//! Contains data structures to deal with Paths in the tvix-castore model.
use std::{borrow::Borrow, mem, ops::Deref, str::FromStr};
use bstr::ByteSlice;
/// 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(Debug, 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 there's no empty components (aka, double forward slashes),
// and all components individually validate.
for component in bytes.split_str(b"/") {
if component.is_empty() {
return None;
}
}
}
// SAFETY: We have verified that the path contains no empty components.
Some(unsafe { Path::from_bytes_unchecked(bytes) })
}
pub fn parent(&self) -> Option<&Path> {
let (parent, _file_name) = self.inner.rsplit_once_str(b"/")?;
// SAFETY: The parent of a valid Path is a valid Path.
Some(unsafe { Path::from_bytes_unchecked(parent) })
}
pub fn join(&self, name: &[u8]) -> Result<PathBuf, std::io::Error> {
if name.contains(&b'/') || name.is_empty() {
return Err(std::io::ErrorKind::InvalidData.into());
}
let mut v = self.inner.to_vec();
if !v.is_empty() {
v.extend_from_slice(b"/");
}
v.extend_from_slice(name);
Ok(PathBuf { inner: 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_slice(&self) -> &[u8] {
&self.inner
}
}
/// 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, Debug, 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 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())
}
}
#[cfg(test)]
mod test {
use super::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_slice(), "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/")]
pub fn from_str_fail(#[case] s: &str) {
s.parse::<PathBuf>().expect_err("must fail");
}
#[rstest]
#[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.as_ref()), p.parent());
// same for Path
let p = p.as_ref();
assert_eq!(Some(exp_parent.as_ref()), p.parent());
}
#[rstest]
#[case::empty("")]
#[case::single("foo")]
pub fn no_parent(#[case] p: PathBuf) {
assert!(p.parent().is_none());
// same for Path
assert!(p.as_ref().parent().is_none());
}
#[rstest]
#[case("a", "b", "a/b")]
#[case("a", "b", "a/b")]
pub fn join(#[case] p: PathBuf, #[case] name: &str, #[case] exp_p: PathBuf) {
assert_eq!(exp_p, p.join(name.as_bytes()).expect("join failed"));
// same for Path
assert_eq!(
exp_p,
p.as_ref().join(name.as_bytes()).expect("join failed")
);
}
#[rstest]
#[case("a", "/")]
#[case("a", "")]
#[case("a", "b/c")]
#[case("", "/")]
#[case("", "")]
#[case("", "b/c")]
pub fn join_fail(#[case] p: PathBuf, #[case] name: &str) {
p.join(name.as_bytes())
.expect_err("join succeeded unexpectedly");
// same for Path
p.as_ref()
.join(name.as_bytes())
.expect_err("join 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<_>>()
);
// same for Path
let p = p.as_ref();
assert_eq!(
exp_components,
p.components()
.map(|x| x.to_str().unwrap())
.collect::<Vec<_>>()
);
}
}
