71 lines
2.3 KiB
Rust
71 lines
2.3 KiB
Rust
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use std::io::{Error, ErrorKind, Result};
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use std::path::Path;
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/// A trait to allow replacing the file system lookup mechanisms.
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///
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/// As it stands, this is imperfect: it’s still using the types and some operations from
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/// `std::path`, which constrain it to the target platform’s norms. This could be ameliorated by
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/// the use of associated types for `Path` and `PathBuf`, and putting all remaining methods on this
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/// trait (`is_absolute`, `parent`, `join`, *&c.*); but that would infect too many other APIs to be
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/// desirable, so we live with it as it is—which is also acceptable, because the motivating example
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/// use case is mostly using this as an optimisation over the real platform underneath.
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pub trait Fs: std::fmt::Debug {
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/// Returns `true` if the path exists on disk and is pointing at a directory.
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fn is_dir(&self, path: &Path) -> bool;
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/// Returns `true` if the path exists on disk and is pointing at a regular file.
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fn is_file(&self, path: &Path) -> bool;
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/// Read the entire contents of a file into a bytes vector.
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fn read(&self, path: &Path) -> Result<Vec<u8>>;
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}
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/// Use [`std::fs`] to read any files from disk.
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///
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/// This is the default file system implementation.
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#[derive(Debug)]
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pub struct StdFs;
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impl Fs for StdFs {
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#[inline]
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fn is_file(&self, path: &Path) -> bool {
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path.is_file()
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}
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#[inline]
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fn is_dir(&self, path: &Path) -> bool {
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path.is_dir()
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}
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#[inline]
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fn read(&self, path: &Path) -> Result<Vec<u8>> {
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std::fs::read(path)
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}
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}
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/// A file system implementation that acts like it’s completely empty.
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///
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/// This may be useful for security as it denies all access to the file system (so `@import` is
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/// prevented from leaking anything); you’ll need to use [`from_string`][crate::from_string] for
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/// this to make any sense (since [`from_path`][crate::from_path] would fail to find a file).
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#[derive(Debug)]
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pub struct NullFs;
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impl Fs for NullFs {
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#[inline]
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fn is_file(&self, _path: &Path) -> bool {
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false
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}
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#[inline]
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fn is_dir(&self, _path: &Path) -> bool {
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false
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}
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#[inline]
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fn read(&self, _path: &Path) -> Result<Vec<u8>> {
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Err(Error::new(
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ErrorKind::NotFound,
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"NullFs, there is no file system",
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))
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}
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}
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