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//! Filesystem utilities
//!
//! These are will be parallel if the `parallel` feature is enabled, at the expense of compiling additional dependencies
//! along with runtime costs for maintaining a global [`rayon`](https://docs.rs/rayon) thread pool.
//!
//! For information on how to use the [`WalkDir`] type, have a look at
//! * [`jwalk::WalkDir`](https://docs.rs/jwalk/0.5.1/jwalk/type.WalkDir.html) if `parallel` feature is enabled
//! * [walkdir::WalkDir](https://docs.rs/walkdir/2.3.1/walkdir/struct.WalkDir.html) otherwise
#[cfg(any(feature = "walkdir", feature = "fs-walkdir-parallel"))]
mod shared {
/// The desired level of parallelism.
pub enum Parallelism {
/// Do not parallelize at all by making a serial traversal on the current thread.
Serial,
/// Create a new thread pool for each traversal with up to 16 threads or the amount of logical cores of the machine.
ThreadPoolPerTraversal {
/// The base name of the threads we create as part of the thread-pool.
thread_name: &'static str,
},
}
}
///
#[cfg(feature = "fs-walkdir-parallel")]
pub mod walkdir {
use std::path::Path;
pub use jwalk::{DirEntry as DirEntryGeneric, DirEntryIter as DirEntryIterGeneric, Error, WalkDir};
pub use super::shared::Parallelism;
/// An alias for an uncustomized directory entry to match the one of the non-parallel version offered by `walkdir`.
pub type DirEntry = DirEntryGeneric<((), ())>;
impl From<Parallelism> for jwalk::Parallelism {
fn from(v: Parallelism) -> Self {
match v {
Parallelism::Serial => jwalk::Parallelism::Serial,
Parallelism::ThreadPoolPerTraversal { thread_name } => {
let pool = jwalk::rayon::ThreadPoolBuilder::new()
.num_threads(num_cpus::get().min(16))
.stack_size(128 * 1024)
.thread_name(move |idx| format!("{thread_name} {idx}"))
.build()
.expect("we only set options that can't cause a build failure");
jwalk::Parallelism::RayonExistingPool {
pool: pool.into(),
busy_timeout: None,
}
}
}
}
}
/// Instantiate a new directory iterator which will not skip hidden files, with the given level of `parallelism`.
pub fn walkdir_new(root: impl AsRef<Path>, parallelism: Parallelism) -> WalkDir {
WalkDir::new(root).skip_hidden(false).parallelism(parallelism.into())
}
/// Instantiate a new directory iterator which will not skip hidden files and is sorted
pub fn walkdir_sorted_new(root: impl AsRef<Path>, parallelism: Parallelism) -> WalkDir {
WalkDir::new(root)
.skip_hidden(false)
.sort(true)
.parallelism(parallelism.into())
}
/// The Iterator yielding directory items
pub type DirEntryIter = DirEntryIterGeneric<((), ())>;
}
#[cfg(all(feature = "walkdir", not(feature = "fs-walkdir-parallel")))]
///
pub mod walkdir {
use std::path::Path;
pub use walkdir::{DirEntry, Error, WalkDir};
pub use super::shared::Parallelism;
/// Instantiate a new directory iterator which will not skip hidden files, with the given level of `parallelism`.
pub fn walkdir_new(root: impl AsRef<Path>, _: Parallelism) -> WalkDir {
WalkDir::new(root)
}
/// Instantiate a new directory iterator which will not skip hidden files and is sorted, with the given level of `parallelism`.
pub fn walkdir_sorted_new(root: impl AsRef<Path>, _: Parallelism) -> WalkDir {
WalkDir::new(root).sort_by_file_name()
}
/// The Iterator yielding directory items
pub type DirEntryIter = walkdir::IntoIter;
}
#[cfg(any(feature = "walkdir", feature = "fs-walkdir-parallel"))]
pub use self::walkdir::{walkdir_new, walkdir_sorted_new, WalkDir};
/// Prepare open options which won't follow symlinks when the file is opened.
///
/// Note: only effective on unix currently.
pub fn open_options_no_follow() -> std::fs::OpenOptions {
#[cfg_attr(not(unix), allow(unused_mut))]
let mut options = std::fs::OpenOptions::new();
#[cfg(unix)]
{
/// Make sure that it's impossible to follow through to the target of symlinks.
/// Note that this will still follow symlinks in the path, which is what we assume
/// has been checked separately.
use std::os::unix::fs::OpenOptionsExt;
options.custom_flags(libc::O_NOFOLLOW);
}
options
}
mod snapshot {
use std::ops::Deref;
use crate::threading::{get_mut, get_ref, MutableOnDemand, OwnShared};
/// A structure holding enough information to reload a value if its on-disk representation changes as determined by its modified time.
#[derive(Debug)]
pub struct Snapshot<T: std::fmt::Debug> {
value: T,
modified: std::time::SystemTime,
}
impl<T: Clone + std::fmt::Debug> Clone for Snapshot<T> {
fn clone(&self) -> Self {
Self {
value: self.value.clone(),
modified: self.modified,
}
}
}
/// A snapshot of a resource which is up-to-date in the moment it is retrieved.
pub type SharedSnapshot<T> = OwnShared<Snapshot<T>>;
/// Use this type for fields in structs that are to store the [`Snapshot`], typically behind an [`OwnShared`].
///
/// Note that the resource itself is behind another [`OwnShared`] to allow it to be used without holding any kind of lock, hence
/// without blocking updates while it is used.
#[derive(Debug, Default)]
pub struct MutableSnapshot<T: std::fmt::Debug>(pub MutableOnDemand<Option<SharedSnapshot<T>>>);
impl<T: std::fmt::Debug> Deref for Snapshot<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.value
}
}
impl<T: std::fmt::Debug> Deref for MutableSnapshot<T> {
type Target = MutableOnDemand<Option<SharedSnapshot<T>>>;
fn deref(&self) -> &Self::Target {
&self.0
}
}
impl<T: std::fmt::Debug> MutableSnapshot<T> {
/// Create a new instance of this type.
///
/// Useful in case `Default::default()` isn't working for some reason.
pub fn new() -> Self {
MutableSnapshot(MutableOnDemand::new(None))
}
/// Refresh `state` forcefully by re-`open`ing the resource. Note that `open()` returns `None` if the resource isn't
/// present on disk, and that it's critical that the modified time is obtained _before_ opening the resource.
pub fn force_refresh<E>(
&self,
open: impl FnOnce() -> Result<Option<(std::time::SystemTime, T)>, E>,
) -> Result<(), E> {
let mut state = get_mut(&self.0);
*state = open()?.map(|(modified, value)| OwnShared::new(Snapshot { value, modified }));
Ok(())
}
/// Assure that the resource in `state` is up-to-date by comparing the `current_modification_time` with the one we know in `state`
/// and by acting accordingly.
/// Returns the potentially updated/reloaded resource if it is still present on disk, which then represents a snapshot that is up-to-date
/// in that very moment, or `None` if the underlying file doesn't exist.
///
/// Note that even though this is racy, each time a request is made there is a chance to see the actual state.
pub fn recent_snapshot<E>(
&self,
mut current_modification_time: impl FnMut() -> Option<std::time::SystemTime>,
open: impl FnOnce() -> Result<Option<T>, E>,
) -> Result<Option<SharedSnapshot<T>>, E> {
let state = get_ref(self);
let recent_modification = current_modification_time();
let buffer = match (&*state, recent_modification) {
(None, None) => (*state).clone(),
(Some(_), None) => {
drop(state);
let mut state = get_mut(self);
*state = None;
(*state).clone()
}
(Some(snapshot), Some(modified_time)) => {
if snapshot.modified < modified_time {
drop(state);
let mut state = get_mut(self);
if let (Some(_snapshot), Some(modified_time)) = (&*state, current_modification_time()) {
*state = open()?.map(|value| {
OwnShared::new(Snapshot {
value,
modified: modified_time,
})
});
}
(*state).clone()
} else {
// Note that this relies on sub-section precision or else is a race when the packed file was just changed.
// It's nothing we can know though, so… up to the caller unfortunately.
Some(snapshot.clone())
}
}
(None, Some(_modified_time)) => {
drop(state);
let mut state = get_mut(self);
// Still in the same situation? If so, load the buffer. This compensates for the trampling herd
// during lazy-loading at the expense of another mtime check.
if let (None, Some(modified_time)) = (&*state, current_modification_time()) {
*state = open()?.map(|value| {
OwnShared::new(Snapshot {
value,
modified: modified_time,
})
});
}
(*state).clone()
}
};
Ok(buffer)
}
}
}
pub use snapshot::{MutableSnapshot, SharedSnapshot, Snapshot};