c++ - 有没有办法从 string_view 创建字符串流而不复制数据？

Question

我认为这是一个非常简单的问题。我特别想使用 std::get_time ，但它需要某种类型的流来使用。我正在 string_view 中传递数据，并且希望避免仅仅为了解析日期而复制它。

Answer 1

您可以使用 Boost.Iostreams 库轻松做到这一点:

#include <boost/iostreams/device/array.hpp>
#include <boost/iostreams/stream.hpp>

#include <iostream>
#include <string>

int main() {
    std::string_view buf{"hello\n"};
    boost::iostreams::stream<boost::iostreams::basic_array_source<char>> stream(buf.begin(), buf.size());

    std::string s;
    stream >> s;
    std::cout << s << '\n';
}

<小时/>

您应该可以使用 std::stringstream 来做到这一点和 std::basic_stringbuf<CharT,Traits,Allocator>::setbuf 但 C++ 标准未能满足其要求:

The effect [of setbuf] is implementation-defined: some implementations do nothing, while some implementations clear the std::string member currently used as the buffer and begin using the user-supplied character array of size n, whose first element is pointed to by s, as the buffer and the input/output character sequence.