721 lines
23 KiB
Rust
721 lines
23 KiB
Rust
#![doc = include_str!("../README.md")]
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#![warn(missing_docs)]
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use std::{
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any::Any,
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cell::{Cell, Ref, RefCell, RefMut},
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error::Error,
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fmt::{Debug, Display},
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marker::PhantomData,
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ops::{Deref, DerefMut},
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rc::Rc,
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};
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use bumpalo::Bump;
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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.0.data.as_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.0.data.as_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!(
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key.try_read().as_deref().unwrap(),
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&"hello world".to_string()
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);
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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_err());
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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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#[cfg(any(debug_assertions, feature = "debug_ownership"))]
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created_at: &'static std::panic::Location<'static>,
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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.0.data.as_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.0.generation.get() == 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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#[track_caller]
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pub fn try_read(&self) -> Result<GenerationalRef<T>, BorrowError> {
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if !self.validate() {
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return Err(BorrowError::Dropped(ValueDroppedError {
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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created_at: self.created_at,
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}));
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}
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self.raw.try_borrow(
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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self.created_at,
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)
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}
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/// Read the value. Panics if the value is no longer valid.
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#[track_caller]
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pub fn read(&self) -> GenerationalRef<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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#[track_caller]
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pub fn try_write(&self) -> Result<GenerationalRefMut<T>, BorrowMutError> {
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if !self.validate() {
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return Err(BorrowMutError::Dropped(ValueDroppedError {
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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created_at: self.created_at,
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}));
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}
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self.raw.try_borrow_mut(
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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self.created_at,
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)
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}
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/// Write the value. Panics if the value is no longer valid.
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#[track_caller]
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pub fn write(&self) -> GenerationalRefMut<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.0.data.borrow_mut() = 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.0.data.as_ptr() == other.raw.0.data.as_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(&'static MemoryLocationInner);
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struct MemoryLocationInner {
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data: RefCell<Option<Box<dyn std::any::Any>>>,
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#[cfg(any(debug_assertions, feature = "check_generation"))]
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generation: Cell<u32>,
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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borrowed_at: RefCell<Vec<&'static std::panic::Location<'static>>>,
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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borrowed_mut_at: Cell<Option<&'static std::panic::Location<'static>>>,
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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.0.data.borrow_mut().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.0.generation.get() + 1;
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self.0.generation.set(new_generation);
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}
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}
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fn replace_with_caller<T: 'static>(
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&mut self,
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value: T,
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#[cfg(any(debug_assertions, feature = "debug_ownership"))]
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caller: &'static std::panic::Location<'static>,
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) -> GenerationalBox<T> {
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let mut inner_mut = self.0.data.borrow_mut();
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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.0.generation.get(),
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#[cfg(any(debug_assertions, feature = "debug_ownership"))]
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created_at: caller,
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_marker: PhantomData,
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}
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}
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#[track_caller]
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fn try_borrow<T: Any>(
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&self,
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#[cfg(any(debug_assertions, feature = "debug_ownership"))]
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created_at: &'static std::panic::Location<'static>,
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) -> Result<GenerationalRef<T>, BorrowError> {
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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self.0
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.borrowed_at
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.borrow_mut()
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.push(std::panic::Location::caller());
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match self.0.data.try_borrow() {
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Ok(borrow) => match Ref::filter_map(borrow, |any| any.as_ref()?.downcast_ref::<T>()) {
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Ok(reference) => Ok(GenerationalRef {
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inner: reference,
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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borrow: GenerationalRefBorrowInfo {
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borrowed_at: std::panic::Location::caller(),
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borrowed_from: self.0,
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},
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}),
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Err(_) => Err(BorrowError::Dropped(ValueDroppedError {
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#[cfg(any(debug_assertions, feature = "debug_ownership"))]
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created_at,
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})),
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},
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Err(_) => Err(BorrowError::AlreadyBorrowedMut(AlreadyBorrowedMutError {
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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borrowed_mut_at: self.0.borrowed_mut_at.get().unwrap(),
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})),
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}
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}
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#[track_caller]
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fn try_borrow_mut<T: Any>(
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&self,
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#[cfg(any(debug_assertions, feature = "debug_ownership"))]
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created_at: &'static std::panic::Location<'static>,
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) -> Result<GenerationalRefMut<T>, BorrowMutError> {
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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{
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self.0
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.borrowed_mut_at
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.set(Some(std::panic::Location::caller()));
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}
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match self.0.data.try_borrow_mut() {
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Ok(borrow_mut) => {
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match RefMut::filter_map(borrow_mut, |any| any.as_mut()?.downcast_mut::<T>()) {
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Ok(reference) => Ok(GenerationalRefMut {
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inner: reference,
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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borrow: GenerationalRefMutBorrowInfo {
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borrowed_from: self.0,
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},
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}),
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Err(_) => Err(BorrowMutError::Dropped(ValueDroppedError {
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#[cfg(any(debug_assertions, feature = "debug_ownership"))]
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created_at,
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})),
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}
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}
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Err(_) => Err(BorrowMutError::AlreadyBorrowed(AlreadyBorrowedError {
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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borrowed_at: self.0.borrowed_at.borrow().clone(),
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})),
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}
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}
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}
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#[derive(Debug, Clone)]
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/// An error that can occur when trying to borrow a value.
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pub enum BorrowError {
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/// The value was dropped.
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Dropped(ValueDroppedError),
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/// The value was already borrowed mutably.
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AlreadyBorrowedMut(AlreadyBorrowedMutError),
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}
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impl Display for BorrowError {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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match self {
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BorrowError::Dropped(error) => Display::fmt(error, f),
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BorrowError::AlreadyBorrowedMut(error) => Display::fmt(error, f),
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}
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}
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}
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impl Error for BorrowError {}
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#[derive(Debug, Clone)]
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/// An error that can occur when trying to borrow a value mutably.
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pub enum BorrowMutError {
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/// The value was dropped.
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Dropped(ValueDroppedError),
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/// The value was already borrowed.
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AlreadyBorrowed(AlreadyBorrowedError),
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/// The value was already borrowed mutably.
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AlreadyBorrowedMut(AlreadyBorrowedMutError),
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}
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impl Display for BorrowMutError {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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match self {
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BorrowMutError::Dropped(error) => Display::fmt(error, f),
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BorrowMutError::AlreadyBorrowedMut(error) => Display::fmt(error, f),
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BorrowMutError::AlreadyBorrowed(error) => Display::fmt(error, f),
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}
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}
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}
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impl Error for BorrowMutError {}
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/// An error that can occur when trying to use a value that has been dropped.
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#[derive(Debug, Copy, Clone)]
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pub struct ValueDroppedError {
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#[cfg(any(debug_assertions, feature = "debug_ownership"))]
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created_at: &'static std::panic::Location<'static>,
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}
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impl Display for ValueDroppedError {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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f.write_str("Failed to borrow because the value was dropped.")?;
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#[cfg(any(debug_assertions, feature = "debug_ownership"))]
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f.write_fmt(format_args!("created_at: {}", self.created_at))?;
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Ok(())
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}
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}
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|
|
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impl std::error::Error for ValueDroppedError {}
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|
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/// An error that can occur when trying to borrow a value that has already been borrowed mutably.
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#[derive(Debug, Copy, Clone)]
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pub struct AlreadyBorrowedMutError {
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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borrowed_mut_at: &'static std::panic::Location<'static>,
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}
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|
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impl Display for AlreadyBorrowedMutError {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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f.write_str("Failed to borrow because the value was already borrowed mutably.")?;
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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f.write_fmt(format_args!("borrowed_mut_at: {}", self.borrowed_mut_at))?;
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Ok(())
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}
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}
|
|
|
|
impl std::error::Error for AlreadyBorrowedMutError {}
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|
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|
/// An error that can occur when trying to borrow a value mutably that has already been borrowed immutably.
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#[derive(Debug, Clone)]
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pub struct AlreadyBorrowedError {
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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borrowed_at: Vec<&'static std::panic::Location<'static>>,
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}
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|
|
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impl Display for AlreadyBorrowedError {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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f.write_str("Failed to borrow mutably because the value was already borrowed immutably.")?;
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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f.write_str("borrowed_at:")?;
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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for location in self.borrowed_at.iter() {
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f.write_fmt(format_args!("\t{}", location))?;
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}
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Ok(())
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}
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}
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|
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impl std::error::Error for AlreadyBorrowedError {}
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/// A reference to a value in a generational box.
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|
pub struct GenerationalRef<T: 'static> {
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inner: Ref<'static, T>,
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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borrow: GenerationalRefBorrowInfo,
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}
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|
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impl<T: 'static> GenerationalRef<T> {
|
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/// Map one ref type to another.
|
|
pub fn map<U, F>(orig: GenerationalRef<T>, f: F) -> GenerationalRef<U>
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|
where
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F: FnOnce(&T) -> &U,
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|
{
|
|
GenerationalRef {
|
|
inner: Ref::map(orig.inner, f),
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#[cfg(any(debug_assertions, feature = "debug_borrows"))]
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borrow: GenerationalRefBorrowInfo {
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borrowed_at: orig.borrow.borrowed_at,
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|
borrowed_from: orig.borrow.borrowed_from,
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},
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|
}
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|
}
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|
|
|
/// Filter one ref type to another.
|
|
pub fn filter_map<U, F>(orig: GenerationalRef<T>, f: F) -> Option<GenerationalRef<U>>
|
|
where
|
|
F: FnOnce(&T) -> Option<&U>,
|
|
{
|
|
let Self {
|
|
inner,
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
borrow,
|
|
} = orig;
|
|
Ref::filter_map(inner, f).ok().map(|inner| GenerationalRef {
|
|
inner,
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
borrow: GenerationalRefBorrowInfo {
|
|
borrowed_at: borrow.borrowed_at,
|
|
borrowed_from: borrow.borrowed_from,
|
|
},
|
|
})
|
|
}
|
|
}
|
|
|
|
impl<T: 'static> Deref for GenerationalRef<T> {
|
|
type Target = T;
|
|
|
|
fn deref(&self) -> &Self::Target {
|
|
self.inner.deref()
|
|
}
|
|
}
|
|
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
struct GenerationalRefBorrowInfo {
|
|
borrowed_at: &'static std::panic::Location<'static>,
|
|
borrowed_from: &'static MemoryLocationInner,
|
|
}
|
|
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
impl Drop for GenerationalRefBorrowInfo {
|
|
fn drop(&mut self) {
|
|
self.borrowed_from
|
|
.borrowed_at
|
|
.borrow_mut()
|
|
.retain(|location| std::ptr::eq(*location, self.borrowed_at as *const _));
|
|
}
|
|
}
|
|
|
|
/// A mutable reference to a value in a generational box.
|
|
pub struct GenerationalRefMut<T: 'static> {
|
|
inner: RefMut<'static, T>,
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
borrow: GenerationalRefMutBorrowInfo,
|
|
}
|
|
|
|
impl<T: 'static> GenerationalRefMut<T> {
|
|
/// Map one ref type to another.
|
|
pub fn map<U, F>(orig: GenerationalRefMut<T>, f: F) -> GenerationalRefMut<U>
|
|
where
|
|
F: FnOnce(&mut T) -> &mut U,
|
|
{
|
|
GenerationalRefMut {
|
|
inner: RefMut::map(orig.inner, f),
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
borrow: orig.borrow,
|
|
}
|
|
}
|
|
|
|
/// Filter one ref type to another.
|
|
pub fn filter_map<U, F>(orig: GenerationalRefMut<T>, f: F) -> Option<GenerationalRefMut<U>>
|
|
where
|
|
F: FnOnce(&mut T) -> Option<&mut U>,
|
|
{
|
|
let Self {
|
|
inner,
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
borrow,
|
|
} = orig;
|
|
RefMut::filter_map(inner, f)
|
|
.ok()
|
|
.map(|inner| GenerationalRefMut {
|
|
inner,
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
borrow,
|
|
})
|
|
}
|
|
}
|
|
|
|
impl<T: 'static> Deref for GenerationalRefMut<T> {
|
|
type Target = T;
|
|
|
|
fn deref(&self) -> &Self::Target {
|
|
self.inner.deref()
|
|
}
|
|
}
|
|
|
|
impl<T: 'static> DerefMut for GenerationalRefMut<T> {
|
|
fn deref_mut(&mut self) -> &mut Self::Target {
|
|
self.inner.deref_mut()
|
|
}
|
|
}
|
|
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
struct GenerationalRefMutBorrowInfo {
|
|
borrowed_from: &'static MemoryLocationInner,
|
|
}
|
|
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
impl Drop for GenerationalRefMutBorrowInfo {
|
|
fn drop(&mut self) {
|
|
self.borrowed_from.borrowed_mut_at.take();
|
|
}
|
|
}
|
|
|
|
/// Handles recycling generational boxes that have been dropped. Your application should have one store or one store per thread.
|
|
#[derive(Clone)]
|
|
pub struct Store {
|
|
bump: &'static Bump,
|
|
recycled: Rc<RefCell<Vec<MemoryLocation>>>,
|
|
}
|
|
|
|
impl Default for Store {
|
|
fn default() -> Self {
|
|
Self {
|
|
bump: Box::leak(Box::new(Bump::new())),
|
|
recycled: Default::default(),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl Store {
|
|
fn recycle(&self, location: MemoryLocation) {
|
|
location.drop();
|
|
self.recycled.borrow_mut().push(location);
|
|
}
|
|
|
|
fn claim(&self) -> MemoryLocation {
|
|
if let Some(location) = self.recycled.borrow_mut().pop() {
|
|
location
|
|
} else {
|
|
let data: &'static MemoryLocationInner = self.bump.alloc(MemoryLocationInner {
|
|
data: RefCell::new(None),
|
|
#[cfg(any(debug_assertions, feature = "check_generation"))]
|
|
generation: Cell::new(0),
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
borrowed_at: Default::default(),
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
borrowed_mut_at: Default::default(),
|
|
});
|
|
MemoryLocation(data)
|
|
}
|
|
}
|
|
|
|
/// Create a new owner. The owner will be responsible for dropping all of the generational boxes that it creates.
|
|
pub fn owner(&self) -> Owner {
|
|
Owner {
|
|
store: self.clone(),
|
|
owned: Default::default(),
|
|
}
|
|
}
|
|
}
|
|
|
|
/// 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.
|
|
pub struct Owner {
|
|
store: Store,
|
|
owned: Rc<RefCell<Vec<MemoryLocation>>>,
|
|
}
|
|
|
|
impl Owner {
|
|
/// Insert a value into the store. The value will be dropped when the owner is dropped.
|
|
#[track_caller]
|
|
pub fn insert<T: 'static>(&self, value: T) -> GenerationalBox<T> {
|
|
let mut location = self.store.claim();
|
|
let key = location.replace_with_caller(
|
|
value,
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
std::panic::Location::caller(),
|
|
);
|
|
self.owned.borrow_mut().push(location);
|
|
key
|
|
}
|
|
|
|
/// Insert a value into the store with a specific location blamed for creating the value. The value will be dropped when the owner is dropped.
|
|
pub fn insert_with_caller<T: 'static>(
|
|
&self,
|
|
value: T,
|
|
#[cfg(any(debug_assertions, feature = "debug_ownership"))]
|
|
caller: &'static std::panic::Location<'static>,
|
|
) -> GenerationalBox<T> {
|
|
let mut location = self.store.claim();
|
|
let key = location.replace_with_caller(
|
|
value,
|
|
#[cfg(any(debug_assertions, feature = "debug_borrows"))]
|
|
caller,
|
|
);
|
|
self.owned.borrow_mut().push(location);
|
|
key
|
|
}
|
|
|
|
/// 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.
|
|
pub fn invalid<T: 'static>(&self) -> GenerationalBox<T> {
|
|
let location = self.store.claim();
|
|
GenerationalBox {
|
|
raw: location,
|
|
#[cfg(any(debug_assertions, feature = "check_generation"))]
|
|
generation: location.0.generation.get(),
|
|
#[cfg(any(debug_assertions, feature = "debug_ownership"))]
|
|
created_at: std::panic::Location::caller(),
|
|
_marker: PhantomData,
|
|
}
|
|
}
|
|
}
|
|
|
|
impl Drop for Owner {
|
|
fn drop(&mut self) {
|
|
for location in self.owned.borrow().iter() {
|
|
self.store.recycle(*location)
|
|
}
|
|
}
|
|
}
|