拥有流的streambuf持续到流的破坏之外吗? [英] Having a stream's streambuf persist beyond stream's destruction?

问题描述

在源流的销毁销毁后，是否有可能使流的 streambuf 持久存在?

Is it possible to have a stream's streambuf persist after the destruction of its originating stream's destruction?

streambuf* f() {
    ifstream my_stream;
    // ...
    return my_stream.rdbuf();
}

void g() {
    streambuf *s = f();
    // ...
    ifstream my_new_stream;
    my_new_stream.rdbuf( s );
}

即，我希望指向 f()返回的 streambuf 对象的指针即使在 my_stream 超出范围后也保持有效.稍后，我想将其他流的 streambuf 设置为保存的 streambuf .

I.e., I want the pointer to the streambuf object returned by f() to remain valid even after my_stream goes out of scope. At some later time, I want to set some other stream's streambuf to the saved streambuf.

这可能吗?如果可以，怎么办?

Is this possible? If so, how?

推荐答案

这是不可能的. std :: ifstream 构造，拥有并销毁其缓冲区.通过 rdbuf 导出"的唯一原因是允许重定向 std :: cin 等.在GNU实现中，缓冲区是一个简单的成员(不是指针).

It's not possible. std::ifstream constructs, owns and destroys its buffer. The only reason it's "exported" through rdbuf is to allow redirection of std::cin etc. In the GNU implementation, the buffer is a simple member (not a pointer).

std :: ifstream 不会导出带有参数的 rdbuf()成员.它的父类之一可以，但是应该重新定义 std :: basic_ifstream 中带有签名的 rdbuf 的影子

std::ifstream does not export the rdbuf() member with an argument. One of its parent classes does, but this should be shadowed by the redefinition of rdbuf in std::basic_ifstream with signature

std::filebuf *rdbuf() const;

std :: filebuf 也是不可复制的.

( rdbuf(std :: streambuf *)成员可以通过强制转换为 std :: ios 来检索.使用此方法会导致熟悉的鼻恶魔.)

(The rdbuf(std::streambuf *) member can be retrieved by casting to std::ios. Using this will cause the familiar nasal demons.)

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