C ++格式化库通常可以回退到* sprintf的数字格式化？ [英] Do C++ formatting libraries generally fall back to *sprintf for numeric formatting?

问题描述

我想知道所有C ++格式化库最终是否会返回到 * sprintf 函数来格式化数字。

我问这是因为：

• 查看Visual C ++附带的iostreams库，我可以看到数字输入到stream将会被格式化为 sprintf_s 。


• Boost.Format只是使用可用的iostreams库。 li>
  

I am wondering whether "all" C++ formatting libraries eventually fall back to a *sprintf function to format numbers.

I am asking this because:

• Looking at the iostreams library that comes with Visual C++, I can see that numbers input into a stream will eventuall be formatted with sprintf_s.
• Boost.Format just uses the available iostreams library as far as I can tell.
• FastFormat eventually uses vsprintf to format a number.

So, are there iostreams implementations that do not use *sprintf and do the formatting themselves? Are there other formatting libraries that do not forward formatting of numbers to *sprintf family of functions?

I would appreciate answers in the form of:

• No: implementation XY uses ABC to format numbers
• Yes: all other (e.g. iostreams) implementations I know (X, Y, Z) also forward number formatting to stdio, because ...

Please avoid overly speculative answers.

解决方案

Boost Spirit doesn't use *printf, as can be seen from the code (real.hpp and int.hpp) and the benchmarks for e.g. ints and doubles.

The benchmark pits Boost Spirit Karma's generators against Boost.Format against sprintf and std::stringstream. Only for gcc compilers does the performance of sprintf come close in that benchmark. Otherwise, Boost Spirit is the clear winner.

• http://www.boost.org/doc/libs/1_47_0/libs/spirit/doc/html/spirit/karma/performance_measurements/numeric_performance.html

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