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use std::{collections::HashMap, sync::Arc};
use super::inodes::{DirectoryInodeData, InodeData};
use crate::B3Digest;
/// InodeTracker keeps track of inodes, stores data being these inodes and deals
/// with inode allocation.
pub struct InodeTracker {
data: HashMap<u64, Arc<InodeData>>,
// lookup table for blobs by their B3Digest
blob_digest_to_inode: HashMap<B3Digest, u64>,
// lookup table for symlinks by their target
symlink_target_to_inode: HashMap<bytes::Bytes, u64>,
// lookup table for directories by their B3Digest.
// Note the corresponding directory may not be present in data yet.
directory_digest_to_inode: HashMap<B3Digest, u64>,
// the next inode to allocate
next_inode: u64,
}
impl Default for InodeTracker {
fn default() -> Self {
Self {
data: Default::default(),
blob_digest_to_inode: Default::default(),
symlink_target_to_inode: Default::default(),
directory_digest_to_inode: Default::default(),
next_inode: 2,
}
}
}
impl InodeTracker {
// Retrieves data for a given inode, if it exists.
pub fn get(&self, ino: u64) -> Option<Arc<InodeData>> {
self.data.get(&ino).cloned()
}
// Replaces data for a given inode.
// Panics if the inode doesn't already exist.
pub fn replace(&mut self, ino: u64, data: Arc<InodeData>) {
if self.data.insert(ino, data).is_none() {
panic!("replace called on unknown inode");
}
}
// Stores data and returns the inode for it.
// In case an inode has already been allocated for the same data, that inode
// is returned, otherwise a new one is allocated.
// In case data is a [InodeData::Directory], inodes for all items are looked
// up
pub fn put(&mut self, data: InodeData) -> u64 {
match data {
InodeData::Regular(ref digest, _, _) => {
match self.blob_digest_to_inode.get(digest) {
Some(found_ino) => {
// We already have it, return the inode.
*found_ino
}
None => self.insert_and_increment(data),
}
}
InodeData::Symlink(ref target) => {
match self.symlink_target_to_inode.get(target) {
Some(found_ino) => {
// We already have it, return the inode.
*found_ino
}
None => self.insert_and_increment(data),
}
}
InodeData::Directory(DirectoryInodeData::Sparse(ref digest, _size)) => {
// check the lookup table if the B3Digest is known.
match self.directory_digest_to_inode.get(digest) {
Some(found_ino) => {
// We already have it, return the inode.
*found_ino
}
None => {
// insert and return the inode
self.insert_and_increment(data)
}
}
}
// Inserting [DirectoryInodeData::Populated] doesn't normally happen,
// only via [replace].
InodeData::Directory(DirectoryInodeData::Populated(..)) => {
unreachable!("should never be called with DirectoryInodeData::Populated")
}
}
}
// Inserts the data and returns the inode it was stored at, while
// incrementing next_inode.
fn insert_and_increment(&mut self, data: InodeData) -> u64 {
let ino = self.next_inode;
// insert into lookup tables
match data {
InodeData::Regular(ref digest, _, _) => {
self.blob_digest_to_inode.insert(digest.clone(), ino);
}
InodeData::Symlink(ref target) => {
self.symlink_target_to_inode.insert(target.clone(), ino);
}
InodeData::Directory(DirectoryInodeData::Sparse(ref digest, _size)) => {
self.directory_digest_to_inode.insert(digest.clone(), ino);
}
// This is currently not used outside test fixtures.
// Usually a [DirectoryInodeData::Sparse] is inserted and later
// "upgraded" with more data.
// However, as a future optimization, a lookup for a PathInfo could trigger a
// [DirectoryService::get_recursive()] request that "forks into
// background" and prepopulates all Directories in a closure.
InodeData::Directory(DirectoryInodeData::Populated(ref digest, _)) => {
self.directory_digest_to_inode.insert(digest.clone(), ino);
}
}
// Insert data
self.data.insert(ino, Arc::new(data));
// increment inode counter and return old inode.
self.next_inode += 1;
ino
}
}
#[cfg(test)]
mod tests {
use crate::fixtures;
use super::InodeData;
use super::InodeTracker;
/// Getting something non-existent should be none
#[test]
fn get_nonexistent() {
let inode_tracker = InodeTracker::default();
assert!(inode_tracker.get(1).is_none());
}
/// Put of a regular file should allocate a uid, which should be the same when inserting again.
#[test]
fn put_regular() {
let mut inode_tracker = InodeTracker::default();
let f = InodeData::Regular(
fixtures::BLOB_A_DIGEST.clone(),
fixtures::BLOB_A.len() as u64,
false,
);
// put it in
let ino = inode_tracker.put(f.clone());
// a get should return the right data
let data = inode_tracker.get(ino).expect("must be some");
match *data {
InodeData::Regular(ref digest, _, _) => {
assert_eq!(&fixtures::BLOB_A_DIGEST.clone(), digest);
}
InodeData::Symlink(_) | InodeData::Directory(..) => panic!("wrong type"),
}
// another put should return the same ino
assert_eq!(ino, inode_tracker.put(f));
// inserting another file should return a different ino
assert_ne!(
ino,
inode_tracker.put(InodeData::Regular(
fixtures::BLOB_B_DIGEST.clone(),
fixtures::BLOB_B.len() as u64,
false,
))
);
}
// Put of a symlink should allocate a uid, which should be the same when inserting again
#[test]
fn put_symlink() {
let mut inode_tracker = InodeTracker::default();
let f = InodeData::Symlink("target".into());
// put it in
let ino = inode_tracker.put(f.clone());
// a get should return the right data
let data = inode_tracker.get(ino).expect("must be some");
match *data {
InodeData::Symlink(ref target) => {
assert_eq!(b"target".to_vec(), *target);
}
InodeData::Regular(..) | InodeData::Directory(..) => panic!("wrong type"),
}
// another put should return the same ino
assert_eq!(ino, inode_tracker.put(f));
// inserting another file should return a different ino
assert_ne!(ino, inode_tracker.put(InodeData::Symlink("target2".into())));
}
}
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