1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135

use std::cell::{RefCell, RefMut};
use std::cmp::Ordering;
use std::collections::HashSet;
use std::fmt;
use std::hash::{Hash, Hasher};
use std::ops::Deref;
use std::rc::{Rc};

pub struct TabledData<T> {
    table: Rc<RefCell<HashSet<Rc<T>>>>,
    pub(crate) module_name: Rc<String>
}

impl<T> Clone for TabledData<T> {
    fn clone(&self) -> Self {
        TabledData { table: self.table.clone(),
                     module_name: self.module_name.clone() }
    }
}

impl<T: PartialEq> PartialEq for TabledData<T> {
    fn eq(&self, other: &TabledData<T>) -> bool
    {
        Rc::ptr_eq(&self.table, &other.table) && self.module_name == other.module_name
    }
}

impl<T: Hash + Eq> TabledData<T> {
    #[inline]
    pub fn new(module_name: Rc<String>) -> Self {
        TabledData {
            table: Rc::new(RefCell::new(HashSet::new())),
            module_name
        }
    }
    
    #[inline]
    pub fn borrow_mut(&self) -> RefMut<HashSet<Rc<T>>> {
        self.table.borrow_mut()
    }
}

pub struct TabledRc<T: Hash + Eq> {
    pub(crate) atom: Rc<T>,
    pub table: TabledData<T>
}

// this Clone instance is manually defined to prevent the compiler
// from complaining when deriving Clone for StringList.
impl<T: Hash + Eq> Clone for TabledRc<T> {
    fn clone(&self) -> Self {
        TabledRc { atom: self.atom.clone(), table: self.table.clone() }
    }
}

impl<T: Ord + Hash + Eq> PartialOrd for TabledRc<T> {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering>
    {
        Some(self.atom.cmp(&other.atom))
    }
}

impl<T: Ord + Hash + Eq> Ord for TabledRc<T> {
    fn cmp(&self, other: &Self) -> Ordering
    {
        self.atom.cmp(&other.atom)
    }
}

impl<T: Hash + Eq> PartialEq for TabledRc<T> {
    fn eq(&self, other: &TabledRc<T>) -> bool
    {
        self.atom == other.atom
    }
}

impl<T: Hash + Eq> Eq for TabledRc<T> {}

impl<T: Hash + Eq> Hash for TabledRc<T> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.atom.hash(state)
    }
}

impl<T: Hash + Eq + ToString> TabledRc<T> {
    pub fn new(atom: T, table: TabledData<T>) -> Self {
        let atom = match table.borrow_mut().take(&atom) {
            Some(atom) => atom.clone(),
            None => Rc::new(atom)
        };

        table.borrow_mut().insert(atom.clone());

        TabledRc { atom, table }
    }
    
    #[inline]
    pub fn inner(&self) -> Rc<T> {
        self.atom.clone()
    }
    
    #[inline]
    pub(crate) fn owning_module(&self) -> Rc<String> {
        self.table.module_name.clone()
    }
}

impl<T: Hash + Eq> Drop for TabledRc<T> {
    fn drop(&mut self) {
        if Rc::strong_count(&self.atom) == 2 {
            self.table.borrow_mut().remove(&self.atom);
        }
    }
}

impl<T: Hash + Eq> Deref for TabledRc<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &*self.atom
    }
}

impl<T: Hash + Eq + fmt::Display> fmt::Display for TabledRc<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", &*self.atom)
    }
}

#[macro_export]
macro_rules! tabled_rc {
    ($e:expr, $tbl:expr) => (
        TabledRc::new(String::from($e), $tbl.clone())
    )
}