rust/crates/vfs/src/file_set.rs
2021-06-13 09:24:16 +05:30

219 lines
6.5 KiB
Rust

//! Partitions a list of files into disjoint subsets.
//!
//! Files which do not belong to any explicitly configured `FileSet` belong to
//! the default `FileSet`.
use std::fmt;
use fst::{IntoStreamer, Streamer};
use rustc_hash::FxHashMap;
use crate::{AnchoredPath, FileId, Vfs, VfsPath};
/// A set of [`VfsPath`]s identified by [`FileId`]s.
#[derive(Default, Clone, Eq, PartialEq)]
pub struct FileSet {
files: FxHashMap<VfsPath, FileId>,
paths: FxHashMap<FileId, VfsPath>,
}
impl FileSet {
/// Returns the number of stored paths.
pub fn len(&self) -> usize {
self.files.len()
}
/// Get the id of the file corresponding to `path`.
///
/// If either `path`'s [`anchor`](AnchoredPath::anchor) or the resolved path is not in
/// the set, returns [`None`].
pub fn resolve_path(&self, path: AnchoredPath<'_>) -> Option<FileId> {
let mut base = self.paths[&path.anchor].clone();
base.pop();
let path = base.join(path.path)?;
self.files.get(&path).copied()
}
/// Get the id corresponding to `path` if it exists in the set.
pub fn file_for_path(&self, path: &VfsPath) -> Option<&FileId> {
self.files.get(path)
}
/// Get the path corresponding to `file` if it exists in the set.
pub fn path_for_file(&self, file: &FileId) -> Option<&VfsPath> {
self.paths.get(file)
}
/// Insert the `file_id, path` pair into the set.
///
/// # Note
/// Multiple [`FileId`] can be mapped to the same [`VfsPath`], and vice-versa.
pub fn insert(&mut self, file_id: FileId, path: VfsPath) {
self.files.insert(path.clone(), file_id);
self.paths.insert(file_id, path);
}
/// Iterate over this set's ids.
pub fn iter(&self) -> impl Iterator<Item = FileId> + '_ {
self.paths.keys().copied()
}
}
impl fmt::Debug for FileSet {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("FileSet").field("n_files", &self.files.len()).finish()
}
}
/// This contains path prefixes to partition a [`Vfs`] into [`FileSet`]s.
///
/// # Example
/// ```rust
/// # use vfs::{file_set::FileSetConfigBuilder, VfsPath, Vfs};
/// let mut builder = FileSetConfigBuilder::default();
/// builder.add_file_set(vec![VfsPath::new_virtual_path("/src".to_string())]);
/// let config = builder.build();
/// let mut file_system = Vfs::default();
/// file_system.set_file_contents(VfsPath::new_virtual_path("/src/main.rs".to_string()), Some(vec![]));
/// file_system.set_file_contents(VfsPath::new_virtual_path("/src/lib.rs".to_string()), Some(vec![]));
/// file_system.set_file_contents(VfsPath::new_virtual_path("/build.rs".to_string()), Some(vec![]));
/// // contains the sets :
/// // { "/src/main.rs", "/src/lib.rs" }
/// // { "build.rs" }
/// let sets = config.partition(&file_system);
/// ```
#[derive(Debug)]
pub struct FileSetConfig {
/// Number of sets that `self` can partition a [`Vfs`] into.
///
/// This should be the number of sets in `self.map` + 1 for files that don't fit in any
/// defined set.
n_file_sets: usize,
/// Map from encoded paths to the set they belong to.
map: fst::Map<Vec<u8>>,
}
impl Default for FileSetConfig {
fn default() -> Self {
FileSetConfig::builder().build()
}
}
impl FileSetConfig {
/// Returns a builder for `FileSetConfig`.
pub fn builder() -> FileSetConfigBuilder {
FileSetConfigBuilder::default()
}
/// Partition `vfs` into `FileSet`s.
///
/// Creates a new [`FileSet`] for every set of prefixes in `self`.
pub fn partition(&self, vfs: &Vfs) -> Vec<FileSet> {
let mut scratch_space = Vec::new();
let mut res = vec![FileSet::default(); self.len()];
for (file_id, path) in vfs.iter() {
let root = self.classify(path, &mut scratch_space);
res[root].insert(file_id, path.clone())
}
res
}
/// Number of sets that `self` can partition a [`Vfs`] into.
fn len(&self) -> usize {
self.n_file_sets
}
/// Returns the set index for the given `path`.
///
/// `scratch_space` is used as a buffer and will be entirely replaced.
fn classify(&self, path: &VfsPath, scratch_space: &mut Vec<u8>) -> usize {
scratch_space.clear();
path.encode(scratch_space);
let automaton = PrefixOf::new(scratch_space.as_slice());
let mut longest_prefix = self.len() - 1;
let mut stream = self.map.search(automaton).into_stream();
while let Some((_, v)) = stream.next() {
longest_prefix = v as usize;
}
longest_prefix
}
}
/// Builder for [`FileSetConfig`].
pub struct FileSetConfigBuilder {
roots: Vec<Vec<VfsPath>>,
}
impl Default for FileSetConfigBuilder {
fn default() -> Self {
FileSetConfigBuilder { roots: Vec::new() }
}
}
impl FileSetConfigBuilder {
/// Returns the number of sets currently held.
pub fn len(&self) -> usize {
self.roots.len()
}
/// Add a new set of paths prefixes.
pub fn add_file_set(&mut self, roots: Vec<VfsPath>) {
self.roots.push(roots)
}
/// Build the `FileSetConfig`.
pub fn build(self) -> FileSetConfig {
let n_file_sets = self.roots.len() + 1;
let map = {
let mut entries = Vec::new();
for (i, paths) in self.roots.into_iter().enumerate() {
for p in paths {
let mut buf = Vec::new();
p.encode(&mut buf);
entries.push((buf, i as u64));
}
}
entries.sort();
entries.dedup_by(|(a, _), (b, _)| a == b);
fst::Map::from_iter(entries).unwrap()
};
FileSetConfig { n_file_sets, map }
}
}
/// Implements [`fst::Automaton`]
///
/// It will match if `prefix_of` is a prefix of the given data.
struct PrefixOf<'a> {
prefix_of: &'a [u8],
}
impl<'a> PrefixOf<'a> {
/// Creates a new `PrefixOf` from the given slice.
fn new(prefix_of: &'a [u8]) -> Self {
Self { prefix_of }
}
}
impl fst::Automaton for PrefixOf<'_> {
type State = usize;
fn start(&self) -> usize {
0
}
fn is_match(&self, &state: &usize) -> bool {
state != !0
}
fn can_match(&self, &state: &usize) -> bool {
state != !0
}
fn accept(&self, &state: &usize, byte: u8) -> usize {
if self.prefix_of.get(state) == Some(&byte) {
state + 1
} else {
!0
}
}
}
#[cfg(test)]
mod tests;