为什么的snprintf速度比ostringstream或者是什么呢？ [英] Why is snprintf faster than ostringstream or is it?

问题描述

我听说的snprintf比ostringstream更快。有没有人有任何经验？如果是的话，为什么它速度更快。

I read somewhere that snprintf is faster than ostringstream. Has anyone has any experiences with it? If yes why is it faster.

推荐答案

的std :: ostringstream 未要求，以比较慢，但是它一般是慢实现时。 FastFormat的网站有一些基准的。

std::ostringstream is not required to be slower, but it is generally slower when implemented. FastFormat's website has some benchmarks.

标准库的设计，流支持大于的snprintf 做得更多。该设计是为了可扩展的，并且包括被公开曝光的方法称为保护 虚拟方法。这使您可以从流类之一派生，以保证，如果你超载保护 ED方法，你会得到你想要的行为。我相信，一个编译器能够避免虚拟函数调用的开销，但我不知道，做任何的编译器。

The Standard library design for streams supports much more than snprintf does. The design is meant to be extensible, and includes protected virtual methods that are called by the publicly exposed methods. This allows you to derive from one of the stream classes, with the assurance that if you overload the protected method you will get the behavior you want. I believe that a compiler could avoid the overhead of the virtual function call, but I'm not aware of any compilers that do.

此外，流操作经常使用可扩展的缓冲区内;这意味着相对较慢的内存分配。

Additionally, stream operations often use growable buffers internally; which implies relatively slow memory allocations.

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