如何检查文件是否是 gzip 压缩的?

问题描述

我有一个 C/C++ 程序，它需要读取一个文件，这个文件可能是也可能不是 gzip 压缩的.我知道我们可以使用 zlib 中的 gzread() 来读取压缩文件和未压缩文件 - 但是，我只想在文件是 gzip 压缩文件时使用 zlib 函数(出于性能原因).

I have a C / C++ program which needs to read in a file that may or may not be gzip compressed. I know we can use gzread() from zlib to read in both compressed and uncompressed files - however, I want to use the zlib functions ONLY if the file is gzip compressed (for performance reasons).

那么有没有办法以编程方式检测或检查某个文件是否是从 C/C++ 压缩的?

So is there any way to programatically detect or check if a certain file is gzipped from C / C++?

推荐答案

文件开头有一个幻数.只需读取前两个字节并检查它们是否等于 0x1f8b.

There is a magic number at the beginning of the file. Just read the first two bytes and check if they are equal to 0x1f8b.

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