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//! Efficient collections for hashconsed data. //! //! This module provide hash set and hash map types with trivial hash functions //! for hashconsed types. The hash of an hashconsed value is its unique //! identifier, verbatim. This is obviously extremely dangerous from a security //! point of view: these collections should **never** be used for cryptographic //! purposes. //! //! Note that you can use `BTreeMap` and `BTreeSet` on hashconsed types since //! they are totally ordered. //! //! # Usage //! //! > TL;DR You need to specify the hashconsed type when creating one of the //! > collections in this module. //! //! There is a bit of internal gymnastic so that the type signatures of these //! collections are natural. If `Term` is the hashconsed version of `RTerm`, //! then you want the type of the sets to be the natural one, *e.g.* //! `HConSet<Term>`. //! //! However, since `Term` is really an alias for `HConsed<RTerm>`, then if we //! wanted to declare `HConSet` as an alias for `HashSet` we would get `type //! HConSet<Inner> = HashSet< HConsed<Inner> >` (omitting the custom hasher). //! That is, our sets would have type `HConSet<RTerm>`, which is not very //! pretty. We could just define an alias though: `type TermSet = //! HConSet<RTerm>`, but it turns out it's better to wrap the actual set in a //! `struct` anyway. Mostly to be able to define `new` and `with_capacity` //! without relying on a trait (users would need to import) to do that. //! //! So actually `HConsed` types automatically implement the internal `trait //! HashConsed { type Inner ; }`. The sole purpose of this trait (currently) is //! to pass the inner type implicitly thanks to a `T: HashConsed` bound. Rust's //! type inference does not seem to really like this, and struggles a bit to //! infer the types at play. In practice, it means that you need to specify the //! type of the hashconsed elements in your set/map. //! //! ``` //! use hashconsing::* ; //! use hashconsing::coll::* ; //! //! #[derive(Hash, Clone, PartialEq, Eq)] //! enum ActualTerm { //! Var(usize), //! Lam(Term), //! App(Term, Term) //! } //! type Term = HConsed<ActualTerm> ; //! //! let mut consign = HConsign::empty() ; //! assert_eq!(consign.len(), 0) ; //! //! let mut map: HConMap<Term,_> = HConMap::with_capacity(100) ; //! let mut set: HConSet<Term> = HConSet::with_capacity(100) ; //! //! let (v1, v1_name) = ( //! consign.mk( ActualTerm::Var(0) ), "v1" //! ) ; //! assert_eq!(consign.len(), 1) ; //! let prev = map.insert(v1.clone(), v1_name) ; //! assert_eq!( prev, None ) ; //! let is_new = set.insert(v1.clone()) ; //! assert!( is_new ) ; //! ``` //! //! The problem completely goes away if you redefine your set/map type, and is //! the recommended way of using these collections. //! //! ``` //! use hashconsing::* ; //! use hashconsing::coll::* ; //! //! #[derive(Hash, Clone, PartialEq, Eq)] //! enum ActualTerm { //! Var(usize), //! Lam(Term), //! App(Term, Term) //! } //! type Term = HConsed<ActualTerm> ; //! type TermMap<T> = HConMap<Term, T> ; //! type TermSet = HConSet<Term> ; //! //! let mut consign = HConsign::empty() ; //! assert_eq!(consign.len(), 0) ; //! //! let mut map = TermMap::with_capacity(100) ; //! let mut set = TermSet::with_capacity(100) ; //! //! let (v1, v1_name) = ( //! consign.mk( ActualTerm::Var(0) ), "v1" //! ) ; //! assert_eq!(consign.len(), 1) ; //! let prev = map.insert(v1.clone(), v1_name) ; //! assert_eq!( prev, None ) ; //! let is_new = set.insert(v1.clone()) ; //! assert!( is_new ) ; //! ``` use std::collections::{HashMap, HashSet}; use std::hash::{Hash, Hasher}; use std::ops::{Deref, DerefMut}; use self::hash::BuildHashU64; use crate::{HConsed, HashConsed}; /// A hash set of hash-consed things with trivial hashing. #[derive(Clone, Debug, Eq)] pub struct HConSet<T> where T: HashConsed, T::Inner: Eq + Hash, { set: HashSet<HConsed<T::Inner>, BuildHashU64>, } impl<T> PartialEq for HConSet<T> where T: HashConsed, T::Inner: Eq + Hash, { fn eq(&self, other: &Self) -> bool { self.len() == other.len() && self.iter().zip(other.iter()).all(|(e_1, e_2)| e_1 == e_2) } } impl<T> Hash for HConSet<T> where T: HashConsed, T::Inner: Eq + Hash, { fn hash<H>(&self, h: &mut H) where H: Hasher, { for elem in self { elem.hash(h) } } } impl<T> Default for HConSet<T> where T: HashConsed, T::Inner: Eq + Hash, { fn default() -> Self { HConSet { set: HashSet::default(), } } } impl<T> HConSet<T> where T: HashConsed, T::Inner: Eq + Hash, { /// An empty set of hashconsed things. #[inline] pub fn new() -> Self { HConSet { set: HashSet::with_hasher(BuildHashU64 {}), } } /// An empty set of hashconsed things with a capacity. #[inline] pub fn with_capacity(capa: usize) -> Self { HConSet { set: HashSet::with_capacity_and_hasher(capa, BuildHashU64 {}), } } /// An iterator visiting all elements. #[inline] pub fn iter(&self) -> ::std::collections::hash_set::Iter<HConsed<T::Inner>> { self.set.iter() } } impl<'a, T> IntoIterator for &'a HConSet<T> where T: HashConsed, T::Inner: Hash + Eq, { type Item = &'a HConsed<T::Inner>; type IntoIter = ::std::collections::hash_set::Iter<'a, HConsed<T::Inner>>; fn into_iter(self) -> Self::IntoIter { (&self.set).into_iter() } } impl<T> IntoIterator for HConSet<T> where T: HashConsed, T::Inner: Hash + Eq, { type Item = HConsed<T::Inner>; type IntoIter = ::std::collections::hash_set::IntoIter<HConsed<T::Inner>>; fn into_iter(self) -> Self::IntoIter { self.set.into_iter() } } impl<T> ::std::iter::FromIterator<HConsed<T::Inner>> for HConSet<T> where T: HashConsed, T::Inner: Hash + Eq, { fn from_iter<I: IntoIterator<Item = HConsed<T::Inner>>>(iter: I) -> Self { HConSet { set: HashSet::from_iter(iter), } } } impl<T> Deref for HConSet<T> where T: HashConsed, T::Inner: Hash + Eq, { type Target = HashSet<HConsed<T::Inner>, BuildHashU64>; fn deref(&self) -> &Self::Target { &self.set } } impl<T> DerefMut for HConSet<T> where T: HashConsed, T::Inner: Hash + Eq, { fn deref_mut(&mut self) -> &mut Self::Target { &mut self.set } } impl<T, Src> From<Src> for HConSet<HConsed<T>> where T: Hash + Eq, Src: Iterator<Item = HConsed<T>>, { fn from(src: Src) -> Self { let mut set = HConSet::new(); for elem in src { set.insert(elem); } set } } /// A hash map of hash-consed things with trivial hashing. #[derive(Clone, Debug, Eq)] pub struct HConMap<T, V> where T: HashConsed, T::Inner: Hash + Eq, { map: HashMap<HConsed<T::Inner>, V, BuildHashU64>, } impl<T, V> PartialEq for HConMap<T, V> where T: HashConsed, T::Inner: Eq + Hash, V: Eq, { fn eq(&self, other: &Self) -> bool { self.len() == other.len() && self .iter() .zip(other.iter()) .all(|((k_1, v_1), (k_2, v_2))| k_1 == k_2 && v_1 == v_2) } } impl<T, V> Hash for HConMap<T, V> where T: HashConsed, T::Inner: Eq + Hash, V: Hash, { fn hash<H>(&self, h: &mut H) where H: Hasher, { for (key, value) in self { key.hash(h); value.hash(h) } } } impl<T, V> Default for HConMap<T, V> where T: HashConsed, T::Inner: Eq + Hash, { fn default() -> Self { HConMap { map: HashMap::default(), } } } impl<T: HashConsed, V> HConMap<T, V> where T::Inner: Hash + Eq, { /// An empty map of hashconsed things. #[inline] pub fn new() -> Self { HConMap { map: HashMap::with_hasher(BuildHashU64 {}), } } /// An empty map of hashconsed things with a capacity. #[inline] pub fn with_capacity(capa: usize) -> Self { HConMap { map: HashMap::with_capacity_and_hasher(capa, BuildHashU64 {}), } } /// An iterator visiting all elements. #[inline] pub fn iter(&self) -> ::std::collections::hash_map::Iter<HConsed<T::Inner>, V> { self.map.iter() } /// An iterator visiting all elements. #[inline] pub fn iter_mut(&mut self) -> ::std::collections::hash_map::IterMut<HConsed<T::Inner>, V> { self.map.iter_mut() } } impl<'a, T, V> IntoIterator for &'a HConMap<T, V> where T: HashConsed, T::Inner: Hash + Eq, { type Item = (&'a HConsed<T::Inner>, &'a V); type IntoIter = ::std::collections::hash_map::Iter<'a, HConsed<T::Inner>, V>; fn into_iter(self) -> Self::IntoIter { (&self.map).into_iter() } } impl<'a, T, V> IntoIterator for &'a mut HConMap<T, V> where T: HashConsed, T::Inner: Hash + Eq, { type Item = (&'a HConsed<T::Inner>, &'a mut V); type IntoIter = ::std::collections::hash_map::IterMut<'a, HConsed<T::Inner>, V>; fn into_iter(self) -> Self::IntoIter { (&mut self.map).into_iter() } } impl<T, V> IntoIterator for HConMap<T, V> where T: HashConsed, T::Inner: Hash + Eq, { type Item = (HConsed<T::Inner>, V); type IntoIter = ::std::collections::hash_map::IntoIter<HConsed<T::Inner>, V>; fn into_iter(self) -> Self::IntoIter { self.map.into_iter() } } impl<T, V> ::std::iter::FromIterator<(HConsed<T::Inner>, V)> for HConMap<T, V> where T: HashConsed, T::Inner: Hash + Eq, { fn from_iter<I: IntoIterator<Item = (HConsed<T::Inner>, V)>>(iter: I) -> Self { HConMap { map: HashMap::from_iter(iter), } } } impl<T: HashConsed, V> Deref for HConMap<T, V> where T::Inner: Hash + Eq, { type Target = HashMap<HConsed<T::Inner>, V, BuildHashU64>; fn deref(&self) -> &Self::Target { &self.map } } impl<T: HashConsed, V> DerefMut for HConMap<T, V> where T::Inner: Hash + Eq, { fn deref_mut(&mut self) -> &mut Self::Target { &mut self.map } } impl<T, V, Src> From<Src> for HConMap<HConsed<T>, V> where T: Hash + Eq, Src: Iterator<Item = (HConsed<T>, V)>, { fn from(src: Src) -> Self { let mut set = HConMap::new(); for (elem, value) in src { set.insert(elem, value); } set } } /// Optimal trivial hash for `usize`s and `u64`s. The former is used for /// wrapped indices, the latter for hashconsed things. /// /// **NEVER USE THIS MODULE DIRECTLY. ONLY THROUGH THE `wrap_usize` MACRO.** /// /// This is kind of unsafe, in a way. The hasher will cause logic errors if /// asked to hash anything else than what it was supposed to hash. /// /// In `debug`, this is actually checked each time something is hashed. This /// check is of course deactivated in `release`. mod hash { use std::hash::{BuildHasher, Hasher}; /// Empty struct used to build `HashU64`. #[derive(Clone)] pub struct BuildHashU64 {} impl BuildHasher for BuildHashU64 { type Hasher = HashU64; fn build_hasher(&self) -> HashU64 { HashU64 { buf: [0; 8] } } } impl Default for BuildHashU64 { fn default() -> Self { BuildHashU64 {} } } /// Trivial hasher for `usize`. **This hasher is only for hashing `usize`s**. pub struct HashU64 { buf: [u8; 8], } impl HashU64 { /// Checks that a slice of bytes has the length of a `usize`. Only active /// in debug. #[cfg(debug)] #[inline(always)] fn test_bytes(bytes: &[u8]) { if bytes.len() != 8 { panic!( "[illegal] `HashU64::hash` \ called with non-`u64` argument ({} bytes, expected {})", bytes.len(), 8 ) } } /// Checks that a slice of bytes has the length of a `usize`. Only active /// in debug. #[cfg(not(debug))] #[inline(always)] fn test_bytes(_: &[u8]) {} } impl Hasher for HashU64 { fn finish(&self) -> u64 { unsafe { ::std::mem::transmute(self.buf) } } fn write(&mut self, bytes: &[u8]) { Self::test_bytes(bytes); self.buf[..8].clone_from_slice(&bytes[..8]) } } }