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Diffstat (limited to 'tvix/castore/src/path.rs')
| -rw-r--r-- | tvix/castore/src/path.rs | 446 |
1 files changed, 446 insertions, 0 deletions
diff --git a/tvix/castore/src/path.rs b/tvix/castore/src/path.rs new file mode 100644 index 0000000000..fcc2bd01fb --- /dev/null +++ b/tvix/castore/src/path.rs @@ -0,0 +1,446 @@ +//! Contains data structures to deal with Paths in the tvix-castore model. + +use std::{ + borrow::Borrow, + fmt::{self, Debug, Display}, + mem, + ops::Deref, + str::FromStr, +}; + +use bstr::ByteSlice; + +use crate::proto::validate_node_name; + +/// Represents a Path in the castore model. +/// These are always relative, and platform-independent, which distinguishes +/// them from the ones provided in the standard library. +#[derive(Eq, Hash, PartialEq)] +#[repr(transparent)] // SAFETY: Representation has to match [u8] +pub struct Path { + // As node names in the castore model cannot contain slashes, + // we use them as component separators here. + inner: [u8], +} + +#[allow(dead_code)] +impl Path { + // SAFETY: The empty path is valid. + pub const ROOT: &'static Path = unsafe { Path::from_bytes_unchecked(&[]) }; + + /// Convert a byte slice to a path, without checking validity. + const unsafe fn from_bytes_unchecked(bytes: &[u8]) -> &Path { + // SAFETY: &[u8] and &Path have the same representation. + unsafe { mem::transmute(bytes) } + } + + fn from_bytes(bytes: &[u8]) -> Option<&Path> { + if !bytes.is_empty() { + // Ensure all components are valid castore node names. + for component in bytes.split_str(b"/") { + validate_node_name(component).ok()?; + } + } + + // SAFETY: We have verified that the path contains no empty components. + Some(unsafe { Path::from_bytes_unchecked(bytes) }) + } + + pub fn into_boxed_bytes(self: Box<Path>) -> Box<[u8]> { + // SAFETY: Box<Path> and Box<[u8]> have the same representation. + unsafe { mem::transmute(self) } + } + + /// Returns the path without its final component, if there is one. + /// + /// Note that the parent of a bare file name is [Path::ROOT]. + /// [Path::ROOT] is the only path without a parent. + pub fn parent(&self) -> Option<&Path> { + // The root does not have a parent. + if self.inner.is_empty() { + return None; + } + + Some( + if let Some((parent, _file_name)) = self.inner.rsplit_once_str(b"/") { + // SAFETY: The parent of a valid Path is a valid Path. + unsafe { Path::from_bytes_unchecked(parent) } + } else { + // The parent of a bare file name is the root. + Path::ROOT + }, + ) + } + + /// Creates a PathBuf with `name` adjoined to self. + pub fn try_join(&self, name: &[u8]) -> Result<PathBuf, std::io::Error> { + let mut v = PathBuf::with_capacity(self.inner.len() + name.len() + 1); + v.inner.extend_from_slice(&self.inner); + v.try_push(name)?; + + Ok(v) + } + + /// Produces an iterator over the components of the path, which are + /// individual byte slices. + /// In case the path is empty, an empty iterator is returned. + pub fn components(&self) -> impl Iterator<Item = &[u8]> { + let mut iter = self.inner.split_str(&b"/"); + + // We don't want to return an empty element, consume it if it's the only one. + if self.inner.is_empty() { + let _ = iter.next(); + } + + iter + } + + /// Returns the final component of the Path, if there is one. + pub fn file_name(&self) -> Option<&[u8]> { + self.components().last() + } + + pub fn as_bytes(&self) -> &[u8] { + &self.inner + } +} + +impl Debug for Path { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + Debug::fmt(self.inner.as_bstr(), f) + } +} + +impl Display for Path { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + Display::fmt(self.inner.as_bstr(), f) + } +} + +impl AsRef<Path> for Path { + fn as_ref(&self) -> &Path { + self + } +} + +/// Represents a owned PathBuf in the castore model. +/// These are always relative, and platform-independent, which distinguishes +/// them from the ones provided in the standard library. +#[derive(Clone, Default, Eq, Hash, PartialEq)] +pub struct PathBuf { + inner: Vec<u8>, +} + +impl Deref for PathBuf { + type Target = Path; + + fn deref(&self) -> &Self::Target { + // SAFETY: PathBuf always contains a valid Path. + unsafe { Path::from_bytes_unchecked(&self.inner) } + } +} + +impl AsRef<Path> for PathBuf { + fn as_ref(&self) -> &Path { + self + } +} + +impl ToOwned for Path { + type Owned = PathBuf; + + fn to_owned(&self) -> Self::Owned { + PathBuf { + inner: self.inner.to_owned(), + } + } +} + +impl Borrow<Path> for PathBuf { + fn borrow(&self) -> &Path { + self + } +} + +impl From<Box<Path>> for PathBuf { + fn from(value: Box<Path>) -> Self { + // SAFETY: Box<Path> is always a valid path. + unsafe { PathBuf::from_bytes_unchecked(value.into_boxed_bytes().into_vec()) } + } +} + +impl From<&Path> for PathBuf { + fn from(value: &Path) -> Self { + value.to_owned() + } +} + +impl FromStr for PathBuf { + type Err = std::io::Error; + + fn from_str(s: &str) -> Result<PathBuf, Self::Err> { + Ok(Path::from_bytes(s.as_bytes()) + .ok_or(std::io::ErrorKind::InvalidData)? + .to_owned()) + } +} + +impl Debug for PathBuf { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + Debug::fmt(&**self, f) + } +} + +impl Display for PathBuf { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + Display::fmt(&**self, f) + } +} + +impl PathBuf { + pub fn new() -> PathBuf { + Self::default() + } + + pub fn with_capacity(capacity: usize) -> PathBuf { + // SAFETY: The empty path is a valid path. + Self { + inner: Vec::with_capacity(capacity), + } + } + + /// Adjoins `name` to self. + pub fn try_push(&mut self, name: &[u8]) -> Result<(), std::io::Error> { + validate_node_name(name).map_err(|_| std::io::ErrorKind::InvalidData)?; + + if !self.inner.is_empty() { + self.inner.push(b'/'); + } + + self.inner.extend_from_slice(name); + + Ok(()) + } + + /// Convert a byte vector to a PathBuf, without checking validity. + unsafe fn from_bytes_unchecked(bytes: Vec<u8>) -> PathBuf { + PathBuf { inner: bytes } + } + + /// Convert from a [&std::path::Path] to [Self]. + /// + /// - Self uses `/` as path separator. + /// - Absolute paths are always rejected, are are these with custom prefixes. + /// - Repeated separators are deduplicated. + /// - Occurrences of `.` are normalized away. + /// - A trailing slash is normalized away. + /// + /// A `canonicalize_dotdot` boolean controls whether `..` will get + /// canonicalized if possible, or should return an error. + /// + /// For more exotic paths, this conversion might produce different results + /// on different platforms, due to different underlying byte + /// representations, which is why it's restricted to unix for now. + #[cfg(unix)] + pub fn from_host_path( + host_path: &std::path::Path, + canonicalize_dotdot: bool, + ) -> Result<Self, std::io::Error> { + let mut p = PathBuf::with_capacity(host_path.as_os_str().len()); + + for component in host_path.components() { + match component { + std::path::Component::Prefix(_) | std::path::Component::RootDir => { + return Err(std::io::Error::new( + std::io::ErrorKind::InvalidData, + "found disallowed prefix or rootdir", + )) + } + std::path::Component::CurDir => continue, // ignore + std::path::Component::ParentDir => { + if canonicalize_dotdot { + // Try popping the last element from the path being constructed. + // FUTUREWORK: pop method? + p = p + .parent() + .ok_or_else(|| { + std::io::Error::new( + std::io::ErrorKind::InvalidData, + "found .. going too far up", + ) + })? + .to_owned(); + } else { + return Err(std::io::Error::new( + std::io::ErrorKind::InvalidData, + "found disallowed ..", + )); + } + } + std::path::Component::Normal(s) => { + // append the new component to the path being constructed. + p.try_push(s.as_encoded_bytes()).map_err(|_| { + std::io::Error::new( + std::io::ErrorKind::InvalidData, + "encountered invalid node in sub_path component", + ) + })? + } + } + } + + Ok(p) + } + + pub fn into_boxed_path(self) -> Box<Path> { + // SAFETY: Box<[u8]> and Box<Path> have the same representation, + // and PathBuf always contains a valid Path. + unsafe { mem::transmute(self.inner.into_boxed_slice()) } + } + + pub fn into_bytes(self) -> Vec<u8> { + self.inner + } +} + +#[cfg(test)] +mod test { + use super::{Path, PathBuf}; + use bstr::ByteSlice; + use rstest::rstest; + + // TODO: add some manual tests including invalid UTF-8 (hard to express + // with rstest) + + #[rstest] + #[case::empty("", 0)] + #[case("a", 1)] + #[case("a/b", 2)] + #[case("a/b/c", 3)] + // add two slightly more cursed variants. + // Technically nothing prevents us from representing this with castore, + // but maybe we want to disallow constructing paths like this as it's a + // bad idea. + #[case::cursed("C:\\a/b", 2)] + #[case::cursed("\\\\tvix-store", 1)] + pub fn from_str(#[case] s: &str, #[case] num_components: usize) { + let p: PathBuf = s.parse().expect("must parse"); + + assert_eq!(s.as_bytes(), p.as_bytes(), "inner bytes mismatch"); + assert_eq!( + num_components, + p.components().count(), + "number of components mismatch" + ); + } + + #[rstest] + #[case::absolute("/a/b")] + #[case::two_forward_slashes_start("//a/b")] + #[case::two_forward_slashes_middle("a/b//c/d")] + #[case::trailing_slash("a/b/")] + #[case::dot(".")] + #[case::dotdot("..")] + #[case::dot_start("./a")] + #[case::dotdot_start("../a")] + #[case::dot_middle("a/./b")] + #[case::dotdot_middle("a/../b")] + #[case::dot_end("a/b/.")] + #[case::dotdot_end("a/b/..")] + #[case::null("fo\0o")] + pub fn from_str_fail(#[case] s: &str) { + s.parse::<PathBuf>().expect_err("must fail"); + } + + #[rstest] + #[case("foo", "")] + #[case("foo/bar", "foo")] + #[case("foo2/bar2", "foo2")] + #[case("foo/bar/baz", "foo/bar")] + pub fn parent(#[case] p: PathBuf, #[case] exp_parent: PathBuf) { + assert_eq!(Some(&*exp_parent), p.parent()); + } + + #[rstest] + pub fn no_parent() { + assert!(Path::ROOT.parent().is_none()); + } + + #[rstest] + #[case("a", "b", "a/b")] + #[case("a", "b", "a/b")] + pub fn join_push(#[case] mut p: PathBuf, #[case] name: &str, #[case] exp_p: PathBuf) { + assert_eq!(exp_p, p.try_join(name.as_bytes()).expect("join failed")); + p.try_push(name.as_bytes()).expect("push failed"); + assert_eq!(exp_p, p); + } + + #[rstest] + #[case("a", "/")] + #[case("a", "")] + #[case("a", "b/c")] + #[case("", "/")] + #[case("", "")] + #[case("", "b/c")] + #[case("", ".")] + #[case("", "..")] + pub fn join_push_fail(#[case] mut p: PathBuf, #[case] name: &str) { + p.try_join(name.as_bytes()) + .expect_err("join succeeded unexpectedly"); + p.try_push(name.as_bytes()) + .expect_err("push succeeded unexpectedly"); + } + + #[rstest] + #[case::empty("", vec![])] + #[case("a", vec!["a"])] + #[case("a/b", vec!["a", "b"])] + #[case("a/b/c", vec!["a","b", "c"])] + pub fn components(#[case] p: PathBuf, #[case] exp_components: Vec<&str>) { + assert_eq!( + exp_components, + p.components() + .map(|x| x.to_str().unwrap()) + .collect::<Vec<_>>() + ); + } + + #[rstest] + #[case::empty("", "", false)] + #[case::path("a", "a", false)] + #[case::path2("a/b", "a/b", false)] + #[case::double_slash_middle("a//b", "a/b", false)] + #[case::dot(".", "", false)] + #[case::dot_start("./a/b", "a/b", false)] + #[case::dot_middle("a/./b", "a/b", false)] + #[case::dot_end("a/b/.", "a/b", false)] + #[case::trailing_slash("a/b/", "a/b", false)] + #[case::dotdot_canonicalize("a/..", "", true)] + #[case::dotdot_canonicalize2("a/../b", "b", true)] + #[cfg_attr(unix, case::faux_prefix("\\\\nix-store", "\\\\nix-store", false))] + #[cfg_attr(unix, case::faux_letter("C:\\foo.txt", "C:\\foo.txt", false))] + pub fn from_host_path( + #[case] host_path: std::path::PathBuf, + #[case] exp_path: PathBuf, + #[case] canonicalize_dotdot: bool, + ) { + let p = PathBuf::from_host_path(&host_path, canonicalize_dotdot).expect("must succeed"); + + assert_eq!(exp_path, p); + } + + #[rstest] + #[case::absolute("/", false)] + #[case::dotdot_root("..", false)] + #[case::dotdot_root_canonicalize("..", true)] + #[case::dotdot_root_no_canonicalize("a/..", false)] + #[case::invalid_name("foo/bar\0", false)] + // #[cfg_attr(windows, case::prefix("\\\\nix-store", false))] + // #[cfg_attr(windows, case::letter("C:\\foo.txt", false))] + pub fn from_host_path_fail( + #[case] host_path: std::path::PathBuf, + #[case] canonicalize_dotdot: bool, + ) { + PathBuf::from_host_path(&host_path, canonicalize_dotdot).expect_err("must fail"); + } +} |