字符串优化加强版–StringPool
之前写过一篇string字符串优化相关的文章，但是里面是使用一个static静态变量。先看下之前的代码
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Lemon
{
public class QString
{
private static StringBuilder CommonStringBuilder = new StringBuilder();
private static StringBuilder InternalStringBuilder = new StringBuilder();
public static StringBuilder GetStringBuilder()
{
CommonStringBuilder.Remove(0, CommonStringBuilder.Length);
return CommonStringBuilder;
}
public static string Concat(string s1, string s2)
{
InternalStringBuilder.Remove(0, InternalStringBuilder.Length);
InternalStringBuilder.Append(s1);
InternalStringBuilder.Append(s2);
return InternalStringBuilder.ToString();
}
public static string Concat(string s1, string s2, string s3)
{
InternalStringBuilder.Remove(0, InternalStringBuilder.Length);
InternalStringBuilder.Append(s1);
InternalStringBuilder.Append(s2);
InternalStringBuilder.Append(s3);
return InternalStringBuilder.ToString();
}
public static string Format(string src, params object[] args)
{
InternalStringBuilder.Remove(0, InternalStringBuilder.Length);
InternalStringBuilder.AppendFormat(src, args);
return InternalStringBuilder.ToString();
}
}
}
QString里面的stringbuilder一共是两个，一个是给外部用的是CommonStringBuilder，一个是内部使用的InternalStringBuilder。
private static StringBuilder CommonStringBuilder = new StringBuilder();
private static StringBuilder InternalStringBuilder = new StringBuilder();
之前一直是在Unity里面主线程上面使用的，没有用到多线程。昨天写东西用到了多线程，因此这里仅一个静态的stringbuilder已经无法满足需求了，因此StringPool产生了，底层实现其实是对stringbuilder使用了pool形式。
大家还记得之前的ObjectPool的文章么，今天就使用ObjectPool来封装一个StringBuilderPool。先贴上ObjectPool的代码。
/**
* Author：onelei
* Copyright © 2019 - 2020 ONELEI. All Rights Reserved
*/
using System.Collections.Generic;
using UnityEngine.Events;
public class ObjectPool<T> where T : new()
{
private readonly Stack<T> m_Stack = new Stack<T>();
private readonly UnityAction<T> m_ActionOnGet;
private readonly UnityAction<T> m_ActionOnRelease;
public int countAll { get; private set; }
public int countActive { get { return countAll - countInactive; } }
public int countInactive { get { return m_Stack.Count; } }
public ObjectPool(UnityAction<T> actionOnGet, UnityAction<T> actionOnRelease)
{
m_ActionOnGet = actionOnGet;
m_ActionOnRelease = actionOnRelease;
}
public T Get()
{
T element;
if (m_Stack.Count == 0)
{
element = new T();
countAll++;
}
else
{
element = m_Stack.Pop();
}
if (m_ActionOnGet != null)
m_ActionOnGet(element);
return element;
}
public void Release(T element)
{
if (m_Stack.Count > 0 && ReferenceEquals(m_Stack.Peek(), element))
QLog.LogError("Internal error. Trying to destroy object that is already released to pool.");
if (m_ActionOnRelease != null)
m_ActionOnRelease(element);
m_Stack.Push(element);
}
}
ObjectPool代码来自UGUI源码。
下面我们看看StringPool的代码如何实现
/**
* Author：onelei
* Copyright © 2019 - 2020 ONELEI. All Rights Reserved
*/
using System.Text;
public static class StringPool
{
private static int MaxCount = 100;
// Object pool to avoid allocations.
private static readonly ObjectPool<StringBuilder> Pool = new ObjectPool<StringBuilder>(Clear, null);
static void Clear(StringBuilder s)
{
if (Pool.countAll >= MaxCount)
{
QLog.LogError("Pool count reach to MaxCount.");
}
s.Remove(0, s.Length);
}
public static StringBuilder GetStringBuilder()
{
StringBuilder stringBuilder = Pool.Get();
return stringBuilder;
}
public static void Release(StringBuilder toRelease)
{
if (Pool.countAll >= MaxCount)
{
QLog.LogError("Pool count reach to MaxCount.");
}
Pool.Release(toRelease);
}
public static string Concat(string s1, string s2)
{
StringBuilder stringBuilder = Pool.Get();
stringBuilder.Append(s1);
stringBuilder.Append(s2);
string result = stringBuilder.ToString();
Release(stringBuilder);
return result;
}
public static string Concat(string s1, string s2, string s3)
{
StringBuilder stringBuilder = Pool.Get();
stringBuilder.Append(s1);
stringBuilder.Append(s2);
stringBuilder.Append(s3);
string result = stringBuilder.ToString();
Release(stringBuilder);
return result;
}
public static string Format(string src, params object[] args)
{
StringBuilder stringBuilder = Pool.Get();
stringBuilder.Remove(0, stringBuilder.Length);
stringBuilder.AppendFormat(src, args);
string result = stringBuilder.ToString();
Release(stringBuilder);
return result;
}
}
我们在StringPool里面使用ObjectPool保存了一个Pool对象池。
// Object pool to avoid allocations.
private static readonly ObjectPool<StringBuilder> Pool = new ObjectPool<StringBuilder>(Clear, null);
static void Clear(StringBuilder s) { s.Remove(0, s.Length); }
同时在Pool的Get函数里面传入Clear函数，在获取到StringBuilder的时候执行Clear函数清除里面的数据。
接下来我们来看如何使用，其实和之前区别并不大，函数接口都没有改动，我们只需要改函数的内部实现即可，先看下Concat函数
public static string Concat(string s1, string s2)
{
StringBuilder stringBuilder = Pool.Get();
stringBuilder.Append(s1);
stringBuilder.Append(s2);
string result = stringBuilder.ToString();
Release(stringBuilder);
return result;
}
首先Pool.Get()在缓存池里面获取一个StringBuilder变量，在操作好之后执行Release函数，将其放回池中。同理Format函数亦是如此。
我们注意到ObjectPool里面有这三个变量
public int countAll { get; private set; }
public int countActive { get { return countAll - countInactive; } }
public int countInactive { get { return m_Stack.Count; } }
countAll是在每次new一个StringBuilder的时候自动加一，也就是池中的对象总数。
countInactive是在每次Release的时候放回m_Stack里面的，也就是被放回池中的，未使用对象。
剩下的countActive就是已经被利用的对象数量。
我们为了防止池没有被合理使用，我们可以设置一个池中的对象总数，作为代码防护，防止内存泄漏。大部分情况下是对象在用完之后，没有被及时执行Release函数，导致池中不断的new一个对象出来，因此我们可以在Get函数里面做一个安全判断，当超过池中最大容量的时候，抛出一个错误。
static void Clear(StringBuilder s)
{
if (Pool.countAll >= MaxCount)
{
QLog.LogError("Pool count reach to MaxCount.");
}
s.Remove(0, s.Length);
}
我们在Get的函数的回调函数Clear里面添加以上判断即可。
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