160 lines
4 KiB
Rust
160 lines
4 KiB
Rust
use std::collections::HashMap;
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use std::fs::{File, remove_file};
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use std::ops::Drop;
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use std::path::PathBuf;
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use std::result::Result as RResult;
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use std::sync::Arc;
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use std::sync::RwLock;
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use fs2::FileExt;
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use entry::Entry;
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use error::{StoreError, StoreErrorKind};
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use storeid::StoreId;
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/// The Result Type returned by any interaction with the store that could fail
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pub type Result<T> = RResult<T, StoreError>;
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#[derive(PartialEq)]
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enum StoreEntryPresence {
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Present,
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Borrowed
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}
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/// A store entry, depending on the option type it is either borrowed currently
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/// or not.
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struct StoreEntry {
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file: File,
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entry: StoreEntryPresence
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}
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impl StoreEntry {
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/// The entry is currently borrowed, meaning that some thread is currently
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/// mutating it
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fn is_borrowed(&self) -> bool {
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self.entry == StoreEntryPresence::Borrowed
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}
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}
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/// The Store itself, through this object one can interact with IMAG's entries
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pub struct Store {
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location: PathBuf,
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/**
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* Internal Path->File cache map
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*
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* Caches the files, so they remain flock()ed
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*
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* Could be optimized for a threadsafe HashMap
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*/
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entries: Arc<RwLock<HashMap<StoreId, StoreEntry>>>,
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}
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impl Store {
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/// Create a new Store object
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pub fn new(location: PathBuf) -> Store {
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Store {
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location: location,
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entries: Arc::new(RwLock::new(HashMap::new())),
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}
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}
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/// Creates the Entry at the given location (inside the entry)
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pub fn create(&self, entry: Entry) -> Result<()> {
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unimplemented!();
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}
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/// Borrow a given Entry. When the `FileLockEntry` is either `update`d or
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/// dropped, the new Entry is written to disk
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pub fn retrieve<'a>(&'a self, id: StoreId) -> Result<FileLockEntry<'a>> {
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unimplemented!();
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}
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/// Return the `FileLockEntry` and write to disk
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pub fn update<'a>(&'a self, entry: FileLockEntry<'a>) -> Result<()> {
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self._update(&entry)
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}
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/// Internal method to write to the filesystem store.
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///
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/// # Assumptions
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/// This method assumes that entry is dropped _right after_ the call, hence
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/// it is not public.
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fn _update<'a>(&'a self, entry: &FileLockEntry<'a>) -> Result<()> {
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unimplemented!();
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}
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/// Retrieve a copy of a given entry, this cannot be used to mutate
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/// the one on disk
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pub fn retrieve_copy(&self, id: StoreId) -> Result<Entry> {
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unimplemented!();
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}
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/// Delete an entry
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pub fn delete(&self, id: StoreId) -> Result<()> {
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let mut entries_lock = self.entries.write();
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let mut entries = entries_lock.unwrap();
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// if the entry is currently modified by the user, we cannot drop it
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if entries.get(&id).map(|e| e.is_borrowed()).unwrap_or(false) {
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return Err(StoreError::new(StoreErrorKind::IdLocked, None));
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}
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// remove the entry first, then the file
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entries.remove(&id);
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remove_file(&id).map_err(|e| StoreError::new(StoreErrorKind::FileError, Some(Box::new(e))))
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}
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}
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impl Drop for Store {
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/**
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* Unlock all files on drop
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*
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* TODO: Error message when file cannot be unlocked?
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*/
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fn drop(&mut self) {
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self.entries.write().unwrap()
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.iter().map(|f| f.1.file.unlock());
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}
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}
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/// A struct that allows you to borrow an Entry
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pub struct FileLockEntry<'a> {
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store: &'a Store,
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entry: Entry,
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key: StoreId,
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}
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impl<'a> FileLockEntry<'a, > {
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fn new(store: &'a Store, entry: Entry, key: StoreId) -> FileLockEntry<'a> {
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FileLockEntry {
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store: store,
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entry: entry,
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key: key,
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}
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}
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}
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impl<'a> ::std::ops::Deref for FileLockEntry<'a> {
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type Target = Entry;
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fn deref(&self) -> &Self::Target {
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&self.entry
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}
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}
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impl<'a> ::std::ops::DerefMut for FileLockEntry<'a> {
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fn deref_mut(&mut self) -> &mut Self::Target {
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&mut self.entry
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}
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}
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impl<'a> Drop for FileLockEntry<'a> {
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fn drop(&mut self) {
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self.store._update(self).unwrap()
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}
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}
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