tame/tamer/src/fs.rs

313 lines
8.2 KiB
Rust
Raw Blame History

This file contains invisible Unicode characters!

This file contains invisible Unicode characters that may be processed differently from what appears below. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to reveal hidden characters.

// Light filesystem abstractions
//
// Copyright (C) 2014-2022 Ryan Specialty Group, LLC.
//
// This file is part of TAME.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//! Lightweight filesystem abstraction.
//!
//! This abstraction is intended to provide generics missing from Rust core,
//! but makes no attempt to be comprehensive---it
//! includes only what is needed for TAMER.
//!
//! - [`File`] provides a trait for operating on files; and
//! - [`Filesystem`] provides a generic way to access files by path.
//!
//! This implements traits directly atop of Rust's core structs where
//! possible.
//!
//!
//! Visiting Files Once
//! ===================
//! [`VisitOnceFilesystem`] produces [`VisitOnceFile::FirstVisit`] the first
//! time it encounters a given path,
//! and [`VisitOnceFile::Visited`] every time thereafter.
use std::collections::hash_map::RandomState;
use std::collections::HashSet;
use std::ffi::OsString;
use std::fs;
use std::hash::BuildHasher;
use std::io::{BufReader, Read, Result};
use std::marker::PhantomData;
use std::path::{Path, PathBuf};
use crate::span::{Context, UNKNOWN_CONTEXT};
use crate::sym::GlobalSymbolIntern;
/// A file.
pub trait File: Read
where
Self: Sized,
{
fn open<P: AsRef<Path>>(path: P) -> Result<Self>;
}
impl File for fs::File {
fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
Self::open(path)
}
}
impl<F: File + Read> File for BufReader<F> {
/// Open the file at `path` and construct a [`BufReader`] from it.
fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
Ok(BufReader::new(F::open(path)?))
}
}
#[derive(Debug, PartialEq)]
pub struct PathFile<F: File>(pub PathBuf, pub F, pub Context);
impl<F: File> File for PathFile<F> {
fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
let buf = path.as_ref().to_path_buf();
let file = F::open(&buf)?;
let ctx = buf
.to_str()
.map(|s| s.intern().into())
.unwrap_or(UNKNOWN_CONTEXT);
Ok(Self(buf, file, ctx))
}
}
impl<F: File> Read for PathFile<F> {
fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
self.1.read(buf)
}
}
/// A filesystem.
///
/// Opening a file (using [`open`](Filesystem::open)) proxies to `F::open`.
/// The type of files opened by this abstraction can therefore be controlled
/// via generics.
pub trait Filesystem<F: File>
where
Self: Sized,
{
fn open<P: AsRef<Path>>(&mut self, path: P) -> Result<F> {
F::open(path)
}
}
/// A potentially visited [`File`].
///
/// See [`VisitOnceFilesystem`] for more information.
#[derive(Debug, PartialEq)]
pub enum VisitOnceFile<F: File> {
/// First time visiting file at requested path.
FirstVisit(F),
/// Requested path has already been visited.
Visited,
}
impl<F: File> File for VisitOnceFile<F> {
fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
F::open(path).map(|file| Self::FirstVisit(file))
}
}
impl<F: File> Read for VisitOnceFile<F> {
fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
match self {
Self::FirstVisit(file) => file.read(buf),
Self::Visited => Ok(0),
}
}
}
/// Opens each path only once.
///
/// When a [`File`] is first opened,
/// it will be wrapped in [`VisitOnceFile::FirstVisit`]
/// Subsequent calls to `open` will yield
/// [`VisitOnceFile::Visited`] without attempting to open the file.
///
/// A file will not be marked as visited if it fails to be opened.
pub struct VisitOnceFilesystem<C, S = RandomState>
where
C: Canonicalizer,
S: BuildHasher,
{
visited: HashSet<OsString, S>,
_c: PhantomData<C>,
}
impl<C, S> VisitOnceFilesystem<C, S>
where
C: Canonicalizer,
S: BuildHasher + Default,
{
/// New filesystem with no recorded paths.
pub fn new() -> Self {
Self {
visited: Default::default(),
_c: PhantomData,
}
}
/// Number of visited paths.
pub fn visit_len(&self) -> usize {
self.visited.len()
}
}
impl<C, S, F> Filesystem<VisitOnceFile<F>> for VisitOnceFilesystem<C, S>
where
C: Canonicalizer,
S: BuildHasher,
F: File,
{
/// Open a file, marking `path` as visited.
///
/// The next time the same path is requested,
/// [`VisitOnceFile::Visited`] will be returned.
///
/// `path` will not be marked as visited if opening fails.
fn open<P: AsRef<Path>>(&mut self, path: P) -> Result<VisitOnceFile<F>> {
let cpath = C::canonicalize(path)?;
let ostr = cpath.as_os_str();
if self.visited.contains(ostr) {
return Ok(VisitOnceFile::Visited);
}
VisitOnceFile::open(ostr).and_then(|file| {
self.visited.insert(ostr.to_os_string());
Ok(file)
})
}
}
/// Vanilla filesystem access.
///
/// This provides access to the filesystem as one would expect.
/// The actual operations are delegated to `F`.
#[derive(Debug)]
pub struct VanillaFilesystem<F: File> {
_file: PhantomData<F>,
}
impl<F: File> Default for VanillaFilesystem<F> {
fn default() -> Self {
Self {
_file: Default::default(),
}
}
}
impl<F: File> Filesystem<F> for VanillaFilesystem<F> {
fn open<P: AsRef<Path>>(&mut self, path: P) -> Result<F> {
F::open(path)
}
}
pub trait Canonicalizer {
fn canonicalize<P: AsRef<Path>>(path: P) -> Result<PathBuf>;
}
pub struct FsCanonicalizer;
impl Canonicalizer for FsCanonicalizer {
fn canonicalize<P: AsRef<Path>>(path: P) -> Result<PathBuf> {
std::fs::canonicalize(path)
}
}
#[cfg(test)]
mod test {
use super::*;
use std::path::PathBuf;
#[derive(Debug, PartialEq)]
struct DummyFile(PathBuf);
impl File for DummyFile {
fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
Ok(Self(path.as_ref().to_path_buf()))
}
}
impl Read for DummyFile {
fn read(&mut self, _buf: &mut [u8]) -> Result<usize> {
Ok(0)
}
}
#[test]
fn buf_reader_file() {
let path: PathBuf = "buf/path".into();
let result: BufReader<DummyFile> = File::open(path.clone()).unwrap();
assert_eq!(DummyFile(path), result.into_inner());
}
#[test]
fn path_file() {
let path: PathBuf = "buf/path".into();
let result: PathFile<DummyFile> = File::open(path.clone()).unwrap();
assert_eq!(
PathFile(
path.clone(),
DummyFile(path.clone()),
"buf/path".intern().into()
),
result
);
}
mod canonicalizer {
use super::*;
struct StubCanonicalizer;
impl Canonicalizer for StubCanonicalizer {
fn canonicalize<P: AsRef<Path>>(path: P) -> Result<PathBuf> {
let mut buf = path.as_ref().to_path_buf();
buf.push("CANONICALIZED");
Ok(buf)
}
}
#[test]
fn vist_once() {
let mut fs =
VisitOnceFilesystem::<StubCanonicalizer, RandomState>::new();
let path: PathBuf = "foo/bar".into();
let result = fs.open(path.clone()).unwrap();
let mut expected_path = path.clone().to_path_buf();
expected_path.push("CANONICALIZED");
// First time, return file.
assert_eq!(
VisitOnceFile::FirstVisit(DummyFile(expected_path)),
result
);
// Second time, already visited.
let result_2: VisitOnceFile<DummyFile> = fs.open(path).unwrap();
assert_eq!(VisitOnceFile::Visited, result_2);
}
}
}