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feat: 添加copy on write list实现 (#260)
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* feat: 添加copy on write list实现

* fix: 优化删除逻辑
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xinghe903 authored Sep 28, 2024
1 parent 6fdf3ad commit 44dea05
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148 changes: 148 additions & 0 deletions list/copy_on_write_array_list.go
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// Copyright 2021 ecodeclub
//
// 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 list

import (
"sync"

"github.com/ecodeclub/ekit/internal/errs"
"github.com/ecodeclub/ekit/internal/slice"
)

var (
_ List[any] = &CopyOnWriteArrayList[any]{}
)

// CopyOnWriteArrayList 基于切片的简单封装 写时加锁,读不加锁,适合于读多写少场景
type CopyOnWriteArrayList[T any] struct {
vals []T
mutex *sync.Mutex
}

// NewCopyOnWriteArrayList
func NewCopyOnWriteArrayList[T any]() *CopyOnWriteArrayList[T] {
m := &sync.Mutex{}
return &CopyOnWriteArrayList[T]{
vals: make([]T, 0),
mutex: m,
}
}

// NewCopyOnWriteArrayListOf 直接使用 ts,会执行复制
func NewCopyOnWriteArrayListOf[T any](ts []T) *CopyOnWriteArrayList[T] {
items := make([]T, len(ts))
copy(items, ts)
m := &sync.Mutex{}
return &CopyOnWriteArrayList[T]{
vals: items,
mutex: m,
}
}

func (a *CopyOnWriteArrayList[T]) Get(index int) (t T, e error) {
l := a.Len()
if index < 0 || index >= l {
return t, errs.NewErrIndexOutOfRange(l, index)
}
return a.vals[index], e
}

// Append 往CopyOnWriteArrayList里追加数据
func (a *CopyOnWriteArrayList[T]) Append(ts ...T) error {
a.mutex.Lock()
defer a.mutex.Unlock()
n := len(a.vals)
newItems := make([]T, n, n+len(ts))
copy(newItems, a.vals)
newItems = append(newItems, ts...)
a.vals = newItems
return nil
}

// Add 在CopyOnWriteArrayList下标为index的位置插入一个元素
// 当index等于CopyOnWriteArrayList长度等同于append
func (a *CopyOnWriteArrayList[T]) Add(index int, t T) (err error) {
a.mutex.Lock()
defer a.mutex.Unlock()
n := len(a.vals)
newItems := make([]T, n, n+1)
copy(newItems, a.vals)
newItems, err = slice.Add(newItems, t, index)
a.vals = newItems
return
}

// Set 设置CopyOnWriteArrayList里index位置的值为t
func (a *CopyOnWriteArrayList[T]) Set(index int, t T) error {
a.mutex.Lock()
defer a.mutex.Unlock()
n := len(a.vals)
if index >= n || index < 0 {
return errs.NewErrIndexOutOfRange(n, index)
}
newItems := make([]T, n)
copy(newItems, a.vals)
newItems[index] = t
a.vals = newItems
return nil
}

// 这里不涉及缩容,每次都是当前内容长度申请的数组容量
func (a *CopyOnWriteArrayList[T]) Delete(index int) (T, error) {
a.mutex.Lock()
defer a.mutex.Unlock()
var ret T
n := len(a.vals)
if index >= n || index < 0 {
return ret, errs.NewErrIndexOutOfRange(n, index)
}
newItems := make([]T, len(a.vals)-1)
item := 0
for i, v := range a.vals {
if i == index {
ret = v
continue
}
newItems[item] = v
item++
}
a.vals = newItems
return ret, nil
}

func (a *CopyOnWriteArrayList[T]) Len() int {
return len(a.vals)
}

func (a *CopyOnWriteArrayList[T]) Cap() int {
return cap(a.vals)
}

func (a *CopyOnWriteArrayList[T]) Range(fn func(index int, t T) error) error {
for key, value := range a.vals {
e := fn(key, value)
if e != nil {
return e
}
}
return nil
}

func (a *CopyOnWriteArrayList[T]) AsSlice() []T {
a.mutex.Lock()
defer a.mutex.Unlock()
res := make([]T, len(a.vals))
copy(res, a.vals)
return res
}
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