我碰到下面的代碼從Writing Large, Responsive .NET Framework Apps。StringBuilder with Caching,ThreadStatic
下面的代碼使用StringBuilder
創建了一個字符串,如SomeType<T1, T2, T3>
,並演示緩存StringBuilder
以提高性能。
public void Test3()
{
Console.WriteLine(GenerateFullTypeName("SomeType", 3));
}
// Constructs a name like "SomeType<T1, T2, T3>"
public string GenerateFullTypeName(string name, int arity)
{
//StringBuilder sb = new StringBuilder();
StringBuilder sb = AcquireBuilder();
sb.Append(name);
if (arity != 0)
{
sb.Append("<");
for (int i = 1; i < arity; i++)
{
sb.Append("T"); sb.Append(i.ToString()); sb.Append(", ");
}
sb.Append("T"); sb.Append(arity.ToString()); sb.Append(">");
}
//return sb.ToString();
/* Use sb as before */
return GetStringAndReleaseBuilder(sb);
}
[ThreadStatic]
private static StringBuilder cachedStringBuilder;
private static StringBuilder AcquireBuilder()
{
StringBuilder result = cachedStringBuilder;
if (result == null)
{
return new StringBuilder();
}
result.Clear();
cachedStringBuilder = null;
return result;
}
private static string GetStringAndReleaseBuilder(StringBuilder sb)
{
string result = sb.ToString();
cachedStringBuilder = sb;
return result;
}
但是,下面的兩個修改方法在緩存StringBuilder方面更好嗎?只有AcquireBuilder需要知道如何緩存它。
private static StringBuilder AcquireBuilder()
{
StringBuilder result = cachedStringBuilder;
if (result == null)
{
//unlike the method above, assign it to the cache
cachedStringBuilder = result = new StringBuilder();
return result;
}
result.Clear();
//no need to null it
// cachedStringBuilder = null;
return result;
}
private static string GetStringAndReleaseBuilder(StringBuilder sb)
{
string result = sb.ToString();
//other method does not to assign it again.
//cachedStringBuilder = sb;
return result;
}
另一個問題是原始方法不是線程安全的,爲什麼ThreadStatic在演示中使用?
下面是'AcquireBuilder'的更好實現:['ObjectPool .Get'](https://docs.microsoft.com/aspnet/core/api/microsoft.extensions.objectpool.objectpool-1) 。這是ASP.NET自己使用的;我不確定爲什麼作者覺得有必要提出一些原創的東西。 –
這已經[內置於框架](https://stackoverflow.com/questions/20029868/understanding-of-net-internal-stringbuildercache-class-configuration)。看起來很相似。請確保您需要它,請記住,沒有過期策略的緩存是內存泄漏。 –