github.com/metacubex/gvisor@v0.0.0-20240320004321-933faba989ec/pkg/pool/pool.go (about)

     1  // Copyright 2018 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Package pool provides a trivial integer pool.
    16  package pool
    17  
    18  import (
    19  	"github.com/metacubex/gvisor/pkg/sync"
    20  )
    21  
    22  // Pool is a simple allocator.
    23  type Pool struct {
    24  	mu sync.Mutex
    25  
    26  	// cache is the set of returned values.
    27  	cache []uint64
    28  
    29  	// Start is the starting value (if needed).
    30  	Start uint64
    31  
    32  	// max is the current maximum issued.
    33  	max uint64
    34  
    35  	// Limit is the upper limit.
    36  	Limit uint64
    37  }
    38  
    39  // Get gets a value from the pool.
    40  func (p *Pool) Get() (uint64, bool) {
    41  	p.mu.Lock()
    42  	defer p.mu.Unlock()
    43  
    44  	// Anything cached?
    45  	if len(p.cache) > 0 {
    46  		v := p.cache[len(p.cache)-1]
    47  		p.cache = p.cache[:len(p.cache)-1]
    48  		return v, true
    49  	}
    50  
    51  	// Over the limit?
    52  	if p.Start == p.Limit {
    53  		return 0, false
    54  	}
    55  
    56  	// Generate a new value.
    57  	v := p.Start
    58  	p.Start++
    59  	return v, true
    60  }
    61  
    62  // Put returns a value to the pool.
    63  func (p *Pool) Put(v uint64) {
    64  	p.mu.Lock()
    65  	p.cache = append(p.cache, v)
    66  	p.mu.Unlock()
    67  }