Question

有谁知道我如何打印和计算我打印的字符数？

说我有一个号码，我通过printf或cout打印。我怎么能算出我打印出来的实际位数？

Answer 1

根据printf man page，printf返回打印的字符数。

int count = printf("%d", 1000);

如果遇到输出错误，则返回负值。

Answer 2

printf返回它打印的字符数

Answer 3

这是滥用Locale在senes后面进行计数的另一种创造性方法这允许您正常使用流，本地将为您记录输出。

这不是生产就绪代码，只是一个概念证明，以展示如何做到这一点：

#include <locale>
#include <iostream>
#include <fstream>

class Counter: public std::codecvt<char,char,std::char_traits<char>::state_type>
{
    public:
    Counter(int& count)
        :m_count(&count)
    {}
    private:
    typedef std::codecvt<char,char,std::char_traits<char>::state_type> MyType;
    typedef MyType::state_type          state_type;
    typedef MyType::result              result;

    virtual bool   do_always_noconv() const throw()
    {
        return false;
    }
    virtual result do_out ( state_type& state,
                    const char* fr, const char* fe, const char*& fn,
                    char*       to, char*       te, char*&       tn ) const
    {
        // Count the number of characters that will be out on the stream
        (*m_count) += (fe - fr);

        // Use the default do_out (which just copies when internal and external are char)
        return MyType::do_out(state,fr,fe,fn,to,te,tn);
    }
    private:
        int*    m_count;

};




int main()
{
    // The variable to store the count in
    int             count   = 0;
    // A local object that contains the counting facet.
    // The counting facet will record output into count.
    std::locale     countingLocale(std::cout.getloc(), new Counter(count));

    std::ofstream   data;
    data.imbue(countingLocale);   // Impue the stream before opening.
    data.open("Plop");
    data << "Stop" << std::endl;

    std::cout << "Count: " << count  << "\n";

    // This should also work with std::cout
    std::cout.imbue(countingLocale)
    // Unfortunately there is a bug in the locale code for me that stops this working.

}

Answer 4

如果您想使用ostream，pcount()会返回放置的字符数。

Answer 5

使用字符串流预先转换，然后轮询该长度。

如何计算作为输出打印的字符数？

5 个答案: