ {
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<-w.donec
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}
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fn(nil, false) // final sentinel
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}()
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return retc
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}
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func (w *chanWorker) pump() {
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inc := w.c
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for inc != nil || w.buf.Len() > 0 {
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outc := w.workc
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var frontNode interface{}
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if e := w.buf.Front(); e != nil {
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frontNode = e.Value
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} else {
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outc = nil
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}
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select {
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case outc <- frontNode:
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w.buf.Remove(w.buf.Front())
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case el, ok := <-inc:
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if !ok {
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inc = nil
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continue
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}
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w.buf.PushBack(el)
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}
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}
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close(w.workc)
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}
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func (w *chanWorker) work() {
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for {
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select {
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case n, ok := <-w.workc:
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if !ok {
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w.donec <- true
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return
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}
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w.fn(n, true)
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}
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}
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}
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