null ostream？ [英] null ostream?
问题描述
如何定义继承公共std :: ostream的空ostream和
忽略否则会输出的任何内容？
How do I define a null ostream that inherits publicly std::ostream and
ignores anything that would otherwise be output?
推荐答案
Angel Tsankov写道：
Angel Tsankov wrote:
如何定义一个公共std :: ostream继承的空ostream，
忽略任何原本会被输出的东西？
How do I define a null ostream that inherits publicly std::ostream and
ignores anything that would otherwise be output?
你可以创建一个写入/ dev / null的ofstream
不可移植，但很容易:)
You could create an ofstream that writes to /dev/null
Not portable, but easy :)
Angel Tsankov写道：
Angel Tsankov wrote:
如何定义一个公共std :: ostream继承的null ostream，
忽略否则会输出的任何东西？
How do I define a null ostream that inherits publicly std::ostream and
ignores anything that would otherwise be output?
我多年前从clc ++中抄袭了这个 - 不记得最初的
作者（但不是我）：
#include< streambuf>
#include< ostream>
template< class cT，阶级特征= std :: char_traits< cT> >
class basic_nullbuf：public std :: basic_streambuf< cT，traits> {
typename traits :: int_type overflow（typename traits :: int_type c）
{
return traits :: not_eof（c）; //表示成功
}
};
模板< class cT，class traits = std :: char_traits< cT> ; >
class basic_onullstream：public std :: basic_ostream< cT，traits> {
public：
basic_onullstream（）：
std :: basic_ios< cT，traits>（& m_sbuf），
std :: basic_ostream< cT，traits>（& m_sbuf）
{
init（& m_sbuf）;
私有：
basic_nullbuf< cT，traits> m_sbuf;
};
typedef basic_onullstream< char> onullstream;
typedef basic_onullstream< wchar_t> wonullstream;
祝你好运，
Tom
I cribbed this from c.l.c++ years ago - don''t remember the original
author (but it''s not me):
#include <streambuf>
#include <ostream>
template <class cT, class traits = std::char_traits<cT> >
class basic_nullbuf: public std::basic_streambuf<cT, traits> {
typename traits::int_type overflow(typename traits::int_type c)
{
return traits::not_eof(c); // indicate success
}
};
template <class cT, class traits = std::char_traits<cT> >
class basic_onullstream: public std::basic_ostream<cT, traits> {
public:
basic_onullstream():
std::basic_ios<cT, traits>(&m_sbuf),
std::basic_ostream<cT, traits>(&m_sbuf)
{
init(&m_sbuf);
}
private:
basic_nullbuf<cT, traits> m_sbuf;
};
typedef basic_onullstream<char> onullstream;
typedef basic_onullstream<wchar_t> wonullstream;
Best regards,
Tom
试试这个：
#include< iostream>
struct null_streambuf
：public std :: streambuf
{
无效溢出（char c）
{
}
};
int main（）
{
null_streambuf nullbuf;
//替换现有流的缓冲区
std :: streambuf * origbuf = std :: cout.rdbuf（& nullbuf）;
std :: cout<< 这会被遗忘;
std :: cout.rdbuf（origbuf）;
//创建null ostream
std :: ostream out（& nullbuf）;
out<< 这也被遗忘......;
}
- 彼得
try this:
#include <iostream>
struct null_streambuf
: public std::streambuf
{
void overflow(char c)
{
}
};
int main()
{
null_streambuf nullbuf;
// replace buffer of existing stream
std::streambuf * origbuf = std::cout.rdbuf(&nullbuf);
std::cout << "this goes into oblivion";
std::cout.rdbuf(origbuf);
// create null ostream
std::ostream out(&nullbuf);
out << "this goes into oblivion too...";
}
-- peter
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