Skip to content
Permalink
master
Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?
Go to file
 
 
Cannot retrieve contributors at this time
// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
/*============================================================
**
** Class: StringBuilderCache
**
** Purpose: provide a cached reusable instance of stringbuilder
** per thread it's an optimisation that reduces the
** number of instances constructed and collected.
**
** Acquire - is used to get a string builder to use of a
** particular size. It can be called any number of
** times, if a stringbuilder is in the cache then
** it will be returned and the cache emptied.
** subsequent calls will return a new stringbuilder.
**
** A StringBuilder instance is cached in
** Thread Local Storage and so there is one per thread
**
** Release - Place the specified builder in the cache if it is
** not too big.
** The stringbuilder should not be used after it has
** been released.
** Unbalanced Releases are perfectly acceptable. It
** will merely cause the runtime to create a new
** stringbuilder next time Acquire is called.
**
** GetStringAndRelease
** - ToString() the stringbuilder, Release it to the
** cache and return the resulting string
**
===========================================================*/
using System.Threading;
namespace System.Text
{
internal static class StringBuilderCache
{
// The value 360 was chosen in discussion with performance experts as a compromise between using
// as litle memory (per thread) as possible and still covering a large part of short-lived
// StringBuilder creations on the startup path of VS designers.
private const int MAX_BUILDER_SIZE = 360;
[ThreadStatic]
private static StringBuilder CachedInstance;
public static StringBuilder Acquire(int capacity = StringBuilder.DefaultCapacity)
{
if(capacity <= MAX_BUILDER_SIZE)
{
StringBuilder sb = StringBuilderCache.CachedInstance;
if (sb != null)
{
// Avoid stringbuilder block fragmentation by getting a new StringBuilder
// when the requested size is larger than the current capacity
if(capacity <= sb.Capacity)
{
StringBuilderCache.CachedInstance = null;
sb.Clear();
return sb;
}
}
}
return new StringBuilder(capacity);
}
public static void Release(StringBuilder sb)
{
if (sb.Capacity <= MAX_BUILDER_SIZE)
{
StringBuilderCache.CachedInstance = sb;
}
}
public static string GetStringAndRelease(StringBuilder sb)
{
string result = sb.ToString();
Release(sb);
return result;
}
}
}