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// // rc-dlist-deque - doubly linked list for Rust // // Copyright (C) 2019-2022 Ian Jackson // // This program is free software: you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation, either version 3 of the License, or // (at your option) any later version. // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // // You should have received a copy of the GNU General Public License // along with this program. If not, see <http://www.gnu.org/licenses/>. //! See the <a href="../index.html">crate-level documentation</a> //! for a discussion of whether to use this crate. //! //! Concepts //! ======== //! //! Your data structure is a collection of `Rc<N>`, where `N` is the //! **node** type. The node type `N` contain the list **link**(s). //! The link type is defined by `rc_dlist_deque` (and, inside, //! contains the back/next pointers). Each link may be on one //! **list**, or on none. //! //! A **pointer** is a reference to a node, qua one of its potential //! list memberships. I.e., it specifies both the node and the link. //! It is not null. Another way to look at it is that it is a //! reference to a specific link within a specific node. //! //! A **cursor** is `Some(pointer)` or `None`. It is used whenever //! a pointer might be null. //! //! The nodes are not mutable, since they are inside `Rc`. //! (The dlist implementation uses `std::cell:Cell` for interior mutability.) //! //! When each node can only be on one list (at once) //! ------------------------------------------------ //! //! If all you need is a simple list where each node is on at most one list //! at once, you can use the convenience types `Node1<T>` and `List1<T>` //! where `T` is your own data type. A `Node1` is simply your `T` plus the //! list link. //! //! Often `T` will be, or contain, a `RefCell` or `Cell`, since the nodes //! themselves are not mutable. //! //! `Pointer1<T>` then represents a pointer to a node. It is a newtype //! wrapper for `Rc<Node1<T>>`. Its type indicates its use as a list //! pointer with //! `Node1<T>` and `List1<T>`. Also relevant is `Option<Pointer1<T>>` //! (also known as `Cursor1<T>`) which is used for pointers which might //! be null. //! //! When each node can be on multiple lists //! --------------------------------------- //! //! If you want to do something more sophisticated, you should //! use the types `List<N,S>` and `Node<N,S>`. //! //! You should define your own node type `N` containing one or more //! `Link<N,S>`. //! //! You also need to define a type `S`, the **selector**. Its type //! and value identifies one of the links in a node. //! //! Simple, static, link selection //! - - - - - - - - - - - - - - - //! //! Suppose at each point you know statically which `Link` is to be //! operated on, and it's the same in in all involved nodes. Ie, //! while you have different classes of list, and multiple links in //! each node, each link in each node belongs to one of the list //! classes. //! //! Then you want the different links and the corresponding lists to //! have distinct types. The intended link node is then identified by //! the type system. //! //! In this case: for each link which appears in your node, define a //! empty struct type (let us call it `FooSelector`). It should //! derive `Debug,Copy,Clone,PartialEq,Eq,Default`. Use the //! `DlistImplSelector` macro. Then the corresponding types //! are `List<N,FooSelector>`, `Pointer<N,FooSelector>` and //! `Link<N,FooSelector>`. //! //! Run-time dynamic link selection //! - - - - - - - - - - - - - - - - //! //! If you need to specify at run-time which link to use, you must //! provide a nontrivial selector type `S`, which is the actual value //! indicating which `Link` to use. //! //! `S` must implement `Selector`. It can still be helpful to use the //! `DlistImplSelector` helper macro to provide the trait //! implementation. //! //! The selector value may be different in different nodes on the same //! list. (Ie, the link contains not only the Rc references to the //! nodes, but <code>Pointer</code>s, including both //! <code>Selector</code>s.) `S` must be `Copy`. //! //! Entrypoints //! =========== //! //! Most of the useful functions are methods on `List`, //! with a few on `Pointer` and `ListIterator`. //! //! Many of the methods take a parameter like `rev : bool` or `tail : bool` //! or `after : bool`. These are bidirectional methods: they can //! operate in either direction, as specified. Generally `false` //! means forwards, or at the beginning. //! //! Ownership //! ========= //! //! A node which is on a list has a (strong) `Rc` reference owned by //! the list. Dropping a list will implictly remove all the items and //! drop those references; whether that drops the nodes depends on //! whether there are other references, as would be expected for `Rc`. //! //! Tangling and panics //! =================== //! //! Linked lists can get tangled, for example if you put a node //! on a list and then, without removing it from the first list, //! insert it into another list. //! It is the user's responsibility to know whether a node is on a //! list, and what list it is on, and only to make appropriate calls. //! //! The specific requirements are indicated in each case a section //! like this in each relevant function description: //! //! > Panics, or tangles the list(s) //! //! **Any operation on a tangled list may panic**; tangled lists //! can also result in infinite loops. //! //! When debug assertions are enabled, the library will nearly always //! detect when a list is about to be tangled and panic immediately. //! When debug assertions are disabled the additional records //! needed for this are compiled out, and tangling a list may go //! undetected, and result in panics some considerable time later. //! //! However, this library contains only safe Rust. So while tangled //! lists can result in panics and algorithmic malfunctions, they //! cannot result in undefined behaviour. #![allow(unused_macros)] #![allow(dead_code)] use std::rc::Rc; use std::cell::Cell; use std::marker::PhantomData; use std::fmt; use std::fmt::Formatter; use std::result::Result; use std::default::Default; // ----- types and the public DefineListEntry macro ----- pub type Cursor<N,S> = Option<Pointer<N,S>>; type ListID = (std::thread::ThreadId, usize); /// In a node, its potential membership of a list. /// /// At least one of these should appear in each node. /// /// Not needed with `Node1`, where this is implicit. /// /// ```struct Link<N,S> where S : Selector<Node=N>``` pub struct Link<N, S> where S : Selector<Node=N> { pn : [ Cell<Cursor<N, S>> ; 2 ], #[cfg(debug_assertions)] busy : Cell<Option<ListID>>, } /// The general list type. /// /// Use `List1` if each node only needs to be on one list a time. /// /// ```struct List<N, S> where S : Selector<Node=N>``` pub struct List<N, S> where S : Selector<Node=N> { ht : [ Cursor<N, S> ; 2 ], #[cfg(debug_assertions)] id : ListID, } /// Reference to a node, with respect to its potential membership /// of a list. /// /// If the node can be a member of multiple lists, /// a reference to a specific one of its potential memberships. /// (Another way to look at this is that a pointer is a reference /// to a particular link within a node.) /// /// May be kept persistently in other data structures. /// /// May point to an element which is not currently on a list, /// but may not point to no element. /// /// Holds an <code>Rc</code> onto the node. pub struct Pointer<N, S> where S : Selector<Node=N> + Clone { node : Rc<N>, // Do not simply change this to Arc<> - see below selector : S, } // Note on thread safety. // // This whole module is not thread safe. The core list manipulation // code is not suitable for simply wrapping up in a mutex and hoping, // at least not without thought. So although it looks like you // might be able to make this threadsafe by switching from Rc to // Arc and from Cell to some mutex, this will not work properly // unless you also consider lock lifetime wrt the list manipulations // (which might otherwise tangle lists on concurrent access) // and lock hierarchy (to avoid deadlock). /// Iterator (forwards) through the list. /// /// Care must be taken if the list is modified while the iterator /// exists: the iterator keeps a reference to the next item to be /// returned. If that item is removed from the list, and maybe put /// onto some other list, the iterator will continue with that item, /// and, thereeafter, whatever its successors are on whatever list it /// ends up on. /// /// However, a consequece is: it _does_ work to iterate over a list, /// sometimes removing the item returned by the iterator. /// Also, modification of the list while it is being iterated over will not /// lead to panics, or undefined behaviour --- only possible /// unexpected results. /// /// (This is actually a wrapper around a `Cursor`: pointing /// to the next element to be returned, or `None`.) pub struct ListIterator<N,S : Selector<Node=N>> (Cursor<N,S>); /// It is not often necessary to implement this directly. /// Use `List1`, `Node1` etc. if you can. /// If your nodes need to a member of multiple lists, /// use [DlistImplSelector!](../macro.DlistImplSelector.html) pub trait Selector : Sized + Copy { type Node; fn link(node : &Self::Node, selector : Self) -> &Link<Self::Node, Self>; } /// Should write a suffix suitable for printing after `{:p}`. /// Used when Pointer is printed with `{:p}`. pub trait SelectorFmt : Selector { fn fmt(&self, f : &mut Formatter) -> Result<(), fmt::Error>; } /// `DlistDefineStaticSelector!( `_SELTYPE_`,` _NODE_` [` _MEMBS_ `]);` /// /// For setting up nodes which can each be a member of multiple lists, /// witb the link within each node identified at compile time. /// /// Arranges that _NODE_ can be part of a `List` by virtue of it /// containing a `Link`. Defines _SELTYPE_ as an empty struct /// implementing `Selector` (and `Copy,Default,...`). /// /// _MEMBS_ is zero or more field selectors (each preceded by /// the `.`), array indices, etc., to find a `Link` inside _NODE_. /// _MEMBS_ must be surrounded by literal `[` and `]` for /// macro parsing reasons. /// /// This macro /// constructs the expression (_somenode MEMBS_) where /// _somenode_ is a reference to a _NODE_, and expects that expression /// to name a `Link<`_NODE,SELTYPE_`>` within _somenode_. /// /// You will need to implement `SelectorFmt` for _SELTYPE_ /// to be able to debug format `Pointer<`_NODE,SELTYPE_`>` #[macro_export] macro_rules! DlistDefineStaticSelector { ( $S:ident, $N:ty [ $($x:tt)* ]) => { #[derive(Debug,Copy,Clone,PartialEq,Eq,Default)] struct $S { } DlistImplSelector!($S, $N, _s [ $($x)* ]); } } /// `DlistImplSelector!( `[ `+(` _TYPEPARAMS_ `)`] _SELTYPE_`,` _NODE_`,` _SELVAR_ `[` _MEMBS_ `]);` /// /// For setting up nodes which can each be a member of multiple lists, /// where the link is identified at runtime. /// /// (Usually when a node wants to potentially be a member of multiple /// lists, the specific list membership is known at compile time. /// In that case use `DlistDefineStaticSelector` if possible.) /// /// Arranges that _NODE_ can be part of a `List` by virtue of it /// containing a `Link` (or a particular collection of `Link`s). /// (Implements `Selector` for _SELTYPE_.) /// /// _SELTYPE_ is a selector /// type (defined by you) which relates a node to one of its potential list /// memberships. /// /// If `+(`_TYPEPARAMS_`)` is specified at the beginning, _TYPEPARAMS_ /// is appended to `impl` in the macro expansion. /// /// _MEMBS_ is zero or more field selectors (each preceded by /// the `.`), array indices, etc., to find a `Link` inside _NODE_. /// In _MEMBS_, _SELVAR_ (conventionally `s`), will be /// an immutable local variable of type _SELTYPE_. /// _MEMBS_ must be surrounded by literal `[` and `]` for /// macro parsing reasons. /// /// The macro /// constructs the expression (_somenode MEMBS_) where /// _somenode_ is a reference to _NODE_, and expects that expression /// to name a `Link<`_NODE,SELTYPE_`>` within _somenode_. /// If this is not suitable, /// you should open-code an impleentation of `Selector` instead. /// /// See the definition of `List1Selector` (in the source to this /// module), and its call to /// `DlistImplSelector!` for an example. /// /// _SELTYPE_ must be `Copy`. It is useful for it to be /// `Debug`, `PartialEq`, and `SelectorFmt`. #[macro_export] macro_rules! DlistImplSelector { ($(+( $($typar:tt)* ))* $S:ty, $N:ty, $s:ident [ $($x:tt)* ]) => { impl $( $($typar)* )* $crate::dlist::Selector for $S { type Node = $N; fn link(n : &$N, $s : $S) -> &Link<$N,$S> { &( n $($x)* ) } } } } // ----- pn and ht access, using types for (some) correctness----- // We write a lot of code to work both `forwards' and `backwards'. // In general in the public API we provide a parameter `rev' or `tail' // which is a boolean. In most of our own code we want to talk about // HEAD and TAIL and PREV and NEXT. So we write, say, HEAD^rev, to // mean `HEAD, except if rev then TAIL'. // // This is enforced by the following arrangments: // Each DefinePairArrayIndex defines something like // enum HT { HEAD, TAIL } // The ^ operator can be used with a bool to flip it. Flipping // generates a PairArrayIndexGeneralised<HT>, which cannot be // flipped again. Array indexing is done with HT::index, which // only takes a PairArrayIndexGeneralised<HT>. This ensures // flipping exactly once, and prevents use of PN instead of HT. // // Everyone here who accesses pn or ht should either use ::index, // or must be vetted to DTRT. But, usually, accesses are done // via the macros get! etc. macro_rules! DefinePairArrayIndex { { $Enum:ident; $False:ident; $True:ident } => { enum $Enum { $False, $True } use self::$Enum::{$False,$True}; impl std::ops::BitXor<bool> for $Enum { type Output = PairArrayIndexGeneralised<$Enum>; fn bitxor(self, flip : bool) -> Self::Output { PairArrayIndexGeneralised( ((self as usize) != 0) ^ flip, std::marker::PhantomData, ) } } impl $Enum { fn index(s : PairArrayIndexGeneralised<$Enum>) -> usize { s.0 as usize } } } } struct PairArrayIndexGeneralised<T> (bool, std::marker::PhantomData<T>); DefinePairArrayIndex!{ HT; HEAD; TAIL } DefinePairArrayIndex!{ PN; PREV; NEXT } fn clone_option_cell<T:Clone>(c : &Cell<Option<T>>) -> Option<T> { let r = c.replace(None); c.set(r.clone()); r } macro_rules! link { ($ptr:expr) => (<S as Selector>::link (&$ptr.node, $ptr.selector)) } macro_rules! get { ($ptr:expr, $pn:expr) => ( clone_option_cell( &link!($ptr).pn[PN::index($pn)]) ) } macro_rules! set { ($ptr:expr, $pn:expr, $nv:expr) => ( link!($ptr).pn[PN::index($pn)].set($nv) ) } macro_rules! end { ($list:expr, $ht:expr) => ( $list.ht[HT::index($ht)] ) } macro_rules! setLinkB { ($ent:expr, $prev:expr,$next:expr, $rev:expr, $list:expr,) => ( setLinkB!($ent,$prev,$next,$rev,$list) ); ($ent:expr, $prev:expr,$next:expr, $rev:expr, $list:expr) => ( set!($ent,PREV^$rev, $prev); set!($ent,NEXT^$rev, $next); #[cfg(debug_assertions)] { link!($ent).busy.set( Some($list.id) ) }; ) } macro_rules! setLinkI { ($ent:expr) => ( set!($ent,PREV^false, None); set!($ent,NEXT^false, None); #[cfg(debug_assertions)] { link!($ent).busy.set(None) }; ) } #[cfg(debug_assertions)] macro_rules! assert_busy{($p:expr,$i:expr)=>($p.debug_assert_busy(Some($i)) )} macro_rules! assert_idle{($p:expr )=>($p.debug_assert_busy(None ) )} #[cfg(not(debug_assertions))] macro_rules! assert_busy{($p:expr,$i:expr)=>() } // ----- other helpful macros ----- // turns // imp!{ N,S, [Trait for,] Type { ... } } // into // impl<N, S : Selector<Node=N>> [Trait for,] Type { ... } } // which saves typing. Sadly, note the necessary spurious comma. macro_rules! imp { { $N:ident, $LE:ident, $tr:path, for $T:ident { $($body:tt)* } } => { impl<$N, $LE : Selector<Node=$N>> $tr for $T<$N, $LE> { $($body)* } }; { $N:ident, $LE:ident, $T:ident { $($body:tt)* } } => { impl<$N, $LE : Selector<Node=$N>> $T<$N, $LE> { $($body)* } }; } // ----- actual implementation! ----- imp!{ N,S, Link { /// Creates a new blank `Link` (ie one which is not on any list). pub fn new() -> Self { Link { pn : [ Cell::new(None), Cell::new(None) ], #[cfg(debug_assertions)] busy : Cell::new(None) } } }} imp!{ N,S, Pointer { /// Makes a pointer out of a reference to a node. /// /// Only possible where the selector type has a default value; /// eg, when called as `Pointer1::new`, or in other situations /// where the relevant link in each node is identified at compile-time. pub fn new(p : &Rc<N>) -> Pointer<N, S> where S : Default { Pointer::with_selector(p, Default::default()) } /// Makes a pointer, with runtime link selection /// /// Given a reference `p` to a node, and `selector`, /// makes them into a pointer --- that is, a reference /// to the node but with respect to that specific possible /// list membership. pub fn with_selector(p : &Rc<N>, selector : S) -> Pointer<N, S> { Pointer { node : p.clone(), selector } } /// Consumes `data`, and returns a reference ready for use with a /// list. pub fn from_data(data : N, selector : S) -> Pointer<N, S> { Pointer { node : Rc::new(data), selector } } /// Returns the selector portion of the pointer. pub fn selector(&self) -> S { self.selector } /// `true` iff the pointers are equal. /// /// Ie, if they both point to the same node and (with runtime link /// selection) have the same selector. Ie, they both refer to the /// same link within the same node. pub fn ptr_eq(a : &Pointer<N,S>, b : &Pointer<N,S>) -> bool where S : PartialEq { Rc::ptr_eq(&a.node, &b.node) && a.selector == b.selector } /// `true` iff both pointers are equal, or both are null (`None`). pub fn cursor_eq(a : &Cursor<N,S>, b : &Cursor<N,S>) -> bool where S : PartialEq { match (a, b) { (None, None ) => true, (Some(ref a), Some(ref b)) => Pointer::ptr_eq(a,b), _ => false, } } /// Returns an iterator starting here /// /// The iterator will process the entry referred to by /// `self`, and subsequent entries. pub fn iter_at(&self) -> ListIterator<N,S> { ListIterator( Some(self.clone()) )} /// Returns a cursor pointing to the next or previous item. pub fn get_next_prev(&self, rev : bool) -> Cursor<N,S> { get!(self,NEXT^rev) } #[allow(unused_variables)] fn debug_assert_busy(&self, expected : Option<&ListID>) { #[cfg(debug_assertions)] { let got = link!(self).busy.get(); debug_assert_eq!(got.as_ref(), expected); } } }} fn set_next_prev<N,S : Selector<Node=N>> ( of : &Pointer<N,S>, to : Cursor<N,S>, head : &mut List<N,S>, rev : bool ) { match get!(of,NEXT^rev) { None => { end!(head,TAIL^rev) = to; }, Some(ref next) => { set!(next,PREV^rev, to); }, } } imp!{ N,S, List { pub fn new() -> Self { List { ht : [ None, None], #[cfg(debug_assertions)] id : { use std::cell::Cell; thread_local!{ static COUNTER : Cell<usize> = Cell::new(0); } (std::thread::current().id(), COUNTER.with(|p| { let r = p.get(); p.set(r + 1); r })) } } } pub fn is_empty(&self) -> bool { end!(self,HEAD^false).is_none() } /// Get `Some` pointer to the first or last element, or `None` /// if the list is empty. pub fn first_last(&self, tail : bool) -> Cursor<N,S> { end!(self,HEAD^tail).clone() } pub fn first(&self) -> Cursor<N,S> { self.first_last(false) } pub fn last (&self) -> Cursor<N,S> { self.first_last(true ) } pub fn iter(&self) -> ListIterator<N,S> { ListIterator( self.first_last(false) ) } /// Inserts `new_entry` into `self` before or after `locaation`. /// /// # Panics, or tangles the list(s): /// /// `new_entry` must not be on any list. /// /// `location` must be on `self` (and not on some other list). pub fn insert(&mut self, new_entry : &Pointer<N,S>, location : &Pointer<N,S>, after : bool, ) { assert_idle!(new_entry); assert_busy!(location, &self.id); setLinkB!( new_entry, get!(location, PREV^after), Some(location.clone()), after, self, ); set!(location, PREV^after, Some(new_entry.clone())); set_next_prev(new_entry, Some(new_entry.clone()), self, !after); } /// Inserts `new_entry` at the start or end of the list. /// /// # Panics, or tangles the list(s): /// /// `new_entry` must not be on any list. pub fn push_at(&mut self, new_entry : &Pointer<N,S>, tail : bool) { assert_idle!(new_entry); setLinkB!( new_entry, None, end!(self,HEAD^tail).clone(), tail, self, ); end!(self,HEAD^tail) = Some(new_entry.clone()); set_next_prev(new_entry, Some(new_entry.clone()), self, tail); } pub fn push_front(&mut self, n : &Pointer<N,S>) { self.push_at(n,false) } pub fn push_back (&mut self, n : &Pointer<N,S>) { self.push_at(n,true ) } /// Removes the entry at the start or end of the list, /// returning `None` if the list is empty. pub fn pop_at(&mut self, tail : bool) -> Cursor<N,S> { let was = end!(self,HEAD^tail).clone(); if let Some(ref node) = was { set_next_prev(node, None, self, tail); end!(self,HEAD^tail) = None; setLinkI!(node); } was } pub fn pop_front(&mut self) -> Cursor<N,S> { self.pop_at(false) } pub fn pop_back (&mut self) -> Cursor<N,S> { self.pop_at(true ) } /// Removes `item`. /// /// # Panics, or tangles the list: /// /// `item` must be on `self`. pub fn remove(&mut self, item : &Pointer<N,S>) { assert_busy!(item, &self.id); for &rev in &[false,true] { set_next_prev(item, get!(item,PREV^rev), self, rev); } setLinkI!(item); } pub fn clear(&mut self) { let mut node = end!(self,HEAD^false).clone(); while node.is_some() { let inner = node.unwrap(); let next_node = get!(inner,NEXT^false); setLinkI!(inner); node = next_node; } self.ht = [ None, None ]; } }} imp!{N,S, Drop, for List { fn drop(&mut self) { self.clear() } }} //----- the iterator ----- imp!{ N,S, ListIterator { /// Moves the iterator one step. /// If the iterator has already reached the end, is a no-op. /// If the iterator's next pointer points at a node which /// is not in any list, `walk` will report that node and /// leave the iterator finished. pub fn walk(&mut self, rev : bool) { let c = self.0.as_ref().and_then( |p| p.get_next_prev(rev) ); *self = ListIterator(c); } /// Returns the current node (the next node to be returned), /// if any, and then advances (or retards) the iterator. pub fn next_prev(&mut self, rev : bool) -> Cursor<N,S> { let was = self.0.clone(); self.walk(rev); was } pub fn cursor(&self) -> Cursor<N,S> { self.0.clone() } // Converts an Option<Pointer> into a ListIterator pub fn from_cursor(c : Cursor<N,S>) -> Self { ListIterator(c) } }} imp!{ N,S, Iterator, for ListIterator { type Item = Pointer<N,S>; fn next(&mut self) -> Option<Pointer<N,S>> { self.next_prev(false) } }} imp!{ N,S, std::ops::Deref , for ListIterator { type Target = Cursor<N,S>; fn deref (& self) -> & Cursor<N,S> { & self.0 } }} imp!{ N,S, std::ops::DerefMut, for ListIterator { fn deref_mut(&mut self) -> &mut Cursor<N,S> { &mut self.0 } }} imp!{ N,S, std::iter::FusedIterator, for ListIterator { }} impl<'l, N, S : Selector<Node=N>> IntoIterator for &'l List<N,S> { type Item = Pointer<N,S>; type IntoIter = ListIterator<N,S>; fn into_iter(self) -> ListIterator<N,S> { self.iter() } } //----- other convenience traits ----- // derive is too stupid to realise that Pointer is Clone even though // N may not be. imp!{ N,S, Clone, for Pointer { fn clone(&self) -> Self { Pointer { node : self.node.clone(), ..*self } } }} imp!{ N,S, std::ops::Deref, for Pointer { type Target = Rc<N>; fn deref (& self) -> & Rc<N> { & self.node } }} imp!{ N,S, std::ops::DerefMut, for Pointer { fn deref_mut(&mut self) -> &mut Rc<N> { &mut self.node } }} imp!{ N,S, Default, for Link { fn default() -> Self { Link ::new() } }} imp!{ N,S, Default, for List { fn default() -> Self { List ::new() } }} impl<N,S : Selector<Node=N> + SelectorFmt> fmt::Pointer for Pointer<N,S> { fn fmt(&self, f : &mut Formatter) -> Result<(), fmt::Error> { write!(f,"{:p}", self.node)?; SelectorFmt::fmt(&self.selector, f)?; Ok(()) } } impl<N,S : Selector<Node=N> + fmt::Debug> fmt::Debug for Pointer<N,S> { fn fmt(&self, f : &mut Formatter) -> Result<(), fmt::Error> { write!(f,"Pointer({:p}, {:?})", &self.node, &self.selector) } } impl<N,S> From<Rc<N>> for Pointer<N,S> where S : Default + Selector<Node=N> { fn from(p : Rc<N>) -> Pointer<N,S> { Pointer { node : p, selector : Default::default() }} } impl<'a,N,S> From<&'a Rc<N>> for Pointer<N,S> where S : Default + Selector<Node=N> { fn from(p : &Rc<N>) -> Pointer<N,S> { Self::from(p.clone()) } } impl<N,S : Default + Selector<Node=N>> From<N> for Pointer<N,S> { fn from(data : N) -> Pointer<N,S> { From::from( Rc::new( data ))} } // ----- convenience List1, Node1, Pointer1 ----- /// Simple list /// - each node is only on one list pub type List1<T> = List<Node1<T>,List1Selector<T>>; /// Node on a simple list. /// /// For when each node is only on one list. /// /// `T` is your own data. You will often want T to be a `Cell` or a /// `RefCell`, since you won't generally have mutable access to it. /// /// Normally you will refer to nodes via `Pointer1`, /// which contains an `Rc<Node1>`, or via `Cursor1`, /// which is `Option<Pointer1<_>>` /// /// ```struct Node1<T>``` pub struct Node1<T> { data : T, ll : Link< Node1<T>, List1Selector<T>, >, } pub type Pointer1<T> = Pointer<Node1<T>,List1Selector<T>>; pub type Cursor1<T> = Option<Pointer1<T>>; /// Selector type for simple List1/Node1 /// /// You do not need to deal with this type directly. #[derive(Eq,PartialEq,Debug)] pub struct List1Selector<T> { marker : PhantomData<T> } DlistImplSelector!(+(<T>) List1Selector<T>, Node1<T>, _s [ .ll ]); // The PhantomData is needed because List1Selector is generic // over the user's node type T. For a fixed node type, // and a fixed link entry within it, the selector can be a struct (). impl<T> Default for List1Selector<T> { fn default() -> List1Selector<T> { List1Selector { marker : PhantomData } } } impl<T> SelectorFmt for List1Selector<T> { fn fmt(&self, _f : &mut Formatter) -> Result<(), fmt::Error> { Ok(()) } } impl<T> Copy for List1Selector<T> { } impl<T> Clone for List1Selector<T> { fn clone(&self) -> Self { *self } } impl<T> Node1<T> { /// Wraps up `data` into a node struct. /// /// You'll normally want `pointer` instead. pub fn new(data : T) -> Self { Node1 { data, ll : Default::default() } } /// Wraps up `data` into a node and an <code>Rc</code>, /// giving a pointer (a reference) ready to be put onto a list. pub fn pointer(data : T) -> Pointer1<T> { From::from( data ) } } impl<T> Default for Node1<T> where T : Default { fn default() -> Node1<T> { Node1::new( T::default() ) } } impl<T> std::ops::Deref for Node1<T> { type Target = T; fn deref (& self) -> & T { & self.data } } impl<T> std::ops::DerefMut for Node1<T> { fn deref_mut(&mut self) -> &mut T { &mut self.data } } impl<T> From<T> for Pointer1<T> { fn from(data : T) -> Pointer1<T> { Pointer::new( &Rc::new( Node1::new( data ))) } } mod test;