在.Net 7中StringBuilder Insert方法优化
前言
在2月份中更新Runtime源码,发现对StingBuilder中的Insert方法进行了优化.放了一个月,看这一块代码没有继续调整.这个优化代码较少.
Insert优化主要在值类型(bool/sbyte/byte/int/long/float/double/decimal/uint/ulong),增加一个泛型方法InsertSpanFormattable.
private StringBuilder InsertSpanFormattable<T>(int index, T value) where T : ISpanFormattable
{
Debug.Assert(typeof(T).Assembly.Equals(typeof(object).Assembly), "Implementation trusts the results of TryFormat because T is expected to be something known");
Span<char> buffer = stackalloc char[256]; //在栈上分配内存
//由每个值类型的TryFormat转为字符串
if (value.TryFormat(buffer, out int charsWritten, format: default, provider: null))
{
//通过接收string参数的Insert添加到内部的字符数组
return Insert(index, buffer.Slice(0, charsWritten), 1);
}
return Insert(index, value.ToString(), 1);
}性能基准测试
[DisassemblyDiagnoser(printSource: true, maxDepth: 2)]
public class StringBuilderInsertTest
{
public StringBuilder sb = new StringBuilder(2048);
public StringBuilder sb1 = new StringBuilder(2048);
[Benchmark]
public void IntTest()
{
for (int times = 0; times < 5; times++)
{
for (int i = 0; i < 1024; i++)
{
sb.Insert(0, i);
}
sb.Clear();
}
}
[Benchmark]
public void LongTest()
{
for (int times = 0; times < 5; times++)
{
for (long i = 0; i < 1024; i++)
{
sb1.Insert(0, i);
}
sb1.Clear();
}
}
}简单对Int和Long两个基础值类型进行基准测试,StringBuilder初始大小为2048.
看测试结果发现int类型只是性能持平,而long类型竟然下降了一些,还好这是预览版.
秋风
2022-04-05