path.rs.html -- source
Description: Source to the Rust file `src\libstd\sys\windows\path.rs`.
Keywords: rust, rustlang, rust-lang

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    use crate::ffi::OsStr;
    use crate::mem;
    use crate::path::Prefix;

    fn os_str_as_u8_slice(s: &OsStr) -> &[u8] {
        unsafe { mem::transmute(s) }
    }
    unsafe fn u8_slice_as_os_str(s: &[u8]) -> &OsStr {
        mem::transmute(s)
    }

    #[inline]
    pub fn is_sep_byte(b: u8) -> bool {
        b == b'/' || b == b'\\'
    }

    #[inline]
    pub fn is_verbatim_sep(b: u8) -> bool {
        b == b'\\'
    }

    pub fn parse_prefix(path: &OsStr) -> Option<Prefix<'_>> {
        use crate::path::Prefix::*;
        unsafe {
            // The unsafety here stems from converting between &OsStr and &[u8]
            // and back. This is safe to do because (1) we only look at ASCII
            // contents of the encoding and (2) new &OsStr values are produced
            // only from ASCII-bounded slices of existing &OsStr values.
            let mut path = os_str_as_u8_slice(path);

            if path.starts_with(br"\\") {
                // \\
                path = &path[2..];
                if path.starts_with(br"?\") {
                    // \\?\
                    path = &path[2..];
                    if path.starts_with(br"UNC\") {
                        // \\?\UNC\server\share
                        path = &path[4..];
                        let (server, share) = match parse_two_comps(path, is_verbatim_sep) {
                            Some((server, share)) => {
                                (u8_slice_as_os_str(server), u8_slice_as_os_str(share))
                            }
                            None => (u8_slice_as_os_str(path), u8_slice_as_os_str(&[])),
                        };
                        return Some(VerbatimUNC(server, share));
                    } else {
                        // \\?\path
                        let idx = path.iter().position(|&b| b == b'\\');
                        if idx == Some(2) && path[1] == b':' {
                            let c = path[0];
                            if c.is_ascii() && (c as char).is_alphabetic() {
                                // \\?\C:\ path
                                return Some(VerbatimDisk(c.to_ascii_uppercase()));
                            }
                        }
                        let slice = &path[..idx.unwrap_or(path.len())];
                        return Some(Verbatim(u8_slice_as_os_str(slice)));
                    }
                } else if path.starts_with(b".\\") {
                    // \\.\path
                    path = &path[2..];
                    let pos = path.iter().position(|&b| b == b'\\');
                    let slice = &path[..pos.unwrap_or(path.len())];
                    return Some(DeviceNS(u8_slice_as_os_str(slice)));
                }
                match parse_two_comps(path, is_sep_byte) {
                    Some((server, share)) if !server.is_empty() && !share.is_empty() => {
                        // \\server\share
                        return Some(UNC(u8_slice_as_os_str(server), u8_slice_as_os_str(share)));
                    }
                    _ => (),
                }
            } else if path.get(1) == Some(&b':') {
                // C:
                let c = path[0];
                if c.is_ascii() && (c as char).is_alphabetic() {
                    return Some(Disk(c.to_ascii_uppercase()));
                }
            }
            return None;
        }

        fn parse_two_comps(mut path: &[u8], f: fn(u8) -> bool) -> Option<(&[u8], &[u8])> {
            let first = &path[..path.iter().position(|x| f(*x))?];
            path = &path[(first.len() + 1)..];
            let idx = path.iter().position(|x| f(*x));
            let second = &path[..idx.unwrap_or(path.len())];
            Some((first, second))
        }
    }

    pub const MAIN_SEP_STR: &str = "\\";
    pub const MAIN_SEP: char = '\\';