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Diffstat (limited to '')
| -rw-r--r-- | library/std/src/sys/windows/path.rs | 333 |
1 files changed, 333 insertions, 0 deletions
diff --git a/library/std/src/sys/windows/path.rs b/library/std/src/sys/windows/path.rs new file mode 100644 index 000000000..beeca1917 --- /dev/null +++ b/library/std/src/sys/windows/path.rs @@ -0,0 +1,333 @@ +use super::{c, fill_utf16_buf, to_u16s}; +use crate::ffi::{OsStr, OsString}; +use crate::io; +use crate::mem; +use crate::path::{Path, PathBuf, Prefix}; +use crate::ptr; + +#[cfg(test)] +mod tests; + +pub const MAIN_SEP_STR: &str = "\\"; +pub const MAIN_SEP: char = '\\'; + +/// # Safety +/// +/// `bytes` must be a valid wtf8 encoded slice +#[inline] +unsafe fn bytes_as_os_str(bytes: &[u8]) -> &OsStr { + // &OsStr is layout compatible with &Slice, which is compatible with &Wtf8, + // which is compatible with &[u8]. + mem::transmute(bytes) +} + +#[inline] +pub fn is_sep_byte(b: u8) -> bool { + b == b'/' || b == b'\\' +} + +#[inline] +pub fn is_verbatim_sep(b: u8) -> bool { + b == b'\\' +} + +/// Returns true if `path` looks like a lone filename. +pub(crate) fn is_file_name(path: &OsStr) -> bool { + !path.bytes().iter().copied().any(is_sep_byte) +} +pub(crate) fn has_trailing_slash(path: &OsStr) -> bool { + let is_verbatim = path.bytes().starts_with(br"\\?\"); + let is_separator = if is_verbatim { is_verbatim_sep } else { is_sep_byte }; + if let Some(&c) = path.bytes().last() { is_separator(c) } else { false } +} + +/// Appends a suffix to a path. +/// +/// Can be used to append an extension without removing an existing extension. +pub(crate) fn append_suffix(path: PathBuf, suffix: &OsStr) -> PathBuf { + let mut path = OsString::from(path); + path.push(suffix); + path.into() +} + +struct PrefixParser<'a, const LEN: usize> { + path: &'a OsStr, + prefix: [u8; LEN], +} + +impl<'a, const LEN: usize> PrefixParser<'a, LEN> { + #[inline] + fn get_prefix(path: &OsStr) -> [u8; LEN] { + let mut prefix = [0; LEN]; + // SAFETY: Only ASCII characters are modified. + for (i, &ch) in path.bytes().iter().take(LEN).enumerate() { + prefix[i] = if ch == b'/' { b'\\' } else { ch }; + } + prefix + } + + fn new(path: &'a OsStr) -> Self { + Self { path, prefix: Self::get_prefix(path) } + } + + fn as_slice(&self) -> PrefixParserSlice<'a, '_> { + PrefixParserSlice { + path: self.path, + prefix: &self.prefix[..LEN.min(self.path.len())], + index: 0, + } + } +} + +struct PrefixParserSlice<'a, 'b> { + path: &'a OsStr, + prefix: &'b [u8], + index: usize, +} + +impl<'a> PrefixParserSlice<'a, '_> { + fn strip_prefix(&self, prefix: &str) -> Option<Self> { + self.prefix[self.index..] + .starts_with(prefix.as_bytes()) + .then(|| Self { index: self.index + prefix.len(), ..*self }) + } + + fn prefix_bytes(&self) -> &'a [u8] { + &self.path.bytes()[..self.index] + } + + fn finish(self) -> &'a OsStr { + // SAFETY: 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. + unsafe { bytes_as_os_str(&self.path.bytes()[self.index..]) } + } +} + +pub fn parse_prefix(path: &OsStr) -> Option<Prefix<'_>> { + use Prefix::{DeviceNS, Disk, Verbatim, VerbatimDisk, VerbatimUNC, UNC}; + + let parser = PrefixParser::<8>::new(path); + let parser = parser.as_slice(); + if let Some(parser) = parser.strip_prefix(r"\\") { + // \\ + + // The meaning of verbatim paths can change when they use a different + // separator. + if let Some(parser) = parser.strip_prefix(r"?\") && !parser.prefix_bytes().iter().any(|&x| x == b'/') { + // \\?\ + if let Some(parser) = parser.strip_prefix(r"UNC\") { + // \\?\UNC\server\share + + let path = parser.finish(); + let (server, path) = parse_next_component(path, true); + let (share, _) = parse_next_component(path, true); + + Some(VerbatimUNC(server, share)) + } else { + let path = parser.finish(); + + // in verbatim paths only recognize an exact drive prefix + if let Some(drive) = parse_drive_exact(path) { + // \\?\C: + Some(VerbatimDisk(drive)) + } else { + // \\?\prefix + let (prefix, _) = parse_next_component(path, true); + Some(Verbatim(prefix)) + } + } + } else if let Some(parser) = parser.strip_prefix(r".\") { + // \\.\COM42 + let path = parser.finish(); + let (prefix, _) = parse_next_component(path, false); + Some(DeviceNS(prefix)) + } else { + let path = parser.finish(); + let (server, path) = parse_next_component(path, false); + let (share, _) = parse_next_component(path, false); + + if !server.is_empty() && !share.is_empty() { + // \\server\share + Some(UNC(server, share)) + } else { + // no valid prefix beginning with "\\" recognized + None + } + } + } else if let Some(drive) = parse_drive(path) { + // C: + Some(Disk(drive)) + } else { + // no prefix + None + } +} + +// Parses a drive prefix, e.g. "C:" and "C:\whatever" +fn parse_drive(path: &OsStr) -> Option<u8> { + // In most DOS systems, it is not possible to have more than 26 drive letters. + // See <https://en.wikipedia.org/wiki/Drive_letter_assignment#Common_assignments>. + fn is_valid_drive_letter(drive: &u8) -> bool { + drive.is_ascii_alphabetic() + } + + match path.bytes() { + [drive, b':', ..] if is_valid_drive_letter(drive) => Some(drive.to_ascii_uppercase()), + _ => None, + } +} + +// Parses a drive prefix exactly, e.g. "C:" +fn parse_drive_exact(path: &OsStr) -> Option<u8> { + // only parse two bytes: the drive letter and the drive separator + if path.bytes().get(2).map(|&x| is_sep_byte(x)).unwrap_or(true) { + parse_drive(path) + } else { + None + } +} + +// Parse the next path component. +// +// Returns the next component and the rest of the path excluding the component and separator. +// Does not recognize `/` as a separator character if `verbatim` is true. +fn parse_next_component(path: &OsStr, verbatim: bool) -> (&OsStr, &OsStr) { + let separator = if verbatim { is_verbatim_sep } else { is_sep_byte }; + + match path.bytes().iter().position(|&x| separator(x)) { + Some(separator_start) => { + let separator_end = separator_start + 1; + + let component = &path.bytes()[..separator_start]; + + // Panic safe + // The max `separator_end` is `bytes.len()` and `bytes[bytes.len()..]` is a valid index. + let path = &path.bytes()[separator_end..]; + + // SAFETY: `path` is a valid wtf8 encoded slice and each of the separators ('/', '\') + // is encoded in a single byte, therefore `bytes[separator_start]` and + // `bytes[separator_end]` must be code point boundaries and thus + // `bytes[..separator_start]` and `bytes[separator_end..]` are valid wtf8 slices. + unsafe { (bytes_as_os_str(component), bytes_as_os_str(path)) } + } + None => (path, OsStr::new("")), + } +} + +/// Returns a UTF-16 encoded path capable of bypassing the legacy `MAX_PATH` limits. +/// +/// This path may or may not have a verbatim prefix. +pub(crate) fn maybe_verbatim(path: &Path) -> io::Result<Vec<u16>> { + // Normally the MAX_PATH is 260 UTF-16 code units (including the NULL). + // However, for APIs such as CreateDirectory[1], the limit is 248. + // + // [1]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createdirectorya#parameters + const LEGACY_MAX_PATH: usize = 248; + // UTF-16 encoded code points, used in parsing and building UTF-16 paths. + // All of these are in the ASCII range so they can be cast directly to `u16`. + const SEP: u16 = b'\\' as _; + const ALT_SEP: u16 = b'/' as _; + const QUERY: u16 = b'?' as _; + const COLON: u16 = b':' as _; + const DOT: u16 = b'.' as _; + const U: u16 = b'U' as _; + const N: u16 = b'N' as _; + const C: u16 = b'C' as _; + + // \\?\ + const VERBATIM_PREFIX: &[u16] = &[SEP, SEP, QUERY, SEP]; + // \??\ + const NT_PREFIX: &[u16] = &[SEP, QUERY, QUERY, SEP]; + // \\?\UNC\ + const UNC_PREFIX: &[u16] = &[SEP, SEP, QUERY, SEP, U, N, C, SEP]; + + let mut path = to_u16s(path)?; + if path.starts_with(VERBATIM_PREFIX) || path.starts_with(NT_PREFIX) || path == &[0] { + // Early return for paths that are already verbatim or empty. + return Ok(path); + } else if path.len() < LEGACY_MAX_PATH { + // Early return if an absolute path is less < 260 UTF-16 code units. + // This is an optimization to avoid calling `GetFullPathNameW` unnecessarily. + match path.as_slice() { + // Starts with `D:`, `D:\`, `D:/`, etc. + // Does not match if the path starts with a `\` or `/`. + [drive, COLON, 0] | [drive, COLON, SEP | ALT_SEP, ..] + if *drive != SEP && *drive != ALT_SEP => + { + return Ok(path); + } + // Starts with `\\`, `//`, etc + [SEP | ALT_SEP, SEP | ALT_SEP, ..] => return Ok(path), + _ => {} + } + } + + // Firstly, get the absolute path using `GetFullPathNameW`. + // https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfullpathnamew + let lpfilename = path.as_ptr(); + fill_utf16_buf( + // SAFETY: `fill_utf16_buf` ensures the `buffer` and `size` are valid. + // `lpfilename` is a pointer to a null terminated string that is not + // invalidated until after `GetFullPathNameW` returns successfully. + |buffer, size| unsafe { c::GetFullPathNameW(lpfilename, size, buffer, ptr::null_mut()) }, + |mut absolute| { + path.clear(); + + // Secondly, add the verbatim prefix. This is easier here because we know the + // path is now absolute and fully normalized (e.g. `/` has been changed to `\`). + let prefix = match absolute { + // C:\ => \\?\C:\ + [_, COLON, SEP, ..] => VERBATIM_PREFIX, + // \\.\ => \\?\ + [SEP, SEP, DOT, SEP, ..] => { + absolute = &absolute[4..]; + VERBATIM_PREFIX + } + // Leave \\?\ and \??\ as-is. + [SEP, SEP, QUERY, SEP, ..] | [SEP, QUERY, QUERY, SEP, ..] => &[], + // \\ => \\?\UNC\ + [SEP, SEP, ..] => { + absolute = &absolute[2..]; + UNC_PREFIX + } + // Anything else we leave alone. + _ => &[], + }; + + path.reserve_exact(prefix.len() + absolute.len() + 1); + path.extend_from_slice(prefix); + path.extend_from_slice(absolute); + path.push(0); + }, + )?; + Ok(path) +} + +/// Make a Windows path absolute. +pub(crate) fn absolute(path: &Path) -> io::Result<PathBuf> { + let path = path.as_os_str(); + let prefix = parse_prefix(path); + // Verbatim paths should not be modified. + if prefix.map(|x| x.is_verbatim()).unwrap_or(false) { + // NULs in verbatim paths are rejected for consistency. + if path.bytes().contains(&0) { + return Err(io::const_io_error!( + io::ErrorKind::InvalidInput, + "strings passed to WinAPI cannot contain NULs", + )); + } + return Ok(path.to_owned().into()); + } + + let path = to_u16s(path)?; + let lpfilename = path.as_ptr(); + fill_utf16_buf( + // SAFETY: `fill_utf16_buf` ensures the `buffer` and `size` are valid. + // `lpfilename` is a pointer to a null terminated string that is not + // invalidated until after `GetFullPathNameW` returns successfully. + |buffer, size| unsafe { c::GetFullPathNameW(lpfilename, size, buffer, ptr::null_mut()) }, + super::os2path, + ) +} |