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Creating CString from nul-terminated data #73100

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r4v3n6101 opened this issue Jun 7, 2020 · 2 comments · Fixed by #73139
Closed

Creating CString from nul-terminated data #73100

r4v3n6101 opened this issue Jun 7, 2020 · 2 comments · Fixed by #73139
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A-ffi Area: Foreign Function Interface (FFI) C-feature-request Category: A feature request, i.e: not implemented / a PR. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue.

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@r4v3n6101
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r4v3n6101 commented Jun 7, 2020

It seems there's no idiomatic way to create CString from nul-terminated Vec<u8>. The only approriate way is to pop() last nul and then from_vec_unchecked will append a new one. Need the method just passes data as is (e.g. CString::from_vec_with_nul such as CStr::from_bytes_with_nul).
Possibly, code should be like:

pub unsafe fn from_vec_with_nul_unchecked(v: Vec<u8>) -> CString {
    CString { inner: v.into_boxed_slice() }
}

and safe version:

pub fn from_vec_with_nul(v: Vec<u8>) -> Result<CString, FromBytesWithNulError> {
    let nul_pos = memchr::memchr(0, bytes);
    match nul_pos {
        Some(nul_pos) if nul_pos + 1 == v.len() => Ok(unsafe { CString::from_vec_with_nul_unchecked(v) }),
        Some(nul_pos) => Err(FromBytesWithNulError::interior_nul(nul_pos)),
        None => Err(FromBytesWithNulError::not_nul_terminated()),
    }
}
@jonas-schievink jonas-schievink added A-ffi Area: Foreign Function Interface (FFI) C-feature-request Category: A feature request, i.e: not implemented / a PR. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. labels Jun 7, 2020
@poliorcetics
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I can do it if the lib team is ok with it being added.

@Xanewok
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Xanewok commented Jun 8, 2020

Not a part of libs team but it seems like it covers a certain gap from std and I know that such PRs are definitely encouraged!

RalfJung added a commit to RalfJung/rust that referenced this issue Jun 15, 2020
…nul, r=dtolnay

Add methods to go from a nul-terminated Vec<u8> to a CString

Fixes rust-lang#73100.

Doc tests have been written and the documentation on the error type
updated too.

I used `#[stable(feature = "cstring_from_vec_with_nul", since = "1.46.0")]` but I don't know if the version is correct.
@bors bors closed this as completed in ec6fe42 Jun 15, 2020
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Labels
A-ffi Area: Foreign Function Interface (FFI) C-feature-request Category: A feature request, i.e: not implemented / a PR. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue.
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4 participants