about summary refs log tree commit diff
path: root/tvix/castore/src/path.rs
blob: 7e0ad391c7ca7718775f1e6c7103cc728bc1f07a (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
//! 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
            },
        )
    }

    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_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)
    }
}

/// 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 {
    /// Convert a byte vector to a PathBuf, without checking validity.
    unsafe fn from_bytes_unchecked(bytes: Vec<u8>) -> PathBuf {
        PathBuf { inner: bytes }
    }

    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(#[case] p: PathBuf, #[case] name: &str, #[case] exp_p: PathBuf) {
        assert_eq!(exp_p, p.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");
    }

    #[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<_>>()
        );
    }
}