commit | eca0287439b8fe62325138b60538124f2e3c08a5 | [log] [tgz] |
---|---|---|
author | Linux Build Service Account <lnxbuild@localhost> | Wed Feb 16 21:44:03 2022 -0800 |
committer | Linux Build Service Account <lnxbuild@localhost> | Wed Feb 16 21:44:03 2022 -0800 |
tree | db428e02daefd369d8c754a70557de3b39686571 | |
parent | f4737b239d54ab97729394e11a7881211ab0969a [diff] | |
parent | a84a2ef7beb648e739c9a70735f7f1a7003bcb09 [diff] |
Merge a84a2ef7beb648e739c9a70735f7f1a7003bcb09 on remote branch Change-Id: I4bceba378352ee3450244718365f950d739d4950
This crate defines several kinds of weak hash maps and sets. See the full API documentation for details.
This crate supports Rust version 1.32 and later.
Here we create a weak hash map and demonstrate that it forgets mappings whose keys expire:
use weak_table::WeakKeyHashMap; use std::sync::{Arc, Weak}; let mut table = <WeakKeyHashMap<Weak<str>, u32>>::new(); let one = Arc::<str>::from("one"); let two = Arc::<str>::from("two"); table.insert(one.clone(), 1); assert_eq!( table.get("one"), Some(&1) ); assert_eq!( table.get("two"), None ); table.insert(two.clone(), 2); *table.get_mut(&one).unwrap() += 10; assert_eq!( table.get("one"), Some(&11) ); assert_eq!( table.get("two"), Some(&2) ); drop(one); assert_eq!( table.get("one"), None ); assert_eq!( table.get("two"), Some(&2) );
Here we use a weak hash set to implement a simple string interning facility:
use weak_table::WeakHashSet; use std::ops::Deref; use std::rc::{Rc, Weak}; #[derive(Clone, Debug)] pub struct Symbol(Rc<str>); impl PartialEq for Symbol { fn eq(&self, other: &Symbol) -> bool { Rc::ptr_eq(&self.0, &other.0) } } impl Eq for Symbol {} impl Deref for Symbol { type Target = str; fn deref(&self) -> &str { &self.0 } } #[derive(Debug, Default)] pub struct SymbolTable(WeakHashSet<Weak<str>>); impl SymbolTable { pub fn new() -> Self { Self::default() } pub fn intern(&mut self, name: &str) -> Symbol { if let Some(rc) = self.0.get(name) { Symbol(rc) } else { let rc = Rc::<str>::from(name); self.0.insert(Rc::clone(&rc)); Symbol(rc) } } } #[test] fn interning() { let mut tab = SymbolTable::new(); let a0 = tab.intern("a"); let a1 = tab.intern("a"); let b = tab.intern("b"); assert_eq!(a0, a1); assert_ne!(a0, b); }