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//! shredder //! ======== //! `shredder` is a library providing a garbage collected smart pointer: `Gc`. //! This is useful for times when you want shared access to some data, but the structure //! of the data has unpredictable cycles in it. (So Arc would not be appropriate.) //! //! `shredder` has the following features: //! - safe: detects error conditions on the fly, and protects you from undefined behavior //! - ergonomic: no need to manually manage roots, just a regular smart pointer //! - deref support: `DerefGc` gives you a garbage collected and `Deref` smart pointer where possible //! - ready for fearless concurrency: works in multi-threaded contexts, with `AtomicGc` for cases where you need atomic operations //! - limited stop-the world: regular processing will rarely be interrupted //! - seamless destruction: regular `drop` for `'static` data //! - clean finalization: optional `finalize` for non-`'static` data //! - concurrent collection: collection happens in the background, improving performance //! - concurrent destruction: destructors are run in the background, improving performance //! //! `shredder` has the following limitations: //! - guarded access: accessing `Gc` data requires acquiring a guard (although you can use `DerefGc` in many cases to avoid this) //! - multiple collectors: only a single global collector is supported //! - can't handle `Rc`/`Arc`: requires all `Gc` objects have straightforward ownership semantics //! - collection optimized for speed, not memory use: `Gc` and internal metadata is small, but there is bloat during collection (will fix!) //! - no no-std support: The collector requires threading and other `std` features (will fix!) #![cfg_attr(feature = "nightly-features", feature(unsize, coerce_unsized))] // We love docs here #![deny(missing_docs)] // Clippy configuration: // I'd like the most pedantic warning level #![warn( clippy::cargo, clippy::needless_borrow, clippy::pedantic, clippy::redundant_clone, clippy::use_self, rust_2018_idioms )] // But I don't care about these ones #![allow( clippy::cast_precision_loss, // There is no way to avoid this precision loss clippy::explicit_deref_methods, // Sometimes calling `deref` directly is clearer clippy::module_name_repetitions, // Sometimes clear naming calls for repetition clippy::multiple_crate_versions // There is no way to easily fix this without modifying our dependencies )] #[macro_use] extern crate crossbeam; #[macro_use] extern crate log; #[macro_use] extern crate rental; /// Atomic gc operations pub mod atomic; mod collector; mod concurrency; mod finalize; /// Marker types pub mod marker; /// Various types used for plumbing, stuff you don't need to care about pub mod plumbing; mod r; mod scan; mod smart_ptr; mod std_impls; /// Helpful wrappers used for convenience methods pub mod wrappers; use std::cell::RefCell; use std::sync::{Mutex, RwLock}; use crate::collector::COLLECTOR; pub use crate::finalize::{Finalize, FinalizeFields}; pub use crate::r::{RMut, R}; pub use crate::scan::{Scan, Scanner, ToScan}; pub use crate::smart_ptr::{DerefGc, Gc, GcGuard}; /// A convenient alias for `Gc<RefCell<T>>`. /// Note that `Gc<RefCell<T>>` has additional specialized methods for working with `RefCell`s inside /// `Gc`s. pub type GRefCell<T> = Gc<RefCell<T>>; /// A convenient alias for `Gc<Mutex<T>>`. /// Note that `Gc<Mutex<T>>` has additional specialized methods for working with `Mutex`s inside /// `Gc`s. pub type GMutex<T> = Gc<Mutex<T>>; /// A convenient alias for `Gc<RwLock<T>>`. /// Note that `Gc<Mutex<T>>` has additional specialized methods for working with `Mutex`s inside /// `Gc`s. pub type GRwLock<T> = Gc<RwLock<T>>; /// Returns how many underlying allocations are currently allocated. /// /// # Example /// ``` /// use shredder::{number_of_tracked_allocations, Gc}; /// /// let data = Gc::new(128); /// assert!(number_of_tracked_allocations() > 0); /// ``` #[must_use] pub fn number_of_tracked_allocations() -> usize { COLLECTOR.tracked_data_count() } /// Returns how many `Gc`s are currently in use. /// /// # Example /// ``` /// use shredder::{number_of_active_handles, Gc}; /// /// let data = Gc::new(128); /// assert!(number_of_active_handles() > 0); /// ``` #[must_use] pub fn number_of_active_handles() -> usize { COLLECTOR.handle_count() } /// Sets the percent more data that'll trigger collection. /// /// `shredder`'s collection automatically triggers when: /// ```text /// allocations > allocations_after_last_collection * (1 + gc_trigger_percent) /// ``` /// The default value of `gc_trigger_percent` is 0.75, but `set_gc_trigger_percent` lets you /// configure it yourself. Only values 0 or greater are allowed. /// (NaNs and negative values will cause a panic.) /// /// # Example /// ``` /// use shredder::set_gc_trigger_percent; /// set_gc_trigger_percent(0.75); // GC will trigger after data exceeds 1.75x previous heap size /// ``` pub fn set_gc_trigger_percent(percent: f32) { if percent < -0.0 || percent.is_nan() { panic!( "The trigger percentage cannot be less than zero or NaN! (percent = {})", percent ) } COLLECTOR.set_gc_trigger_percent(percent) } /// A function for manually running a collection, ignoring the heuristic that governs normal /// garbage collector operations. /// /// This can be an extremely slow operation, since the algorithm is /// designed to be run in the background, while this method runs it on the thread that calls the /// method. Additionally, you may end up blocking waiting to collect, since `shredder` doesn't allow /// two collections at once (and if this happens, you'll effectively get two collections in a row). /// /// # Example /// ``` /// use shredder::collect; /// collect(); // Manually run GC /// ``` pub fn collect() { COLLECTOR.collect(); } /// Block the current thread until the background thread has finished running the destructors for /// all data that was marked as garbage at the point this method was called. /// /// This method is most useful for testing, as well as cleaning up at the termination of your /// program. /// # Example /// ``` /// use shredder::{collect, synchronize_destructors}; /// // Create some data /// // <SNIP> /// // Gc happens /// collect(); /// // We cleanup /// synchronize_destructors(); /// // At this point all destructors for garbage will have been run /// ``` pub fn synchronize_destructors() { COLLECTOR.synchronize_destructors() } /// A convenience method for helping ensure your destructors are run. /// /// In Rust you can never assume that destructors run, but using this method helps `shredder` not /// contribute to that problem. /// # Example /// ``` /// use shredder::{run_with_gc_cleanup}; /// /// // Generally you'd put this in `main` /// run_with_gc_cleanup(|| { /// // Your code goes here! /// }) /// ``` pub fn run_with_gc_cleanup<T, F: FnOnce() -> T>(f: F) -> T { let res = f(); collect(); synchronize_destructors(); res } // Re-export the Scan derive, at the bottom cause the documentation is long /// The `Scan` derive, powering `#[derive(Scan)]`. Important details here! /// /// Doing `#[derive(Scan)]` will in fact derive `Scan`. However, it actually can auto-implement /// four traits: /// - `Scan` (automatic) [requires all fields be `Scan`] /// - `GcSafe` (automatic) [requires all fields be `GcSafe`] /// - `GcDrop` (opt-out) [requires all fields be `GcDrop`] /// - `GcDeref`(opt-in) [requires all fields be `GcDeref`] /// /// `Scan` and `GcSafe` are the fundamental things that this derive implements. There is no way /// to opt out. /// /// To opt out of `GcDrop`, supply the `cant_drop` flag. Ex: /// ``` /// use shredder::DerefGc; /// use shredder::Scan; /// /// #[derive(Scan)] /// #[shredder(cant_drop)] /// struct WontBeDrop { /// v: DerefGc<u32> /// } /// ``` /// /// To opt into `GcDeref`, supply the `can_deref` flag: /// ``` /// use shredder::DerefGc; /// use shredder::Scan; /// /// #[derive(Scan)] /// #[shredder(can_deref, cant_drop)] /// struct WillBeDeref { /// v: DerefGc<u32> /// } /// ``` /// /// Now there are also field flags, which will remove the recursive checks for that trait: /// - `skip_scan` (skips check for `Scan`) /// - `unsafe_skip_gc_deref` (skips check for `GcDeref`. Unsafe!) /// - `unsafe_skip_gc_drop` (skips check for `GcDrop`. Unsafe!) /// - `unsafe_skip_gc_safe` (skips check for `GcSafe`. Unsafe!) /// - `unsafe_skip_all` (skips check for all traits. Unsafe!) /// /// For safety, if you use unsafe flags, you must ensure those fields satisfy the trait requirements /// anyway. /// /// Here is an example of skip usage /// ``` /// use shredder::DerefGc; /// use shredder::Scan; /// /// #[derive(Scan)] /// struct WillBeDeref { /// #[shredder(skip_scan, unsafe_skip_gc_safe, unsafe_skip_gc_drop)] /// v: *const u32 // Assume this is always a valid ptr /// } /// ``` pub use shredder_derive::Scan; /// The `Finalize` derive, powering `#[derive(Finalize)]` /// /// Much more straightforward than the `Scan` derive, it implements `Finalize` by delegating /// to each field's `finalize` method. /// /// A simple example would be: /// ``` /// use shredder::DerefGc; /// use shredder::Finalize; /// /// #[derive(Finalize)] /// struct WillBeFinalize { /// v: DerefGc<u32> /// } /// ``` /// /// You can also skip fields with `skip_finalize`: /// ``` /// use shredder::DerefGc; /// use shredder::Finalize; /// /// struct NotFinalize; /// /// #[derive(Finalize)] /// struct StillFinalize { /// #[shredder(skip_finalize)] /// v: NotFinalize /// } /// ``` /// `unsafe_skip_all` also includes `skip_finalize` pub use shredder_derive::Finalize; /// The `FinalizeFields` derive, powering `#[derive(FinalizeFields)]` /// /// Works exactly the same as `#[derive(Finalize)]`, but derives `FinalizeFields` instead. This is /// primarily useful if you want to implement `Finalize` yourself, but don't want to manually /// finalize each field. This way that logic is autogenerated, and you just need to call /// `finalize_fields` at the end of your `finalize` method. pub use shredder_derive::FinalizeFields;