如果 NUL 终止符不在切片的末尾，如何从 NUL 终止的字节切片中获取“&str"? [英] How to get a '&str' from a NUL-terminated byte slice if the NUL terminator isn't at the end of the slice?

问题描述

虽然 CStr 通常用于 FFI，但我正在从 &[u8] 读取，它以 NUL 结尾并确保为有效的 UTF-8，因此无需检查.

While CStr is typically used for FFI, I am reading from a &[u8] which is NUL-terminated and is ensured to be valid UTF-8 so no checks are needed.

然而，NUL 终止符不一定在切片的末尾.将其作为 &str 获取的好方法是什么?

However the NUL terminator isn't necessarily at the end of the slice. What's a good way to get this as a &str?

建议使用 CStr::from_bytes_with_nul，但这会在内部 \0 字符上出现恐慌(当 \0 不是t 最后一个字符).

It was suggested to use CStr::from_bytes_with_nul, but this panics on an interior \0 character (when the \0 isn't the last character).

推荐答案

我会使用迭代器适配器来查找第一个零字节的索引:

I would use iterator adaptors to find the index of the first zero byte:

pub unsafe fn str_from_u8_nul_utf8_unchecked(utf8_src: &[u8]) -> &str {
    let nul_range_end = utf8_src.iter()
        .position(|&c| c == b'\0')
        .unwrap_or(utf8_src.len()); // default to length if no `\0` present
    ::std::str::from_utf8_unchecked(&utf8_src[0..nul_range_end])
}

这有一个主要优点，就是要求一个人捕获所有情况(比如数组中没有 0).

This has the major advantage of requiring one to catch all cases (like no 0 in the array).

如果您想要检查格式良好的 UTF-8 的版本:

If you want the version that checks for well-formed UTF-8:

pub fn str_from_u8_nul_utf8(utf8_src: &[u8]) -> Result<&str, std::str::Utf8Error> {
    let nul_range_end = utf8_src.iter()
        .position(|&c| c == b'\0')
        .unwrap_or(utf8_src.len()); // default to length if no `\0` present
    ::std::str::from_utf8(&utf8_src[0..nul_range_end])
}

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