非复制istringstream [英] non-copying istringstream

问题描述

因此 istringstream 在初始化时复制字符串的内容，例如

So istringstream copies the contents of a string when initialised, e.g

string moo("one two three four");
istringstream iss(moo.c_str());

我想知道是否有一种方法使 std :: istringstream 使用给定的 c_str 作为其缓冲区而不复制任何东西。这样，在将 std :: istringstream& 传递给需要 istream& 作为参数。

I was wondering if there's a way to make std::istringstream use the given c_str as its buffer without copying things. This way, it won't have to copy large bits of memory before passing the std::istringstream& to functions that take istream& as an argument.

我一直想做的是转换一些函数，只需要 std :: ifstream& / code>参数（它们大多是解析器）转换为采用 istream& 。

What I've been trying to do is convert some functions which only take std::ifstream& arguments (they're mostly parsers) into taking istream& as well. Would I have to make my own istream subclass for this?

推荐答案

我需要为自己创建 istream 编写从给定内存区域读取的基本 std :: streambuf 类是相当微不足道的。然后，您可以从中构造一个 istream ，并从中读取。

It's fairly trivial to write a basic std::streambuf class that reads from a given memory area. You can then construct an istream from this and read from that.

http://stackoverflow.com/questions/1448467/initializing-ac-stdistringstream-from-an -in-memory-buffer / 1449527＃1449527

请注意，缓冲区的生命周期指向 c_str code>是非常有限，虽然，并不能保证调用 c_str（）想要导致一些复制，虽然我不知道任何实现

Note that the lifetime of the buffer pointed to be c_str() is very limited, though, and there's no guarantee that a call to c_str() want cause some copying although I don't know of any implementations where it does.

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