问题描述
我有一些程序可以处理文件或内存缓冲区中的某些数据.我想提供统一的方式来处理这些情况.
I have some program handling some data either in a file or in some memory buffer. I want to provide uniform way to handle these cases.
我可以:1)映射文件，以便我们可以将它们作为内存缓冲区统一处理； 2)使用fopen和fmemopen创建FILE *，以便像FILE *一样统一访问它们.
I can either 1) mmap the file so we can handle them uniformly as a memory buffer; 2) create FILE* using fopen and fmemopen so access them uniformly as FILE*.
但是，我不能使用上述任何一种方法.我需要将它们都当作文件描述符处理，因为我使用的其中一个库仅采用文件描述符，并且对文件描述符执行mmap.
However, I can't use either ways above. I need to handle them both as file descriptor, because one of the libraries I use only takes file descriptor, and it does mmap on the file descriptor.
所以我的问题是，给定一个内存缓冲区(我们可以假定它与4K对齐)，我们能否获得由该内存缓冲区支持的文件描述符?我在其他问题中看到popen是一个答案，但我认为popen中的fd不能被映射.
So my question is, given a memory buffer (we can assume it is aligned to 4K), can we get a file descriptor that backed by this memory buffer? I saw in some other question popen is an answer but I don't think fd in popen can be mmap-ed.
推荐答案
您无法轻松地从某些内存区域"创建文件描述符(除了C标准库之外，这没有帮助).但是，您可以创建共享内存区域，以获取文件描述符作为回报.
You cannot easily create a file descriptor (other than a C standard library one, which is not helpful) from "some memory region". However, you can create a shared memory region, getting a file descriptor in return.
来自 shm_overview(7):
列出的接口中有mmap，这意味着您可以像对普通文件进行内存映射一样，对内存进行内存映射".
Among the listed interfaces is mmap, which means that you can "memory map" the shared memory the same as you would memory map a regular file.
因此，在两种情况下(文件或内存缓冲区)都使用mmap应该可以无缝运行，如果仅由您控制内存缓冲区"的创建.
Thus, using mmap for both situations (file or memory buffer) should work seamlessly, if only you control creation of that "memory buffer".
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