Add CStr::from_bytes

[nagisa]

Add a CStr::from_bytes function with a following API (or something along the lines):

enum CStrFromBytesError {
     InteriorNullBytes,
     NoEndingNullByte,
};
impl CStr {
    fn from_bytes(bytes: &[u8]) -> Result<&CStr, CStrFromBytesError>;
}

Which converts a bytestring with a trailing null byte to a C string slice. If the slice does not have a trailing null byte or has a null byte in any position that’s not the last byte appropriate error is returned.

This is useful in APIs where a &CStr is expected and you can/want to pass in a static string (e.g. b"helloworld\0").

[cristicbz]

Ooh, big 👍. I've on occasion written my own Cow version of c-strings which allocates iff there's an interior nul or missing terminating nul.

[oberien]

IMO this should be implemented in a crate but not std. AFAIK there is no use case for converting a "rust"-string to a c-string other than passing it to other non-rust libraries, which need/expect a c-type string. Therefore having this conversion in std could result in "rust"-libs wanting to have a CStr, resulting in a lot of different types for each lib...

Is there some use case for CStr when writing solely in rust?

[nagisa]

CStr::from_bytes_with_nul has been stabilised in 1.10 (rust-lang/rust#31190).