/
prefetch.go
61 lines (53 loc) · 1.26 KB
/
prefetch.go
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/*
* JuiceFS, Copyright 2020 Juicedata, Inc.
*
* 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 chunk
import "sync"
type prefetcher struct {
sync.Mutex
pending chan string
busy map[string]bool
op func(key string)
}
func newPrefetcher(parallel int, fetch func(string)) *prefetcher {
p := &prefetcher{
pending: make(chan string, 10),
busy: make(map[string]bool),
op: fetch,
}
for i := 0; i < parallel; i++ {
go p.do()
}
return p
}
func (p *prefetcher) do() {
for key := range p.pending {
p.Lock()
if _, ok := p.busy[key]; !ok {
p.busy[key] = true
p.Unlock()
p.op(key)
p.Lock()
delete(p.busy, key)
}
p.Unlock()
}
}
func (p *prefetcher) fetch(key string) {
select {
case p.pending <- key:
default:
}
}