有没有一种简单的方法来获取用C ++打印的字符数？ [英] Is there a simple way to get the number of characters printed in C++?

问题描述

printf（...）返回输出到控制台的字符数，这对设计某些程序很有帮助。因此，我想知道C ++中是否存在类似功能，因为cout<<是没有返回类型的运算符（至少从我的理解）。

printf(...) returns the number of characters output to the console, which I find very helpful in designing certain programs. So, I was wondering if there is a similar feature in C++, since the cout<< is an operator without a return type (at least from what I understand of it).

推荐答案

您可以将自己的 streambuf 关联到 cout 来计算字符。

You can associate your own streambuf to cout to count the characters.

这是包装所有内容的类：

This is the class that wraps it all:

class CCountChars {
public:
    CCountChars(ostream &s1) : m_s1(s1), m_buf(s1.rdbuf()), m_s1OrigBuf(s1.rdbuf(&m_buf)) {}
    ~CCountChars() { m_s1.rdbuf(m_s1OrigBuf); m_s1 << endl << "output " << m_buf.GetCount() << " chars" << endl; }

private:
    CCountChars &operator =(CCountChars &rhs) = delete;

    class CCountCharsBuf : public streambuf {
    public:
        CCountCharsBuf(streambuf* sb1) : m_sb1(sb1) {}
        size_t GetCount() const { return m_count; }

    protected:
        virtual int_type overflow(int_type c) {
            if (streambuf::traits_type::eq_int_type(c, streambuf::traits_type::eof()))
                return c;
            else {
                ++m_count;
                return m_sb1->sputc((streambuf::char_type)c);
            }
        }
        virtual int sync() {
            return m_sb1->pubsync();
        }

        streambuf *m_sb1;
        size_t m_count = 0;
    };

    ostream &m_s1;
    CCountCharsBuf m_buf;
    streambuf * const m_s1OrigBuf;
};

您可以这样使用：

{
    CCountChars c(cout);
    cout << "bla" << 3 << endl;
}

当对象实例存在时，它将计算cout输出的所有字符。

While the object instance exists it counts all characters output by cout.

请记住，这只会计算通过 cout 输出的字符，而不是通过 printf打印的字符。

Keep in mind that this will only count characters output via cout, not characters printed with printf.

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