github.com/aaabigfish/gopkg@v1.1.0/internal/benchmark/msq/msq.go (about)

     1  // Copyright 2021 ByteDance Inc.
     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 msq
    16  
    17  import (
    18  	"sync"
    19  	"sync/atomic"
    20  	"unsafe"
    21  )
    22  
    23  var msqv1pool *sync.Pool = &sync.Pool{New: func() interface{} { return new(msqv1node) }}
    24  
    25  type MSQueue struct {
    26  	head unsafe.Pointer // *msqv1node
    27  	tail unsafe.Pointer // *msqv1node
    28  }
    29  
    30  type msqv1node struct {
    31  	value uint64
    32  	next  unsafe.Pointer // *msqv1node
    33  }
    34  
    35  func New() *MSQueue {
    36  	node := unsafe.Pointer(new(msqv1node))
    37  	return &MSQueue{head: node, tail: node}
    38  }
    39  
    40  func loadMSQPointer(p *unsafe.Pointer) *msqv1node {
    41  	return (*msqv1node)(atomic.LoadPointer(p))
    42  }
    43  
    44  func (q *MSQueue) Enqueue(value uint64) bool {
    45  	node := &msqv1node{value: value}
    46  	for {
    47  		tail := atomic.LoadPointer(&q.tail)
    48  		tailstruct := (*msqv1node)(tail)
    49  		next := atomic.LoadPointer(&tailstruct.next)
    50  		if tail == atomic.LoadPointer(&q.tail) {
    51  			if next == nil {
    52  				// tail.next is empty, inset new node
    53  				if atomic.CompareAndSwapPointer(&tailstruct.next, next, unsafe.Pointer(node)) {
    54  					atomic.CompareAndSwapPointer(&q.tail, tail, unsafe.Pointer(node))
    55  					break
    56  				}
    57  			} else {
    58  				atomic.CompareAndSwapPointer(&q.tail, tail, next)
    59  			}
    60  		}
    61  	}
    62  	return true
    63  }
    64  
    65  func (q *MSQueue) Dequeue() (value uint64, ok bool) {
    66  	for {
    67  		head := atomic.LoadPointer(&q.head)
    68  		tail := atomic.LoadPointer(&q.tail)
    69  		headstruct := (*msqv1node)(head)
    70  		next := atomic.LoadPointer(&headstruct.next)
    71  		if head == atomic.LoadPointer(&q.head) {
    72  			if head == tail {
    73  				if next == nil {
    74  					return 0, false
    75  				}
    76  				atomic.CompareAndSwapPointer(&q.tail, tail, next)
    77  			} else {
    78  				value = ((*msqv1node)(next)).value
    79  				if atomic.CompareAndSwapPointer(&q.head, head, next) {
    80  					return value, true
    81  				}
    82  			}
    83  		}
    84  	}
    85  }