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// Copyright 2016 Amanieu d'Antras // // Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or // http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or // http://opensource.org/licenses/MIT>, at your option. This file may not be // copied, modified, or distributed except according to those terms. use crate::IntrusivePointer; /// Trait for a adapter which allows a type to be inserted into an intrusive /// collection. The `Link` type contains the collection-specific metadata which /// allows an object to be inserted into an intrusive collection. This type /// needs to match the collection type (eg. `LinkedListLink` for inserting /// in a `LinkedList`). /// /// `Value` is the actual object type managed by the collection. This type will /// typically have an instance of `Link` as a struct field. /// /// `Pointer` is a pointer type which "owns" an object of type `Value`. /// Operations which insert an element into an intrusive collection will accept /// such a pointer and operations which remove an element will return this type. /// /// A single object type may have multiple adapters, which allows it to be part /// of multiple intrusive collections simultaneously. /// /// In most cases you do not need to implement this trait manually: the /// `intrusive_adapter!` macro will generate the necessary implementation for a /// given type and its link field. However it is possible to implement it /// manually if the intrusive link is not a direct field of the object type. /// /// It is also possible to create stateful adapters. This allows links and /// containers to be separated and avoids the need for objects to be modified to /// contain a link. /// /// # Safety /// /// It must be possible to get back a reference to the container by passing a /// pointer returned by `get_link` to `get_container`. pub unsafe trait Adapter { /// Collection-specific link type which allows an object to be inserted in /// an intrusive collection. type Link; /// Object type which is inserted in an intrusive collection. type Value: ?Sized; /// Pointer type which owns an instance of a value. type Pointer: IntrusivePointer<Self::Value>; /// Gets a reference to an object from a reference to a link in that object. unsafe fn get_value(&self, link: *const Self::Link) -> *const Self::Value; /// Gets a reference to the link for the given object. unsafe fn get_link(&self, value: *const Self::Value) -> *const Self::Link; } /// Macro to get the offset of a struct field in bytes from the address of the /// struct. #[macro_export(local_inner_macros)] macro_rules! offset_of { ($($inner:tt)*) => { ($crate::__memoffset::offset_of!($($inner)*) as isize) } } /// Unsafe macro to get a raw pointer to an outer object from a pointer to one /// of its fields. /// /// # Examples /// /// ``` /// # #[macro_use] extern crate intrusive_collections; /// # fn main() { /// struct S { x: u32, y: u32 }; /// let container = S { x: 1, y: 2 }; /// let field = &container.x; /// let container2: *const S = unsafe { container_of!(field, S, x) }; /// assert_eq!(&container as *const S, container2); /// # } /// ``` /// /// # Safety /// /// This is unsafe because it assumes that the given expression is a valid /// pointer to the specified field of some container type. #[macro_export(local_inner_macros)] macro_rules! container_of { ($ptr:expr, $container:path, $field:ident) => { #[allow(clippy::cast_ptr_alignment)] { ($ptr as *const _ as *const u8).offset(-offset_of!($container, $field)) as *mut $container } }; } /// Macro to generate an implementation of `Adapter` for a given set of types. /// In particular this will automatically generate implementations of the /// `get_value` and `get_link` methods for a given named field in a struct. /// /// The basic syntax to create an adapter is: /// /// ```rust,ignore /// intrusive_adapter!(Adapter = Pointer: Value { link_field: LinkType }); /// ``` /// /// You can create a new instance of an adapter using the `new` method or the /// `NEW` associated constant. The adapter also implements the `Default` trait. /// /// # Generics /// /// This macro supports generic arguments: /// /// ```rust,ignore /// intrusive_adapter!( /// Adapter<'lifetime, Type, Type2: ?Sized> = /// Pointer: Value { /// link_field: LinkType /// } /// where /// Type: Copy, /// Type2: 'lifetime /// ); /// ``` /// /// Note that due to macro parsing limitations, only `?Trait` style bounds are /// allowed in the generic argument list. In most cases this is only needed for /// `?Sized`. Other bounds can be specified in the `where` clause at the end /// the macro. /// /// # Examples /// /// ``` /// #[macro_use] /// extern crate intrusive_collections; /// use intrusive_collections::{LinkedListLink, RBTreeLink}; /// /// pub struct Test { /// link: LinkedListLink, /// link2: RBTreeLink, /// } /// intrusive_adapter!(MyAdapter = Box<Test>: Test { link: LinkedListLink }); /// intrusive_adapter!(pub MyAdapter2 = Box<Test>: Test { link2: RBTreeLink }); /// /// pub struct Test2<T: ?Sized> /// where T: Clone /// { /// link: LinkedListLink, /// val: T, /// } /// intrusive_adapter!(MyAdapter3<'a, T: ?Sized> = &'a Test2<T>: Test2<T> { link: LinkedListLink } where T: Clone + 'a); /// # fn main() {} /// ``` #[macro_export(local_inner_macros)] macro_rules! intrusive_adapter { (@impl ($($privacy:tt)*) $name:ident ($($args:tt $(: ?$bound:tt)*),*) = $pointer:ty: $value:path { $field:ident: $link:ty } $($where_:tt)* ) => { #[allow(explicit_outlives_requirements)] $($privacy)* struct $name<$($args),*>($crate::__core::marker::PhantomData<$pointer>) $($where_)*; unsafe impl<$($args $(: ?$bound)*),*> Send for $name<$($args),*> $($where_)* {} unsafe impl<$($args $(: ?$bound)*),*> Sync for $name<$($args),*> $($where_)* {} impl<$($args $(: ?$bound)*),*> Copy for $name<$($args),*> $($where_)* {} impl<$($args $(: ?$bound)*),*> Clone for $name<$($args),*> $($where_)* { fn clone(&self) -> Self { *self } } impl<$($args $(: ?$bound)*),*> Default for $name<$($args),*> $($where_)* { fn default() -> Self { Self::NEW } } #[allow(dead_code)] impl<$($args $(: ?$bound)*),*> $name<$($args),*> $($where_)* { pub const NEW: Self = $name($crate::__core::marker::PhantomData); pub fn new() -> Self { Self::NEW } } #[allow(dead_code, unsafe_code)] unsafe impl<$($args $(: ?$bound)*),*> $crate::Adapter for $name<$($args),*> $($where_)* { type Link = $link; type Value = $value; type Pointer = $pointer; #[inline] unsafe fn get_value(&self, link: *const $link) -> *const $value { container_of!(link, $value, $field) } #[inline] unsafe fn get_link(&self, value: *const $value) -> *const $link { &(*value).$field } } }; (@find_generic ($($privacy:tt)*) $name:tt ($($prev:tt)*) > $($rest:tt)* ) => { intrusive_adapter!(@impl ($($privacy)*) $name ($($prev)*) $($rest)* ); }; (@find_generic ($($privacy:tt)*) $name:tt ($($prev:tt)*) $cur:tt $($rest:tt)* ) => { intrusive_adapter!(@find_generic ($($privacy)*) $name ($($prev)* $cur) $($rest)* ); }; (@find_if_generic ($($privacy:tt)*) $name:tt < $($rest:tt)* ) => { intrusive_adapter!(@find_generic ($($privacy)*) $name () $($rest)* ); }; (@find_if_generic ($($privacy:tt)*) $name:tt $($rest:tt)* ) => { intrusive_adapter!(@impl ($($privacy)*) $name () $($rest)* ); }; (pub $name:tt $($rest:tt)*) => { intrusive_adapter!(@find_if_generic (pub) $name $($rest)* ); }; ($name:tt $($rest:tt)*) => { intrusive_adapter!(@find_if_generic () $name $($rest)* ); }; }