gix_path/
realpath.rs

1/// The error returned by [`realpath()`][super::realpath()].
2#[derive(Debug, thiserror::Error)]
3#[allow(missing_docs)]
4pub enum Error {
5    #[error("The maximum allowed number {} of symlinks in path is exceeded", .max_symlinks)]
6    MaxSymlinksExceeded { max_symlinks: u8 },
7    #[error("Cannot resolve symlinks in path with more than {max_symlink_checks} components (takes too long)")]
8    ExcessiveComponentCount { max_symlink_checks: usize },
9    #[error(transparent)]
10    ReadLink(std::io::Error),
11    #[error(transparent)]
12    CurrentWorkingDir(std::io::Error),
13    #[error("Empty is not a valid path")]
14    EmptyPath,
15    #[error("Ran out of path components while following parent component '..'")]
16    MissingParent,
17}
18
19/// The default amount of symlinks we may follow when resolving a path in [`realpath()`][crate::realpath()].
20pub const MAX_SYMLINKS: u8 = 32;
21
22pub(crate) mod function {
23    use std::path::{
24        Component::{CurDir, Normal, ParentDir, Prefix, RootDir},
25        Path, PathBuf,
26    };
27
28    use super::Error;
29    use crate::realpath::MAX_SYMLINKS;
30
31    /// Check each component of `path` and see if it is a symlink. If so, resolve it.
32    /// Do not fail for non-existing components, but assume these are as is.
33    ///
34    /// If `path` is relative, the current working directory be used to make it absolute.
35    /// Note that the returned path will be verbatim, and repositories with `core.precomposeUnicode`
36    /// set will probably want to precompose the paths unicode.
37    pub fn realpath(path: impl AsRef<Path>) -> Result<PathBuf, Error> {
38        let path = path.as_ref();
39        let cwd = path
40            .is_relative()
41            .then(std::env::current_dir)
42            .unwrap_or_else(|| Ok(PathBuf::default()))
43            .map_err(Error::CurrentWorkingDir)?;
44        realpath_opts(path, &cwd, MAX_SYMLINKS)
45    }
46
47    /// The same as [`realpath()`], but allow to configure `max_symlinks` to configure how many symbolic links we are going to follow.
48    /// This serves to avoid running into cycles or doing unreasonable amounts of work.
49    pub fn realpath_opts(path: &Path, cwd: &Path, max_symlinks: u8) -> Result<PathBuf, Error> {
50        if path.as_os_str().is_empty() {
51            return Err(Error::EmptyPath);
52        }
53
54        let mut real_path = PathBuf::new();
55        if path.is_relative() {
56            real_path.push(cwd);
57        }
58
59        let mut num_symlinks = 0;
60        let mut path_backing: PathBuf;
61        let mut components = path.components();
62        const MAX_SYMLINK_CHECKS: usize = 2048;
63        let mut symlink_checks = 0;
64        while let Some(component) = components.next() {
65            match component {
66                part @ (RootDir | Prefix(_)) => real_path.push(part),
67                CurDir => {}
68                ParentDir => {
69                    if !real_path.pop() {
70                        return Err(Error::MissingParent);
71                    }
72                }
73                Normal(part) => {
74                    real_path.push(part);
75                    symlink_checks += 1;
76                    if real_path.is_symlink() {
77                        num_symlinks += 1;
78                        if num_symlinks > max_symlinks {
79                            return Err(Error::MaxSymlinksExceeded { max_symlinks });
80                        }
81                        let mut link_destination = std::fs::read_link(real_path.as_path()).map_err(Error::ReadLink)?;
82                        if link_destination.is_absolute() {
83                            // pushing absolute path to real_path resets it to the pushed absolute path
84                        } else {
85                            assert!(real_path.pop(), "we just pushed a component");
86                        }
87                        link_destination.extend(components);
88                        path_backing = link_destination;
89                        components = path_backing.components();
90                    }
91                    if symlink_checks > MAX_SYMLINK_CHECKS {
92                        return Err(Error::ExcessiveComponentCount {
93                            max_symlink_checks: MAX_SYMLINK_CHECKS,
94                        });
95                    }
96                }
97            }
98        }
99        Ok(real_path)
100    }
101}
gix_path/realpath.rs

gix_path/
realpath.rs
