go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/logdog/client/butler/bundler/counter.go (about)

     1  // Copyright 2015 The LUCI 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 bundler
    16  
    17  import (
    18  	"sync/atomic"
    19  )
    20  
    21  // counter is a goroutine-safe monotonically-increasing counter.
    22  type counter struct {
    23  	// current is the current counter value.
    24  	//
    25  	// It must be the first field in the struct to ensure it's 64-bit aligned
    26  	// for atomic operations.
    27  	current int64
    28  }
    29  
    30  func (c *counter) next() int64 {
    31  	// AddInt64 returns the value + 1, so subtract one to get its previous value
    32  	// (current counter value).
    33  	return atomic.AddInt64(&c.current, 1) - 1
    34  }