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// Copyright 2018 The gVisor Authors.
//
// 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 p9
import (
"sync"
)
// pool is a simple allocator.
//
// It is used for both tags and FIDs.
type pool struct {
mu sync.Mutex
// cache is the set of returned values.
cache []uint64
// start is the starting value (if needed).
start uint64
// limit is the upper limit.
limit uint64
}
// Get gets a value from the pool.
func (p *pool) Get() (uint64, bool) {
p.mu.Lock()
defer p.mu.Unlock()
// Anything cached?
if len(p.cache) > 0 {
v := p.cache[len(p.cache)-1]
p.cache = p.cache[:len(p.cache)-1]
return v, true
}
// Over the limit?
if p.start == p.limit {
return 0, false
}
// Generate a new value.
v := p.start
p.start++
return v, true
}
// Put returns a value to the pool.
func (p *pool) Put(v uint64) {
p.mu.Lock()
p.cache = append(p.cache, v)
p.mu.Unlock()
}
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