在std :: string中使用自定义分配器重新使用已分配的char缓冲区 [英] Using a custom allocator in std::string to re-use an already allocated char buffer

问题描述

我需要在std :: string对象中使用已经分配的char *缓冲区(带有字符串内容).经过一番研究，我发现这几乎是不可能的，并且std :: string总是具有自己的数据私有副本.我能想到的唯一剩下的方法是使用自定义分配器，该分配器将返回已分配的char缓冲区的地址.为此，std :: string应该仅使用分配器分配内存来保存其字符串数据，而别无其他.是这样吗

I need to use an already allocated char* buffer (with the string content) in a std::string object. After some research I found that this is almost impossible and std::string would have its own private copy of data always. The only remaining way I can think of to do this is to use a custom allocator that will return the address of the already allocated char buffer. For this to work, std::string should only use the allocator to allocate memory to hold its string data and for nothing else. Is this the case?

推荐答案

std::string是basic_string的typedef，已经已明确使用默认分配器. std::string无法使用其他分配器.即使使用所需的分配器创建了basic_string的新typedef，也无法将其传递给期望std::string的API.

std::string is a typedef of basic_string that already explicitly uses the default allocator. There is no way for std::string to use a different allocator. Even if you created a new typedef of basic_string with the allocator you wanted, it couldn't be passed to an API expecting a std::string.

不幸的是，除非您能够以某种方式放宽一个或多个要求，否则我看不到任何方法可以满足您在任何当前C ++标准中指定的所有需求.

Unfortunately I can't see any way to meet all the needs you've specified in any of the current C++ standards, unless you're able to somehow relax one or more of your requirements.

如果可能的话，一种可能的创造性解决方案是利用resize将原始" char*缓冲区分配为std::string .然后，您可以将该字符串swap放入新字符串中，以取得所有权.

One possible creative solution, if you're able to do so, would be to allocate your "orignal" char* buffer as a std::string, utilizing resize. Then you could swap that string into your new one to make it take ownership.

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