github.com/cloudwego/kitex@v0.9.0/pkg/utils/max_counter.go (about)

     1  /*
     2   * Copyright 2021 CloudWeGo Authors
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package utils
    18  
    19  import "sync/atomic"
    20  
    21  // MaxCounter is an integer counter with upper limit.
    22  type MaxCounter struct {
    23  	now int64
    24  	max int
    25  }
    26  
    27  // NewMaxCounter returns a new MaxCounter.
    28  func NewMaxCounter(max int) *MaxCounter {
    29  	return &MaxCounter{
    30  		max: max,
    31  	}
    32  }
    33  
    34  // Inc increases the counter by one and returns if the operation succeeds.
    35  func (cl *MaxCounter) Inc() bool {
    36  	if atomic.AddInt64(&cl.now, 1) > int64(cl.max) {
    37  		atomic.AddInt64(&cl.now, -1)
    38  		return false
    39  	}
    40  	return true
    41  }
    42  
    43  // Dec decreases the counter by one.
    44  func (cl *MaxCounter) Dec() {
    45  	atomic.AddInt64(&cl.now, -1)
    46  }
    47  
    48  // DecN decreases the counter by n.
    49  func (cl *MaxCounter) DecN(n int64) {
    50  	atomic.AddInt64(&cl.now, -n)
    51  }
    52  
    53  func (cl *MaxCounter) Now() int64 {
    54  	return atomic.LoadInt64(&cl.now)
    55  }