369 lines
10 KiB
Rust
369 lines
10 KiB
Rust
#![doc = include_str!("../README.md")]
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#![warn(missing_docs)]
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use parking_lot::{
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MappedRwLockReadGuard, MappedRwLockWriteGuard, Mutex, RwLock, RwLockReadGuard, RwLockWriteGuard,
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};
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use std::{
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cell::RefCell,
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fmt::Debug,
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marker::PhantomData,
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rc::Rc,
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sync::{atomic::AtomicU32, Arc},
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};
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mod testing;
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/// # Example
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///
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/// ```compile_fail
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/// let data = String::from("hello world");
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/// let store = Store::default();
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/// let owner = store.owner();
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/// let key = owner.insert(&data);
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/// drop(data);
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/// assert_eq!(*key.read(), "hello world");
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/// ```
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#[allow(unused)]
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fn compile_fail() {}
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#[test]
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fn reused() {
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let store = Store::default();
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let first_ptr;
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{
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let owner = store.owner();
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first_ptr = owner.insert(1).raw.data.data_ptr();
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drop(owner);
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}
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{
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let owner = store.owner();
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let second_ptr = owner.insert(1234).raw.data.data_ptr();
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assert_eq!(first_ptr, second_ptr);
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drop(owner);
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}
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}
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#[test]
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fn leaking_is_ok() {
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let data = String::from("hello world");
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let store = Store::default();
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let key;
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{
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// create an owner
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let owner = store.owner();
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// insert data into the store
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key = owner.insert(data);
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// don't drop the owner
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std::mem::forget(owner);
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}
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assert_eq!(key.try_read().as_deref(), Some(&"hello world".to_string()));
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}
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#[test]
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fn drops() {
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let data = String::from("hello world");
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let store = Store::default();
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let key;
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{
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// create an owner
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let owner = store.owner();
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// insert data into the store
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key = owner.insert(data);
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// drop the owner
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}
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assert!(key.try_read().is_none());
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}
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#[test]
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fn works() {
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let store = Store::default();
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let owner = store.owner();
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let key = owner.insert(1);
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assert_eq!(*key.read(), 1);
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}
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#[test]
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fn insert_while_reading() {
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let store = Store::default();
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let owner = store.owner();
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let key;
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{
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let data: String = "hello world".to_string();
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key = owner.insert(data);
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}
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let value = key.read();
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owner.insert(&1);
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assert_eq!(*value, "hello world");
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}
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#[test]
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#[should_panic]
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fn panics() {
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let store = Store::default();
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let owner = store.owner();
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let key = owner.insert(1);
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drop(owner);
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assert_eq!(*key.read(), 1);
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}
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#[test]
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fn fuzz() {
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fn maybe_owner_scope(
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store: &Store,
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valid_keys: &mut Vec<GenerationalBox<String>>,
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invalid_keys: &mut Vec<GenerationalBox<String>>,
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path: &mut Vec<u8>,
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) {
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let branch_cutoff = 5;
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let children = if path.len() < branch_cutoff {
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rand::random::<u8>() % 4
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} else {
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rand::random::<u8>() % 2
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};
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for i in 0..children {
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let owner = store.owner();
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let key = owner.insert(format!("hello world {path:?}"));
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valid_keys.push(key);
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path.push(i);
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// read all keys
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println!("{:?}", path);
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for key in valid_keys.iter() {
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let value = key.read();
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println!("{:?}", value);
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assert!(value.starts_with("hello world"));
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}
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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for key in invalid_keys.iter() {
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assert!(!key.validate());
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}
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maybe_owner_scope(store, valid_keys, invalid_keys, path);
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invalid_keys.push(valid_keys.pop().unwrap());
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path.pop();
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}
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}
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for _ in 0..10 {
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let store = Store::default();
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maybe_owner_scope(&store, &mut Vec::new(), &mut Vec::new(), &mut Vec::new());
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}
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}
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/// The core Copy state type. The generational box will be dropped when the [Owner] is dropped.
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pub struct GenerationalBox<T> {
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raw: MemoryLocation,
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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generation: u32,
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_marker: PhantomData<T>,
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}
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impl<T: 'static> Debug for GenerationalBox<T> {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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f.write_fmt(format_args!(
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"{:?}@{:?}",
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self.raw.data.data_ptr(),
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self.generation
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))?;
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#[cfg(not(any(debug_assertions, feature = "check_generation")))]
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f.write_fmt(format_args!("{:?}", self.raw.data.as_ptr()))?;
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Ok(())
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}
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}
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impl<T: 'static> GenerationalBox<T> {
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#[inline(always)]
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fn validate(&self) -> bool {
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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{
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self.raw
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.generation
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.load(std::sync::atomic::Ordering::Relaxed)
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== self.generation
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}
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#[cfg(not(any(debug_assertions, feature = "check_generation")))]
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{
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true
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}
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}
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/// Try to read the value. Returns None if the value is no longer valid.
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pub fn try_read(&self) -> Option<MappedRwLockReadGuard<'static, T>> {
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self.validate()
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.then(|| {
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RwLockReadGuard::try_map(self.raw.data.read(), |any| {
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any.as_ref()?.downcast_ref::<T>()
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})
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.ok()
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})
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.flatten()
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}
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/// Read the value. Panics if the value is no longer valid.
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pub fn read(&self) -> MappedRwLockReadGuard<'static, T> {
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self.try_read().unwrap()
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}
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/// Try to write the value. Returns None if the value is no longer valid.
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pub fn try_write(&self) -> Option<MappedRwLockWriteGuard<'static, T>> {
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self.validate()
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.then(|| {
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RwLockWriteGuard::try_map(self.raw.data.write(), |any| {
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any.as_mut()?.downcast_mut::<T>()
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})
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.ok()
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})
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.flatten()
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}
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/// Write the value. Panics if the value is no longer valid.
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pub fn write(&self) -> MappedRwLockWriteGuard<'static, T> {
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self.try_write().unwrap()
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}
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/// Set the value. Panics if the value is no longer valid.
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pub fn set(&self, value: T) {
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self.validate().then(|| {
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*self.raw.data.write() = Some(Box::new(value));
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});
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}
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/// Returns true if the pointer is equal to the other pointer.
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pub fn ptr_eq(&self, other: &Self) -> bool {
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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{
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self.raw.data.data_ptr() == other.raw.data.data_ptr()
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&& self.generation == other.generation
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}
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#[cfg(not(any(debug_assertions, feature = "check_generation")))]
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{
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self.raw.data.as_ptr() == other.raw.data.as_ptr()
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}
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}
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}
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impl<T> Copy for GenerationalBox<T> {}
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impl<T> Clone for GenerationalBox<T> {
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fn clone(&self) -> Self {
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*self
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}
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}
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#[derive(Clone, Copy)]
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struct MemoryLocation {
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data: &'static RwLock<Option<Box<dyn std::any::Any>>>,
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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generation: &'static AtomicU32,
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}
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impl MemoryLocation {
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#[allow(unused)]
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fn drop(&self) {
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let old = self.data.write().take();
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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if old.is_some() {
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drop(old);
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let new_generation = self.generation.load(std::sync::atomic::Ordering::Relaxed) + 1;
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self.generation
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.store(new_generation, std::sync::atomic::Ordering::Relaxed);
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}
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}
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fn replace<T: 'static>(&mut self, value: T) -> GenerationalBox<T> {
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let mut inner_mut = self.data.write();
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let raw = Box::new(value);
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let old = inner_mut.replace(raw);
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assert!(old.is_none());
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GenerationalBox {
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raw: *self,
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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generation: self.generation.load(std::sync::atomic::Ordering::Relaxed),
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_marker: PhantomData,
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}
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}
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}
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/// Handles recycling generational boxes that have been dropped. Your application should have one store or one store per thread.
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#[derive(Clone)]
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pub struct Store {
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recycled: Arc<Mutex<Vec<MemoryLocation>>>,
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}
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impl Default for Store {
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fn default() -> Self {
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Self {
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recycled: Default::default(),
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}
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}
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}
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impl Store {
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fn recycle(&self, location: MemoryLocation) {
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location.drop();
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self.recycled.lock().push(location);
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}
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fn claim(&self) -> MemoryLocation {
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if let Some(location) = self.recycled.lock().pop() {
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location
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} else {
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let data: &'static RwLock<_> = Box::leak(Box::new(RwLock::new(None)));
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MemoryLocation {
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data,
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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generation: Box::leak(Box::new(Default::default())),
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}
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}
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}
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/// Create a new owner. The owner will be responsible for dropping all of the generational boxes that it creates.
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pub fn owner(&self) -> Owner {
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Owner {
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store: self.clone(),
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owned: Default::default(),
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}
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}
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}
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/// Owner: Handles dropping generational boxes. The owner acts like a runtime lifetime guard. Any states that you create with an owner will be dropped when that owner is dropped.
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pub struct Owner {
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store: Store,
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owned: Rc<RefCell<Vec<MemoryLocation>>>,
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}
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impl Owner {
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/// Insert a value into the store. The value will be dropped when the owner is dropped.
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pub fn insert<T: 'static>(&self, value: T) -> GenerationalBox<T> {
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let mut location = self.store.claim();
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let key = location.replace(value);
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self.owned.borrow_mut().push(location);
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key
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}
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/// Creates an invalid handle. This is useful for creating a handle that will be filled in later. If you use this before the value is filled in, you will get may get a panic or an out of date value.
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pub fn invalid<T: 'static>(&self) -> GenerationalBox<T> {
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let location = self.store.claim();
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GenerationalBox {
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raw: location,
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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generation: location
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.generation
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.load(std::sync::atomic::Ordering::Relaxed),
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_marker: PhantomData,
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}
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}
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}
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impl Drop for Owner {
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fn drop(&mut self) {
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for location in self.owned.borrow().iter() {
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self.store.recycle(*location)
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}
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}
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}
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