c++ string_view

c++ 17的std::string_view是轻量级字符串视图类。测试下：

// 接收 string_view，零拷贝，支持传入多种字符串类型
static void process_text(std::string_view text) {
    std::cout << "字符串内容: " << text << ", 字符串长度: " << text.size() << std::endl;
}

void testString_view(void) { // 测试c++ 17的std::string_view
    std::string str = "Hello, vicky du";
    const char* cstr = "only you...";
    process_text(str);      // 传入 std::string
    process_text(cstr);     // 传入 C 风格字符串
    process_text("张良，萧何，陈平，周勃，韩信，樊哙，英布，彭越，卢绾");// 传入字面量

    std::string_view persons = "张良，萧何，陈平，周勃，韩信，樊哙，英布，彭越，卢绾";
    auto char_count = std::ranges::count_if(persons, [](char c) {
        return (c & 0xC0) != 0x80;
    }); 
    std::cout << "UTF‑8字符数量(汉字+标点): "<< char_count << std::endl;

    // 零拷贝截取子串
    std::string_view sv = "love u";
    std::string_view sub = sv.substr(2, 2); // 仅调整指针和长度
    std::cout << "子串: " << sub << std::endl;
}

运行：

ok.